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 1020unlimited. 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 always needs some heap memory, so setting a 1034value of zero guarantees a "heap limit exceeded" error. Details of how 1035<b>pcre2_match()</b> uses the heap are given in the 1036<a href="pcre2perform.html"><b>pcre2perform</b></a> 1037documentation. 1038</P> 1039<P> 1040For <b>pcre2_dfa_match()</b>, a vector on the system stack is used when 1041processing pattern recursions, lookarounds, or atomic groups, and only if this 1042is not big enough is heap memory used. In this case, setting a value of zero 1043disables the use of the heap. 1044<br> 1045<br> 1046<b>int pcre2_set_match_limit(pcre2_match_context *<i>mcontext</i>,</b> 1047<b> uint32_t <i>value</i>);</b> 1048<br> 1049<br> 1050The <i>match_limit</i> parameter provides a means of preventing PCRE2 from using 1051up too many computing resources when processing patterns that are not going to 1052match, but which have a very large number of possibilities in their search 1053trees. The classic example is a pattern that uses nested unlimited repeats. 1054</P> 1055<P> 1056There is an internal counter in <b>pcre2_match()</b> that is incremented each 1057time round its main matching loop. If this value reaches the match limit, 1058<b>pcre2_match()</b> returns the negative value PCRE2_ERROR_MATCHLIMIT. This has 1059the effect of limiting the amount of backtracking that can take place. For 1060patterns that are not anchored, the count restarts from zero for each position 1061in the subject string. This limit also applies to <b>pcre2_dfa_match()</b>, 1062though the counting is done in a different way. 1063</P> 1064<P> 1065When <b>pcre2_match()</b> is called with a pattern that was successfully 1066processed by <b>pcre2_jit_compile()</b>, the way in which matching is executed 1067is entirely different. However, there is still the possibility of runaway 1068matching that goes on for a very long time, and so the <i>match_limit</i> value 1069is also used in this case (but in a different way) to limit how long the 1070matching can continue. 1071</P> 1072<P> 1073The default value for the limit can be set when PCRE2 is built; the default 1074default is 10 million, which handles all but the most extreme cases. A value 1075for the match limit may also be supplied by an item at the start of a pattern 1076of the form 1077<pre> 1078 (*LIMIT_MATCH=ddd) 1079</pre> 1080where ddd is a decimal number. However, such a setting is ignored unless ddd is 1081less than the limit set by the caller of <b>pcre2_match()</b> or 1082<b>pcre2_dfa_match()</b> or, if no such limit is set, less than the default. 1083<br> 1084<br> 1085<b>int pcre2_set_depth_limit(pcre2_match_context *<i>mcontext</i>,</b> 1086<b> uint32_t <i>value</i>);</b> 1087<br> 1088<br> 1089This parameter limits the depth of nested backtracking in <b>pcre2_match()</b>. 1090Each time a nested backtracking point is passed, a new memory frame is used 1091to remember the state of matching at that point. Thus, this parameter 1092indirectly limits the amount of memory that is used in a match. However, 1093because the size of each memory frame depends on the number of capturing 1094parentheses, the actual memory limit varies from pattern to pattern. This limit 1095was more useful in versions before 10.30, where function recursion was used for 1096backtracking. 1097</P> 1098<P> 1099The depth limit is not relevant, and is ignored, when matching is done using 1100JIT compiled code. However, it is supported by <b>pcre2_dfa_match()</b>, which 1101uses it to limit the depth of nested internal recursive function calls that 1102implement atomic groups, lookaround assertions, and pattern recursions. This 1103limits, indirectly, the amount of system stack that is used. It was more useful 1104in versions before 10.32, when stack memory was used for local workspace 1105vectors for recursive function calls. From version 10.32, only local variables 1106are allocated on the stack and as each call uses only a few hundred bytes, even 1107a small stack can support quite a lot of recursion. 