1<html> 2<head> 3<title>pcre2api specification</title> 4</head> 5<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> 6<h1>pcre2api man page</h1> 7<p> 8Return to the <a href="index.html">PCRE2 index page</a>. 9</p> 10<p> 11This page is part of the PCRE2 HTML documentation. It was generated 12automatically from the original man page. If there is any nonsense in it, 13please consult the man page, in case the conversion went wrong. 14<br> 15<ul> 16<li><a name="TOC1" href="#SEC1">PCRE2 NATIVE API BASIC FUNCTIONS</a> 17<li><a name="TOC2" href="#SEC2">PCRE2 NATIVE API AUXILIARY MATCH FUNCTIONS</a> 18<li><a name="TOC3" href="#SEC3">PCRE2 NATIVE API GENERAL CONTEXT FUNCTIONS</a> 19<li><a name="TOC4" href="#SEC4">PCRE2 NATIVE API COMPILE CONTEXT FUNCTIONS</a> 20<li><a name="TOC5" href="#SEC5">PCRE2 NATIVE API MATCH CONTEXT FUNCTIONS</a> 21<li><a name="TOC6" href="#SEC6">PCRE2 NATIVE API STRING EXTRACTION FUNCTIONS</a> 22<li><a name="TOC7" href="#SEC7">PCRE2 NATIVE API STRING SUBSTITUTION FUNCTION</a> 23<li><a name="TOC8" href="#SEC8">PCRE2 NATIVE API JIT FUNCTIONS</a> 24<li><a name="TOC9" href="#SEC9">PCRE2 NATIVE API SERIALIZATION FUNCTIONS</a> 25<li><a name="TOC10" href="#SEC10">PCRE2 NATIVE API AUXILIARY FUNCTIONS</a> 26<li><a name="TOC11" href="#SEC11">PCRE2 NATIVE API OBSOLETE FUNCTIONS</a> 27<li><a name="TOC12" href="#SEC12">PCRE2 EXPERIMENTAL PATTERN CONVERSION FUNCTIONS</a> 28<li><a name="TOC13" href="#SEC13">PCRE2 8-BIT, 16-BIT, AND 32-BIT LIBRARIES</a> 29<li><a name="TOC14" href="#SEC14">PCRE2 API OVERVIEW</a> 30<li><a name="TOC15" href="#SEC15">STRING LENGTHS AND OFFSETS</a> 31<li><a name="TOC16" href="#SEC16">NEWLINES</a> 32<li><a name="TOC17" href="#SEC17">MULTITHREADING</a> 33<li><a name="TOC18" href="#SEC18">PCRE2 CONTEXTS</a> 34<li><a name="TOC19" href="#SEC19">CHECKING BUILD-TIME OPTIONS</a> 35<li><a name="TOC20" href="#SEC20">COMPILING A PATTERN</a> 36<li><a name="TOC21" href="#SEC21">JUST-IN-TIME (JIT) COMPILATION</a> 37<li><a name="TOC22" href="#SEC22">LOCALE SUPPORT</a> 38<li><a name="TOC23" href="#SEC23">INFORMATION ABOUT A COMPILED PATTERN</a> 39<li><a name="TOC24" href="#SEC24">INFORMATION ABOUT A PATTERN'S CALLOUTS</a> 40<li><a name="TOC25" href="#SEC25">SERIALIZATION AND PRECOMPILING</a> 41<li><a name="TOC26" href="#SEC26">THE MATCH DATA BLOCK</a> 42<li><a name="TOC27" href="#SEC27">MATCHING A PATTERN: THE TRADITIONAL FUNCTION</a> 43<li><a name="TOC28" href="#SEC28">NEWLINE HANDLING WHEN MATCHING</a> 44<li><a name="TOC29" href="#SEC29">HOW PCRE2_MATCH() RETURNS A STRING AND CAPTURED SUBSTRINGS</a> 45<li><a name="TOC30" href="#SEC30">OTHER INFORMATION ABOUT A MATCH</a> 46<li><a name="TOC31" href="#SEC31">ERROR RETURNS FROM <b>pcre2_match()</b></a> 47<li><a name="TOC32" href="#SEC32">OBTAINING A TEXTUAL ERROR MESSAGE</a> 48<li><a name="TOC33" href="#SEC33">EXTRACTING CAPTURED SUBSTRINGS BY NUMBER</a> 49<li><a name="TOC34" href="#SEC34">EXTRACTING A LIST OF ALL CAPTURED SUBSTRINGS</a> 50<li><a name="TOC35" href="#SEC35">EXTRACTING CAPTURED SUBSTRINGS BY NAME</a> 51<li><a name="TOC36" href="#SEC36">CREATING A NEW STRING WITH SUBSTITUTIONS</a> 52<li><a name="TOC37" href="#SEC37">DUPLICATE CAPTURE GROUP NAMES</a> 53<li><a name="TOC38" href="#SEC38">FINDING ALL POSSIBLE MATCHES AT ONE POSITION</a> 54<li><a name="TOC39" href="#SEC39">MATCHING A PATTERN: THE ALTERNATIVE FUNCTION</a> 55<li><a name="TOC40" href="#SEC40">SEE ALSO</a> 56<li><a name="TOC41" href="#SEC41">AUTHOR</a> 57<li><a name="TOC42" href="#SEC42">REVISION</a> 58</ul> 59<P> 60<b>#include <pcre2.h></b> 61<br> 62<br> 63PCRE2 is a new API for PCRE, starting at release 10.0. This document contains a 64description of all its native functions. See the 65<a href="pcre2.html"><b>pcre2</b></a> 66document for an overview of all the PCRE2 documentation. 67</P> 68<br><a name="SEC1" href="#TOC1">PCRE2 NATIVE API BASIC FUNCTIONS</a><br> 69<P> 70<b>pcre2_code *pcre2_compile(PCRE2_SPTR <i>pattern</i>, PCRE2_SIZE <i>length</i>,</b> 71<b> uint32_t <i>options</i>, int *<i>errorcode</i>, PCRE2_SIZE *<i>erroroffset,</i></b> 72<b> pcre2_compile_context *<i>ccontext</i>);</b> 73<br> 74<br> 75<b>void pcre2_code_free(pcre2_code *<i>code</i>);</b> 76<br> 77<br> 78<b>pcre2_match_data *pcre2_match_data_create(uint32_t <i>ovecsize</i>,</b> 79<b> pcre2_general_context *<i>gcontext</i>);</b> 80<br> 81<br> 82<b>pcre2_match_data *pcre2_match_data_create_from_pattern(</b> 83<b> const pcre2_code *<i>code</i>, pcre2_general_context *<i>gcontext</i>);</b> 84<br> 85<br> 86<b>int pcre2_match(const pcre2_code *<i>code</i>, PCRE2_SPTR <i>subject</i>,</b> 87<b> PCRE2_SIZE <i>length</i>, PCRE2_SIZE <i>startoffset</i>,</b> 88<b> uint32_t <i>options</i>, pcre2_match_data *<i>match_data</i>,</b> 89<b> pcre2_match_context *<i>mcontext</i>);</b> 90<br> 91<br> 92<b>int pcre2_dfa_match(const pcre2_code *<i>code</i>, PCRE2_SPTR <i>subject</i>,</b> 93<b> PCRE2_SIZE <i>length</i>, PCRE2_SIZE <i>startoffset</i>,</b> 94<b> uint32_t <i>options</i>, pcre2_match_data *<i>match_data</i>,</b> 95<b> pcre2_match_context *<i>mcontext</i>,</b> 96<b> int *<i>workspace</i>, PCRE2_SIZE <i>wscount</i>);</b> 97<br> 98<br> 99<b>void pcre2_match_data_free(pcre2_match_data *<i>match_data</i>);</b> 100</P> 101<br><a name="SEC2" href="#TOC1">PCRE2 NATIVE API AUXILIARY MATCH FUNCTIONS</a><br> 102<P> 103<b>PCRE2_SPTR pcre2_get_mark(pcre2_match_data *<i>match_data</i>);</b> 104<br> 105<br> 106<b>uint32_t pcre2_get_ovector_count(pcre2_match_data *<i>match_data</i>);</b> 107<br> 108<br> 109<b>PCRE2_SIZE *pcre2_get_ovector_pointer(pcre2_match_data *<i>match_data</i>);</b> 110<br> 111<br> 112<b>PCRE2_SIZE pcre2_get_startchar(pcre2_match_data *<i>match_data</i>);</b> 113</P> 114<br><a name="SEC3" href="#TOC1">PCRE2 NATIVE API GENERAL CONTEXT FUNCTIONS</a><br> 115<P> 116<b>pcre2_general_context *pcre2_general_context_create(</b> 117<b> void *(*<i>private_malloc</i>)(PCRE2_SIZE, void *),</b> 118<b> void (*<i>private_free</i>)(void *, void *), void *<i>memory_data</i>);</b> 119<br> 120<br> 121<b>pcre2_general_context *pcre2_general_context_copy(</b> 122<b> pcre2_general_context *<i>gcontext</i>);</b> 123<br> 124<br> 125<b>void pcre2_general_context_free(pcre2_general_context *<i>gcontext</i>);</b> 126</P> 127<br><a name="SEC4" href="#TOC1">PCRE2 NATIVE API COMPILE CONTEXT FUNCTIONS</a><br> 128<P> 129<b>pcre2_compile_context *pcre2_compile_context_create(</b> 130<b> pcre2_general_context *<i>gcontext</i>);</b> 131<br> 132<br> 133<b>pcre2_compile_context *pcre2_compile_context_copy(</b> 134<b> pcre2_compile_context *<i>ccontext</i>);</b> 135<br> 136<br> 137<b>void pcre2_compile_context_free(pcre2_compile_context *<i>ccontext</i>);</b> 138<br> 139<br> 140<b>int pcre2_set_bsr(pcre2_compile_context *<i>ccontext</i>,</b> 141<b> uint32_t <i>value</i>);</b> 142<br> 143<br> 144<b>int pcre2_set_character_tables(pcre2_compile_context *<i>ccontext</i>,</b> 145<b> const uint8_t *<i>tables</i>);</b> 146<br> 147<br> 148<b>int pcre2_set_compile_extra_options(pcre2_compile_context *<i>ccontext</i>,</b> 149<b> uint32_t <i>extra_options</i>);</b> 150<br> 151<br> 152<b>int pcre2_set_max_pattern_length(pcre2_compile_context *<i>ccontext</i>,</b> 153<b> PCRE2_SIZE <i>value</i>);</b> 154<br> 155<br> 156<b>int pcre2_set_newline(pcre2_compile_context *<i>ccontext</i>,</b> 157<b> uint32_t <i>value</i>);</b> 158<br> 159<br> 160<b>int pcre2_set_parens_nest_limit(pcre2_compile_context *<i>ccontext</i>,</b> 161<b> uint32_t <i>value</i>);</b> 162<br> 163<br> 164<b>int pcre2_set_compile_recursion_guard(pcre2_compile_context *<i>ccontext</i>,</b> 165<b> int (*<i>guard_function</i>)(uint32_t, void *), void *<i>user_data</i>);</b> 166</P> 167<br><a name="SEC5" href="#TOC1">PCRE2 NATIVE API MATCH CONTEXT FUNCTIONS</a><br> 168<P> 169<b>pcre2_match_context *pcre2_match_context_create(</b> 170<b> pcre2_general_context *<i>gcontext</i>);</b> 171<br> 172<br> 173<b>pcre2_match_context *pcre2_match_context_copy(</b> 174<b> pcre2_match_context *<i>mcontext</i>);</b> 175<br> 176<br> 177<b>void pcre2_match_context_free(pcre2_match_context *<i>mcontext</i>);</b> 178<br> 179<br> 180<b>int pcre2_set_callout(pcre2_match_context *<i>mcontext</i>,</b> 181<b> int (*<i>callout_function</i>)(pcre2_callout_block *, void *),</b> 182<b> void *<i>callout_data</i>);</b> 183<br> 184<br> 185<b>int pcre2_set_substitute_callout(pcre2_match_context *<i>mcontext</i>,</b> 186<b> int (*<i>callout_function</i>)(pcre2_substitute_callout_block *, void *),</b> 187<b> void *<i>callout_data</i>);</b> 188<br> 189<br> 190<b>int pcre2_set_offset_limit(pcre2_match_context *<i>mcontext</i>,</b> 191<b> PCRE2_SIZE <i>value</i>);</b> 192<br> 193<br> 194<b>int pcre2_set_heap_limit(pcre2_match_context *<i>mcontext</i>,</b> 195<b> uint32_t <i>value</i>);</b> 196<br> 197<br> 198<b>int pcre2_set_match_limit(pcre2_match_context *<i>mcontext</i>,</b> 199<b> uint32_t <i>value</i>);</b> 200<br> 201<br> 202<b>int pcre2_set_depth_limit(pcre2_match_context *<i>mcontext</i>,</b> 203<b> uint32_t <i>value</i>);</b> 204</P> 205<br><a name="SEC6" href="#TOC1">PCRE2 NATIVE API STRING EXTRACTION FUNCTIONS</a><br> 206<P> 207<b>int pcre2_substring_copy_byname(pcre2_match_data *<i>match_data</i>,</b> 208<b> PCRE2_SPTR <i>name</i>, PCRE2_UCHAR *<i>buffer</i>, PCRE2_SIZE *<i>bufflen</i>);</b> 209<br> 210<br> 211<b>int pcre2_substring_copy_bynumber(pcre2_match_data *<i>match_data</i>,</b> 212<b> uint32_t <i>number</i>, PCRE2_UCHAR *<i>buffer</i>,</b> 213<b> PCRE2_SIZE *<i>bufflen</i>);</b> 214<br> 215<br> 216<b>void pcre2_substring_free(PCRE2_UCHAR *<i>buffer</i>);</b> 217<br> 218<br> 219<b>int pcre2_substring_get_byname(pcre2_match_data *<i>match_data</i>,</b> 220<b> PCRE2_SPTR <i>name</i>, PCRE2_UCHAR **<i>bufferptr</i>, PCRE2_SIZE *<i>bufflen</i>);</b> 221<br> 222<br> 223<b>int pcre2_substring_get_bynumber(pcre2_match_data *<i>match_data</i>,</b> 224<b> uint32_t <i>number</i>, PCRE2_UCHAR **<i>bufferptr</i>,</b> 225<b> PCRE2_SIZE *<i>bufflen</i>);</b> 226<br> 227<br> 228<b>int pcre2_substring_length_byname(pcre2_match_data *<i>match_data</i>,</b> 229<b> PCRE2_SPTR <i>name</i>, PCRE2_SIZE *<i>length</i>);</b> 230<br> 231<br> 232<b>int pcre2_substring_length_bynumber(pcre2_match_data *<i>match_data</i>,</b> 233<b> uint32_t <i>number</i>, PCRE2_SIZE *<i>length</i>);</b> 234<br> 235<br> 236<b>int pcre2_substring_nametable_scan(const pcre2_code *<i>code</i>,</b> 237<b> PCRE2_SPTR <i>name</i>, PCRE2_SPTR *<i>first</i>, PCRE2_SPTR *<i>last</i>);</b> 238<br> 239<br> 240<b>int pcre2_substring_number_from_name(const pcre2_code *<i>code</i>,</b> 241<b> PCRE2_SPTR <i>name</i>);</b> 242<br> 243<br> 244<b>void pcre2_substring_list_free(PCRE2_SPTR *<i>list</i>);</b> 245<br> 246<br> 247<b>int pcre2_substring_list_get(pcre2_match_data *<i>match_data</i>,</b> 248<b>" PCRE2_UCHAR ***<i>listptr</i>, PCRE2_SIZE **<i>lengthsptr</i>);</b> 249</P> 250<br><a name="SEC7" href="#TOC1">PCRE2 NATIVE API STRING SUBSTITUTION FUNCTION</a><br> 251<P> 252<b>int pcre2_substitute(const pcre2_code *<i>code</i>, PCRE2_SPTR <i>subject</i>,</b> 253<b> PCRE2_SIZE <i>length</i>, PCRE2_SIZE <i>startoffset</i>,</b> 254<b> uint32_t <i>options</i>, pcre2_match_data *<i>match_data</i>,</b> 255<b> pcre2_match_context *<i>mcontext</i>, PCRE2_SPTR <i>replacementz</i>,</b> 256<b> PCRE2_SIZE <i>rlength</i>, PCRE2_UCHAR *<i>outputbuffer</i>,</b> 257<b> PCRE2_SIZE *<i>outlengthptr</i>);</b> 258</P> 259<br><a name="SEC8" href="#TOC1">PCRE2 NATIVE API JIT FUNCTIONS</a><br> 260<P> 261<b>int pcre2_jit_compile(pcre2_code *<i>code</i>, uint32_t <i>options</i>);</b> 262<br> 263<br> 264<b>int pcre2_jit_match(const pcre2_code *<i>code</i>, PCRE2_SPTR <i>subject</i>,</b> 265<b> PCRE2_SIZE <i>length</i>, PCRE2_SIZE <i>startoffset</i>,</b> 266<b> uint32_t <i>options</i>, pcre2_match_data *<i>match_data</i>,</b> 267<b> pcre2_match_context *<i>mcontext</i>);</b> 268<br> 269<br> 270<b>void pcre2_jit_free_unused_memory(pcre2_general_context *<i>gcontext</i>);</b> 271<br> 272<br> 273<b>pcre2_jit_stack *pcre2_jit_stack_create(PCRE2_SIZE <i>startsize</i>,</b> 274<b> PCRE2_SIZE <i>maxsize</i>, pcre2_general_context *<i>gcontext</i>);</b> 275<br> 276<br> 277<b>void pcre2_jit_stack_assign(pcre2_match_context *<i>mcontext</i>,</b> 278<b> pcre2_jit_callback <i>callback_function</i>, void *<i>callback_data</i>);</b> 279<br> 280<br> 281<b>void pcre2_jit_stack_free(pcre2_jit_stack *<i>jit_stack</i>);</b> 282</P> 283<br><a name="SEC9" href="#TOC1">PCRE2 NATIVE API SERIALIZATION FUNCTIONS</a><br> 284<P> 285<b>int32_t pcre2_serialize_decode(pcre2_code **<i>codes</i>,</b> 286<b> int32_t <i>number_of_codes</i>, const uint8_t *<i>bytes</i>,</b> 287<b> pcre2_general_context *<i>gcontext</i>);</b> 288<br> 289<br> 290<b>int32_t pcre2_serialize_encode(const pcre2_code **<i>codes</i>,</b> 291<b> int32_t <i>number_of_codes</i>, uint8_t **<i>serialized_bytes</i>,</b> 292<b> PCRE2_SIZE *<i>serialized_size</i>, pcre2_general_context *<i>gcontext</i>);</b> 293<br> 294<br> 295<b>void pcre2_serialize_free(uint8_t *<i>bytes</i>);</b> 296<br> 297<br> 298<b>int32_t pcre2_serialize_get_number_of_codes(const uint8_t *<i>bytes</i>);</b> 299</P> 300<br><a name="SEC10" href="#TOC1">PCRE2 NATIVE API AUXILIARY FUNCTIONS</a><br> 301<P> 302<b>pcre2_code *pcre2_code_copy(const pcre2_code *<i>code</i>);</b> 303<br> 304<br> 305<b>pcre2_code *pcre2_code_copy_with_tables(const pcre2_code *<i>code</i>);</b> 306<br> 307<br> 308<b>int pcre2_get_error_message(int <i>errorcode</i>, PCRE2_UCHAR *<i>buffer</i>,</b> 309<b> PCRE2_SIZE <i>bufflen</i>);</b> 310<br> 311<br> 312<b>const uint8_t *pcre2_maketables(pcre2_general_context *<i>gcontext</i>);</b> 313<br> 314<br> 315<b>void pcre2_maketables_free(pcre2_general_context *<i>gcontext</i>,</b> 316<b> const uint8_t *<i>tables</i>);</b> 317<br> 318<br> 319<b>int pcre2_pattern_info(const pcre2_code *<i>code</i>, uint32_t <i>what</i>,</b> 320<b> void *<i>where</i>);</b> 321<br> 322<br> 323<b>int pcre2_callout_enumerate(const pcre2_code *<i>code</i>,</b> 324<b> int (*<i>callback</i>)(pcre2_callout_enumerate_block *, void *),</b> 325<b> void *<i>user_data</i>);</b> 326<br> 327<br> 328<b>int pcre2_config(uint32_t <i>what</i>, void *<i>where</i>);</b> 329</P> 330<br><a name="SEC11" href="#TOC1">PCRE2 NATIVE API OBSOLETE FUNCTIONS</a><br> 331<P> 332<b>int pcre2_set_recursion_limit(pcre2_match_context *<i>mcontext</i>,</b> 333<b> uint32_t <i>value</i>);</b> 334<br> 335<br> 336<b>int pcre2_set_recursion_memory_management(</b> 337<b> pcre2_match_context *<i>mcontext</i>,</b> 338<b> void *(*<i>private_malloc</i>)(PCRE2_SIZE, void *),</b> 339<b> void (*<i>private_free</i>)(void *, void *), void *<i>memory_data</i>);</b> 340<br> 341<br> 342These functions became obsolete at release 10.30 and are retained only for 343backward compatibility. They should not be used in new code. The first is 344replaced by <b>pcre2_set_depth_limit()</b>; the second is no longer needed and 345has no effect (it always returns zero). 346</P> 347<br><a name="SEC12" href="#TOC1">PCRE2 EXPERIMENTAL PATTERN CONVERSION FUNCTIONS</a><br> 348<P> 349<b>pcre2_convert_context *pcre2_convert_context_create(</b> 350<b> pcre2_general_context *<i>gcontext</i>);</b> 351<br> 352<br> 353<b>pcre2_convert_context *pcre2_convert_context_copy(</b> 354<b> pcre2_convert_context *<i>cvcontext</i>);</b> 355<br> 356<br> 357<b>void pcre2_convert_context_free(pcre2_convert_context *<i>cvcontext</i>);</b> 358<br> 359<br> 360<b>int pcre2_set_glob_escape(pcre2_convert_context *<i>cvcontext</i>,</b> 361<b> uint32_t <i>escape_char</i>);</b> 362<br> 363<br> 364<b>int pcre2_set_glob_separator(pcre2_convert_context *<i>cvcontext</i>,</b> 365<b> uint32_t <i>separator_char</i>);</b> 366<br> 367<br> 368<b>int pcre2_pattern_convert(PCRE2_SPTR <i>pattern</i>, PCRE2_SIZE <i>length</i>,</b> 369<b> uint32_t <i>options</i>, PCRE2_UCHAR **<i>buffer</i>,</b> 370<b> PCRE2_SIZE *<i>blength</i>, pcre2_convert_context *<i>cvcontext</i>);</b> 371<br> 372<br> 373<b>void pcre2_converted_pattern_free(PCRE2_UCHAR *<i>converted_pattern</i>);</b> 374<br> 375<br> 376These functions provide a way of converting non-PCRE2 patterns into 377patterns that can be processed by <b>pcre2_compile()</b>. This facility is 378experimental and may be changed in future releases. At present, "globs" and 379POSIX basic and extended patterns can be converted. Details are given in the 380<a href="pcre2convert.html"><b>pcre2convert</b></a> 381documentation. 382</P> 383<br><a name="SEC13" href="#TOC1">PCRE2 8-BIT, 16-BIT, AND 32-BIT LIBRARIES</a><br> 384<P> 385There are three PCRE2 libraries, supporting 8-bit, 16-bit, and 32-bit code 386units, respectively. However, there is just one header file, <b>pcre2.h</b>. 387This contains the function prototypes and other definitions for all three 388libraries. One, two, or all three can be installed simultaneously. On Unix-like 389systems the libraries are called <b>libpcre2-8</b>, <b>libpcre2-16</b>, and 390<b>libpcre2-32</b>, and they can also co-exist with the original PCRE libraries. 391</P> 392<P> 393Character strings are passed to and from a PCRE2 library as a sequence of 394unsigned integers in code units of the appropriate width. Every PCRE2 function 395comes in three different forms, one for each library, for example: 396<pre> 397 <b>pcre2_compile_8()</b> 398 <b>pcre2_compile_16()</b> 399 <b>pcre2_compile_32()</b> 400</pre> 401There are also three different sets of data types: 402<pre> 403 <b>PCRE2_UCHAR8, PCRE2_UCHAR16, PCRE2_UCHAR32</b> 404 <b>PCRE2_SPTR8, PCRE2_SPTR16, PCRE2_SPTR32</b> 405</pre> 406The UCHAR types define unsigned code units of the appropriate widths. For 407example, PCRE2_UCHAR16 is usually defined as `uint16_t'. The SPTR types are 408constant pointers to the equivalent UCHAR types, that is, they are pointers to 409vectors of unsigned code units. 410</P> 411<P> 412Many applications use only one code unit width. For their convenience, macros 413are defined whose names are the generic forms such as <b>pcre2_compile()</b> and 414PCRE2_SPTR. These macros use the value of the macro PCRE2_CODE_UNIT_WIDTH to 415generate the appropriate width-specific function and macro names. 416PCRE2_CODE_UNIT_WIDTH is not defined by default. An application must define it 417to be 8, 16, or 32 before including <b>pcre2.h</b> in order to make use of the 418generic names. 419</P> 420<P> 421Applications that use more than one code unit width can be linked with more 422than one PCRE2 library, but must define PCRE2_CODE_UNIT_WIDTH to be 0 before 423including <b>pcre2.h</b>, and then use the real function names. Any code that is 424to be included in an environment where the value of PCRE2_CODE_UNIT_WIDTH is 425unknown should also use the real function names. (Unfortunately, it is not 426possible in C code to save and restore the value of a macro.) 427</P> 428<P> 429If PCRE2_CODE_UNIT_WIDTH is not defined before including <b>pcre2.h</b>, a 430compiler error occurs. 431</P> 432<P> 433When using multiple libraries in an application, you must take care when 434processing any particular pattern to use only functions from a single library. 435For example, if you want to run a match using a pattern that was compiled with 436<b>pcre2_compile_16()</b>, you must do so with <b>pcre2_match_16()</b>, not 437<b>pcre2_match_8()</b> or <b>pcre2_match_32()</b>. 438</P> 439<P> 440In the function summaries above, and in the rest of this document and other 441PCRE2 documents, functions and data types are described using their generic 442names, without the _8, _16, or _32 suffix. 443</P> 444<br><a name="SEC14" href="#TOC1">PCRE2 API OVERVIEW</a><br> 445<P> 446PCRE2 has its own native API, which is described in this document. There are 447also some wrapper functions for the 8-bit library that correspond to the 448POSIX regular expression API, but they do not give access to all the 449functionality of PCRE2. They are described in the 450<a href="pcre2posix.html"><b>pcre2posix</b></a> 451documentation. Both these APIs define a set of C function calls. 452</P> 453<P> 454The native API C data types, function prototypes, option values, and error 455codes are defined in the header file <b>pcre2.h</b>, which also contains 456definitions of PCRE2_MAJOR and PCRE2_MINOR, the major and minor release numbers 457for the library. Applications can use these to include support for different 458releases of PCRE2. 459</P> 460<P> 461In a Windows environment, if you want to statically link an application program 462against a non-dll PCRE2 library, you must define PCRE2_STATIC before including 463<b>pcre2.h</b>. 464</P> 465<P> 466The functions <b>pcre2_compile()</b> and <b>pcre2_match()</b> are used for 467compiling and matching regular expressions in a Perl-compatible manner. A 468sample program that demonstrates the simplest way of using them is provided in 469the file called <i>pcre2demo.c</i> in the PCRE2 source distribution. A listing 470of this program is given in the 471<a href="pcre2demo.html"><b>pcre2demo</b></a> 472documentation, and the 473<a href="pcre2sample.html"><b>pcre2sample</b></a> 474documentation describes how to compile and run it. 475</P> 476<P> 477The compiling and matching functions recognize various options that are passed 478as bits in an options argument. There are also some more complicated parameters 479such as custom memory management functions and resource limits that are passed 480in "contexts" (which are just memory blocks, described below). Simple 481applications do not need to make use of contexts. 482</P> 483<P> 484Just-in-time (JIT) compiler support is an optional feature of PCRE2 that can be 485built in appropriate hardware environments. It greatly speeds up the matching 486performance of many patterns. Programs can request that it be used if 487available by calling <b>pcre2_jit_compile()</b> after a pattern has been 488successfully compiled by <b>pcre2_compile()</b>. This does nothing if JIT 489support is not available. 490</P> 491<P> 492More complicated programs might need to make use of the specialist functions 493<b>pcre2_jit_stack_create()</b>, <b>pcre2_jit_stack_free()</b>, and 494<b>pcre2_jit_stack_assign()</b> in order to control the JIT code's memory usage. 495</P> 496<P> 497JIT matching is automatically used by <b>pcre2_match()</b> if it is available, 498unless the PCRE2_NO_JIT option is set. There is also a direct interface for JIT 499matching, which gives improved performance at the expense of less sanity 500checking. The JIT-specific functions are discussed in the 501<a href="pcre2jit.html"><b>pcre2jit</b></a> 502documentation. 503</P> 504<P> 505A second matching function, <b>pcre2_dfa_match()</b>, which is not 506Perl-compatible, is also provided. This uses a different algorithm for the 507matching. The alternative algorithm finds all possible matches (at a given 508point in the subject), and scans the subject just once (unless there are 509lookaround assertions). However, this algorithm does not return captured 510substrings. A description of the two matching algorithms and their advantages 511and disadvantages is given in the 512<a href="pcre2matching.html"><b>pcre2matching</b></a> 513documentation. There is no JIT support for <b>pcre2_dfa_match()</b>. 514</P> 515<P> 516In addition to the main compiling and matching functions, there are convenience 517functions for extracting captured substrings from a subject string that has 518been matched by <b>pcre2_match()</b>. They are: 519<pre> 520 <b>pcre2_substring_copy_byname()</b> 521 <b>pcre2_substring_copy_bynumber()</b> 522 <b>pcre2_substring_get_byname()</b> 523 <b>pcre2_substring_get_bynumber()</b> 524 <b>pcre2_substring_list_get()</b> 525 <b>pcre2_substring_length_byname()</b> 526 <b>pcre2_substring_length_bynumber()</b> 527 <b>pcre2_substring_nametable_scan()</b> 528 <b>pcre2_substring_number_from_name()</b> 529</pre> 530<b>pcre2_substring_free()</b> and <b>pcre2_substring_list_free()</b> are also 531provided, to free memory used for extracted strings. If either of these 532functions is called with a NULL argument, the function returns immediately 533without doing anything. 534</P> 535<P> 536The function <b>pcre2_substitute()</b> can be called to match a pattern and 537return a copy of the subject string with substitutions for parts that were 538matched. 539</P> 540<P> 541Functions whose names begin with <b>pcre2_serialize_</b> are used for saving 542compiled patterns on disc or elsewhere, and reloading them later. 543</P> 544<P> 545Finally, there are functions for finding out information about a compiled 546pattern (<b>pcre2_pattern_info()</b>) and about the configuration with which 547PCRE2 was built (<b>pcre2_config()</b>). 548</P> 549<P> 550Functions with names ending with <b>_free()</b> are used for freeing memory 551blocks of various sorts. In all cases, if one of these functions is called with 552a NULL argument, it does nothing. 553</P> 554<br><a name="SEC15" href="#TOC1">STRING LENGTHS AND OFFSETS</a><br> 555<P> 556The PCRE2 API uses string lengths and offsets into strings of code units in 557several places. These values are always of type PCRE2_SIZE, which is an 558unsigned integer type, currently always defined as <i>size_t</i>. The largest 559value that can be stored in such a type (that is ~(PCRE2_SIZE)0) is reserved 560as a special indicator for zero-terminated strings and unset offsets. 561Therefore, the longest string that can be handled is one less than this 562maximum. 563<a name="newlines"></a></P> 564<br><a name="SEC16" href="#TOC1">NEWLINES</a><br> 565<P> 566PCRE2 supports five different conventions for indicating line breaks in 567strings: a single CR (carriage return) character, a single LF (linefeed) 568character, the two-character sequence CRLF, any of the three preceding, or any 569Unicode newline sequence. The Unicode newline sequences are the three just 570mentioned, plus the single characters VT (vertical tab, U+000B), FF (form feed, 571U+000C), NEL (next line, U+0085), LS (line separator, U+2028), and PS 572(paragraph separator, U+2029). 573</P> 574<P> 575Each of the first three conventions is used by at least one operating system as 576its standard newline sequence. When PCRE2 is built, a default can be specified. 577If it is not, the default is set to LF, which is the Unix standard. However, 578the newline convention can be changed by an application when calling 579<b>pcre2_compile()</b>, or it can be specified by special text at the start of 580the pattern itself; this overrides any other settings. See the 581<a href="pcre2pattern.html"><b>pcre2pattern</b></a> 582page for details of the special character sequences. 583</P> 584<P> 585In the PCRE2 documentation the word "newline" is used to mean "the character or 586pair of characters that indicate a line break". The choice of newline 587convention affects the handling of the dot, circumflex, and dollar 588metacharacters, the handling of #-comments in /x mode, and, when CRLF is a 589recognized line ending sequence, the match position advancement for a 590non-anchored pattern. There is more detail about this in the 591<a href="#matchoptions">section on <b>pcre2_match()</b> options</a> 592below. 593</P> 594<P> 595The choice of newline convention does not affect the interpretation of 596the \n or \r escape sequences, nor does it affect what \R matches; this has 597its own separate convention. 598</P> 599<br><a name="SEC17" href="#TOC1">MULTITHREADING</a><br> 600<P> 601In a multithreaded application it is important to keep thread-specific data 602separate from data that can be shared between threads. The PCRE2 library code 603itself is thread-safe: it contains no static or global variables. The API is 604designed to be fairly simple for non-threaded applications while at the same 605time ensuring that multithreaded applications can use it. 606</P> 607<P> 608There are several different blocks of data that are used to pass information 609between the application and the PCRE2 libraries. 610</P> 611<br><b> 612The compiled pattern 613</b><br> 614<P> 615A pointer to the compiled form of a pattern is returned to the user when 616<b>pcre2_compile()</b> is successful. The data in the compiled pattern is fixed, 617and does not change when the pattern is matched. Therefore, it is thread-safe, 618that is, the same compiled pattern can be used by more than one thread 619simultaneously. For example, an application can compile all its patterns at the 620start, before forking off multiple threads that use them. However, if the 621just-in-time (JIT) optimization feature is being used, it needs separate memory 622stack areas for each thread. See the 623<a href="pcre2jit.html"><b>pcre2jit</b></a> 624documentation for more details. 625</P> 626<P> 627In a more complicated situation, where patterns are compiled only when they are 628first needed, but are still shared between threads, pointers to compiled 629patterns must be protected from simultaneous writing by multiple threads. This 630is somewhat tricky to do correctly. If you know that writing to a pointer is 631atomic in your environment, you can use logic like this: 632<pre> 633 Get a read-only (shared) lock (mutex) for pointer 634 if (pointer == NULL) 635 { 636 Get a write (unique) lock for pointer 637 if (pointer == NULL) pointer = pcre2_compile(... 638 } 639 Release the lock 640 Use pointer in pcre2_match() 641</pre> 642Of course, testing for compilation errors should also be included in the code. 643</P> 644<P> 645The reason for checking the pointer a second time is as follows: Several 646threads may have acquired the shared lock and tested the pointer for being 647NULL, but only one of them will be given the write lock, with the rest kept 648waiting. The winning thread will compile the pattern and store the result. 649After this thread releases the write lock, another thread will get it, and if 650it does not retest pointer for being NULL, will recompile the pattern and 651overwrite the pointer, creating a memory leak and possibly causing other 652issues. 653</P> 654<P> 655In an environment where writing to a pointer may not be atomic, the above logic 656is not sufficient. The thread that is doing the compiling may be descheduled 657after writing only part of the pointer, which could cause other threads to use 658an invalid value. Instead of checking the pointer itself, a separate "pointer 659is valid" flag (that can be updated atomically) must be used: 660<pre> 661 Get a read-only (shared) lock (mutex) for pointer 662 if (!pointer_is_valid) 663 { 664 Get a write (unique) lock for pointer 665 if (!pointer_is_valid) 666 { 667 pointer = pcre2_compile(... 668 pointer_is_valid = TRUE 669 } 670 } 671 Release the lock 672 Use pointer in pcre2_match() 673</pre> 674If JIT is being used, but the JIT compilation is not being done immediately 675(perhaps waiting to see if the pattern is used often enough), similar logic is 676required. JIT compilation updates a value within the compiled code block, so a 677thread must gain unique write access to the pointer before calling 678<b>pcre2_jit_compile()</b>. Alternatively, <b>pcre2_code_copy()</b> or 679<b>pcre2_code_copy_with_tables()</b> can be used to obtain a private copy of the 680compiled code before calling the JIT compiler. 681</P> 682<br><b> 683Context blocks 684</b><br> 685<P> 686The next main section below introduces the idea of "contexts" in which PCRE2 687functions are called. A context is nothing more than a collection of parameters 688that control the way PCRE2 operates. Grouping a number of parameters together 689in a context is a convenient way of passing them to a PCRE2 function without 690using lots of arguments. The parameters that are stored in contexts are in some 691sense "advanced features" of the API. Many straightforward applications will 692not need to use contexts. 693</P> 694<P> 695In a multithreaded application, if the parameters in a context are values that 696are never changed, the same context can be used by all the threads. However, if 697any thread needs to change any value in a context, it must make its own 698thread-specific copy. 699</P> 700<br><b> 701Match blocks 702</b><br> 703<P> 704The matching functions need a block of memory for storing the results of a 705match. This includes details of what was matched, as well as additional 706information such as the name of a (*MARK) setting. Each thread must provide its 707own copy of this memory. 708</P> 709<br><a name="SEC18" href="#TOC1">PCRE2 CONTEXTS</a><br> 710<P> 711Some PCRE2 functions have a lot of parameters, many of which are used only by 712specialist applications, for example, those that use custom memory management 713or non-standard character tables. To keep function argument lists at a 714reasonable size, and at the same time to keep the API extensible, "uncommon" 715parameters are passed to certain functions in a <b>context</b> instead of 716directly. A context is just a block of memory that holds the parameter values. 717Applications that do not need to adjust any of the context parameters can pass 718NULL when a context pointer is required. 719</P> 720<P> 721There are three different types of context: a general context that is relevant 722for several PCRE2 operations, a compile-time context, and a match-time context. 723</P> 724<br><b> 725The general context 726</b><br> 727<P> 728At present, this context just contains pointers to (and data for) external 729memory management functions that are called from several places in the PCRE2 730library. The context is named `general' rather than specifically `memory' 731because in future other fields may be added. If you do not want to supply your 732own custom memory management functions, you do not need to bother with a 733general context. A general context is created by: 734<br> 735<br> 736<b>pcre2_general_context *pcre2_general_context_create(</b> 737<b> void *(*<i>private_malloc</i>)(PCRE2_SIZE, void *),</b> 738<b> void (*<i>private_free</i>)(void *, void *), void *<i>memory_data</i>);</b> 739<br> 740<br> 741The two function pointers specify custom memory management functions, whose 742prototypes are: 743<pre> 744 <b>void *private_malloc(PCRE2_SIZE, void *);</b> 745 <b>void private_free(void *, void *);</b> 746</pre> 747Whenever code in PCRE2 calls these functions, the final argument is the value 748of <i>memory_data</i>. Either of the first two arguments of the creation 749function may be NULL, in which case the system memory management functions 750<i>malloc()</i> and <i>free()</i> are used. (This is not currently useful, as 751there are no other fields in a general context, but in future there might be.) 752The <i>private_malloc()</i> function is used (if supplied) to obtain memory for 753storing the context, and all three values are saved as part of the context. 754</P> 755<P> 756Whenever PCRE2 creates a data block of any kind, the block contains a pointer 757to the <i>free()</i> function that matches the <i>malloc()</i> function that was 758used. When the time comes to free the block, this function is called. 759</P> 760<P> 761A general context can be copied by calling: 762<br> 763<br> 764<b>pcre2_general_context *pcre2_general_context_copy(</b> 765<b> pcre2_general_context *<i>gcontext</i>);</b> 766<br> 767<br> 768The memory used for a general context should be freed by calling: 769<br> 770<br> 771<b>void pcre2_general_context_free(pcre2_general_context *<i>gcontext</i>);</b> 772<br> 773<br> 774If this function is passed a NULL argument, it returns immediately without 775doing anything. 776<a name="compilecontext"></a></P> 777<br><b> 778The compile context 779</b><br> 780<P> 781A compile context is required if you want to provide an external function for 782stack checking during compilation or to change the default values of any of the 783following compile-time parameters: 784<pre> 785 What \R matches (Unicode newlines or CR, LF, CRLF only) 786 PCRE2's character tables 787 The newline character sequence 788 The compile time nested parentheses limit 789 The maximum length of the pattern string 790 The extra options bits (none set by default) 791</pre> 792A compile context is also required if you are using custom memory management. 793If none of these apply, just pass NULL as the context argument of 794<i>pcre2_compile()</i>. 795</P> 796<P> 797A compile context is created, copied, and freed by the following functions: 798<br> 799<br> 800<b>pcre2_compile_context *pcre2_compile_context_create(</b> 801<b> pcre2_general_context *<i>gcontext</i>);</b> 802<br> 803<br> 804<b>pcre2_compile_context *pcre2_compile_context_copy(</b> 805<b> pcre2_compile_context *<i>ccontext</i>);</b> 806<br> 807<br> 808<b>void pcre2_compile_context_free(pcre2_compile_context *<i>ccontext</i>);</b> 809<br> 810<br> 811A compile context is created with default values for its parameters. These can 812be changed by calling the following functions, which return 0 on success, or 813PCRE2_ERROR_BADDATA if invalid data is detected. 814<br> 815<br> 816<b>int pcre2_set_bsr(pcre2_compile_context *<i>ccontext</i>,</b> 817<b> uint32_t <i>value</i>);</b> 818<br> 819<br> 820The value must be PCRE2_BSR_ANYCRLF, to specify that \R matches only CR, LF, 821or CRLF, or PCRE2_BSR_UNICODE, to specify that \R matches any Unicode line 822ending sequence. The value is used by the JIT compiler and by the two 823interpreted matching functions, <i>pcre2_match()</i> and 824<i>pcre2_dfa_match()</i>. 825<br> 826<br> 827<b>int pcre2_set_character_tables(pcre2_compile_context *<i>ccontext</i>,</b> 828<b> const uint8_t *<i>tables</i>);</b> 829<br> 830<br> 831The value must be the result of a call to <b>pcre2_maketables()</b>, whose only 832argument is a general context. This function builds a set of character tables 833in the current locale. 834<br> 835<br> 836<b>int pcre2_set_compile_extra_options(pcre2_compile_context *<i>ccontext</i>,</b> 837<b> uint32_t <i>extra_options</i>);</b> 838<br> 839<br> 840As PCRE2 has developed, almost all the 32 option bits that are available in 841the <i>options</i> argument of <b>pcre2_compile()</b> have been used up. To avoid 842running out, the compile context contains a set of extra option bits which are 843used for some newer, assumed rarer, options. This function sets those bits. It 844always sets all the bits (either on or off). It does not modify any existing 845setting. The available options are defined in the section entitled "Extra 846compile options" 847<a href="#extracompileoptions">below.</a> 848<br> 849<br> 850<b>int pcre2_set_max_pattern_length(pcre2_compile_context *<i>ccontext</i>,</b> 851<b> PCRE2_SIZE <i>value</i>);</b> 852<br> 853<br> 854This sets a maximum length, in code units, for any pattern string that is 855compiled with this context. If the pattern is longer, an error is generated. 856This facility is provided so that applications that accept patterns from 857external sources can limit their size. The default is the largest number that a 858PCRE2_SIZE variable can hold, which is effectively unlimited. 859<br> 860<br> 861<b>int pcre2_set_newline(pcre2_compile_context *<i>ccontext</i>,</b> 862<b> uint32_t <i>value</i>);</b> 863<br> 864<br> 865This specifies which characters or character sequences are to be recognized as 866newlines. The value must be one of PCRE2_NEWLINE_CR (carriage return only), 867PCRE2_NEWLINE_LF (linefeed only), PCRE2_NEWLINE_CRLF (the two-character 868sequence CR followed by LF), PCRE2_NEWLINE_ANYCRLF (any of the above), 869PCRE2_NEWLINE_ANY (any Unicode newline sequence), or PCRE2_NEWLINE_NUL (the 870NUL character, that is a binary zero). 871</P> 872<P> 873A pattern can override the value set in the compile context by starting with a 874sequence such as (*CRLF). See the 875<a href="pcre2pattern.html"><b>pcre2pattern</b></a> 876page for details. 877</P> 878<P> 879When a pattern is compiled with the PCRE2_EXTENDED or PCRE2_EXTENDED_MORE 880option, the newline convention affects the recognition of the end of internal 881comments starting with #. The value is saved with the compiled pattern for 882subsequent use by the JIT compiler and by the two interpreted matching 883functions, <i>pcre2_match()</i> and <i>pcre2_dfa_match()</i>. 884<br> 885<br> 886<b>int pcre2_set_parens_nest_limit(pcre2_compile_context *<i>ccontext</i>,</b> 887<b> uint32_t <i>value</i>);</b> 888<br> 889<br> 890This parameter adjusts the limit, set when PCRE2 is built (default 250), on the 891depth of parenthesis nesting in a pattern. This limit stops rogue patterns 892using up too much system stack when being compiled. The limit applies to 893parentheses of all kinds, not just capturing parentheses. 894<br> 895<br> 896<b>int pcre2_set_compile_recursion_guard(pcre2_compile_context *<i>ccontext</i>,</b> 897<b> int (*<i>guard_function</i>)(uint32_t, void *), void *<i>user_data</i>);</b> 898<br> 899<br> 900There is at least one application that runs PCRE2 in threads with very limited 901system stack, where running out of stack is to be avoided at all costs. The 902parenthesis limit above cannot take account of how much stack is actually 903available during compilation. For a finer control, you can supply a function 904that is called whenever <b>pcre2_compile()</b> starts to compile a parenthesized 905part of a pattern. This function can check the actual stack size (or anything 906else that it wants to, of course). 907</P> 908<P> 909The first argument to the callout function gives the current depth of 910nesting, and the second is user data that is set up by the last argument of 911<b>pcre2_set_compile_recursion_guard()</b>. The callout function should return 912zero if all is well, or non-zero to force an error. 913<a name="matchcontext"></a></P> 914<br><b> 915The match context 916</b><br> 917<P> 918A match context is required if you want to: 919<pre> 920 Set up a callout function 921 Set an offset limit for matching an unanchored pattern 922 Change the limit on the amount of heap used when matching 923 Change the backtracking match limit 924 Change the backtracking depth limit 925 Set custom memory management specifically for the match 926</pre> 927If none of these apply, just pass NULL as the context argument of 928<b>pcre2_match()</b>, <b>pcre2_dfa_match()</b>, or <b>pcre2_jit_match()</b>. 929</P> 930<P> 931A match context is created, copied, and freed by the following functions: 932<br> 933<br> 934<b>pcre2_match_context *pcre2_match_context_create(</b> 935<b> pcre2_general_context *<i>gcontext</i>);</b> 936<br> 937<br> 938<b>pcre2_match_context *pcre2_match_context_copy(</b> 939<b> pcre2_match_context *<i>mcontext</i>);</b> 940<br> 941<br> 942<b>void pcre2_match_context_free(pcre2_match_context *<i>mcontext</i>);</b> 943<br> 944<br> 945A match context is created with default values for its parameters. These can 946be changed by calling the following functions, which return 0 on success, or 947PCRE2_ERROR_BADDATA if invalid data is detected. 948<br> 949<br> 950<b>int pcre2_set_callout(pcre2_match_context *<i>mcontext</i>,</b> 951<b> int (*<i>callout_function</i>)(pcre2_callout_block *, void *),</b> 952<b> void *<i>callout_data</i>);</b> 953<br> 954<br> 955This sets up a callout function for PCRE2 to call at specified points 956during a matching operation. Details are given in the 957<a href="pcre2callout.html"><b>pcre2callout</b></a> 958documentation. 959<br> 960<br> 961<b>int pcre2_set_substitute_callout(pcre2_match_context *<i>mcontext</i>,</b> 962<b> int (*<i>callout_function</i>)(pcre2_substitute_callout_block *, void *),</b> 963<b> void *<i>callout_data</i>);</b> 964<br> 965<br> 966This sets up a callout function for PCRE2 to call after each substitution 967made by <b>pcre2_substitute()</b>. Details are given in the section entitled 968"Creating a new string with substitutions" 969<a href="#substitutions">below.</a> 970<br> 971<br> 972<b>int pcre2_set_offset_limit(pcre2_match_context *<i>mcontext</i>,</b> 973<b> PCRE2_SIZE <i>value</i>);</b> 974<br> 975<br> 976The <i>offset_limit</i> parameter limits how far an unanchored search can 977advance in the subject string. The default value is PCRE2_UNSET. The 978<b>pcre2_match()</b> and <b>pcre2_dfa_match()</b> functions return 979PCRE2_ERROR_NOMATCH if a match with a starting point before or at the given 980offset is not found. The <b>pcre2_substitute()</b> function makes no more 981substitutions. 982</P> 983<P> 984For example, if the pattern /abc/ is matched against "123abc" with an offset 985limit less than 3, the result is PCRE2_ERROR_NOMATCH. A match can never be 986found if the <i>startoffset</i> argument of <b>pcre2_match()</b>, 987<b>pcre2_dfa_match()</b>, or <b>pcre2_substitute()</b> is greater than the offset 988limit set in the match context. 989</P> 990<P> 991When using this facility, you must set the PCRE2_USE_OFFSET_LIMIT option when 992calling <b>pcre2_compile()</b> so that when JIT is in use, different code can be 993compiled. If a match is started with a non-default match limit when 994PCRE2_USE_OFFSET_LIMIT is not set, an error is generated. 995</P> 996<P> 997The offset limit facility can be used to track progress when searching large 998subject strings or to limit the extent of global substitutions. See also the 999PCRE2_FIRSTLINE option, which requires a match to start before or at the first 1000newline that follows the start of matching in the subject. If this is set with 1001an offset limit, a match must occur in the first line and also within the 1002offset limit. In other words, whichever limit comes first is used. 1003<br> 1004<br> 1005<b>int pcre2_set_heap_limit(pcre2_match_context *<i>mcontext</i>,</b> 1006<b> uint32_t <i>value</i>);</b> 1007<br> 1008<br> 1009The <i>heap_limit</i> parameter specifies, in units of kibibytes (1024 bytes), 1010the maximum amount of heap memory that <b>pcre2_match()</b> may use to hold 1011backtracking information when running an interpretive match. This limit also 1012applies to <b>pcre2_dfa_match()</b>, which may use the heap when processing 1013patterns with a lot of nested pattern recursion or lookarounds or atomic 1014groups. This limit does not apply to matching with the JIT optimization, which 1015has its own memory control arrangements (see the 1016<a href="pcre2jit.html"><b>pcre2jit</b></a> 1017documentation for more details). If the limit is reached, the negative error 1018code PCRE2_ERROR_HEAPLIMIT is returned. The default limit can be set when PCRE2 1019is built; if it is not, the default is set very large and is essentially 1020"unlimited". 1021</P> 1022<P> 1023A value for the heap limit may also be supplied by an item at the start of a 1024pattern of the form 1025<pre> 1026 (*LIMIT_HEAP=ddd) 1027</pre> 1028where ddd is a decimal number. However, such a setting is ignored unless ddd is 1029less than the limit set by the caller of <b>pcre2_match()</b> or, if no such 1030limit is set, less than the default. 1031</P> 1032<P> 1033The <b>pcre2_match()</b> function starts out using a 20KiB vector on the system 1034stack for recording backtracking points. The more nested backtracking points 1035there are (that is, the deeper the search tree), the more memory is needed. 1036Heap memory is used only if the initial vector is too small. If the heap limit 1037is set to a value less than 21 (in particular, zero) no heap memory will be 1038used. In this case, only patterns that do not have a lot of nested backtracking 1039can be successfully processed. 1040</P> 1041<P> 1042Similarly, for <b>pcre2_dfa_match()</b>, a vector on the system stack is used 1043when processing pattern recursions, lookarounds, or atomic groups, and only if 1044this is not big enough is heap memory used. In this case, too, setting a value 1045of zero disables the use of the heap. 1046<br> 1047<br> 1048<b>int pcre2_set_match_limit(pcre2_match_context *<i>mcontext</i>,</b> 1049<b> uint32_t <i>value</i>);</b> 1050<br> 1051<br> 1052The <i>match_limit</i> parameter provides a means of preventing PCRE2 from using 1053up too many computing resources when processing patterns that are not going to 1054match, but which have a very large number of possibilities in their search 1055trees. The classic example is a pattern that uses nested unlimited repeats. 1056</P> 1057<P> 1058There is an internal counter in <b>pcre2_match()</b> that is incremented each 1059time round its main matching loop. If this value reaches the match limit, 1060<b>pcre2_match()</b> returns the negative value PCRE2_ERROR_MATCHLIMIT. This has 1061the effect of limiting the amount of backtracking that can take place. For 1062patterns that are not anchored, the count restarts from zero for each position 1063in the subject string. This limit also applies to <b>pcre2_dfa_match()</b>, 1064though the counting is done in a different way. 1065</P> 1066<P> 1067When <b>pcre2_match()</b> is called with a pattern that was successfully 1068processed by <b>pcre2_jit_compile()</b>, the way in which matching is executed 1069is entirely different. However, there is still the possibility of runaway 1070matching that goes on for a very long time, and so the <i>match_limit</i> value 1071is also used in this case (but in a different way) to limit how long the 1072matching can continue. 1073</P> 1074<P> 1075The default value for the limit can be set when PCRE2 is built; the default 1076default is 10 million, which handles all but the most extreme cases. A value 1077for the match limit may also be supplied by an item at the start of a pattern 1078of the form 1079<pre> 1080 (*LIMIT_MATCH=ddd) 1081</pre> 1082where ddd is a decimal number. However, such a setting is ignored unless ddd is 1083less than the limit set by the caller of <b>pcre2_match()</b> or 1084<b>pcre2_dfa_match()</b> or, if no such limit is set, less than the default. 1085<br> 1086<br> 1087<b>int pcre2_set_depth_limit(pcre2_match_context *<i>mcontext</i>,</b> 1088<b> uint32_t <i>value</i>);</b> 1089<br> 1090<br> 1091This parameter limits the depth of nested backtracking in <b>pcre2_match()</b>. 1092Each time a nested backtracking point is passed, a new memory "frame" is used 1093to remember the state of matching at that point. Thus, this parameter 1094indirectly limits the amount of memory that is used in a match. However, 1095because the size of each memory "frame" depends on the number of capturing 1096parentheses, the actual memory limit varies from pattern to pattern. This limit 1097was more useful in versions before 10.30, where function recursion was used for 1098backtracking. 