1108</P> 1109<P> 1110If the depth of internal recursive function calls is great enough, local 1111workspace vectors are allocated on the heap from version 10.32 onwards, so the 1112depth limit also indirectly limits the amount of heap memory that is used. A 1113recursive pattern such as /(.(?2))((?1)|)/, when matched to a very long string 1114using <b>pcre2_dfa_match()</b>, can use a great deal of memory. However, it is 1115probably better to limit heap usage directly by calling 1116<b>pcre2_set_heap_limit()</b>. 1117</P> 1118<P> 1119The default value for the depth limit can be set when PCRE2 is built; if it is 1120not, the default is set to the same value as the default for the match limit. 1121If the limit is exceeded, <b>pcre2_match()</b> or <b>pcre2_dfa_match()</b> 1122returns PCRE2_ERROR_DEPTHLIMIT. A value for the depth limit may also be 1123supplied by an item at the start of a pattern of the form 1124<pre> 1125 (*LIMIT_DEPTH=ddd) 1126</pre> 1127where ddd is a decimal number. However, such a setting is ignored unless ddd is 1128less than the limit set by the caller of <b>pcre2_match()</b> or 1129<b>pcre2_dfa_match()</b> or, if no such limit is set, less than the default. 1130</P> 1131<br><a name="SEC19" href="#TOC1">CHECKING BUILD-TIME OPTIONS</a><br> 1132<P> 1133<b>int pcre2_config(uint32_t <i>what</i>, void *<i>where</i>);</b> 1134</P> 1135<P> 1136The function <b>pcre2_config()</b> makes it possible for a PCRE2 client to find 1137the value of certain configuration parameters and to discover which optional 1138features have been compiled into the PCRE2 library. The 1139<a href="pcre2build.html"><b>pcre2build</b></a> 1140documentation has more details about these features. 1141</P> 1142<P> 1143The first argument for <b>pcre2_config()</b> specifies which information is 1144required. The second argument is a pointer to memory into which the information 1145is placed. If NULL is passed, the function returns the amount of memory that is 1146needed for the requested information. For calls that return numerical values, 1147the value is in bytes; when requesting these values, <i>where</i> should point 1148to appropriately aligned memory. For calls that return strings, the required 1149length is given in code units, not counting the terminating zero. 1150</P> 1151<P> 1152When requesting information, the returned value from <b>pcre2_config()</b> is 1153non-negative on success, or the negative error code PCRE2_ERROR_BADOPTION if 1154the value in the first argument is not recognized. The following information is 1155available: 1156<pre> 1157 PCRE2_CONFIG_BSR 1158</pre> 1159The output is a uint32_t integer whose value indicates what character 1160sequences the \R escape sequence matches by default. A value of 1161PCRE2_BSR_UNICODE means that \R matches any Unicode line ending sequence; a 1162value of PCRE2_BSR_ANYCRLF means that \R matches only CR, LF, or CRLF. The 1163default can be overridden when a pattern is compiled. 1164<pre> 1165 PCRE2_CONFIG_COMPILED_WIDTHS 1166</pre> 1167The output is a uint32_t integer whose lower bits indicate which code unit 1168widths were selected when PCRE2 was built. The 1-bit indicates 8-bit support, 1169and the 2-bit and 4-bit indicate 16-bit and 32-bit support, respectively. 1170<pre> 1171 PCRE2_CONFIG_DEPTHLIMIT 1172</pre> 1173The output is a uint32_t integer that gives the default limit for the depth of 1174nested backtracking in <b>pcre2_match()</b> or the depth of nested recursions, 1175lookarounds, and atomic groups in <b>pcre2_dfa_match()</b>. Further details are 1176given with <b>pcre2_set_depth_limit()</b> above. 