1099</P> 1100<P> 1101The depth limit is not relevant, and is ignored, when matching is done using 1102JIT compiled code. However, it is supported by <b>pcre2_dfa_match()</b>, which 1103uses it to limit the depth of nested internal recursive function calls that 1104implement atomic groups, lookaround assertions, and pattern recursions. This 1105limits, indirectly, the amount of system stack that is used. It was more useful 1106in versions before 10.32, when stack memory was used for local workspace 1107vectors for recursive function calls. From version 10.32, only local variables 1108are allocated on the stack and as each call uses only a few hundred bytes, even 1109a small stack can support quite a lot of recursion. 1110</P> 1111<P> 1112If the depth of internal recursive function calls is great enough, local 1113workspace vectors are allocated on the heap from version 10.32 onwards, so the 1114depth limit also indirectly limits the amount of heap memory that is used. A 1115recursive pattern such as /(.(?2))((?1)|)/, when matched to a very long string 1116using <b>pcre2_dfa_match()</b>, can use a great deal of memory. However, it is 1117probably better to limit heap usage directly by calling 1118<b>pcre2_set_heap_limit()</b>. 1119</P> 1120<P> 1121The default value for the depth limit can be set when PCRE2 is built; if it is 1122not, the default is set to the same value as the default for the match limit. 1123If the limit is exceeded, <b>pcre2_match()</b> or <b>pcre2_dfa_match()</b> 1124returns PCRE2_ERROR_DEPTHLIMIT. A value for the depth limit may also be 1125supplied by an item at the start of a pattern of the form 1126<pre> 1127 (*LIMIT_DEPTH=ddd) 1128</pre> 1129where ddd is a decimal number. However, such a setting is ignored unless ddd is 1130less than the limit set by the caller of <b>pcre2_match()</b> or 1131<b>pcre2_dfa_match()</b> or, if no such limit is set, less than the default. 1132</P> 1133<br><a name="SEC19" href="#TOC1">CHECKING BUILD-TIME OPTIONS</a><br> 1134<P> 1135<b>int pcre2_config(uint32_t <i>what</i>, void *<i>where</i>);</b> 1136</P> 1137<P> 1138The function <b>pcre2_config()</b> makes it possible for a PCRE2 client to find 1139the value of certain configuration parameters and to discover which optional 1140features have been compiled into the PCRE2 library. The 1141<a href="pcre2build.html"><b>pcre2build</b></a> 1142documentation has more details about these features. 1143</P> 1144<P> 1145The first argument for <b>pcre2_config()</b> specifies which information is 1146required. The second argument is a pointer to memory into which the information 1147is placed. If NULL is passed, the function returns the amount of memory that is 1148needed for the requested information. For calls that return numerical values, 1149the value is in bytes; when requesting these values, <i>where</i> should point 1150to appropriately aligned memory. For calls that return strings, the required 1151length is given in code units, not counting the terminating zero. 1152</P> 1153<P> 1154When requesting information, the returned value from <b>pcre2_config()</b> is 1155non-negative on success, or the negative error code PCRE2_ERROR_BADOPTION if 1156the value in the first argument is not recognized. The following information is 1157available: 1158<pre> 1159 PCRE2_CONFIG_BSR 1160</pre> 1161The output is a uint32_t integer whose value indicates what character 1162sequences the \R escape sequence matches by default. A value of 1163PCRE2_BSR_UNICODE means that \R matches any Unicode line ending sequence; a 1164value of PCRE2_BSR_ANYCRLF means that \R matches only CR, LF, or CRLF. The 1165default can be overridden when a pattern is compiled. 1166<pre> 1167 PCRE2_CONFIG_COMPILED_WIDTHS 1168</pre> 1169The output is a uint32_t integer whose lower bits indicate which code unit 1170widths were selected when PCRE2 was built. The 1-bit indicates 8-bit support, 1171and the 2-bit and 4-bit indicate 16-bit and 32-bit support, respectively. 1172<pre> 1173 PCRE2_CONFIG_DEPTHLIMIT 1174</pre> 1175The output is a uint32_t integer that gives the default limit for the depth of 1176nested backtracking in <b>pcre2_match()</b> or the depth of nested recursions, 1177lookarounds, and atomic groups in <b>pcre2_dfa_match()</b>. Further details are 1178given with <b>pcre2_set_depth_limit()</b> above. 1179<pre> 1180 PCRE2_CONFIG_HEAPLIMIT 1181</pre> 1182The output is a uint32_t integer that gives, in kibibytes, the default limit 1183for the amount of heap memory used by <b>pcre2_match()</b> or 1184<b>pcre2_dfa_match()</b>. Further details are given with 1185<b>pcre2_set_heap_limit()</b> above. 1186<pre> 1187 PCRE2_CONFIG_JIT 1188</pre> 1189The output is a uint32_t integer that is set to one if support for just-in-time 1190compiling is available; otherwise it is set to zero. 1191<pre> 1192 PCRE2_CONFIG_JITTARGET 1193</pre> 1194The <i>where</i> argument should point to a buffer that is at least 48 code 1195units long. (The exact length required can be found by calling 1196<b>pcre2_config()</b> with <b>where</b> set to NULL.) The buffer is filled with a 1197string that contains the name of the architecture for which the JIT compiler is 1198configured, for example "x86 32bit (little endian + unaligned)". If JIT support 1199is not available, PCRE2_ERROR_BADOPTION is returned, otherwise the number of 1200code units used is returned. This is the length of the string, plus one unit 1201for the terminating zero. 1202<pre> 1203 PCRE2_CONFIG_LINKSIZE 1204</pre> 1205The output is a uint32_t integer that contains the number of bytes used for 1206internal linkage in compiled regular expressions. When PCRE2 is configured, the 1207value can be set to 2, 3, or 4, with the default being 2. This is the value 1208that is returned by <b>pcre2_config()</b>. However, when the 16-bit library is 1209compiled, a value of 3 is rounded up to 4, and when the 32-bit library is 1210compiled, internal linkages always use 4 bytes, so the configured value is not 1211relevant. 1212</P> 1213<P> 1214The default value of 2 for the 8-bit and 16-bit libraries is sufficient for all 1215but the most massive patterns, since it allows the size of the compiled pattern 1216to be up to 65535 code units. Larger values allow larger regular expressions to 1217be compiled by those two libraries, but at the expense of slower matching. 1218<pre> 1219 PCRE2_CONFIG_MATCHLIMIT 1220</pre> 1221The output is a uint32_t integer that gives the default match limit for 1222<b>pcre2_match()</b>. Further details are given with 1223<b>pcre2_set_match_limit()</b> above. 1224<pre> 1225 PCRE2_CONFIG_NEWLINE 1226</pre> 1227The output is a uint32_t integer whose value specifies the default character 1228sequence that is recognized as meaning "newline". The values are: 1229<pre> 1230 PCRE2_NEWLINE_CR Carriage return (CR) 1231 PCRE2_NEWLINE_LF Linefeed (LF) 1232 PCRE2_NEWLINE_CRLF Carriage return, linefeed (CRLF) 1233 PCRE2_NEWLINE_ANY Any Unicode line ending 1234 PCRE2_NEWLINE_ANYCRLF Any of CR, LF, or CRLF 1235 PCRE2_NEWLINE_NUL The NUL character (binary zero) 1236</pre> 1237The default should normally correspond to the standard sequence for your 1238operating system. 1239<pre> 1240 PCRE2_CONFIG_NEVER_BACKSLASH_C 1241</pre> 1242The output is a uint32_t integer that is set to one if the use of \C was 1243permanently disabled when PCRE2 was built; otherwise it is set to zero. 1244<pre> 1245 PCRE2_CONFIG_PARENSLIMIT 1246</pre> 1247The output is a uint32_t integer that gives the maximum depth of nesting 1248of parentheses (of any kind) in a pattern. This limit is imposed to cap the 1249amount of system stack used when a pattern is compiled. It is specified when 1250PCRE2 is built; the default is 250. This limit does not take into account the 1251stack that may already be used by the calling application. For finer control 1252over compilation stack usage, see <b>pcre2_set_compile_recursion_guard()</b>. 1253<pre> 1254 PCRE2_CONFIG_STACKRECURSE 1255</pre> 1256This parameter is obsolete and should not be used in new code. The output is a 1257uint32_t integer that is always set to zero. 1258<pre> 1259 PCRE2_CONFIG_TABLES_LENGTH 1260</pre> 1261The output is a uint32_t integer that gives the length of PCRE2's character 1262processing tables in bytes. For details of these tables see the 1263<a href="#localesupport">section on locale support</a> 1264below. 1265<pre> 1266 PCRE2_CONFIG_UNICODE_VERSION 1267</pre> 1268The <i>where</i> argument should point to a buffer that is at least 24 code 1269units long. (The exact length required can be found by calling 1270<b>pcre2_config()</b> with <b>where</b> set to NULL.) If PCRE2 has been compiled 1271without Unicode support, the buffer is filled with the text "Unicode not 1272supported". Otherwise, the Unicode version string (for example, "8.0.0") is 1273inserted. The number of code units used is returned. This is the length of the 1274string plus one unit for the terminating zero. 1275<pre> 1276 PCRE2_CONFIG_UNICODE 1277</pre> 1278The output is a uint32_t integer that is set to one if Unicode support is 1279available; otherwise it is set to zero. Unicode support implies UTF support. 1280<pre> 1281 PCRE2_CONFIG_VERSION 1282</pre> 1283The <i>where</i> argument should point to a buffer that is at least 24 code 1284units long. (The exact length required can be found by calling 1285<b>pcre2_config()</b> with <b>where</b> set to NULL.) The buffer is filled with 1286the PCRE2 version string, zero-terminated. The number of code units used is 1287returned. This is the length of the string plus one unit for the terminating 1288zero. 1289<a name="compiling"></a></P> 1290<br><a name="SEC20" href="#TOC1">COMPILING A PATTERN</a><br> 1291<P> 1292<b>pcre2_code *pcre2_compile(PCRE2_SPTR <i>pattern</i>, PCRE2_SIZE <i>length</i>,</b> 1293<b> uint32_t <i>options</i>, int *<i>errorcode</i>, PCRE2_SIZE *<i>erroroffset,</i></b> 1294<b> pcre2_compile_context *<i>ccontext</i>);</b> 1295<br> 1296<br> 1297<b>void pcre2_code_free(pcre2_code *<i>code</i>);</b> 1298<br> 1299<br> 1300<b>pcre2_code *pcre2_code_copy(const pcre2_code *<i>code</i>);</b> 1301<br> 1302<br> 1303<b>pcre2_code *pcre2_code_copy_with_tables(const pcre2_code *<i>code</i>);</b> 1304</P> 1305<P> 1306The <b>pcre2_compile()</b> function compiles a pattern into an internal form. 1307The pattern is defined by a pointer to a string of code units and a length (in 1308code units). If the pattern is zero-terminated, the length can be specified as 1309PCRE2_ZERO_TERMINATED. The function returns a pointer to a block of memory that 1310contains the compiled pattern and related data, or NULL if an error occurred. 1311</P> 1312<P> 1313If the compile context argument <i>ccontext</i> is NULL, memory for the compiled 1314pattern is obtained by calling <b>malloc()</b>. Otherwise, it is obtained from 1315the same memory function that was used for the compile context. The caller must 1316free the memory by calling <b>pcre2_code_free()</b> when it is no longer needed. 1317If <b>pcre2_code_free()</b> is called with a NULL argument, it returns 1318immediately, without doing anything. 1319</P> 1320<P> 1321The function <b>pcre2_code_copy()</b> makes a copy of the compiled code in new 1322memory, using the same memory allocator as was used for the original. However, 1323if the code has been processed by the JIT compiler (see 1324<a href="#jitcompiling">below),</a> 1325the JIT information cannot be copied (because it is position-dependent). 1326The new copy can initially be used only for non-JIT matching, though it can be 1327passed to <b>pcre2_jit_compile()</b> if required. If <b>pcre2_code_copy()</b> is 1328called with a NULL argument, it returns NULL. 1329</P> 1330<P> 1331The <b>pcre2_code_copy()</b> function provides a way for individual threads in a 1332multithreaded application to acquire a private copy of shared compiled code. 1333However, it does not make a copy of the character tables used by the compiled 1334pattern; the new pattern code points to the same tables as the original code. 1335(See 1336<a href="#jitcompiling">"Locale Support"</a> 1337below for details of these character tables.) In many applications the same 1338tables are used throughout, so this behaviour is appropriate. Nevertheless, 1339there are occasions when a copy of a compiled pattern and the relevant tables 1340are needed. The <b>pcre2_code_copy_with_tables()</b> provides this facility. 1341Copies of both the code and the tables are made, with the new code pointing to 1342the new tables. The memory for the new tables is automatically freed when 1343<b>pcre2_code_free()</b> is called for the new copy of the compiled code. If 1344<b>pcre2_code_copy_with_tables()</b> is called with a NULL argument, it returns 1345NULL. 1346</P> 1347<P> 1348NOTE: When one of the matching functions is called, pointers to the compiled 1349pattern and the subject string are set in the match data block so that they can 1350be referenced by the substring extraction functions after a successful match. 1351After running a match, you must not free a compiled pattern or a subject string 1352until after all operations on the 1353<a href="#matchdatablock">match data block</a> 1354have taken place, unless, in the case of the subject string, you have used the 1355PCRE2_COPY_MATCHED_SUBJECT option, which is described in the section entitled 1356"Option bits for <b>pcre2_match()</b>" 1357<a href="#matchoptions>">below.</a> 1358</P> 1359<P> 1360The <i>options</i> argument for <b>pcre2_compile()</b> contains various bit 1361settings that affect the compilation. It should be zero if none of them are 1362required. The available options are described below. Some of them (in 1363particular, those that are compatible with Perl, but some others as well) can 1364also be set and unset from within the pattern (see the detailed description in 1365the 1366<a href="pcre2pattern.html"><b>pcre2pattern</b></a> 1367documentation). 1368</P> 1369<P> 1370For those options that can be different in different parts of the pattern, the 1371contents of the <i>options</i> argument specifies their settings at the start of 1372compilation. The PCRE2_ANCHORED, PCRE2_ENDANCHORED, and PCRE2_NO_UTF_CHECK 1373options can be set at the time of matching as well as at compile time. 1374</P> 1375<P> 1376Some additional options and less frequently required compile-time parameters 1377(for example, the newline setting) can be provided in a compile context (as 1378described 1379<a href="#compilecontext">above).</a> 1380</P> 1381<P> 1382If <i>errorcode</i> or <i>erroroffset</i> is NULL, <b>pcre2_compile()</b> returns 1383NULL immediately. Otherwise, the variables to which these point are set to an 1384error code and an offset (number of code units) within the pattern, 1385respectively, when <b>pcre2_compile()</b> returns NULL because a compilation 1386error has occurred. The values are not defined when compilation is successful 1387and <b>pcre2_compile()</b> returns a non-NULL value. 1388</P> 1389<P> 1390There are nearly 100 positive error codes that <b>pcre2_compile()</b> may return 1391if it finds an error in the pattern. There are also some negative error codes 1392that are used for invalid UTF strings when validity checking is in force. These 1393are the same as given by <b>pcre2_match()</b> and <b>pcre2_dfa_match()</b>, and 1394are described in the 1395<a href="pcre2unicode.html"><b>pcre2unicode</b></a> 1396documentation. There is no separate documentation for the positive error codes, 1397because the textual error messages that are obtained by calling the 1398<b>pcre2_get_error_message()</b> function (see "Obtaining a textual error 1399message" 1400<a href="#geterrormessage">below)</a> 1401should be self-explanatory. Macro names starting with PCRE2_ERROR_ are defined 1402for both positive and negative error codes in <b>pcre2.h</b>. 1403</P> 1404<P> 1405The value returned in <i>erroroffset</i> is an indication of where in the 1406pattern the error occurred. It is not necessarily the furthest point in the 1407pattern that was read. For example, after the error "lookbehind assertion is 1408not fixed length", the error offset points to the start of the failing 1409assertion. For an invalid UTF-8 or UTF-16 string, the offset is that of the 1410first code unit of the failing character. 1411</P> 1412<P> 1413Some errors are not detected until the whole pattern has been scanned; in these 1414cases, the offset passed back is the length of the pattern. Note that the 1415offset is in code units, not characters, even in a UTF mode. It may sometimes 1416point into the middle of a UTF-8 or UTF-16 character. 1417</P> 1418<P> 1419This code fragment shows a typical straightforward call to 1420<b>pcre2_compile()</b>: 1421<pre> 1422 pcre2_code *re; 1423 PCRE2_SIZE erroffset; 1424 int errorcode; 1425 re = pcre2_compile( 1426 "^A.*Z", /* the pattern */ 1427 PCRE2_ZERO_TERMINATED, /* the pattern is zero-terminated */ 1428 0, /* default options */ 1429 &errorcode, /* for error code */ 1430 &erroffset, /* for error offset */ 1431 NULL); /* no compile context */ 1432 1433</PRE> 1434</P> 1435<br><b> 1436Main compile options 1437</b><br> 1438<P> 1439The following names for option bits are defined in the <b>pcre2.h</b> header 1440file: 1441<pre> 1442 PCRE2_ANCHORED 1443</pre> 1444If this bit is set, the pattern is forced to be "anchored", that is, it is 1445constrained to match only at the first matching point in the string that is 1446being searched (the "subject string"). This effect can also be achieved by 1447appropriate constructs in the pattern itself, which is the only way to do it in 1448Perl. 1449<pre> 1450 PCRE2_ALLOW_EMPTY_CLASS 1451</pre> 1452By default, for compatibility with Perl, a closing square bracket that 1453immediately follows an opening one is treated as a data character for the 1454class. When PCRE2_ALLOW_EMPTY_CLASS is set, it terminates the class, which 1455therefore contains no characters and so can never match. 1456<pre> 1457 PCRE2_ALT_BSUX 1458</pre> 1459This option request alternative handling of three escape sequences, which 1460makes PCRE2's behaviour more like ECMAscript (aka JavaScript). When it is set: 1461</P> 1462<P> 1463(1) \U matches an upper case "U" character; by default \U causes a compile 1464time error (Perl uses \U to upper case subsequent characters). 1465</P> 1466<P> 1467(2) \u matches a lower case "u" character unless it is followed by four 1468hexadecimal digits, in which case the hexadecimal number defines the code point 1469to match. By default, \u causes a compile time error (Perl uses it to upper 1470case the following character). 1471</P> 1472<P> 1473(3) \x matches a lower case "x" character unless it is followed by two 1474hexadecimal digits, in which case the hexadecimal number defines the code point 1475to match. By default, as in Perl, a hexadecimal number is always expected after 1476\x, but it may have zero, one, or two digits (so, for example, \xz matches a 1477binary zero character followed by z). 1478</P> 1479<P> 1480ECMAscript 6 added additional functionality to \u. This can be accessed using 1481the PCRE2_EXTRA_ALT_BSUX extra option (see "Extra compile options" 1482<a href="#extracompileoptions">below).</a> 1483Note that this alternative escape handling applies only to patterns. Neither of 1484these options affects the processing of replacement strings passed to 1485<b>pcre2_substitute()</b>. 1486<pre> 1487 PCRE2_ALT_CIRCUMFLEX 1488</pre> 1489In multiline mode (when PCRE2_MULTILINE is set), the circumflex metacharacter 1490matches at the start of the subject (unless PCRE2_NOTBOL is set), and also 1491after any internal newline. However, it does not match after a newline at the 1492end of the subject, for compatibility with Perl. If you want a multiline 1493circumflex also to match after a terminating newline, you must set 1494PCRE2_ALT_CIRCUMFLEX. 1495<pre> 1496 PCRE2_ALT_VERBNAMES 1497</pre> 1498By default, for compatibility with Perl, the name in any verb sequence such as 1499(*MARK:NAME) is any sequence of characters that does not include a closing 1500parenthesis. The name is not processed in any way, and it is not possible to 1501include a closing parenthesis in the name. However, if the PCRE2_ALT_VERBNAMES 1502option is set, normal backslash processing is applied to verb names and only an 1503unescaped closing parenthesis terminates the name. A closing parenthesis can be 1504included in a name either as \) or between \Q and \E. If the PCRE2_EXTENDED 1505or PCRE2_EXTENDED_MORE option is set with PCRE2_ALT_VERBNAMES, unescaped 1506whitespace in verb names is skipped and #-comments are recognized, exactly as 1507in the rest of the pattern. 1508<pre> 1509 PCRE2_AUTO_CALLOUT 1510</pre> 1511If this bit is set, <b>pcre2_compile()</b> automatically inserts callout items, 1512all with number 255, before each pattern item, except immediately before or 1513after an explicit callout in the pattern. For discussion of the callout 1514facility, see the 1515<a href="pcre2callout.html"><b>pcre2callout</b></a> 1516documentation. 1517<pre> 1518 PCRE2_CASELESS 1519</pre> 1520If this bit is set, letters in the pattern match both upper and lower case 1521letters in the subject. It is equivalent to Perl's /i option, and it can be 1522changed within a pattern by a (?i) option setting. If either PCRE2_UTF or 1523PCRE2_UCP is set, Unicode properties are used for all characters with more than 1524one other case, and for all characters whose code points are greater than 1525U+007F. Note that there are two ASCII characters, K and S, that, in addition to 1526their lower case ASCII equivalents, are case-equivalent with U+212A (Kelvin 1527sign) and U+017F (long S) respectively. For lower valued characters with only 1528one other case, a lookup table is used for speed. When neither PCRE2_UTF nor 1529PCRE2_UCP is set, a lookup table is used for all code points less than 256, and 1530higher code points (available only in 16-bit or 32-bit mode) are treated as not 1531having another case. 1532<pre> 1533 PCRE2_DOLLAR_ENDONLY 1534</pre> 1535If this bit is set, a dollar metacharacter in the pattern matches only at the 1536end of the subject string. Without this option, a dollar also matches 1537immediately before a newline at the end of the string (but not before any other 1538newlines). The PCRE2_DOLLAR_ENDONLY option is ignored if PCRE2_MULTILINE is 1539set. There is no equivalent to this option in Perl, and no way to set it within 1540a pattern. 1541<pre> 1542 PCRE2_DOTALL 1543</pre> 1544If this bit is set, a dot metacharacter in the pattern matches any character, 1545including one that indicates a newline. However, it only ever matches one 1546character, even if newlines are coded as CRLF. Without this option, a dot does 1547not match when the current position in the subject is at a newline. This option 1548is equivalent to Perl's /s option, and it can be changed within a pattern by a 1549(?s) option setting. A negative class such as [^a] always matches newline 1550characters, and the \N escape sequence always matches a non-newline character, 1551independent of the setting of PCRE2_DOTALL. 1552<pre> 1553 PCRE2_DUPNAMES 1554</pre> 1555If this bit is set, names used to identify capture groups need not be unique. 1556This can be helpful for certain types of pattern when it is known that only one 1557instance of the named group can ever be matched. There are more details of 1558named capture groups below; see also the 1559<a href="pcre2pattern.html"><b>pcre2pattern</b></a> 1560documentation. 1561<pre> 1562 PCRE2_ENDANCHORED 1563</pre> 1564If this bit is set, the end of any pattern match must be right at the end of 1565the string being searched (the "subject string"). If the pattern match 1566succeeds by reaching (*ACCEPT), but does not reach the end of the subject, the 1567match fails at the current starting point. For unanchored patterns, a new match 1568is then tried at the next starting point. However, if the match succeeds by 1569reaching the end of the pattern, but not the end of the subject, backtracking 1570occurs and an alternative match may be found. Consider these two patterns: 1571<pre> 1572 .(*ACCEPT)|.. 1573 .|.. 1574</pre> 1575If matched against "abc" with PCRE2_ENDANCHORED set, the first matches "c" 1576whereas the second matches "bc". The effect of PCRE2_ENDANCHORED can also be 1577achieved by appropriate constructs in the pattern itself, which is the only way 1578to do it in Perl. 1579</P> 1580<P> 1581For DFA matching with <b>pcre2_dfa_match()</b>, PCRE2_ENDANCHORED applies only 1582to the first (that is, the longest) matched string. Other parallel matches, 1583which are necessarily substrings of the first one, must obviously end before 1584the end of the subject. 1585<pre> 1586 PCRE2_EXTENDED 1587</pre> 1588If this bit is set, most white space characters in the pattern are totally 1589ignored except when escaped or inside a character class. However, white space 1590is not allowed within sequences such as (?> that introduce various 1591parenthesized groups, nor within numerical quantifiers such as {1,3}. Ignorable 1592white space is permitted between an item and a following quantifier and between 1593a quantifier and a following + that indicates possessiveness. PCRE2_EXTENDED is 1594equivalent to Perl's /x option, and it can be changed within a pattern by a 1595(?x) option setting. 1596</P> 1597<P> 1598When PCRE2 is compiled without Unicode support, PCRE2_EXTENDED recognizes as 1599white space only those characters with code points less than 256 that are 1600flagged as white space in its low-character table. The table is normally 1601created by 1602<a href="pcre2_maketables.html"><b>pcre2_maketables()</b>,</a> 1603which uses the <b>isspace()</b> function to identify space characters. In most 1604ASCII environments, the relevant characters are those with code points 0x0009 1605(tab), 0x000A (linefeed), 0x000B (vertical tab), 0x000C (formfeed), 0x000D 1606(carriage return), and 0x0020 (space). 1607</P> 1608<P> 1609When PCRE2 is compiled with Unicode support, in addition to these characters, 1610five more Unicode "Pattern White Space" characters are recognized by 1611PCRE2_EXTENDED. These are U+0085 (next line), U+200E (left-to-right mark), 1612U+200F (right-to-left mark), U+2028 (line separator), and U+2029 (paragraph 1613separator). This set of characters is the same as recognized by Perl's /x 1614option. Note that the horizontal and vertical space characters that are matched 1615by the \h and \v escapes in patterns are a much bigger set. 1616</P> 1617<P> 1618As well as ignoring most white space, PCRE2_EXTENDED also causes characters 1619between an unescaped # outside a character class and the next newline, 1620inclusive, to be ignored, which makes it possible to include comments inside 1621complicated patterns. Note that the end of this type of comment is a literal 1622newline sequence in the pattern; escape sequences that happen to represent a 1623newline do not count. 1624</P> 1625<P> 1626Which characters are interpreted as newlines can be specified by a setting in 1627the compile context that is passed to <b>pcre2_compile()</b> or by a special 1628sequence at the start of the pattern, as described in the section entitled 1629<a href="pcre2pattern.html#newlines">"Newline conventions"</a> 1630in the <b>pcre2pattern</b> documentation. A default is defined when PCRE2 is 1631built. 1632<pre> 1633 PCRE2_EXTENDED_MORE 1634</pre> 1635This option has the effect of PCRE2_EXTENDED, but, in addition, unescaped space 1636and horizontal tab characters are ignored inside a character class. Note: only 1637these two characters are ignored, not the full set of pattern white space 1638characters that are ignored outside a character class. PCRE2_EXTENDED_MORE is 1639equivalent to Perl's /xx option, and it can be changed within a pattern by a 1640(?xx) option setting. 1641<pre> 1642 PCRE2_FIRSTLINE 1643</pre> 1644If this option is set, the start of an unanchored pattern match must be before 1645or at the first newline in the subject string following the start of matching, 1646though the matched text may continue over the newline. If <i>startoffset</i> is 1647non-zero, the limiting newline is not necessarily the first newline in the 1648subject. For example, if the subject string is "abc\nxyz" (where \n 1649represents a single-character newline) a pattern match for "yz" succeeds with 1650PCRE2_FIRSTLINE if <i>startoffset</i> is greater than 3. See also 1651PCRE2_USE_OFFSET_LIMIT, which provides a more general limiting facility. If 1652PCRE2_FIRSTLINE is set with an offset limit, a match must occur in the first 1653line and also within the offset limit. In other words, whichever limit comes 1654first is used. 1655<pre> 1656 PCRE2_LITERAL 1657</pre> 1658If this option is set, all meta-characters in the pattern are disabled, and it 1659is treated as a literal string. Matching literal strings with a regular 1660expression engine is not the most efficient way of doing it. If you are doing a 1661lot of literal matching and are worried about efficiency, you should consider 1662using other approaches. The only other main options that are allowed with 1663PCRE2_LITERAL are: PCRE2_ANCHORED, PCRE2_ENDANCHORED, PCRE2_AUTO_CALLOUT, 1664PCRE2_CASELESS, PCRE2_FIRSTLINE, PCRE2_MATCH_INVALID_UTF, 1665PCRE2_NO_START_OPTIMIZE, PCRE2_NO_UTF_CHECK, PCRE2_UTF, and 1666PCRE2_USE_OFFSET_LIMIT. The extra options PCRE2_EXTRA_MATCH_LINE and 1667PCRE2_EXTRA_MATCH_WORD are also supported. Any other options cause an error. 1668<pre> 1669 PCRE2_MATCH_INVALID_UTF 1670</pre> 1671This option forces PCRE2_UTF (see below) and also enables support for matching 1672by <b>pcre2_match()</b> in subject strings that contain invalid UTF sequences. 1673This facility is not supported for DFA matching. For details, see the 1674<a href="pcre2unicode.html"><b>pcre2unicode</b></a> 1675documentation. 1676<pre> 1677 PCRE2_MATCH_UNSET_BACKREF 1678</pre> 1679If this option is set, a backreference to an unset capture group matches an 1680empty string (by default this causes the current matching alternative to fail). 1681A pattern such as (\1)(a) succeeds when this option is set (assuming it can 1682find an "a" in the subject), whereas it fails by default, for Perl 1683compatibility. Setting this option makes PCRE2 behave more like ECMAscript (aka 1684JavaScript). 1685<pre> 1686 PCRE2_MULTILINE 1687</pre> 1688By default, for the purposes of matching "start of line" and "end of line", 1689PCRE2 treats the subject string as consisting of a single line of characters, 1690even if it actually contains newlines. The "start of line" metacharacter (^) 1691matches only at the start of the string, and the "end of line" metacharacter 1692($) matches only at the end of the string, or before a terminating newline 1693(except when PCRE2_DOLLAR_ENDONLY is set). Note, however, that unless 1694PCRE2_DOTALL is set, the "any character" metacharacter (.) does not match at a 1695newline. This behaviour (for ^, $, and dot) is the same as Perl. 1696</P> 1697<P> 1698When PCRE2_MULTILINE it is set, the "start of line" and "end of line" 1699constructs match immediately following or immediately before internal newlines 1700in the subject string, respectively, as well as at the very start and end. This 1701is equivalent to Perl's /m option, and it can be changed within a pattern by a 1702(?m) option setting. Note that the "start of line" metacharacter does not match 1703after a newline at the end of the subject, for compatibility with Perl. 1704However, you can change this by setting the PCRE2_ALT_CIRCUMFLEX option. If 1705there are no newlines in a subject string, or no occurrences of ^ or $ in a 1706pattern, setting PCRE2_MULTILINE has no effect. 1707<pre> 1708 PCRE2_NEVER_BACKSLASH_C 1709</pre> 1710This option locks out the use of \C in the pattern that is being compiled. 1711This escape can cause unpredictable behaviour in UTF-8 or UTF-16 modes, because 1712it may leave the current matching point in the middle of a multi-code-unit 1713character. This option may be useful in applications that process patterns from 1714external sources. Note that there is also a build-time option that permanently 1715locks out the use of \C. 1716<pre> 1717 PCRE2_NEVER_UCP 1718</pre> 1719This option locks out the use of Unicode properties for handling \B, \b, \D, 1720\d, \S, \s, \W, \w, and some of the POSIX character classes, as described 1721for the PCRE2_UCP option below. In particular, it prevents the creator of the 1722pattern from enabling this facility by starting the pattern with (*UCP). This 1723option may be useful in applications that process patterns from external 1724sources. The option combination PCRE_UCP and PCRE_NEVER_UCP causes an error. 1725<pre> 1726 PCRE2_NEVER_UTF 1727</pre> 1728This option locks out interpretation of the pattern as UTF-8, UTF-16, or 1729UTF-32, depending on which library is in use. In particular, it prevents the 1730creator of the pattern from switching to UTF interpretation by starting the 1731pattern with (*UTF). This option may be useful in applications that process 1732patterns from external sources. The combination of PCRE2_UTF and 1733PCRE2_NEVER_UTF causes an error. 1734<pre> 1735 PCRE2_NO_AUTO_CAPTURE 1736</pre> 1737If this option is set, it disables the use of numbered capturing parentheses in 1738the pattern. Any opening parenthesis that is not followed by ? behaves as if it 1739were followed by ?: but named parentheses can still be used for capturing (and 1740they acquire numbers in the usual way). This is the same as Perl's /n option. 1741Note that, when this option is set, references to capture groups 1742(backreferences or recursion/subroutine calls) may only refer to named groups, 1743though the reference can be by name or by number. 1744<pre> 1745 PCRE2_NO_AUTO_POSSESS 1746</pre> 1747If this option is set, it disables "auto-possessification", which is an 1748optimization that, for example, turns a+b into a++b in order to avoid 1749backtracks into a+ that can never be successful. However, if callouts are in 1750use, auto-possessification means that some callouts are never taken. You can 1751set this option if you want the matching functions to do a full unoptimized 1752search and run all the callouts, but it is mainly provided for testing 1753purposes. 1754<pre> 1755 PCRE2_NO_DOTSTAR_ANCHOR 1756</pre> 1757If this option is set, it disables an optimization that is applied when .* is 1758the first significant item in a top-level branch of a pattern, and all the 1759other branches also start with .* or with \A or \G or ^. The optimization is 1760automatically disabled for .* if it is inside an atomic group or a capture 1761group that is the subject of a backreference, or if the pattern contains 1762(*PRUNE) or (*SKIP). When the optimization is not disabled, such a pattern is 1763automatically anchored if PCRE2_DOTALL is set for all the .* items and 1764PCRE2_MULTILINE is not set for any ^ items. Otherwise, the fact that any match 1765must start either at the start of the subject or following a newline is 1766remembered. Like other optimizations, this can cause callouts to be skipped. 1767<pre> 1768 PCRE2_NO_START_OPTIMIZE 1769</pre> 1770This is an option whose main effect is at matching time. It does not change 1771what <b>pcre2_compile()</b> generates, but it does affect the output of the JIT 1772compiler. 1773</P> 1774<P> 1775There are a number of optimizations that may occur at the start of a match, in 1776order to speed up the process. For example, if it is known that an unanchored 1777match must start with a specific code unit value, the matching code searches 1778the subject for that value, and fails immediately if it cannot find it, without 1779actually running the main matching function. This means that a special item 1780such as (*COMMIT) at the start of a pattern is not considered until after a 1781suitable starting point for the match has been found. Also, when callouts or 1782(*MARK) items are in use, these "start-up" optimizations can cause them to be 1783skipped if the pattern is never actually used. The start-up optimizations are 1784in effect a pre-scan of the subject that takes place before the pattern is run. 1785</P> 1786<P> 1787The PCRE2_NO_START_OPTIMIZE option disables the start-up optimizations, 1788possibly causing performance to suffer, but ensuring that in cases where the 1789result is "no match", the callouts do occur, and that items such as (*COMMIT) 1790and (*MARK) are considered at every possible starting position in the subject 1791string. 1792</P> 1793<P> 1794Setting PCRE2_NO_START_OPTIMIZE may change the outcome of a matching operation. 1795Consider the pattern 1796<pre> 1797 (*COMMIT)ABC 1798</pre> 1799When this is compiled, PCRE2 records the fact that a match must start with the 1800character "A". Suppose the subject string is "DEFABC". The start-up 1801optimization scans along the subject, finds "A" and runs the first match 1802attempt from there. The (*COMMIT) item means that the pattern must match the 1803current starting position, which in this case, it does. However, if the same 1804match is run with PCRE2_NO_START_OPTIMIZE set, the initial scan along the 1805subject string does not happen. The first match attempt is run starting from 1806"D" and when this fails, (*COMMIT) prevents any further matches being tried, so 1807the overall result is "no match". 1808</P> 1809<P> 1810As another start-up optimization makes use of a minimum length for a matching 1811subject, which is recorded when possible. Consider the pattern 1812<pre> 1813 (*MARK:1)B(*MARK:2)(X|Y) 1814</pre> 1815The minimum length for a match is two characters. If the subject is "XXBB", the 1816"starting character" optimization skips "XX", then tries to match "BB", which 1817is long enough. In the process, (*MARK:2) is encountered and remembered. When 1818the match attempt fails, the next "B" is found, but there is only one character 1819left, so there are no more attempts, and "no match" is returned with the "last 1820mark seen" set to "2". If NO_START_OPTIMIZE is set, however, matches are tried 1821at every possible starting position, including at the end of the subject, where 1822(*MARK:1) is encountered, but there is no "B", so the "last mark seen" that is 1823returned is "1". In this case, the optimizations do not affect the overall 1824match result, which is still "no match", but they do affect the auxiliary 1825information that is returned. 1826<pre> 1827 PCRE2_NO_UTF_CHECK 1828</pre> 1829When PCRE2_UTF is set, the validity of the pattern as a UTF string is 1830automatically checked. There are discussions about the validity of 1831<a href="pcre2unicode.html#utf8strings">UTF-8 strings,</a> 1832<a href="pcre2unicode.html#utf16strings">UTF-16 strings,</a> 1833and 1834<a href="pcre2unicode.html#utf32strings">UTF-32 strings</a> 1835in the 1836<a href="pcre2unicode.html"><b>pcre2unicode</b></a> 1837document. If an invalid UTF sequence is found, <b>pcre2_compile()</b> returns a 1838negative error code. 1839</P> 1840<P> 1841If you know that your pattern is a valid UTF string, and you want to skip this 1842check for performance reasons, you can set the PCRE2_NO_UTF_CHECK option. When 1843it is set, the effect of passing an invalid UTF string as a pattern is 1844undefined. It may cause your program to crash or loop. 1845</P> 1846<P> 1847Note that this option can also be passed to <b>pcre2_match()</b> and 1848<b>pcre2_dfa_match()</b>, to suppress UTF validity checking of the subject 1849string. 1850</P> 1851<P> 1852Note also that setting PCRE2_NO_UTF_CHECK at compile time does not disable the 1853error that is given if an escape sequence for an invalid Unicode code point is 1854encountered in the pattern. In particular, the so-called "surrogate" code 1855points (0xd800 to 0xdfff) are invalid. If you want to allow escape sequences 1856such as \x{d800} you can set the PCRE2_EXTRA_ALLOW_SURROGATE_ESCAPES extra 1857option, as described in the section entitled "Extra compile options" 1858<a href="#extracompileoptions">below.</a> 1859However, this is possible only in UTF-8 and UTF-32 modes, because these values 1860are not representable in UTF-16. 1861<pre> 1862 PCRE2_UCP 1863</pre> 1864This option has two effects. Firstly, it change the way PCRE2 processes \B, 1865\b, \D, \d, \S, \s, \W, \w, and some of the POSIX character classes. By 1866default, only ASCII characters are recognized, but if PCRE2_UCP is set, Unicode 1867properties are used instead to classify characters. More details are given in 1868the section on 1869<a href="pcre2pattern.html#genericchartypes">generic character types</a> 1870in the 1871<a href="pcre2pattern.html"><b>pcre2pattern</b></a> 1872page. If you set PCRE2_UCP, matching one of the items it affects takes much 1873longer. 1874</P> 1875<P> 1876The second effect of PCRE2_UCP is to force the use of Unicode properties for 1877upper/lower casing operations on characters with code points greater than 127, 1878even when PCRE2_UTF is not set. This makes it possible, for example, to process 1879strings in the 16-bit UCS-2 code. This option is available only if PCRE2 has 1880been compiled with Unicode support (which is the default). 1881<pre> 1882 PCRE2_UNGREEDY 1883</pre> 1884This option inverts the "greediness" of the quantifiers so that they are not 1885greedy by default, but become greedy if followed by "?". It is not compatible 1886with Perl. It can also be set by a (?U) option setting within the pattern. 1887<pre> 1888 PCRE2_USE_OFFSET_LIMIT 1889</pre> 1890This option must be set for <b>pcre2_compile()</b> if 1891<b>pcre2_set_offset_limit()</b> is going to be used to set a non-default offset 1892limit in a match context for matches that use this pattern. An error is 1893generated if an offset limit is set without this option. For more details, see 1894the description of <b>pcre2_set_offset_limit()</b> in the 1895<a href="#matchcontext">section</a> 1896that describes match contexts. See also the PCRE2_FIRSTLINE 1897option above. 1898<pre> 1899 PCRE2_UTF 1900</pre> 1901This option causes PCRE2 to regard both the pattern and the subject strings 1902that are subsequently processed as strings of UTF characters instead of 1903single-code-unit strings. It is available when PCRE2 is built to include 1904Unicode support (which is the default). If Unicode support is not available, 1905the use of this option provokes an error. Details of how PCRE2_UTF changes the 1906behaviour of PCRE2 are given in the 1907<a href="pcre2unicode.html"><b>pcre2unicode</b></a> 1908page. In particular, note that it changes the way PCRE2_CASELESS handles 1909characters with code points greater than 127. 1910<a name="extracompileoptions"></a></P> 1911<br><b> 1912Extra compile options 1913</b><br> 1914<P> 1915The option bits that can be set in a compile context by calling the 1916<b>pcre2_set_compile_extra_options()</b> function are as follows: 1917<pre> 1918 PCRE2_EXTRA_ALLOW_LOOKAROUND_BSK 1919</pre> 1920Since release 10.38 PCRE2 has forbidden the use of \K within lookaround 1921assertions, following Perl's lead. This option is provided to re-enable the 1922previous behaviour (act in positive lookarounds, ignore in negative ones) in 1923case anybody is relying on it. 1924<pre> 1925 PCRE2_EXTRA_ALLOW_SURROGATE_ESCAPES 1926</pre> 1927This option applies when compiling a pattern in UTF-8 or UTF-32 mode. It is 1928forbidden in UTF-16 mode, and ignored in non-UTF modes. Unicode "surrogate" 1929code points in the range 0xd800 to 0xdfff are used in pairs in UTF-16 to encode 1930code points with values in the range 0x10000 to 0x10ffff. The surrogates cannot 1931therefore be represented in UTF-16. They can be represented in UTF-8 and 1932UTF-32, but are defined as invalid code points, and cause errors if encountered 1933in a UTF-8 or UTF-32 string that is being checked for validity by PCRE2. 1934</P> 1935<P> 1936These values also cause errors if encountered in escape sequences such as 1937\x{d912} within a pattern. However, it seems that some applications, when 1938using PCRE2 to check for unwanted characters in UTF-8 strings, explicitly test 1939for the surrogates using escape sequences. The PCRE2_NO_UTF_CHECK option does 1940not disable the error that occurs, because it applies only to the testing of 1941input strings for UTF validity. 1942</P> 1943<P> 1944If the extra option PCRE2_EXTRA_ALLOW_SURROGATE_ESCAPES is set, surrogate code 1945point values in UTF-8 and UTF-32 patterns no longer provoke errors and are 1946incorporated in the compiled pattern. However, they can only match subject 1947characters if the matching function is called with PCRE2_NO_UTF_CHECK set. 1948<pre> 1949 PCRE2_EXTRA_ALT_BSUX 1950</pre> 1951The original option PCRE2_ALT_BSUX causes PCRE2 to process \U, \u, and \x in 1952the way that ECMAscript (aka JavaScript) does. Additional functionality was 1953defined by ECMAscript 6; setting PCRE2_EXTRA_ALT_BSUX has the effect of 1954PCRE2_ALT_BSUX, but in addition it recognizes \u{hhh..} as a hexadecimal 1955character code, where hhh.. is any number of hexadecimal digits. 1956<pre> 1957 PCRE2_EXTRA_BAD_ESCAPE_IS_LITERAL 1958</pre> 1959This is a dangerous option. Use with care. By default, an unrecognized escape 1960such as \j or a malformed one such as \x{2z} causes a compile-time error when 1961detected by <b>pcre2_compile()</b>. Perl is somewhat inconsistent in handling 1962such items: for example, \j is treated as a literal "j", and non-hexadecimal 1963digits in \x{} are just ignored, though warnings are given in both cases if 1964Perl's warning switch is enabled. However, a malformed octal number after \o{ 1965always causes an error in Perl. 1966</P> 1967<P> 1968If the PCRE2_EXTRA_BAD_ESCAPE_IS_LITERAL extra option is passed to 1969<b>pcre2_compile()</b>, all unrecognized or malformed escape sequences are 1970treated as single-character escapes. For example, \j is a literal "j" and 1971\x{2z} is treated as the literal string "x{2z}". Setting this option means 1972that typos in patterns may go undetected and have unexpected results. Also note 1973that a sequence such as [\N{] is interpreted as a malformed attempt at 1974[\N{...}] and so is treated as [N{] whereas [\N] gives an error because an 1975unqualified \N is a valid escape sequence but is not supported in a character 1976class. To reiterate: this is a dangerous option. Use with great care. 1977<pre> 1978 PCRE2_EXTRA_ESCAPED_CR_IS_LF 1979</pre> 1980There are some legacy applications where the escape sequence \r in a pattern 1981is expected to match a newline. If this option is set, \r in a pattern is 1982converted to \n so that it matches a LF (linefeed) instead of a CR (carriage 1983return) character. The option does not affect a literal CR in the pattern, nor 1984does it affect CR specified as an explicit code point such as \x{0D}. 1985<pre> 1986 PCRE2_EXTRA_MATCH_LINE 1987</pre> 1988This option is provided for use by the <b>-x</b> option of <b>pcre2grep</b>. It 1989causes the pattern only to match complete lines. This is achieved by 1990automatically inserting the code for "^(?:" at the start of the compiled 1991pattern and ")$" at the end. Thus, when PCRE2_MULTILINE is set, the matched 1992line may be in the middle of the subject string. This option can be used with 1993PCRE2_LITERAL. 1994<pre> 1995 PCRE2_EXTRA_MATCH_WORD 1996</pre> 1997This option is provided for use by the <b>-w</b> option of <b>pcre2grep</b>. It 1998causes the pattern only to match strings that have a word boundary at the start 1999and the end. This is achieved by automatically inserting the code for "\b(?:" 2000at the start of the compiled pattern and ")\b" at the end. The option may be 2001used with PCRE2_LITERAL. However, it is ignored if PCRE2_EXTRA_MATCH_LINE is 2002also set. 2003<a name="jitcompiling"></a></P> 2004<br><a name="SEC21" href="#TOC1">JUST-IN-TIME (JIT) COMPILATION</a><br> 2005<P> 2006<b>int pcre2_jit_compile(pcre2_code *<i>code</i>, uint32_t <i>options</i>);</b> 2007<br> 2008<br> 2009<b>int pcre2_jit_match(const pcre2_code *<i>code</i>, PCRE2_SPTR <i>subject</i>,</b> 2010<b> PCRE2_SIZE <i>length</i>, PCRE2_SIZE <i>startoffset</i>,</b> 2011<b> uint32_t <i>options</i>, pcre2_match_data *<i>match_data</i>,</b> 2012<b> pcre2_match_context *<i>mcontext</i>);</b> 2013<br> 2014<br> 2015<b>void pcre2_jit_free_unused_memory(pcre2_general_context *<i>gcontext</i>);</b> 2016<br> 2017<br> 2018<b>pcre2_jit_stack *pcre2_jit_stack_create(PCRE2_SIZE <i>startsize</i>,</b> 2019<b> PCRE2_SIZE <i>maxsize</i>, pcre2_general_context *<i>gcontext</i>);</b> 2020<br> 2021<br> 2022<b>void pcre2_jit_stack_assign(pcre2_match_context *<i>mcontext</i>,</b> 2023<b> pcre2_jit_callback <i>callback_function</i>, void *<i>callback_data</i>);</b> 2024<br> 2025<br> 2026<b>void pcre2_jit_stack_free(pcre2_jit_stack *<i>jit_stack</i>);</b> 2027</P> 2028<P> 2029These functions provide support for JIT compilation, which, if the just-in-time 2030compiler is available, further processes a compiled pattern into machine code 2031that executes much faster than the <b>pcre2_match()</b> interpretive matching 2032function. Full details are given in the 2033<a href="pcre2jit.html"><b>pcre2jit</b></a> 2034documentation. 2035</P> 2036<P> 2037JIT compilation is a heavyweight optimization. It can take some time for 2038patterns to be analyzed, and for one-off matches and simple patterns the 2039benefit of faster execution might be offset by a much slower compilation time. 2040Most (but not all) patterns can be optimized by the JIT compiler. 2041<a name="localesupport"></a></P> 2042<br><a name="SEC22" href="#TOC1">LOCALE SUPPORT</a><br> 2043<P> 2044<b>const uint8_t *pcre2_maketables(pcre2_general_context *<i>gcontext</i>);</b> 2045<br> 2046<br> 2047<b>void pcre2_maketables_free(pcre2_general_context *<i>gcontext</i>,</b> 2048<b> const uint8_t *<i>tables</i>);</b> 2049</P> 2050<P> 2051PCRE2 handles caseless matching, and determines whether characters are letters, 2052digits, or whatever, by reference to a set of tables, indexed by character code 2053point. However, this applies only to characters whose code points are less than 2054256. By default, higher-valued code points never match escapes such as \w or 2055\d. 2056</P> 2057<P> 2058When PCRE2 is built with Unicode support (the default), certain Unicode 2059character properties can be tested with \p and \P, or, alternatively, the 2060PCRE2_UCP option can be set when a pattern is compiled; this causes \w and 2061friends to use Unicode property support instead of the built-in tables. 2062PCRE2_UCP also causes upper/lower casing operations on characters with code 2063points greater than 127 to use Unicode properties. These effects apply even 2064when PCRE2_UTF is not set. 2065</P> 2066<P> 2067The use of locales with Unicode is discouraged. If you are handling characters 2068with code points greater than 127, you should either use Unicode support, or 2069use locales, but not try to mix the two. 2070</P> 2071<P> 2072PCRE2 contains a built-in set of character tables that are used by default. 2073These are sufficient for many applications. Normally, the internal tables 2074recognize only ASCII characters. However, when PCRE2 is built, it is possible 2075to cause the internal tables to be rebuilt in the default "C" locale of the 2076local system, which may cause them to be different. 2077</P> 2078<P> 2079The built-in tables can be overridden by tables supplied by the application 2080that calls PCRE2. These may be created in a different locale from the default. 2081As more and more applications change to using Unicode, the need for this locale 2082support is expected to die away. 2083</P> 2084<P> 2085External tables are built by calling the <b>pcre2_maketables()</b> function, in 2086the relevant locale. The only argument to this function is a general context, 2087which can be used to pass a custom memory allocator. If the argument is NULL, 2088the system <b>malloc()</b> is used. The result can be passed to 2089<b>pcre2_compile()</b> as often as necessary, by creating a compile context and 2090calling <b>pcre2_set_character_tables()</b> to set the tables pointer therein. 2091</P> 2092<P> 2093For example, to build and use tables that are appropriate for the French locale 2094(where accented characters with values greater than 127 are treated as 2095letters), the following code could be used: 2096<pre> 2097 setlocale(LC_CTYPE, "fr_FR"); 2098 tables = pcre2_maketables(NULL); 2099 ccontext = pcre2_compile_context_create(NULL); 2100 pcre2_set_character_tables(ccontext, tables); 2101 re = pcre2_compile(..., ccontext); 2102</pre> 2103The locale name "fr_FR" is used on Linux and other Unix-like systems; if you 2104are using Windows, the name for the French locale is "french". 2105</P> 2106<P> 2107The pointer that is passed (via the compile context) to <b>pcre2_compile()</b> 2108is saved with the compiled pattern, and the same tables are used by the 2109matching functions. Thus, for any single pattern, compilation and matching both 2110happen in the same locale, but different patterns can be processed in different 2111locales. 2112</P> 2113<P> 2114It is the caller's responsibility to ensure that the memory containing the 2115tables remains available while they are still in use. When they are no longer 2116needed, you can discard them using <b>pcre2_maketables_free()</b>, which should 2117pass as its first parameter the same global context that was used to create the 2118tables. 2119</P> 2120<br><b> 2121Saving locale tables 2122</b><br> 2123<P> 2124The tables described above are just a sequence of binary bytes, which makes 2125them independent of hardware characteristics such as endianness or whether the 2126processor is 32-bit or 64-bit. A copy of the result of <b>pcre2_maketables()</b> 2127can therefore be saved in a file or elsewhere and re-used later, even in a 2128different program or on another computer. The size of the tables (number of 2129bytes) must be obtained by calling <b>pcre2_config()</b> with the 2130PCRE2_CONFIG_TABLES_LENGTH option because <b>pcre2_maketables()</b> does not 2131return this value. Note that the <b>pcre2_dftables</b> program, which is part of 2132the PCRE2 build system, can be used stand-alone to create a file that contains 2133a set of binary tables. See the 2134<a href="pcre2build.html#createtables"><b>pcre2build</b></a> 2135documentation for details. 2136<a name="infoaboutpattern"></a></P> 2137<br><a name="SEC23" href="#TOC1">INFORMATION ABOUT A COMPILED PATTERN</a><br> 2138<P> 2139<b>int pcre2_pattern_info(const pcre2 *<i>code</i>, uint32_t <i>what</i>, void *<i>where</i>);</b> 2140</P> 2141<P> 2142The <b>pcre2_pattern_info()</b> function returns general information about a 2143compiled pattern. For information about callouts, see the 2144<a href="#infoaboutcallouts">next section.</a> 2145The first argument for <b>pcre2_pattern_info()</b> is a pointer to the compiled 2146pattern. The second argument specifies which piece of information is required, 2147and the third argument is a pointer to a variable to receive the data. If the 2148third argument is NULL, the first argument is ignored, and the function returns 2149the size in bytes of the variable that is required for the information 2150requested. Otherwise, the yield of the function is zero for success, or one of 2151the following negative numbers: 2152<pre> 2153 PCRE2_ERROR_NULL the argument <i>code</i> was NULL 2154 PCRE2_ERROR_BADMAGIC the "magic number" was not found 2155 PCRE2_ERROR_BADOPTION the value of <i>what</i> was invalid 2156 PCRE2_ERROR_UNSET the requested field is not set 2157</pre> 2158The "magic number" is placed at the start of each compiled pattern as a simple 2159check against passing an arbitrary memory pointer. Here is a typical call of 2160<b>pcre2_pattern_info()</b>, to obtain the length of the compiled pattern: 2161<pre> 2162 int rc; 2163 size_t length; 2164 rc = pcre2_pattern_info( 2165 re, /* result of pcre2_compile() */ 2166 PCRE2_INFO_SIZE, /* what is required */ 2167 &length); /* where to put the data */ 2168</pre> 2169The possible values for the second argument are defined in <b>pcre2.h</b>, and 2170are as follows: 2171<pre> 2172 PCRE2_INFO_ALLOPTIONS 2173 PCRE2_INFO_ARGOPTIONS 2174 PCRE2_INFO_EXTRAOPTIONS 2175</pre> 2176Return copies of the pattern's options. The third argument should point to a 2177<b>uint32_t</b> variable. PCRE2_INFO_ARGOPTIONS returns exactly the options that 2178were passed to <b>pcre2_compile()</b>, whereas PCRE2_INFO_ALLOPTIONS returns 2179the compile options as modified by any top-level (*XXX) option settings such as 2180(*UTF) at the start of the pattern itself. PCRE2_INFO_EXTRAOPTIONS returns the 2181extra options that were set in the compile context by calling the 2182pcre2_set_compile_extra_options() function. 2183</P> 2184<P> 2185For example, if the pattern /(*UTF)abc/ is compiled with the PCRE2_EXTENDED 2186option, the result for PCRE2_INFO_ALLOPTIONS is PCRE2_EXTENDED and PCRE2_UTF. 2187Option settings such as (?i) that can change within a pattern do not affect the 2188result of PCRE2_INFO_ALLOPTIONS, even if they appear right at the start of the 2189pattern. (This was different in some earlier releases.) 2190</P> 2191<P> 2192A pattern compiled without PCRE2_ANCHORED is automatically anchored by PCRE2 if 2193the first significant item in every top-level branch is one of the following: 2194<pre> 2195 ^ unless PCRE2_MULTILINE is set 2196 \A always 2197 \G always 2198 .* sometimes - see below 2199</pre> 2200When .* is the first significant item, anchoring is possible only when all the 2201following are true: 2202<pre> 2203 .* is not in an atomic group 2204 .* is not in a capture group that is the subject of a backreference 2205 PCRE2_DOTALL is in force for .* 2206 Neither (*PRUNE) nor (*SKIP) appears in the pattern 2207 PCRE2_NO_DOTSTAR_ANCHOR is not set 2208</pre> 2209For patterns that are auto-anchored, the PCRE2_ANCHORED bit is set in the 2210options returned for PCRE2_INFO_ALLOPTIONS. 2211<pre> 2212 PCRE2_INFO_BACKREFMAX 2213</pre> 2214Return the number of the highest backreference in the pattern. The third 2215argument should point to a <b>uint32_t</b> variable. Named capture groups 2216acquire numbers as well as names, and these count towards the highest 2217backreference. Backreferences such as \4 or \g{12} match the captured 2218characters of the given group, but in addition, the check that a capture 2219group is set in a conditional group such as (?(3)a|b) is also a backreference. 2220Zero is returned if there are no backreferences. 2221<pre> 2222 PCRE2_INFO_BSR 2223</pre> 2224The output is a uint32_t integer whose value indicates what character sequences 2225the \R escape sequence matches. A value of PCRE2_BSR_UNICODE means that \R 2226matches any Unicode line ending sequence; a value of PCRE2_BSR_ANYCRLF means 2227that \R matches only CR, LF, or CRLF. 2228<pre> 2229 PCRE2_INFO_CAPTURECOUNT 2230</pre> 2231Return the highest capture group number in the pattern. In patterns where (?| 2232is not used, this is also the total number of capture groups. The third 2233argument should point to a <b>uint32_t</b> variable. 2234<pre> 2235 PCRE2_INFO_DEPTHLIMIT 2236</pre> 2237If the pattern set a backtracking depth limit by including an item of the form 2238(*LIMIT_DEPTH=nnnn) at the start, the value is returned. The third argument 2239should point to a uint32_t integer. If no such value has been set, the call to 2240<b>pcre2_pattern_info()</b> returns the error PCRE2_ERROR_UNSET. Note that this 2241limit will only be used during matching if it is less than the limit set or 2242defaulted by the caller of the match function. 2243<pre> 2244 PCRE2_INFO_FIRSTBITMAP 2245</pre> 2246In the absence of a single first code unit for a non-anchored pattern, 2247<b>pcre2_compile()</b> may construct a 256-bit table that defines a fixed set of 2248values for the first code unit in any match. For example, a pattern that starts 2249with [abc] results in a table with three bits set. When code unit values 2250greater than 255 are supported, the flag bit for 255 means "any code unit of 2251value 255 or above". If such a table was constructed, a pointer to it is 2252returned. Otherwise NULL is returned. The third argument should point to a 2253<b>const uint8_t *</b> variable. 2254<pre> 2255 PCRE2_INFO_FIRSTCODETYPE 2256</pre> 2257Return information about the first code unit of any matched string, for a 2258non-anchored pattern. The third argument should point to a <b>uint32_t</b> 2259variable. If there is a fixed first value, for example, the letter "c" from a 2260pattern such as (cat|cow|coyote), 1 is returned, and the value can be retrieved 2261using PCRE2_INFO_FIRSTCODEUNIT. If there is no fixed first value, but it is 2262known that a match can occur only at the start of the subject or following a 2263newline in the subject, 2 is returned. Otherwise, and for anchored patterns, 0 2264is returned. 2265<pre> 2266 PCRE2_INFO_FIRSTCODEUNIT 2267</pre> 2268Return the value of the first code unit of any matched string for a pattern 2269where PCRE2_INFO_FIRSTCODETYPE returns 1; otherwise return 0. The third 2270argument should point to a <b>uint32_t</b> variable. In the 8-bit library, the 2271value is always less than 256. In the 16-bit library the value can be up to 22720xffff. In the 32-bit library in UTF-32 mode the value can be up to 0x10ffff, 2273and up to 0xffffffff when not using UTF-32 mode. 2274<pre> 2275 PCRE2_INFO_FRAMESIZE 2276</pre> 2277Return the size (in bytes) of the data frames that are used to remember 2278backtracking positions when the pattern is processed by <b>pcre2_match()</b> 2279without the use of JIT. The third argument should point to a <b>size_t</b> 2280variable. The frame size depends on the number of capturing parentheses in the 2281pattern. Each additional capture group adds two PCRE2_SIZE variables. 2282<pre> 2283 PCRE2_INFO_HASBACKSLASHC 2284</pre> 2285Return 1 if the pattern contains any instances of \C, otherwise 0. The third 2286argument should point to a <b>uint32_t</b> variable. 2287<pre> 2288 PCRE2_INFO_HASCRORLF 2289</pre> 2290Return 1 if the pattern contains any explicit matches for CR or LF characters, 2291otherwise 0. The third argument should point to a <b>uint32_t</b> variable. An 2292explicit match is either a literal CR or LF character, or \r or \n or one of 2293the equivalent hexadecimal or octal escape sequences. 2294<pre> 2295 PCRE2_INFO_HEAPLIMIT 2296</pre> 2297If the pattern set a heap memory limit by including an item of the form 2298(*LIMIT_HEAP=nnnn) at the start, the value is returned. The third argument 2299should point to a uint32_t integer. If no such value has been set, the call to 2300<b>pcre2_pattern_info()</b> returns the error PCRE2_ERROR_UNSET. Note that this 2301limit will only be used during matching if it is less than the limit set or 2302defaulted by the caller of the match function. 2303<pre> 2304 PCRE2_INFO_JCHANGED 2305</pre> 2306Return 1 if the (?J) or (?-J) option setting is used in the pattern, otherwise 23070. The third argument should point to a <b>uint32_t</b> variable. (?J) and 2308(?-J) set and unset the local PCRE2_DUPNAMES option, respectively. 2309<pre> 2310 PCRE2_INFO_JITSIZE 2311</pre> 2312If the compiled pattern was successfully processed by 2313<b>pcre2_jit_compile()</b>, return the size of the JIT compiled code, otherwise 2314return zero. The third argument should point to a <b>size_t</b> variable. 2315<pre> 2316 PCRE2_INFO_LASTCODETYPE 2317</pre> 2318Returns 1 if there is a rightmost literal code unit that must exist in any 2319matched string, other than at its start. The third argument should point to a 2320<b>uint32_t</b> variable. If there is no such value, 0 is returned. When 1 is 2321returned, the code unit value itself can be retrieved using 2322PCRE2_INFO_LASTCODEUNIT. For anchored patterns, a last literal value is 2323recorded only if it follows something of variable length. For example, for the 2324pattern /^a\d+z\d+/ the returned value is 1 (with "z" returned from 2325PCRE2_INFO_LASTCODEUNIT), but for /^a\dz\d/ the returned value is 0. 2326<pre> 2327 PCRE2_INFO_LASTCODEUNIT 2328</pre> 2329Return the value of the rightmost literal code unit that must exist in any 2330matched string, other than at its start, for a pattern where 2331PCRE2_INFO_LASTCODETYPE returns 1. Otherwise, return 0. The third argument 2332should point to a <b>uint32_t</b> variable. 2333<pre> 2334 PCRE2_INFO_MATCHEMPTY 2335</pre> 2336Return 1 if the pattern might match an empty string, otherwise 0. The third 2337argument should point to a <b>uint32_t</b> variable. When a pattern contains 2338recursive subroutine calls it is not always possible to determine whether or 2339not it can match an empty string. PCRE2 takes a cautious approach and returns 1 2340in such cases. 2341<pre> 2342 PCRE2_INFO_MATCHLIMIT 2343</pre> 2344If the pattern set a match limit by including an item of the form 2345(*LIMIT_MATCH=nnnn) at the start, the value is returned. The third argument 2346should point to a uint32_t integer. If no such value has been set, the call to 2347<b>pcre2_pattern_info()</b> returns the error PCRE2_ERROR_UNSET. Note that this 2348limit will only be used during matching if it is less than the limit set or 2349defaulted by the caller of the match function. 2350<pre> 2351 PCRE2_INFO_MAXLOOKBEHIND 2352</pre> 2353A lookbehind assertion moves back a certain number of characters (not code 2354units) when it starts to process each of its branches. This request returns the 2355largest of these backward moves. The third argument should point to a uint32_t 2356integer. The simple assertions \b and \B require a one-character lookbehind 2357and cause PCRE2_INFO_MAXLOOKBEHIND to return 1 in the absence of anything 2358longer. \A also registers a one-character lookbehind, though it does not 2359actually inspect the previous character. 2360</P> 2361<P> 2362Note that this information is useful for multi-segment matching only 2363if the pattern contains no nested lookbehinds. For example, the pattern 2364(?<=a(?<=ba)c) returns a maximum lookbehind of 2, but when it is processed, the 2365first lookbehind moves back by two characters, matches one character, then the 2366nested lookbehind also moves back by two characters. This puts the matching 2367point three characters earlier than it was at the start. 2368PCRE2_INFO_MAXLOOKBEHIND is really only useful as a debugging tool. See the 2369<a href="pcre2partial.html"><b>pcre2partial</b></a> 2370documentation for a discussion of multi-segment matching. 2371<pre> 2372 PCRE2_INFO_MINLENGTH 2373</pre> 2374If a minimum length for matching subject strings was computed, its value is 2375returned. Otherwise the returned value is 0. This value is not computed when 2376PCRE2_NO_START_OPTIMIZE is set. The value is a number of characters, which in 2377UTF mode may be different from the number of code units. The third argument 2378should point to a <b>uint32_t</b> variable. The value is a lower bound to the 2379length of any matching string. There may not be any strings of that length that 2380do actually match, but every string that does match is at least that long. 2381<pre> 2382 PCRE2_INFO_NAMECOUNT 2383 PCRE2_INFO_NAMEENTRYSIZE 2384 PCRE2_INFO_NAMETABLE 2385</pre> 2386PCRE2 supports the use of named as well as numbered capturing parentheses. The 2387names are just an additional way of identifying the parentheses, which still 2388acquire numbers. Several convenience functions such as 2389<b>pcre2_substring_get_byname()</b> are provided for extracting captured 2390substrings by name. It is also possible to extract the data directly, by first 2391converting the name to a number in order to access the correct pointers in the 2392output vector (described with <b>pcre2_match()</b> below). To do the conversion, 2393you need to use the name-to-number map, which is described by these three 2394values. 2395</P> 2396<P> 2397The map consists of a number of fixed-size entries. PCRE2_INFO_NAMECOUNT gives 2398the number of entries, and PCRE2_INFO_NAMEENTRYSIZE gives the size of each 2399entry in code units; both of these return a <b>uint32_t</b> value. The entry 2400size depends on the length of the longest name. 2401</P> 2402<P> 2403PCRE2_INFO_NAMETABLE returns a pointer to the first entry of the table. This is 2404a PCRE2_SPTR pointer to a block of code units. In the 8-bit library, the first 2405two bytes of each entry are the number of the capturing parenthesis, most 2406significant byte first. In the 16-bit library, the pointer points to 16-bit 2407code units, the first of which contains the parenthesis number. In the 32-bit 2408library, the pointer points to 32-bit code units, the first of which contains 2409the parenthesis number. The rest of the entry is the corresponding name, zero 2410terminated. 2411</P> 2412<P> 2413The names are in alphabetical order. If (?| is used to create multiple capture 2414groups with the same number, as described in the 2415<a href="pcre2pattern.html#dupgroupnumber">section on duplicate group numbers</a> 2416in the 2417<a href="pcre2pattern.html"><b>pcre2pattern</b></a> 2418page, the groups may be given the same name, but there is only one entry in the 2419table. Different names for groups of the same number are not permitted. 2420</P> 2421<P> 2422Duplicate names for capture groups with different numbers are permitted, but 2423only if PCRE2_DUPNAMES is set. They appear in the table in the order in which 2424they were found in the pattern. In the absence of (?| this is the order of 2425increasing number; when (?| is used this is not necessarily the case because 2426later capture groups may have lower numbers. 2427</P> 2428<P> 2429As a simple example of the name/number table, consider the following pattern 2430after compilation by the 8-bit library (assume PCRE2_EXTENDED is set, so white 2431space - including newlines - is ignored): 2432<pre> 2433 (?<date> (?<year>(\d\d)?\d\d) - (?<month>\d\d) - (?<day>\d\d) ) 2434</pre> 2435There are four named capture groups, so the table has four entries, and each 2436entry in the table is eight bytes long. The table is as follows, with 2437non-printing bytes shows in hexadecimal, and undefined bytes shown as ??: 2438<pre> 2439 00 01 d a t e 00 ?? 2440 00 05 d a y 00 ?? ?? 2441 00 04 m o n t h 00 2442 00 02 y e a r 00 ?? 2443</pre> 2444When writing code to extract data from named capture groups using the 2445name-to-number map, remember that the length of the entries is likely to be 2446different for each compiled pattern. 2447<pre> 2448 PCRE2_INFO_NEWLINE 2449</pre> 2450The output is one of the following <b>uint32_t</b> values: 2451<pre> 2452 PCRE2_NEWLINE_CR Carriage return (CR) 2453 PCRE2_NEWLINE_LF Linefeed (LF) 2454 PCRE2_NEWLINE_CRLF Carriage return, linefeed (CRLF) 2455 PCRE2_NEWLINE_ANY Any Unicode line ending 2456 PCRE2_NEWLINE_ANYCRLF Any of CR, LF, or CRLF 2457 PCRE2_NEWLINE_NUL The NUL character (binary zero) 2458</pre> 2459This identifies the character sequence that will be recognized as meaning 2460"newline" while matching. 2461<pre> 2462 PCRE2_INFO_SIZE 2463</pre> 2464Return the size of the compiled pattern in bytes (for all three libraries). The 2465third argument should point to a <b>size_t</b> variable. This value includes the 2466size of the general data block that precedes the code units of the compiled 2467pattern itself. The value that is used when <b>pcre2_compile()</b> is getting 2468memory in which to place the compiled pattern may be slightly larger than the 2469value returned by this option, because there are cases where the code that 2470calculates the size has to over-estimate. Processing a pattern with the JIT 2471compiler does not alter the value returned by this option. 2472<a name="infoaboutcallouts"></a></P> 2473<br><a name="SEC24" href="#TOC1">INFORMATION ABOUT A PATTERN'S CALLOUTS</a><br> 2474<P> 2475<b>int pcre2_callout_enumerate(const pcre2_code *<i>code</i>,</b> 2476<b> int (*<i>callback</i>)(pcre2_callout_enumerate_block *, void *),</b> 2477<b> void *<i>user_data</i>);</b> 2478<br> 2479<br> 2480A script language that supports the use of string arguments in callouts might 2481like to scan all the callouts in a pattern before running the match. This can 2482be done by calling <b>pcre2_callout_enumerate()</b>. The first argument is a 2483pointer to a compiled pattern, the second points to a callback function, and 2484the third is arbitrary user data. The callback function is called for every 2485callout in the pattern in the order in which they appear. Its first argument is 2486a pointer to a callout enumeration block, and its second argument is the 2487<i>user_data</i> value that was passed to <b>pcre2_callout_enumerate()</b>. The 2488contents of the callout enumeration block are described in the 2489<a href="pcre2callout.html"><b>pcre2callout</b></a> 2490documentation, which also gives further details about callouts. 2491</P> 2492<br><a name="SEC25" href="#TOC1">SERIALIZATION AND PRECOMPILING</a><br> 2493<P> 2494It is possible to save compiled patterns on disc or elsewhere, and reload them 2495later, subject to a number of restrictions. The host on which the patterns are 2496reloaded must be running the same version of PCRE2, with the same code unit 2497width, and must also have the same endianness, pointer width, and PCRE2_SIZE 2498type. Before compiled patterns can be saved, they must be converted to a 2499"serialized" form, which in the case of PCRE2 is really just a bytecode dump. 2500The functions whose names begin with <b>pcre2_serialize_</b> are used for 2501converting to and from the serialized form. They are described in the 2502<a href="pcre2serialize.html"><b>pcre2serialize</b></a> 2503documentation. Note that PCRE2 serialization does not convert compiled patterns 2504to an abstract format like Java or .NET serialization. 2505<a name="matchdatablock"></a></P> 2506<br><a name="SEC26" href="#TOC1">THE MATCH DATA BLOCK</a><br> 2507<P> 2508<b>pcre2_match_data *pcre2_match_data_create(uint32_t <i>ovecsize</i>,</b> 2509<b> pcre2_general_context *<i>gcontext</i>);</b> 2510<br> 2511<br> 2512<b>pcre2_match_data *pcre2_match_data_create_from_pattern(</b> 2513<b> const pcre2_code *<i>code</i>, pcre2_general_context *<i>gcontext</i>);</b> 2514<br> 2515<br> 2516<b>void pcre2_match_data_free(pcre2_match_data *<i>match_data</i>);</b> 2517</P> 2518<P> 2519Information about a successful or unsuccessful match is placed in a match 2520data block, which is an opaque structure that is accessed by function calls. In 2521particular, the match data block contains a vector of offsets into the subject 2522string that define the matched parts of the subject. This is known as the 2523<i>ovector</i>. 2524</P> 2525<P> 2526Before calling <b>pcre2_match()</b>, <b>pcre2_dfa_match()</b>, or 2527<b>pcre2_jit_match()</b> you must create a match data block by calling one of 2528the creation functions above. For <b>pcre2_match_data_create()</b>, the first 2529argument is the number of pairs of offsets in the <i>ovector</i>. 2530</P> 2531<P> 2532When using <b>pcre2_match()</b>, one pair of offsets is required to identify the 2533string that matched the whole pattern, with an additional pair for each 2534captured substring. For example, a value of 4 creates enough space to record 2535the matched portion of the subject plus three captured substrings. 2536</P> 2537<P> 2538When using <b>pcre2_dfa_match()</b> there may be multiple matched substrings of 2539different lengths at the same point in the subject. The ovector should be made 2540large enough to hold as many as are expected. 2541</P> 2542<P> 2543A minimum of at least 1 pair is imposed by <b>pcre2_match_data_create()</b>, so 2544it is always possible to return the overall matched string in the case of 2545<b>pcre2_match()</b> or the longest match in the case of 2546<b>pcre2_dfa_match()</b>. 2547</P> 2548<P> 2549The second argument of <b>pcre2_match_data_create()</b> is a pointer to a 2550general context, which can specify custom memory management for obtaining the 2551memory for the match data block. If you are not using custom memory management, 2552pass NULL, which causes <b>malloc()</b> to be used. 2553</P> 2554<P> 2555For <b>pcre2_match_data_create_from_pattern()</b>, the first argument is a 2556pointer to a compiled pattern. The ovector is created to be exactly the right 2557size to hold all the substrings a pattern might capture when matched using 2558<b>pcre2_match()</b>. You should not use this call when matching with 2559<b>pcre2_dfa_match()</b>. The second argument is again a pointer to a general 2560context, but in this case if NULL is passed, the memory is obtained using the 2561same allocator that was used for the compiled pattern (custom or default). 2562</P> 2563<P> 2564A match data block can be used many times, with the same or different compiled 2565patterns. You can extract information from a match data block after a match 2566operation has finished, using functions that are described in the sections on 2567<a href="#matchedstrings">matched strings</a> 2568and 2569<a href="#matchotherdata">other match data</a> 2570below. 2571</P> 2572<P> 2573When a call of <b>pcre2_match()</b> fails, valid data is available in the match 2574block only when the error is PCRE2_ERROR_NOMATCH, PCRE2_ERROR_PARTIAL, or one 2575of the error codes for an invalid UTF string. Exactly what is available depends 2576on the error, and is detailed below. 2577</P> 2578<P> 2579When one of the matching functions is called, pointers to the compiled pattern 2580and the subject string are set in the match data block so that they can be 2581referenced by the extraction functions after a successful match. After running 2582a match, you must not free a compiled pattern or a subject string until after 2583all operations on the match data block (for that match) have taken place, 2584unless, in the case of the subject string, you have used the 2585PCRE2_COPY_MATCHED_SUBJECT option, which is described in the section entitled 2586"Option bits for <b>pcre2_match()</b>" 2587<a href="#matchoptions>">below.</a> 2588</P> 2589<P> 2590When a match data block itself is no longer needed, it should be freed by 2591calling <b>pcre2_match_data_free()</b>. If this function is called with a NULL 2592argument, it returns immediately, without doing anything. 2593</P> 2594<br><a name="SEC27" href="#TOC1">MATCHING A PATTERN: THE TRADITIONAL FUNCTION</a><br> 2595<P> 2596<b>int pcre2_match(const pcre2_code *<i>code</i>, PCRE2_SPTR <i>subject</i>,</b> 2597<b> PCRE2_SIZE <i>length</i>, PCRE2_SIZE <i>startoffset</i>,</b> 2598<b> uint32_t <i>options</i>, pcre2_match_data *<i>match_data</i>,</b> 2599<b> pcre2_match_context *<i>mcontext</i>);</b> 2600</P> 2601<P> 2602The function <b>pcre2_match()</b> is called to match a subject string against a 2603compiled pattern, which is passed in the <i>code</i> argument. You can call 2604<b>pcre2_match()</b> with the same <i>code</i> argument as many times as you 2605like, in order to find multiple matches in the subject string or to match 2606different subject strings with the same pattern. 2607</P> 2608<P> 2609This function is the main matching facility of the library, and it operates in 2610a Perl-like manner. For specialist use there is also an alternative matching 2611function, which is described 2612<a href="#dfamatch">below</a> 2613in the section about the <b>pcre2_dfa_match()</b> function. 2614</P> 2615<P> 2616Here is an example of a simple call to <b>pcre2_match()</b>: 2617<pre> 2618 pcre2_match_data *md = pcre2_match_data_create(4, NULL); 2619 int rc = pcre2_match( 2620 re, /* result of pcre2_compile() */ 2621 "some string", /* the subject string */ 2622 11, /* the length of the subject string */ 2623 0, /* start at offset 0 in the subject */ 2624 0, /* default options */ 2625 md, /* the match data block */ 2626 NULL); /* a match context; NULL means use defaults */ 2627</pre> 2628If the subject string is zero-terminated, the length can be given as 2629PCRE2_ZERO_TERMINATED. A match context must be provided if certain less common 2630matching parameters are to be changed. For details, see the section on 2631<a href="#matchcontext">the match context</a> 2632above. 2633</P> 2634<br><b> 2635The string to be matched by <b>pcre2_match()</b> 2636</b><br> 2637<P> 2638The subject string is passed to <b>pcre2_match()</b> as a pointer in 2639<i>subject</i>, a length in <i>length</i>, and a starting offset in 2640<i>startoffset</i>. The length and offset are in code units, not characters. 2641That is, they are in bytes for the 8-bit library, 16-bit code units for the 264216-bit library, and 32-bit code units for the 32-bit library, whether or not 2643UTF processing is enabled. As a special case, if <i>subject</i> is NULL and 2644<i>length</i> is zero, the subject is assumed to be an empty string. If 2645<i>length</i> is non-zero, an error occurs if <i>subject</i> is NULL. 2646</P> 2647<P> 2648If <i>startoffset</i> is greater than the length of the subject, 2649<b>pcre2_match()</b> returns PCRE2_ERROR_BADOFFSET. When the starting offset is 2650zero, the search for a match starts at the beginning of the subject, and this 2651is by far the most common case. In UTF-8 or UTF-16 mode, the starting offset 2652must point to the start of a character, or to the end of the subject (in UTF-32 2653mode, one code unit equals one character, so all offsets are valid). Like the 2654pattern string, the subject may contain binary zeros. 2655</P> 2656<P> 2657A non-zero starting offset is useful when searching for another match in the 2658same subject by calling <b>pcre2_match()</b> again after a previous success. 2659Setting <i>startoffset</i> differs from passing over a shortened string and 2660setting PCRE2_NOTBOL in the case of a pattern that begins with any kind of 2661lookbehind. For example, consider the pattern 2662<pre> 2663 \Biss\B 2664</pre> 2665which finds occurrences of "iss" in the middle of words. (\B matches only if 2666the current position in the subject is not a word boundary.) When applied to 2667the string "Mississippi" the first call to <b>pcre2_match()</b> finds the first 2668occurrence. If <b>pcre2_match()</b> is called again with just the remainder of 2669the subject, namely "issippi", it does not match, because \B is always false 2670at the start of the subject, which is deemed to be a word boundary. However, if 2671<b>pcre2_match()</b> is passed the entire string again, but with 2672<i>startoffset</i> set to 4, it finds the second occurrence of "iss" because it 2673is able to look behind the starting point to discover that it is preceded by a 2674letter. 2675</P> 2676<P> 2677Finding all the matches in a subject is tricky when the pattern can match an 2678empty string. It is possible to emulate Perl's /g behaviour by first trying the 2679match again at the same offset, with the PCRE2_NOTEMPTY_ATSTART and 2680PCRE2_ANCHORED options, and then if that fails, advancing the starting offset 2681and trying an ordinary match again. There is some code that demonstrates how to 2682do this in the 2683<a href="pcre2demo.html"><b>pcre2demo</b></a> 2684sample program. In the most general case, you have to check to see if the 2685newline convention recognizes CRLF as a newline, and if so, and the current 2686character is CR followed by LF, advance the starting offset by two characters 2687instead of one. 2688</P> 2689<P> 2690If a non-zero starting offset is passed when the pattern is anchored, a single 2691attempt to match at the given offset is made. This can only succeed if the 2692pattern does not require the match to be at the start of the subject. In other 2693words, the anchoring must be the result of setting the PCRE2_ANCHORED option or 2694the use of .* with PCRE2_DOTALL, not by starting the pattern with ^ or \A. 2695<a name="matchoptions"></a></P> 2696<br><b> 2697Option bits for <b>pcre2_match()</b> 2698</b><br> 2699<P> 2700The unused bits of the <i>options</i> argument for <b>pcre2_match()</b> must be 2701zero. The only bits that may be set are PCRE2_ANCHORED, 2702PCRE2_COPY_MATCHED_SUBJECT, PCRE2_ENDANCHORED, PCRE2_NOTBOL, PCRE2_NOTEOL, 2703PCRE2_NOTEMPTY, PCRE2_NOTEMPTY_ATSTART, PCRE2_NO_JIT, PCRE2_NO_UTF_CHECK, 2704PCRE2_PARTIAL_HARD, and PCRE2_PARTIAL_SOFT. Their action is described below. 2705</P> 2706<P> 2707Setting PCRE2_ANCHORED or PCRE2_ENDANCHORED at match time is not supported by 2708the just-in-time (JIT) compiler. If it is set, JIT matching is disabled and the 2709interpretive code in <b>pcre2_match()</b> is run. Apart from PCRE2_NO_JIT 2710(obviously), the remaining options are supported for JIT matching. 2711<pre> 2712 PCRE2_ANCHORED 2713</pre> 2714The PCRE2_ANCHORED option limits <b>pcre2_match()</b> to matching at the first 2715matching position. If a pattern was compiled with PCRE2_ANCHORED, or turned out 2716to be anchored by virtue of its contents, it cannot be made unachored at 2717matching time. Note that setting the option at match time disables JIT 2718matching. 2719<pre> 2720 PCRE2_COPY_MATCHED_SUBJECT 2721</pre> 2722By default, a pointer to the subject is remembered in the match data block so 2723that, after a successful match, it can be referenced by the substring 2724extraction functions. This means that the subject's memory must not be freed 2725until all such operations are complete. For some applications where the 2726lifetime of the subject string is not guaranteed, it may be necessary to make a 2727copy of the subject string, but it is wasteful to do this unless the match is 2728successful. After a successful match, if PCRE2_COPY_MATCHED_SUBJECT is set, the 2729subject is copied and the new pointer is remembered in the match data block 2730instead of the original subject pointer. The memory allocator that was used for 2731the match block itself is used. The copy is automatically freed when 2732<b>pcre2_match_data_free()</b> is called to free the match data block. It is also 2733automatically freed if the match data block is re-used for another match 2734operation. 2735<pre> 2736 PCRE2_ENDANCHORED 2737</pre> 2738If the PCRE2_ENDANCHORED option is set, any string that <b>pcre2_match()</b> 2739matches must be right at the end of the subject string. Note that setting the 2740option at match time disables JIT matching. 2741<pre> 2742 PCRE2_NOTBOL 2743</pre> 2744This option specifies that first character of the subject string is not the 2745beginning of a line, so the circumflex metacharacter should not match before 2746it. Setting this without having set PCRE2_MULTILINE at compile time causes 2747circumflex never to match. This option affects only the behaviour of the 2748circumflex metacharacter. It does not affect \A. 2749<pre> 2750 PCRE2_NOTEOL 2751</pre> 2752This option specifies that the end of the subject string is not the end of a 2753line, so the dollar metacharacter should not match it nor (except in multiline 2754mode) a newline immediately before it. Setting this without having set 2755PCRE2_MULTILINE at compile time causes dollar never to match. This option 2756affects only the behaviour of the dollar metacharacter. It does not affect \Z 2757or \z. 2758<pre> 2759 PCRE2_NOTEMPTY 2760</pre> 2761An empty string is not considered to be a valid match if this option is set. If 2762there are alternatives in the pattern, they are tried. If all the alternatives 2763match the empty string, the entire match fails. For example, if the pattern 2764<pre> 2765 a?b? 2766</pre> 2767is applied to a string not beginning with "a" or "b", it matches an empty 2768string at the start of the subject. With PCRE2_NOTEMPTY set, this match is not 2769valid, so <b>pcre2_match()</b> searches further into the string for occurrences 2770of "a" or "b". 2771<pre> 2772 PCRE2_NOTEMPTY_ATSTART 2773</pre> 2774This is like PCRE2_NOTEMPTY, except that it locks out an empty string match 2775only at the first matching position, that is, at the start of the subject plus 2776the starting offset. An empty string match later in the subject is permitted. 2777If the pattern is anchored, such a match can occur only if the pattern contains 2778\K. 2779<pre> 2780 PCRE2_NO_JIT 2781</pre> 2782By default, if a pattern has been successfully processed by 2783<b>pcre2_jit_compile()</b>, JIT is automatically used when <b>pcre2_match()</b> 2784is called with options that JIT supports. Setting PCRE2_NO_JIT disables the use 2785of JIT; it forces matching to be done by the interpreter. 2786<pre> 2787 PCRE2_NO_UTF_CHECK 2788</pre> 2789When PCRE2_UTF is set at compile time, the validity of the subject as a UTF 2790string is checked unless PCRE2_NO_UTF_CHECK is passed to <b>pcre2_match()</b> or 2791PCRE2_MATCH_INVALID_UTF was passed to <b>pcre2_compile()</b>. The latter special 2792case is discussed in detail in the 2793<a href="pcre2unicode.html"><b>pcre2unicode</b></a> 2794documentation. 2795</P> 2796<P> 2797In the default case, if a non-zero starting offset is given, the check is 2798applied only to that part of the subject that could be inspected during 2799matching, and there is a check that the starting offset points to the first 2800code unit of a character or to the end of the subject. If there are no 2801lookbehind assertions in the pattern, the check starts at the starting offset. 2802Otherwise, it starts at the length of the longest lookbehind before the 2803starting offset, or at the start of the subject if there are not that many 2804characters before the starting offset. Note that the sequences \b and \B are 2805one-character lookbehinds. 2806</P> 2807<P> 2808The check is carried out before any other processing takes place, and a 2809negative error code is returned if the check fails. There are several UTF error 2810codes for each code unit width, corresponding to different problems with the 2811code unit sequence. There are discussions about the validity of 2812<a href="pcre2unicode.html#utf8strings">UTF-8 strings,</a> 2813<a href="pcre2unicode.html#utf16strings">UTF-16 strings,</a> 2814and 2815<a href="pcre2unicode.html#utf32strings">UTF-32 strings</a> 2816in the 2817<a href="pcre2unicode.html"><b>pcre2unicode</b></a> 2818documentation. 2819</P> 2820<P> 2821If you know that your subject is valid, and you want to skip this check for 2822performance reasons, you can set the PCRE2_NO_UTF_CHECK option when calling 2823<b>pcre2_match()</b>. You might want to do this for the second and subsequent 2824calls to <b>pcre2_match()</b> if you are making repeated calls to find multiple 2825matches in the same subject string. 2826</P> 2827<P> 2828<b>Warning:</b> Unless PCRE2_MATCH_INVALID_UTF was set at compile time, when 2829PCRE2_NO_UTF_CHECK is set at match time the effect of passing an invalid 2830string as a subject, or an invalid value of <i>startoffset</i>, is undefined. 2831Your program may crash or loop indefinitely or give wrong results. 2832<pre> 2833 PCRE2_PARTIAL_HARD 2834 PCRE2_PARTIAL_SOFT 2835</pre> 2836These options turn on the partial matching feature. A partial match occurs if 2837the end of the subject string is reached successfully, but there are not enough 2838subject characters to complete the match. In addition, either at least one 2839character must have been inspected or the pattern must contain a lookbehind, or 2840the pattern must be one that could match an empty string. 2841</P> 2842<P> 2843If this situation arises when PCRE2_PARTIAL_SOFT (but not PCRE2_PARTIAL_HARD) 2844is set, matching continues by testing any remaining alternatives. Only if no 2845complete match can be found is PCRE2_ERROR_PARTIAL returned instead of 2846PCRE2_ERROR_NOMATCH. In other words, PCRE2_PARTIAL_SOFT specifies that the 2847caller is prepared to handle a partial match, but only if no complete match can 2848be found. 2849</P> 2850<P> 2851If PCRE2_PARTIAL_HARD is set, it overrides PCRE2_PARTIAL_SOFT. In this case, if 2852a partial match is found, <b>pcre2_match()</b> immediately returns 2853PCRE2_ERROR_PARTIAL, without considering any other alternatives. In other 2854words, when PCRE2_PARTIAL_HARD is set, a partial match is considered to be more 2855important that an alternative complete match. 2856</P> 2857<P> 2858There is a more detailed discussion of partial and multi-segment matching, with 2859examples, in the 2860<a href="pcre2partial.html"><b>pcre2partial</b></a> 2861documentation. 2862</P> 2863<br><a name="SEC28" href="#TOC1">NEWLINE HANDLING WHEN MATCHING</a><br> 2864<P> 2865When PCRE2 is built, a default newline convention is set; this is usually the 2866standard convention for the operating system. The default can be overridden in 2867a 2868<a href="#compilecontext">compile context</a> 2869by calling <b>pcre2_set_newline()</b>. It can also be overridden by starting a 2870pattern string with, for example, (*CRLF), as described in the 2871<a href="pcre2pattern.html#newlines">section on newline conventions</a> 2872in the 2873<a href="pcre2pattern.html"><b>pcre2pattern</b></a> 2874page. During matching, the newline choice affects the behaviour of the dot, 2875circumflex, and dollar metacharacters. It may also alter the way the match 2876starting position is advanced after a match failure for an unanchored pattern. 2877</P> 2878<P> 2879When PCRE2_NEWLINE_CRLF, PCRE2_NEWLINE_ANYCRLF, or PCRE2_NEWLINE_ANY is set as 2880the newline convention, and a match attempt for an unanchored pattern fails 2881when the current starting position is at a CRLF sequence, and the pattern 2882contains no explicit matches for CR or LF characters, the match position is 2883advanced by two characters instead of one, in other words, to after the CRLF. 2884</P> 2885<P> 2886The above rule is a compromise that makes the most common cases work as 2887expected. For example, if the pattern is .+A (and the PCRE2_DOTALL option is 2888not set), it does not match the string "\r\nA" because, after failing at the 2889start, it skips both the CR and the LF before retrying. However, the pattern 2890[\r\n]A does match that string, because it contains an explicit CR or LF 2891reference, and so advances only by one character after the first failure. 2892</P> 2893<P> 2894An explicit match for CR of LF is either a literal appearance of one of those 2895characters in the pattern, or one of the \r or \n or equivalent octal or 2896hexadecimal escape sequences. Implicit matches such as [^X] do not count, nor 2897does \s, even though it includes CR and LF in the characters that it matches. 2898</P> 2899<P> 2900Notwithstanding the above, anomalous effects may still occur when CRLF is a 2901valid newline sequence and explicit \r or \n escapes appear in the pattern. 2902<a name="matchedstrings"></a></P> 2903<br><a name="SEC29" href="#TOC1">HOW PCRE2_MATCH() RETURNS A STRING AND CAPTURED SUBSTRINGS</a><br> 2904<P> 2905<b>uint32_t pcre2_get_ovector_count(pcre2_match_data *<i>match_data</i>);</b> 2906<br> 2907<br> 2908<b>PCRE2_SIZE *pcre2_get_ovector_pointer(pcre2_match_data *<i>match_data</i>);</b> 2909</P> 2910<P> 2911In general, a pattern matches a certain portion of the subject, and in 2912addition, further substrings from the subject may be picked out by 2913parenthesized parts of the pattern. Following the usage in Jeffrey Friedl's 2914book, this is called "capturing" in what follows, and the phrase "capture 2915group" (Perl terminology) is used for a fragment of a pattern that picks out a 2916substring. PCRE2 supports several other kinds of parenthesized group that do 2917not cause substrings to be captured. The <b>pcre2_pattern_info()</b> function 2918can be used to find out how many capture groups there are in a compiled 2919pattern. 2920</P> 2921<P> 2922You can use auxiliary functions for accessing captured substrings 2923<a href="#extractbynumber">by number</a> 2924or 2925<a href="#extractbyname">by name,</a> 2926as described in sections below. 2927</P> 2928<P> 2929Alternatively, you can make direct use of the vector of PCRE2_SIZE values, 2930called the <b>ovector</b>, which contains the offsets of captured strings. It is 2931part of the 2932<a href="#matchdatablock">match data block.</a> 2933The function <b>pcre2_get_ovector_pointer()</b> returns the address of the 2934ovector, and <b>pcre2_get_ovector_count()</b> returns the number of pairs of 2935values it contains. 2936</P> 2937<P> 2938Within the ovector, the first in each pair of values is set to the offset of 2939the first code unit of a substring, and the second is set to the offset of the 2940first code unit after the end of a substring. These values are always code unit 2941offsets, not character offsets. That is, they are byte offsets in the 8-bit 2942library, 16-bit offsets in the 16-bit library, and 32-bit offsets in the 32-bit 2943library. 2944</P> 2945<P> 2946After a partial match (error return PCRE2_ERROR_PARTIAL), only the first pair 2947of offsets (that is, <i>ovector[0]</i> and <i>ovector[1]</i>) are set. They 2948identify the part of the subject that was partially matched. See the 2949<a href="pcre2partial.html"><b>pcre2partial</b></a> 2950documentation for details of partial matching. 2951</P> 2952<P> 2953After a fully successful match, the first pair of offsets identifies the 2954portion of the subject string that was matched by the entire pattern. The next 2955pair is used for the first captured substring, and so on. The value returned by 2956<b>pcre2_match()</b> is one more than the highest numbered pair that has been 2957set. For example, if two substrings have been captured, the returned value is 29583. If there are no captured substrings, the return value from a successful 2959match is 1, indicating that just the first pair of offsets has been set. 2960</P> 2961<P> 2962If a pattern uses the \K escape sequence within a positive assertion, the 2963reported start of a successful match can be greater than the end of the match. 2964For example, if the pattern (?=ab\K) is matched against "ab", the start and 2965end offset values for the match are 2 and 0. 2966</P> 2967<P> 2968If a capture group is matched repeatedly within a single match operation, it is 2969the last portion of the subject that it matched that is returned. 2970</P> 2971<P> 2972If the ovector is too small to hold all the captured substring offsets, as much 2973as possible is filled in, and the function returns a value of zero. If captured 2974substrings are not of interest, <b>pcre2_match()</b> may be called with a match 2975data block whose ovector is of minimum length (that is, one pair). 2976</P> 2977<P> 2978It is possible for capture group number <i>n+1</i> to match some part of the 2979subject when group <i>n</i> has not been used at all. For example, if the string 2980"abc" is matched against the pattern (a|(z))(bc) the return from the function 2981is 4, and groups 1 and 3 are matched, but 2 is not. When this happens, both 2982values in the offset pairs corresponding to unused groups are set to 2983PCRE2_UNSET. 2984</P> 2985<P> 2986Offset values that correspond to unused groups at the end of the expression are 2987also set to PCRE2_UNSET. For example, if the string "abc" is matched against 2988the pattern (abc)(x(yz)?)? groups 2 and 3 are not matched. The return from the 2989function is 2, because the highest used capture group number is 1. The offsets 2990for for the second and third capture groupss (assuming the vector is large 2991enough, of course) are set to PCRE2_UNSET. 2992</P> 2993<P> 2994Elements in the ovector that do not correspond to capturing parentheses in the 2995pattern are never changed. That is, if a pattern contains <i>n</i> capturing 2996parentheses, no more than <i>ovector[0]</i> to <i>ovector[2n+1]</i> are set by 2997<b>pcre2_match()</b>. The other elements retain whatever values they previously 2998had. After a failed match attempt, the contents of the ovector are unchanged. 2999<a name="matchotherdata"></a></P> 3000<br><a name="SEC30" href="#TOC1">OTHER INFORMATION ABOUT A MATCH</a><br> 3001<P> 3002<b>PCRE2_SPTR pcre2_get_mark(pcre2_match_data *<i>match_data</i>);</b> 3003<br> 3004<br> 3005<b>PCRE2_SIZE pcre2_get_startchar(pcre2_match_data *<i>match_data</i>);</b> 3006</P> 3007<P> 3008As well as the offsets in the ovector, other information about a match is 3009retained in the match data block and can be retrieved by the above functions in 3010appropriate circumstances. If they are called at other times, the result is 3011undefined. 3012</P> 3013<P> 3014After a successful match, a partial match (PCRE2_ERROR_PARTIAL), or a failure 3015to match (PCRE2_ERROR_NOMATCH), a mark name may be available. The function 3016<b>pcre2_get_mark()</b> can be called to access this name, which can be 3017specified in the pattern by any of the backtracking control verbs, not just 3018(*MARK). The same function applies to all the verbs. It returns a pointer to 3019the zero-terminated name, which is within the compiled pattern. If no name is 3020available, NULL is returned. The length of the name (excluding the terminating 3021zero) is stored in the code unit that precedes the name. You should use this 3022length instead of relying on the terminating zero if the name might contain a 3023binary zero. 3024</P> 3025<P> 3026After a successful match, the name that is returned is the last mark name 3027encountered on the matching path through the pattern. Instances of backtracking 3028verbs without names do not count. Thus, for example, if the matching path 3029contains (*MARK:A)(*PRUNE), the name "A" is returned. After a "no match" or a 3030partial match, the last encountered name is returned. For example, consider 3031this pattern: 3032<pre> 3033 ^(*MARK:A)((*MARK:B)a|b)c 3034</pre> 3035When it matches "bc", the returned name is A. The B mark is "seen" in the first 3036branch of the group, but it is not on the matching path. On the other hand, 3037when this pattern fails to match "bx", the returned name is B. 3038</P> 3039<P> 3040<b>Warning:</b> By default, certain start-of-match optimizations are used to 3041give a fast "no match" result in some situations. For example, if the anchoring 3042is removed from the pattern above, there is an initial check for the presence 3043of "c" in the subject before running the matching engine. This check fails for 3044"bx", causing a match failure without seeing any marks. You can disable the 3045start-of-match optimizations by setting the PCRE2_NO_START_OPTIMIZE option for 3046<b>pcre2_compile()</b> or by starting the pattern with (*NO_START_OPT). 3047</P> 3048<P> 3049After a successful match, a partial match, or one of the invalid UTF errors 3050(for example, PCRE2_ERROR_UTF8_ERR5), <b>pcre2_get_startchar()</b> can be 3051called. After a successful or partial match it returns the code unit offset of 3052the character at which the match started. For a non-partial match, this can be 3053different to the value of <i>ovector[0]</i> if the pattern contains the \K 3054escape sequence. After a partial match, however, this value is always the same 3055as <i>ovector[0]</i> because \K does not affect the result of a partial match. 3056</P> 3057<P> 3058After a UTF check failure, <b>pcre2_get_startchar()</b> can be used to obtain 3059the code unit offset of the invalid UTF character. Details are given in the 3060<a href="pcre2unicode.html"><b>pcre2unicode</b></a> 3061page. 3062<a name="errorlist"></a></P> 3063<br><a name="SEC31" href="#TOC1">ERROR RETURNS FROM <b>pcre2_match()</b></a><br> 3064<P> 3065If <b>pcre2_match()</b> fails, it returns a negative number. This can be 3066converted to a text string by calling the <b>pcre2_get_error_message()</b> 3067function (see "Obtaining a textual error message" 3068<a href="#geterrormessage">below).</a> 3069Negative error codes are also returned by other functions, and are documented 3070with them. The codes are given names in the header file. If UTF checking is in 3071force and an invalid UTF subject string is detected, one of a number of 3072UTF-specific negative error codes is returned. Details are given in the 3073<a href="pcre2unicode.html"><b>pcre2unicode</b></a> 3074page. The following are the other errors that may be returned by 3075<b>pcre2_match()</b>: 3076<pre> 3077 PCRE2_ERROR_NOMATCH 3078</pre> 3079The subject string did not match the pattern. 3080<pre> 3081 PCRE2_ERROR_PARTIAL 3082</pre> 3083The subject string did not match, but it did match partially. See the 3084<a href="pcre2partial.html"><b>pcre2partial</b></a> 3085documentation for details of partial matching. 3086<pre> 3087 PCRE2_ERROR_BADMAGIC 3088</pre> 3089PCRE2 stores a 4-byte "magic number" at the start of the compiled code, to 3090catch the case when it is passed a junk pointer. This is the error that is 3091returned when the magic number is not present. 3092<pre> 3093 PCRE2_ERROR_BADMODE 3094</pre> 3095This error is given when a compiled pattern is passed to a function in a 3096library of a different code unit width, for example, a pattern compiled by 3097the 8-bit library is passed to a 16-bit or 32-bit library function. 3098<pre> 3099 PCRE2_ERROR_BADOFFSET 3100</pre> 3101The value of <i>startoffset</i> was greater than the length of the subject. 3102<pre> 3103 PCRE2_ERROR_BADOPTION 3104</pre> 3105An unrecognized bit was set in the <i>options</i> argument. 3106<pre> 3107 PCRE2_ERROR_BADUTFOFFSET 3108</pre> 3109The UTF code unit sequence that was passed as a subject was checked and found 3110to be valid (the PCRE2_NO_UTF_CHECK option was not set), but the value of 3111<i>startoffset</i> did not point to the beginning of a UTF character or the end 3112of the subject. 3113<pre> 3114 PCRE2_ERROR_CALLOUT 3115</pre> 3116This error is never generated by <b>pcre2_match()</b> itself. It is provided for 3117use by callout functions that want to cause <b>pcre2_match()</b> or 3118<b>pcre2_callout_enumerate()</b> to return a distinctive error code. See the 3119<a href="pcre2callout.html"><b>pcre2callout</b></a> 3120documentation for details. 3121<pre> 3122 PCRE2_ERROR_DEPTHLIMIT 3123</pre> 3124The nested backtracking depth limit was reached. 3125<pre> 3126 PCRE2_ERROR_HEAPLIMIT 3127</pre> 3128The heap limit was reached. 3129<pre> 3130 PCRE2_ERROR_INTERNAL 3131</pre> 3132An unexpected internal error has occurred. This error could be caused by a bug 3133in PCRE2 or by overwriting of the compiled pattern. 3134<pre> 3135 PCRE2_ERROR_JIT_STACKLIMIT 3136</pre> 3137This error is returned when a pattern that was successfully studied using JIT 3138is being matched, but the memory available for the just-in-time processing 3139stack is not large enough. See the 3140<a href="pcre2jit.html"><b>pcre2jit</b></a> 3141documentation for more details. 3142<pre> 3143 PCRE2_ERROR_MATCHLIMIT 3144</pre> 3145The backtracking match limit was reached. 3146<pre> 3147 PCRE2_ERROR_NOMEMORY 3148</pre> 3149If a pattern contains many nested backtracking points, heap memory is used to 3150remember them. This error is given when the memory allocation function (default 3151or custom) fails. Note that a different error, PCRE2_ERROR_HEAPLIMIT, is given 3152if the amount of memory needed exceeds the heap limit. PCRE2_ERROR_NOMEMORY is 3153also returned if PCRE2_COPY_MATCHED_SUBJECT is set and memory allocation fails. 3154<pre> 3155 PCRE2_ERROR_NULL 3156</pre> 3157Either the <i>code</i>, <i>subject</i>, or <i>match_data</i> argument was passed 3158as NULL. 3159<pre> 3160 PCRE2_ERROR_RECURSELOOP 3161</pre> 3162This error is returned when <b>pcre2_match()</b> detects a recursion loop within 3163the pattern. Specifically, it means that either the whole pattern or a 3164capture group has been called recursively for the second time at the same 3165position in the subject string. Some simple patterns that might do this are 3166detected and faulted at compile time, but more complicated cases, in particular 3167mutual recursions between two different groups, cannot be detected until 3168matching is attempted. 3169<a name="geterrormessage"></a></P> 3170<br><a name="SEC32" href="#TOC1">OBTAINING A TEXTUAL ERROR MESSAGE</a><br> 3171<P> 3172<b>int pcre2_get_error_message(int <i>errorcode</i>, PCRE2_UCHAR *<i>buffer</i>,</b> 3173<b> PCRE2_SIZE <i>bufflen</i>);</b> 3174</P> 3175<P> 3176A text message for an error code from any PCRE2 function (compile, match, or 3177auxiliary) can be obtained by calling <b>pcre2_get_error_message()</b>. The code 3178is passed as the first argument, with the remaining two arguments specifying a 3179code unit buffer and its length in code units, into which the text message is 3180placed. The message is returned in code units of the appropriate width for the 3181library that is being used. 3182</P> 3183<P> 3184The returned message is terminated with a trailing zero, and the function 3185returns the number of code units used, excluding the trailing zero. If the 3186error number is unknown, the negative error code PCRE2_ERROR_BADDATA is 3187returned. If the buffer is too small, the message is truncated (but still with 3188a trailing zero), and the negative error code PCRE2_ERROR_NOMEMORY is returned. 3189None of the messages are very long; a buffer size of 120 code units is ample. 3190<a name="extractbynumber"></a></P> 3191<br><a name="SEC33" href="#TOC1">EXTRACTING CAPTURED SUBSTRINGS BY NUMBER</a><br> 3192<P> 3193<b>int pcre2_substring_length_bynumber(pcre2_match_data *<i>match_data</i>,</b> 3194<b> uint32_t <i>number</i>, PCRE2_SIZE *<i>length</i>);</b> 3195<br> 3196<br> 3197<b>int pcre2_substring_copy_bynumber(pcre2_match_data *<i>match_data</i>,</b> 3198<b> uint32_t <i>number</i>, PCRE2_UCHAR *<i>buffer</i>,</b> 3199<b> PCRE2_SIZE *<i>bufflen</i>);</b> 3200<br> 3201<br> 3202<b>int pcre2_substring_get_bynumber(pcre2_match_data *<i>match_data</i>,</b> 3203<b> uint32_t <i>number</i>, PCRE2_UCHAR **<i>bufferptr</i>,</b> 3204<b> PCRE2_SIZE *<i>bufflen</i>);</b> 3205<br> 3206<br> 3207<b>void pcre2_substring_free(PCRE2_UCHAR *<i>buffer</i>);</b> 3208</P> 3209<P> 3210Captured substrings can be accessed directly by using the ovector as described 3211<a href="#matchedstrings">above.</a> 3212For convenience, auxiliary functions are provided for extracting captured 3213substrings as new, separate, zero-terminated strings. A substring that contains 3214a binary zero is correctly extracted and has a further zero added on the end, 3215but the result is not, of course, a C string. 3216</P> 3217<P> 3218The functions in this section identify substrings by number. The number zero 3219refers to the entire matched substring, with higher numbers referring to 3220substrings captured by parenthesized groups. After a partial match, only 3221substring zero is available. An attempt to extract any other substring gives 3222the error PCRE2_ERROR_PARTIAL. The next section describes similar functions for 3223extracting captured substrings by name. 3224</P> 3225<P> 3226If a pattern uses the \K escape sequence within a positive assertion, the 3227reported start of a successful match can be greater than the end of the match. 3228For example, if the pattern (?=ab\K) is matched against "ab", the start and 3229end offset values for the match are 2 and 0. In this situation, calling these 3230functions with a zero substring number extracts a zero-length empty string. 3231</P> 3232<P> 3233You can find the length in code units of a captured substring without 3234extracting it by calling <b>pcre2_substring_length_bynumber()</b>. The first 3235argument is a pointer to the match data block, the second is the group number, 3236and the third is a pointer to a variable into which the length is placed. If 3237you just want to know whether or not the substring has been captured, you can 3238pass the third argument as NULL. 3239</P> 3240<P> 3241The <b>pcre2_substring_copy_bynumber()</b> function copies a captured substring 3242into a supplied buffer, whereas <b>pcre2_substring_get_bynumber()</b> copies it 3243into new memory, obtained using the same memory allocation function that was 3244used for the match data block. The first two arguments of these functions are a 3245pointer to the match data block and a capture group number. 3246</P> 3247<P> 3248The final arguments of <b>pcre2_substring_copy_bynumber()</b> are a pointer to 3249the buffer and a pointer to a variable that contains its length in code units. 3250This is updated to contain the actual number of code units used for the 3251extracted substring, excluding the terminating zero. 3252</P> 3253<P> 3254For <b>pcre2_substring_get_bynumber()</b> the third and fourth arguments point 3255to variables that are updated with a pointer to the new memory and the number 3256of code units that comprise the substring, again excluding the terminating 3257zero. When the substring is no longer needed, the memory should be freed by 3258calling <b>pcre2_substring_free()</b>. 3259</P> 3260<P> 3261The return value from all these functions is zero for success, or a negative 3262error code. If the pattern match failed, the match failure code is returned. 3263If a substring number greater than zero is used after a partial match, 3264PCRE2_ERROR_PARTIAL is returned. Other possible error codes are: 3265<pre> 3266 PCRE2_ERROR_NOMEMORY 3267</pre> 3268The buffer was too small for <b>pcre2_substring_copy_bynumber()</b>, or the 3269attempt to get memory failed for <b>pcre2_substring_get_bynumber()</b>. 3270<pre> 3271 PCRE2_ERROR_NOSUBSTRING 3272</pre> 3273There is no substring with that number in the pattern, that is, the number is 3274greater than the number of capturing parentheses. 3275<pre> 3276 PCRE2_ERROR_UNAVAILABLE 3277</pre> 3278The substring number, though not greater than the number of captures in the 3279pattern, is greater than the number of slots in the ovector, so the substring 3280could not be captured. 3281<pre> 3282 PCRE2_ERROR_UNSET 3283</pre> 3284The substring did not participate in the match. For example, if the pattern is 3285(abc)|(def) and the subject is "def", and the ovector contains at least two 3286capturing slots, substring number 1 is unset. 3287</P> 3288<br><a name="SEC34" href="#TOC1">EXTRACTING A LIST OF ALL CAPTURED SUBSTRINGS</a><br> 3289<P> 3290<b>int pcre2_substring_list_get(pcre2_match_data *<i>match_data</i>,</b> 3291<b>" PCRE2_UCHAR ***<i>listptr</i>, PCRE2_SIZE **<i>lengthsptr</i>);</b> 3292<br> 3293<br> 3294<b>void pcre2_substring_list_free(PCRE2_SPTR *<i>list</i>);</b> 3295</P> 3296<P> 3297The <b>pcre2_substring_list_get()</b> function extracts all available substrings 3298and builds a list of pointers to them. It also (optionally) builds a second 3299list that contains their lengths (in code units), excluding a terminating zero 3300that is added to each of them. All this is done in a single block of memory 3301that is obtained using the same memory allocation function that was used to get 3302the match data block. 3303</P> 3304<P> 3305This function must be called only after a successful match. If called after a 3306partial match, the error code PCRE2_ERROR_PARTIAL is returned. 3307</P> 3308<P> 3309The address of the memory block is returned via <i>listptr</i>, which is also 3310the start of the list of string pointers. The end of the list is marked by a 3311NULL pointer. The address of the list of lengths is returned via 3312<i>lengthsptr</i>. If your strings do not contain binary zeros and you do not 3313therefore need the lengths, you may supply NULL as the <b>lengthsptr</b> 3314argument to disable the creation of a list of lengths. The yield of the 3315function is zero if all went well, or PCRE2_ERROR_NOMEMORY if the memory block 3316could not be obtained. When the list is no longer needed, it should be freed by 3317calling <b>pcre2_substring_list_free()</b>. 3318</P> 3319<P> 3320If this function encounters a substring that is unset, which can happen when 3321capture group number <i>n+1</i> matches some part of the subject, but group 3322<i>n</i> has not been used at all, it returns an empty string. This can be 3323distinguished from a genuine zero-length substring by inspecting the 3324appropriate offset in the ovector, which contain PCRE2_UNSET for unset 3325substrings, or by calling <b>pcre2_substring_length_bynumber()</b>. 3326<a name="extractbyname"></a></P> 3327<br><a name="SEC35" href="#TOC1">EXTRACTING CAPTURED SUBSTRINGS BY NAME</a><br> 3328<P> 3329<b>int pcre2_substring_number_from_name(const pcre2_code *<i>code</i>,</b> 3330<b> PCRE2_SPTR <i>name</i>);</b> 3331<br> 3332<br> 3333<b>int pcre2_substring_length_byname(pcre2_match_data *<i>match_data</i>,</b> 3334<b> PCRE2_SPTR <i>name</i>, PCRE2_SIZE *<i>length</i>);</b> 3335<br> 3336<br> 3337<b>int pcre2_substring_copy_byname(pcre2_match_data *<i>match_data</i>,</b> 3338<b> PCRE2_SPTR <i>name</i>, PCRE2_UCHAR *<i>buffer</i>, PCRE2_SIZE *<i>bufflen</i>);</b> 3339<br> 3340<br> 3341<b>int pcre2_substring_get_byname(pcre2_match_data *<i>match_data</i>,</b> 3342<b> PCRE2_SPTR <i>name</i>, PCRE2_UCHAR **<i>bufferptr</i>, PCRE2_SIZE *<i>bufflen</i>);</b> 3343<br> 3344<br> 3345<b>void pcre2_substring_free(PCRE2_UCHAR *<i>buffer</i>);</b> 3346</P> 3347<P> 3348To extract a substring by name, you first have to find associated number. 3349For example, for this pattern: 3350<pre> 3351 (a+)b(?<xxx>\d+)... 3352</pre> 3353the number of the capture group called "xxx" is 2. If the name is known to be 3354unique (PCRE2_DUPNAMES was not set), you can find the number from the name by 3355calling <b>pcre2_substring_number_from_name()</b>. The first argument is the 3356compiled pattern, and the second is the name. The yield of the function is the 3357group number, PCRE2_ERROR_NOSUBSTRING if there is no group with that name, or 3358PCRE2_ERROR_NOUNIQUESUBSTRING if there is more than one group with that name. 3359Given the number, you can extract the substring directly from the ovector, or 3360use one of the "bynumber" functions described above. 3361</P> 3362<P> 3363For convenience, there are also "byname" functions that correspond to the 3364"bynumber" functions, the only difference being that the second argument is a 3365name instead of a number. If PCRE2_DUPNAMES is set and there are duplicate 3366names, these functions scan all the groups with the given name, and return the 3367captured substring from the first named group that is set. 3368</P> 3369<P> 3370If there are no groups with the given name, PCRE2_ERROR_NOSUBSTRING is 3371returned. If all groups with the name have numbers that are greater than the 3372number of slots in the ovector, PCRE2_ERROR_UNAVAILABLE is returned. If there 3373is at least one group with a slot in the ovector, but no group is found to be 3374set, PCRE2_ERROR_UNSET is returned. 3375</P> 3376<P> 3377<b>Warning:</b> If the pattern uses the (?| feature to set up multiple 3378capture groups with the same number, as described in the 3379<a href="pcre2pattern.html#dupgroupnumber">section on duplicate group numbers</a> 3380in the 3381<a href="pcre2pattern.html"><b>pcre2pattern</b></a> 3382page, you cannot use names to distinguish the different capture groups, because 3383names are not included in the compiled code. The matching process uses only 3384numbers. For this reason, the use of different names for groups with the 3385same number causes an error at compile time. 3386<a name="substitutions"></a></P> 3387<br><a name="SEC36" href="#TOC1">CREATING A NEW STRING WITH SUBSTITUTIONS</a><br> 3388<P> 3389<b>int pcre2_substitute(const pcre2_code *<i>code</i>, PCRE2_SPTR <i>subject</i>,</b> 3390<b> PCRE2_SIZE <i>length</i>, PCRE2_SIZE <i>startoffset</i>,</b> 3391<b> uint32_t <i>options</i>, pcre2_match_data *<i>match_data</i>,</b> 3392<b> pcre2_match_context *<i>mcontext</i>, PCRE2_SPTR <i>replacement</i>,</b> 3393<b> PCRE2_SIZE <i>rlength</i>, PCRE2_UCHAR *<i>outputbuffer</i>,</b> 3394<b> PCRE2_SIZE *<i>outlengthptr</i>);</b> 3395</P> 3396<P> 3397This function optionally calls <b>pcre2_match()</b> and then makes a copy of the 3398subject string in <i>outputbuffer</i>, replacing parts that were matched with 3399the <i>replacement</i> string, whose length is supplied in <b>rlength</b>, which 3400can be given as PCRE2_ZERO_TERMINATED for a zero-terminated string. As a 3401special case, if <i>replacement</i> is NULL and <i>rlength</i> is zero, the 3402replacement is assumed to be an empty string. If <i>rlength</i> is non-zero, an 3403error occurs if <i>replacement</i> is NULL. 3404</P> 3405<P> 3406There is an option (see PCRE2_SUBSTITUTE_REPLACEMENT_ONLY below) to return just 3407the replacement string(s). The default action is to perform just one 3408replacement if the pattern matches, but there is an option that requests 3409multiple replacements (see PCRE2_SUBSTITUTE_GLOBAL below). 3410</P> 3411<P> 3412If successful, <b>pcre2_substitute()</b> returns the number of substitutions 3413that were carried out. This may be zero if no match was found, and is never 3414greater than one unless PCRE2_SUBSTITUTE_GLOBAL is set. A negative value is 3415returned if an error is detected. 3416</P> 3417<P> 3418Matches in which a \K item in a lookahead in the pattern causes the match to 3419end before it starts are not supported, and give rise to an error return. For 3420global replacements, matches in which \K in a lookbehind causes the match to 3421start earlier than the point that was reached in the previous iteration are 3422also not supported. 3423</P> 3424<P> 3425The first seven arguments of <b>pcre2_substitute()</b> are the same as for 3426<b>pcre2_match()</b>, except that the partial matching options are not 3427permitted, and <i>match_data</i> may be passed as NULL, in which case a match 3428data block is obtained and freed within this function, using memory management 3429functions from the match context, if provided, or else those that were used to 3430allocate memory for the compiled code. 3431</P> 3432<P> 3433If <i>match_data</i> is not NULL and PCRE2_SUBSTITUTE_MATCHED is not set, the 3434provided block is used for all calls to <b>pcre2_match()</b>, and its contents 3435afterwards are the result of the final call. For global changes, this will 3436always be a no-match error. The contents of the ovector within the match data 3437block may or may not have been changed. 3438</P> 3439<P> 3440As well as the usual options for <b>pcre2_match()</b>, a number of additional 3441options can be set in the <i>options</i> argument of <b>pcre2_substitute()</b>. 3442One such option is PCRE2_SUBSTITUTE_MATCHED. When this is set, an external 3443<i>match_data</i> block must be provided, and it must have already been used for 3444an external call to <b>pcre2_match()</b> with the same pattern and subject 3445arguments. The data in the <i>match_data</i> block (return code, offset vector) 3446is then used for the first substitution instead of calling <b>pcre2_match()</b> 3447from within <b>pcre2_substitute()</b>. This allows an application to check for a 3448match before choosing to substitute, without having to repeat the match. 3449</P> 3450<P> 3451The contents of the externally supplied match data block are not changed when 3452PCRE2_SUBSTITUTE_MATCHED is set. If PCRE2_SUBSTITUTE_GLOBAL is also set, 3453<b>pcre2_match()</b> is called after the first substitution to check for further 3454matches, but this is done using an internally obtained match data block, thus 3455always leaving the external block unchanged. 3456</P> 3457<P> 3458The <i>code</i> argument is not used for matching before the first substitution 3459when PCRE2_SUBSTITUTE_MATCHED is set, but it must be provided, even when 3460PCRE2_SUBSTITUTE_GLOBAL is not set, because it contains information such as the 3461UTF setting and the number of capturing parentheses in the pattern. 3462</P> 3463<P> 3464The default action of <b>pcre2_substitute()</b> is to return a copy of the 3465subject string with matched substrings replaced. However, if 3466PCRE2_SUBSTITUTE_REPLACEMENT_ONLY is set, only the replacement substrings are 3467returned. In the global case, multiple replacements are concatenated in the 3468output buffer. Substitution callouts (see 3469<a href="#subcallouts">below)</a> 3470can be used to separate them if necessary. 3471</P> 3472<P> 3473The <i>outlengthptr</i> argument of <b>pcre2_substitute()</b> must point to a 3474variable that contains the length, in code units, of the output buffer. If the 3475function is successful, the value is updated to contain the length in code 3476units of the new string, excluding the trailing zero that is automatically 3477added. 3478</P> 3479<P> 3480If the function is not successful, the value set via <i>outlengthptr</i> depends 3481on the type of error. For syntax errors in the replacement string, the value is 3482the offset in the replacement string where the error was detected. For other 3483errors, the value is PCRE2_UNSET by default. This includes the case of the 3484output buffer being too small, unless PCRE2_SUBSTITUTE_OVERFLOW_LENGTH is set. 3485</P> 3486<P> 3487PCRE2_SUBSTITUTE_OVERFLOW_LENGTH changes what happens when the output buffer is 3488too small. The default action is to return PCRE2_ERROR_NOMEMORY immediately. If 3489this option is set, however, <b>pcre2_substitute()</b> continues to go through 3490the motions of matching and substituting (without, of course, writing anything) 3491in order to compute the size of buffer that is needed. This value is passed 3492back via the <i>outlengthptr</i> variable, with the result of the function still 3493being PCRE2_ERROR_NOMEMORY. 3494</P> 3495<P> 3496Passing a buffer size of zero is a permitted way of finding out how much memory 3497is needed for given substitution. However, this does mean that the entire 3498operation is carried out twice. Depending on the application, it may be more 3499efficient to allocate a large buffer and free the excess afterwards, instead of 3500using PCRE2_SUBSTITUTE_OVERFLOW_LENGTH. 3501</P> 3502<P> 3503The replacement string, which is interpreted as a UTF string in UTF mode, is 3504checked for UTF validity unless PCRE2_NO_UTF_CHECK is set. An invalid UTF 3505replacement string causes an immediate return with the relevant UTF error code. 3506</P> 3507<P> 3508If PCRE2_SUBSTITUTE_LITERAL is set, the replacement string is not interpreted 3509in any way. By default, however, a dollar character is an escape character that 3510can specify the insertion of characters from capture groups and names from 3511(*MARK) or other control verbs in the pattern. The following forms are always 3512recognized: 3513<pre> 3514 $$ insert a dollar character 3515 $<n> or ${<n>} insert the contents of group <n> 3516 $*MARK or ${*MARK} insert a control verb name 3517</pre> 3518Either a group number or a group name can be given for <n>. Curly brackets are 3519required only if the following character would be interpreted as part of the 3520number or name. The number may be zero to include the entire matched string. 3521For example, if the pattern a(b)c is matched with "=abc=" and the replacement 3522string "+$1$0$1+", the result is "=+babcb+=". 3523</P> 3524<P> 3525$*MARK inserts the name from the last encountered backtracking control verb on 3526the matching path that has a name. (*MARK) must always include a name, but the 3527other verbs need not. For example, in the case of (*MARK:A)(*PRUNE) the name 3528inserted is "A", but for (*MARK:A)(*PRUNE:B) the relevant name is "B". This 3529facility can be used to perform simple simultaneous substitutions, as this 3530<b>pcre2test</b> example shows: 3531<pre> 3532 /(*MARK:pear)apple|(*MARK:orange)lemon/g,replace=${*MARK} 3533 apple lemon 3534 2: pear orange 3535</pre> 3536PCRE2_SUBSTITUTE_GLOBAL causes the function to iterate over the subject string, 3537replacing every matching substring. If this option is not set, only the first 3538matching substring is replaced. The search for matches takes place in the 3539original subject string (that is, previous replacements do not affect it). 3540Iteration is implemented by advancing the <i>startoffset</i> value for each 3541search, which is always passed the entire subject string. If an offset limit is 3542set in the match context, searching stops when that limit is reached. 3543</P> 3544<P> 3545You can restrict the effect of a global substitution to a portion of the 3546subject string by setting either or both of <i>startoffset</i> and an offset 3547limit. Here is a <b>pcre2test</b> example: 3548<pre> 3549 /B/g,replace=!,use_offset_limit 3550 ABC ABC ABC ABC\=offset=3,offset_limit=12 3551 2: ABC A!C A!C ABC 3552</pre> 3553When continuing with global substitutions after matching a substring with zero 3554length, an attempt to find a non-empty match at the same offset is performed. 3555If this is not successful, the offset is advanced by one character except when 3556CRLF is a valid newline sequence and the next two characters are CR, LF. In 3557this case, the offset is advanced by two characters. 3558</P> 3559<P> 3560PCRE2_SUBSTITUTE_UNKNOWN_UNSET causes references to capture groups that do 3561not appear in the pattern to be treated as unset groups. This option should be 3562used with care, because it means that a typo in a group name or number no 3563longer causes the PCRE2_ERROR_NOSUBSTRING error. 3564</P> 3565<P> 3566PCRE2_SUBSTITUTE_UNSET_EMPTY causes unset capture groups (including unknown 3567groups when PCRE2_SUBSTITUTE_UNKNOWN_UNSET is set) to be treated as empty 3568strings when inserted as described above. If this option is not set, an attempt 3569to insert an unset group causes the PCRE2_ERROR_UNSET error. This option does 3570not influence the extended substitution syntax described below. 3571</P> 3572<P> 3573PCRE2_SUBSTITUTE_EXTENDED causes extra processing to be applied to the 3574replacement string. Without this option, only the dollar character is special, 3575and only the group insertion forms listed above are valid. When 3576PCRE2_SUBSTITUTE_EXTENDED is set, two things change: 3577</P> 3578<P> 3579Firstly, backslash in a replacement string is interpreted as an escape 3580character. The usual forms such as \n or \x{ddd} can be used to specify 3581particular character codes, and backslash followed by any non-alphanumeric 3582character quotes that character. Extended quoting can be coded using \Q...\E, 3583exactly as in pattern strings. 3584</P> 3585<P> 3586There are also four escape sequences for forcing the case of inserted letters. 3587The insertion mechanism has three states: no case forcing, force upper case, 3588and force lower case. The escape sequences change the current state: \U and 3589\L change to upper or lower case forcing, respectively, and \E (when not 3590terminating a \Q quoted sequence) reverts to no case forcing. The sequences 3591\u and \l force the next character (if it is a letter) to upper or lower 3592case, respectively, and then the state automatically reverts to no case 3593forcing. Case forcing applies to all inserted characters, including those from 3594capture groups and letters within \Q...\E quoted sequences. If either 3595PCRE2_UTF or PCRE2_UCP was set when the pattern was compiled, Unicode 3596properties are used for case forcing characters whose code points are greater 3597than 127. 3598</P> 3599<P> 3600Note that case forcing sequences such as \U...\E do not nest. For example, 3601the result of processing "\Uaa\LBB\Ecc\E" is "AAbbcc"; the final \E has no 3602effect. Note also that the PCRE2_ALT_BSUX and PCRE2_EXTRA_ALT_BSUX options do 3603not apply to replacement strings. 3604</P> 3605<P> 3606The second effect of setting PCRE2_SUBSTITUTE_EXTENDED is to add more 3607flexibility to capture group substitution. The syntax is similar to that used 3608by Bash: 3609<pre> 3610 ${<n>:-<string>} 3611 ${<n>:+<string1>:<string2>} 3612</pre> 3613As before, <n> may be a group number or a name. The first form specifies a 3614default value. If group <n> is set, its value is inserted; if not, <string> is 3615expanded and the result inserted. The second form specifies strings that are 3616expanded and inserted when group <n> is set or unset, respectively. The first 3617form is just a convenient shorthand for 3618<pre> 3619 ${<n>:+${<n>}:<string>} 3620</pre> 3621Backslash can be used to escape colons and closing curly brackets in the 3622replacement strings. A change of the case forcing state within a replacement 3623string remains in force afterwards, as shown in this <b>pcre2test</b> example: 3624<pre> 3625 /(some)?(body)/substitute_extended,replace=${1:+\U:\L}HeLLo 3626 body 3627 1: hello 3628 somebody 3629 1: HELLO 3630</pre> 3631The PCRE2_SUBSTITUTE_UNSET_EMPTY option does not affect these extended 3632substitutions. However, PCRE2_SUBSTITUTE_UNKNOWN_UNSET does cause unknown 3633groups in the extended syntax forms to be treated as unset. 3634</P> 3635<P> 3636If PCRE2_SUBSTITUTE_LITERAL is set, PCRE2_SUBSTITUTE_UNKNOWN_UNSET, 3637PCRE2_SUBSTITUTE_UNSET_EMPTY, and PCRE2_SUBSTITUTE_EXTENDED are irrelevant and 3638are ignored. 3639</P> 3640<br><b> 3641Substitution errors 3642</b><br> 3643<P> 3644In the event of an error, <b>pcre2_substitute()</b> returns a negative error 3645code. Except for PCRE2_ERROR_NOMATCH (which is never returned), errors from 3646<b>pcre2_match()</b> are passed straight back. 3647</P> 3648<P> 3649PCRE2_ERROR_NOSUBSTRING is returned for a non-existent substring insertion, 3650unless PCRE2_SUBSTITUTE_UNKNOWN_UNSET is set. 3651</P> 3652<P> 3653PCRE2_ERROR_UNSET is returned for an unset substring insertion (including an 3654unknown substring when PCRE2_SUBSTITUTE_UNKNOWN_UNSET is set) when the simple 3655(non-extended) syntax is used and PCRE2_SUBSTITUTE_UNSET_EMPTY is not set. 3656</P> 3657<P> 3658PCRE2_ERROR_NOMEMORY is returned if the output buffer is not big enough. If the 3659PCRE2_SUBSTITUTE_OVERFLOW_LENGTH option is set, the size of buffer that is 3660needed is returned via <i>outlengthptr</i>. Note that this does not happen by 3661default. 3662</P> 3663<P> 3664PCRE2_ERROR_NULL is returned if PCRE2_SUBSTITUTE_MATCHED is set but the 3665<i>match_data</i> argument is NULL or if the <i>subject</i> or <i>replacement</i> 3666arguments are NULL. For backward compatibility reasons an exception is made for 3667the <i>replacement</i> argument if the <i>rlength</i> argument is also 0. 3668</P> 3669<P> 3670PCRE2_ERROR_BADREPLACEMENT is used for miscellaneous syntax errors in the 3671replacement string, with more particular errors being PCRE2_ERROR_BADREPESCAPE 3672(invalid escape sequence), PCRE2_ERROR_REPMISSINGBRACE (closing curly bracket 3673not found), PCRE2_ERROR_BADSUBSTITUTION (syntax error in extended group 3674substitution), and PCRE2_ERROR_BADSUBSPATTERN (the pattern match ended before 3675it started or the match started earlier than the current position in the 3676subject, which can happen if \K is used in an assertion). 3677</P> 3678<P> 3679As for all PCRE2 errors, a text message that describes the error can be 3680obtained by calling the <b>pcre2_get_error_message()</b> function (see 3681"Obtaining a textual error message" 3682<a href="#geterrormessage">above).</a> 3683<a name="subcallouts"></a></P> 3684<br><b> 3685Substitution callouts 3686</b><br> 3687<P> 3688<b>int pcre2_set_substitute_callout(pcre2_match_context *<i>mcontext</i>,</b> 3689<b> int (*<i>callout_function</i>)(pcre2_substitute_callout_block *, void *),</b> 3690<b> void *<i>callout_data</i>);</b> 3691<br> 3692<br> 3693The <b>pcre2_set_substitution_callout()</b> function can be used to specify a 3694callout function for <b>pcre2_substitute()</b>. This information is passed in 3695a match context. The callout function is called after each substitution has 3696been processed, but it can cause the replacement not to happen. The callout 3697function is not called for simulated substitutions that happen as a result of 3698the PCRE2_SUBSTITUTE_OVERFLOW_LENGTH option. 3699</P> 3700<P> 3701The first argument of the callout function is a pointer to a substitute callout 3702block structure, which contains the following fields, not necessarily in this 3703order: 3704<pre> 3705 uint32_t <i>version</i>; 3706 uint32_t <i>subscount</i>; 3707 PCRE2_SPTR <i>input</i>; 3708 PCRE2_SPTR <i>output</i>; 3709 PCRE2_SIZE <i>*ovector</i>; 3710 uint32_t <i>oveccount</i>; 3711 PCRE2_SIZE <i>output_offsets[2]</i>; 3712</pre> 3713The <i>version</i> field contains the version number of the block format. The 3714current version is 0. The version number will increase in future if more fields 3715are added, but the intention is never to remove any of the existing fields. 3716</P> 3717<P> 3718The <i>subscount</i> field is the number of the current match. It is 1 for the 3719first callout, 2 for the second, and so on. The <i>input</i> and <i>output</i> 3720pointers are copies of the values passed to <b>pcre2_substitute()</b>. 3721</P> 3722<P> 3723The <i>ovector</i> field points to the ovector, which contains the result of the 3724most recent match. The <i>oveccount</i> field contains the number of pairs that 3725are set in the ovector, and is always greater than zero. 3726</P> 3727<P> 3728The <i>output_offsets</i> vector contains the offsets of the replacement in the 3729output string. This has already been processed for dollar and (if requested) 3730backslash substitutions as described above. 3731</P> 3732<P> 3733The second argument of the callout function is the value passed as 3734<i>callout_data</i> when the function was registered. The value returned by the 3735callout function is interpreted as follows: 3736</P> 3737<P> 3738If the value is zero, the replacement is accepted, and, if 3739PCRE2_SUBSTITUTE_GLOBAL is set, processing continues with a search for the next 3740match. If the value is not zero, the current replacement is not accepted. If 3741the value is greater than zero, processing continues when 3742PCRE2_SUBSTITUTE_GLOBAL is set. Otherwise (the value is less than zero or 3743PCRE2_SUBSTITUTE_GLOBAL is not set), the the rest of the input is copied to the 3744output and the call to <b>pcre2_substitute()</b> exits, returning the number of 3745matches so far. 3746</P> 3747<br><a name="SEC37" href="#TOC1">DUPLICATE CAPTURE GROUP NAMES</a><br> 3748<P> 3749<b>int pcre2_substring_nametable_scan(const pcre2_code *<i>code</i>,</b> 3750<b> PCRE2_SPTR <i>name</i>, PCRE2_SPTR *<i>first</i>, PCRE2_SPTR *<i>last</i>);</b> 3751</P> 3752<P> 3753When a pattern is compiled with the PCRE2_DUPNAMES option, names for capture 3754groups are not required to be unique. Duplicate names are always allowed for 3755groups with the same number, created by using the (?| feature. Indeed, if such 3756groups are named, they are required to use the same names. 3757</P> 3758<P> 3759Normally, patterns that use duplicate names are such that in any one match, 3760only one of each set of identically-named groups participates. An example is 3761shown in the 3762<a href="pcre2pattern.html"><b>pcre2pattern</b></a> 3763documentation. 3764</P> 3765<P> 3766When duplicates are present, <b>pcre2_substring_copy_byname()</b> and 3767<b>pcre2_substring_get_byname()</b> return the first substring corresponding to 3768the given name that is set. Only if none are set is PCRE2_ERROR_UNSET is 3769returned. The <b>pcre2_substring_number_from_name()</b> function returns the 3770error PCRE2_ERROR_NOUNIQUESUBSTRING when there are duplicate names. 3771</P> 3772<P> 3773If you want to get full details of all captured substrings for a given name, 3774you must use the <b>pcre2_substring_nametable_scan()</b> function. The first 3775argument is the compiled pattern, and the second is the name. If the third and 3776fourth arguments are NULL, the function returns a group number for a unique 3777name, or PCRE2_ERROR_NOUNIQUESUBSTRING otherwise. 3778</P> 3779<P> 3780When the third and fourth arguments are not NULL, they must be pointers to 3781variables that are updated by the function. After it has run, they point to the 3782first and last entries in the name-to-number table for the given name, and the 3783function returns the length of each entry in code units. In both cases, 3784PCRE2_ERROR_NOSUBSTRING is returned if there are no entries for the given name. 3785</P> 3786<P> 3787The format of the name table is described 3788<a href="#infoaboutpattern">above</a> 3789in the section entitled <i>Information about a pattern</i>. Given all the 3790relevant entries for the name, you can extract each of their numbers, and hence 3791the captured data. 3792</P> 3793<br><a name="SEC38" href="#TOC1">FINDING ALL POSSIBLE MATCHES AT ONE POSITION</a><br> 3794<P> 3795The traditional matching function uses a similar algorithm to Perl, which stops 3796when it finds the first match at a given point in the subject. If you want to 3797find all possible matches, or the longest possible match at a given position, 3798consider using the alternative matching function (see below) instead. If you 3799cannot use the alternative function, you can kludge it up by making use of the 3800callout facility, which is described in the 3801<a href="pcre2callout.html"><b>pcre2callout</b></a> 3802documentation. 3803</P> 3804<P> 3805What you have to do is to insert a callout right at the end of the pattern. 3806When your callout function is called, extract and save the current matched 3807substring. Then return 1, which forces <b>pcre2_match()</b> to backtrack and try 3808other alternatives. Ultimately, when it runs out of matches, 3809<b>pcre2_match()</b> will yield PCRE2_ERROR_NOMATCH. 3810<a name="dfamatch"></a></P> 3811<br><a name="SEC39" href="#TOC1">MATCHING A PATTERN: THE ALTERNATIVE FUNCTION</a><br> 3812<P> 3813<b>int pcre2_dfa_match(const pcre2_code *<i>code</i>, PCRE2_SPTR <i>subject</i>,</b> 3814<b> PCRE2_SIZE <i>length</i>, PCRE2_SIZE <i>startoffset</i>,</b> 3815<b> uint32_t <i>options</i>, pcre2_match_data *<i>match_data</i>,</b> 3816<b> pcre2_match_context *<i>mcontext</i>,</b> 3817<b> int *<i>workspace</i>, PCRE2_SIZE <i>wscount</i>);</b> 3818</P> 3819<P> 3820The function <b>pcre2_dfa_match()</b> is called to match a subject string 3821against a compiled pattern, using a matching algorithm that scans the subject 3822string just once (not counting lookaround assertions), and does not backtrack 3823(except when processing lookaround assertions). This has different 3824characteristics to the normal algorithm, and is not compatible with Perl. Some 3825of the features of PCRE2 patterns are not supported. Nevertheless, there are 3826times when this kind of matching can be useful. For a discussion of the two 3827matching algorithms, and a list of features that <b>pcre2_dfa_match()</b> does 3828not support, see the 3829<a href="pcre2matching.html"><b>pcre2matching</b></a> 3830documentation. 3831</P> 3832<P> 3833The arguments for the <b>pcre2_dfa_match()</b> function are the same as for 3834<b>pcre2_match()</b>, plus two extras. The ovector within the match data block 3835is used in a different way, and this is described below. The other common 3836arguments are used in the same way as for <b>pcre2_match()</b>, so their 3837description is not repeated here. 3838</P> 3839<P> 3840The two additional arguments provide workspace for the function. The workspace 3841vector should contain at least 20 elements. It is used for keeping track of 3842multiple paths through the pattern tree. More workspace is needed for patterns 3843and subjects where there are a lot of potential matches. 3844</P> 3845<P> 3846Here is an example of a simple call to <b>pcre2_dfa_match()</b>: 3847<pre> 3848 int wspace[20]; 3849 pcre2_match_data *md = pcre2_match_data_create(4, NULL); 3850 int rc = pcre2_dfa_match( 3851 re, /* result of pcre2_compile() */ 3852 "some string", /* the subject string */ 3853 11, /* the length of the subject string */ 3854 0, /* start at offset 0 in the subject */ 3855 0, /* default options */ 3856 md, /* the match data block */ 3857 NULL, /* a match context; NULL means use defaults */ 3858 wspace, /* working space vector */ 3859 20); /* number of elements (NOT size in bytes) */ 3860</PRE> 3861</P> 3862<br><b> 3863Option bits for <b>pcre2_dfa_match()</b> 3864</b><br> 3865<P> 3866The unused bits of the <i>options</i> argument for <b>pcre2_dfa_match()</b> must 3867be zero. The only bits that may be set are PCRE2_ANCHORED, 3868PCRE2_COPY_MATCHED_SUBJECT, PCRE2_ENDANCHORED, PCRE2_NOTBOL, PCRE2_NOTEOL, 3869PCRE2_NOTEMPTY, PCRE2_NOTEMPTY_ATSTART, PCRE2_NO_UTF_CHECK, PCRE2_PARTIAL_HARD, 3870PCRE2_PARTIAL_SOFT, PCRE2_DFA_SHORTEST, and PCRE2_DFA_RESTART. All but the last 3871four of these are exactly the same as for <b>pcre2_match()</b>, so their 3872description is not repeated here. 3873<pre> 3874 PCRE2_PARTIAL_HARD 3875 PCRE2_PARTIAL_SOFT 3876</pre> 3877These have the same general effect as they do for <b>pcre2_match()</b>, but the 3878details are slightly different. When PCRE2_PARTIAL_HARD is set for 3879<b>pcre2_dfa_match()</b>, it returns PCRE2_ERROR_PARTIAL if the end of the 3880subject is reached and there is still at least one matching possibility that 3881requires additional characters. This happens even if some complete matches have 3882already been found. When PCRE2_PARTIAL_SOFT is set, the return code 3883PCRE2_ERROR_NOMATCH is converted into PCRE2_ERROR_PARTIAL if the end of the 3884subject is reached, there have been no complete matches, but there is still at 3885least one matching possibility. The portion of the string that was inspected 3886when the longest partial match was found is set as the first matching string in 3887both cases. There is a more detailed discussion of partial and multi-segment 3888matching, with examples, in the 3889<a href="pcre2partial.html"><b>pcre2partial</b></a> 3890documentation. 3891<pre> 3892 PCRE2_DFA_SHORTEST 3893</pre> 3894Setting the PCRE2_DFA_SHORTEST option causes the matching algorithm to stop as 3895soon as it has found one match. Because of the way the alternative algorithm 3896works, this is necessarily the shortest possible match at the first possible 3897matching point in the subject string. 3898<pre> 3899 PCRE2_DFA_RESTART 3900</pre> 3901When <b>pcre2_dfa_match()</b> returns a partial match, it is possible to call it 3902again, with additional subject characters, and have it continue with the same 3903match. The PCRE2_DFA_RESTART option requests this action; when it is set, the 3904<i>workspace</i> and <i>wscount</i> options must reference the same vector as 3905before because data about the match so far is left in them after a partial 3906match. There is more discussion of this facility in the 3907<a href="pcre2partial.html"><b>pcre2partial</b></a> 3908documentation. 3909</P> 3910<br><b> 3911Successful returns from <b>pcre2_dfa_match()</b> 3912</b><br> 3913<P> 3914When <b>pcre2_dfa_match()</b> succeeds, it may have matched more than one 3915substring in the subject. Note, however, that all the matches from one run of 3916the function start at the same point in the subject. The shorter matches are 3917all initial substrings of the longer matches. For example, if the pattern 3918<pre> 3919 <.*> 3920</pre> 3921is matched against the string 3922<pre> 3923 This is <something> <something else> <something further> no more 3924</pre> 3925the three matched strings are 3926<pre> 3927 <something> <something else> <something further> 3928 <something> <something else> 3929 <something> 3930</pre> 3931On success, the yield of the function is a number greater than zero, which is 3932the number of matched substrings. The offsets of the substrings are returned in 3933the ovector, and can be extracted by number in the same way as for 3934<b>pcre2_match()</b>, but the numbers bear no relation to any capture groups 3935that may exist in the pattern, because DFA matching does not support capturing. 3936</P> 3937<P> 3938Calls to the convenience functions that extract substrings by name 3939return the error PCRE2_ERROR_DFA_UFUNC (unsupported function) if used after a 3940DFA match. The convenience functions that extract substrings by number never 3941return PCRE2_ERROR_NOSUBSTRING. 3942</P> 3943<P> 3944The matched strings are stored in the ovector in reverse order of length; that 3945is, the longest matching string is first. If there were too many matches to fit 3946into the ovector, the yield of the function is zero, and the vector is filled 3947with the longest matches. 3948</P> 3949<P> 3950NOTE: PCRE2's "auto-possessification" optimization usually applies to character 3951repeats at the end of a pattern (as well as internally). For example, the 3952pattern "a\d+" is compiled as if it were "a\d++". For DFA matching, this 3953means that only one possible match is found. If you really do want multiple 3954matches in such cases, either use an ungreedy repeat such as "a\d+?" or set 3955the PCRE2_NO_AUTO_POSSESS option when compiling. 3956</P> 3957<br><b> 3958Error returns from <b>pcre2_dfa_match()</b> 3959</b><br> 3960<P> 3961The <b>pcre2_dfa_match()</b> function returns a negative number when it fails. 3962Many of the errors are the same as for <b>pcre2_match()</b>, as described 3963<a href="#errorlist">above.</a> 3964There are in addition the following errors that are specific to 3965<b>pcre2_dfa_match()</b>: 3966<pre> 3967 PCRE2_ERROR_DFA_UITEM 3968</pre> 3969This return is given if <b>pcre2_dfa_match()</b> encounters an item in the 3970pattern that it does not support, for instance, the use of \C in a UTF mode or 3971a backreference. 3972<pre> 3973 PCRE2_ERROR_DFA_UCOND 3974</pre> 3975This return is given if <b>pcre2_dfa_match()</b> encounters a condition item 3976that uses a backreference for the condition, or a test for recursion in a 3977specific capture group. These are not supported. 3978<pre> 3979 PCRE2_ERROR_DFA_UINVALID_UTF 3980</pre> 3981This return is given if <b>pcre2_dfa_match()</b> is called for a pattern that 3982was compiled with PCRE2_MATCH_INVALID_UTF. This is not supported for DFA 3983matching. 3984<pre> 3985 PCRE2_ERROR_DFA_WSSIZE 3986</pre> 3987This return is given if <b>pcre2_dfa_match()</b> runs out of space in the 3988<i>workspace</i> vector. 3989<pre> 3990 PCRE2_ERROR_DFA_RECURSE 3991</pre> 3992When a recursion or subroutine call is processed, the matching function calls 3993itself recursively, using private memory for the ovector and <i>workspace</i>. 3994This error is given if the internal ovector is not large enough. This should be 3995extremely rare, as a vector of size 1000 is used. 3996<pre> 3997 PCRE2_ERROR_DFA_BADRESTART 3998</pre> 3999When <b>pcre2_dfa_match()</b> is called with the <b>PCRE2_DFA_RESTART</b> option, 4000some plausibility checks are made on the contents of the workspace, which 4001should contain data about the previous partial match. If any of these checks 4002fail, this error is given. 4003</P> 4004<br><a name="SEC40" href="#TOC1">SEE ALSO</a><br> 4005<P> 4006<b>pcre2build</b>(3), <b>pcre2callout</b>(3), <b>pcre2demo(3)</b>, 4007<b>pcre2matching</b>(3), <b>pcre2partial</b>(3), <b>pcre2posix</b>(3), 4008<b>pcre2sample</b>(3), <b>pcre2unicode</b>(3). 4009</P> 4010<br><a name="SEC41" href="#TOC1">AUTHOR</a><br> 4011<P> 4012Philip Hazel 4013<br> 4014Retired from University Computing Service 4015<br> 4016Cambridge, England. 4017<br> 4018</P> 4019<br><a name="SEC42" href="#TOC1">REVISION</a><br> 4020<P> 4021Last updated: 14 December 2021 4022<br> 4023Copyright © 1997-2021 University of Cambridge. 4024<br> 4025<p> 4026Return to the <a href="index.html">PCRE2 index page</a>. 4027</p> 4028