1177<pre> 1178 PCRE2_CONFIG_HEAPLIMIT 1179</pre> 1180The output is a uint32_t integer that gives, in kibibytes, the default limit 1181for the amount of heap memory used by <b>pcre2_match()</b> or 1182<b>pcre2_dfa_match()</b>. Further details are given with 1183<b>pcre2_set_heap_limit()</b> above. 1184<pre> 1185 PCRE2_CONFIG_JIT 1186</pre> 1187The output is a uint32_t integer that is set to one if support for just-in-time 1188compiling is available; otherwise it is set to zero. 1189<pre> 1190 PCRE2_CONFIG_JITTARGET 1191</pre> 1192The <i>where</i> argument should point to a buffer that is at least 48 code 1193units long. (The exact length required can be found by calling 1194<b>pcre2_config()</b> with <b>where</b> set to NULL.) The buffer is filled with a 1195string that contains the name of the architecture for which the JIT compiler is 1196configured, for example "x86 32bit (little endian + unaligned)". If JIT support 1197is not available, PCRE2_ERROR_BADOPTION is returned, otherwise the number of 1198code units used is returned. This is the length of the string, plus one unit 1199for the terminating zero. 1200<pre> 1201 PCRE2_CONFIG_LINKSIZE 1202</pre> 1203The output is a uint32_t integer that contains the number of bytes used for 1204internal linkage in compiled regular expressions. When PCRE2 is configured, the 1205value can be set to 2, 3, or 4, with the default being 2. This is the value 1206that is returned by <b>pcre2_config()</b>. However, when the 16-bit library is 1207compiled, a value of 3 is rounded up to 4, and when the 32-bit library is 1208compiled, internal linkages always use 4 bytes, so the configured value is not 1209relevant. 1210</P> 1211<P> 1212The default value of 2 for the 8-bit and 16-bit libraries is sufficient for all 1213but the most massive patterns, since it allows the size of the compiled pattern 1214to be up to 65535 code units. Larger values allow larger regular expressions to 1215be compiled by those two libraries, but at the expense of slower matching. 1216<pre> 1217 PCRE2_CONFIG_MATCHLIMIT 1218</pre> 1219The output is a uint32_t integer that gives the default match limit for 1220<b>pcre2_match()</b>. Further details are given with 1221<b>pcre2_set_match_limit()</b> above. 1222<pre> 1223 PCRE2_CONFIG_NEWLINE 1224</pre> 1225The output is a uint32_t integer whose value specifies the default character 1226sequence that is recognized as meaning "newline". The values are: 1227<pre> 1228 PCRE2_NEWLINE_CR Carriage return (CR) 1229 PCRE2_NEWLINE_LF Linefeed (LF) 1230 PCRE2_NEWLINE_CRLF Carriage return, linefeed (CRLF) 1231 PCRE2_NEWLINE_ANY Any Unicode line ending 1232 PCRE2_NEWLINE_ANYCRLF Any of CR, LF, or CRLF 1233 PCRE2_NEWLINE_NUL The NUL character (binary zero) 1234</pre> 1235The default should normally correspond to the standard sequence for your 1236operating system. 1237<pre> 1238 PCRE2_CONFIG_NEVER_BACKSLASH_C 1239</pre> 1240The output is a uint32_t integer that is set to one if the use of \C was 1241permanently disabled when PCRE2 was built; otherwise it is set to zero. 1242<pre> 1243 PCRE2_CONFIG_PARENSLIMIT 1244</pre> 1245The output is a uint32_t integer that gives the maximum depth of nesting 1246of parentheses (of any kind) in a pattern. This limit is imposed to cap the 1247amount of system stack used when a pattern is compiled. It is specified when 1248PCRE2 is built; the default is 250. This limit does not take into account the 1249stack that may already be used by the calling application. For finer control 1250over compilation stack usage, see <b>pcre2_set_compile_recursion_guard()</b>. 1251<pre> 1252 PCRE2_CONFIG_STACKRECURSE 1253</pre> 1254This parameter is obsolete and should not be used in new code. The output is a 1255uint32_t integer that is always set to zero. 1256<pre> 1257 PCRE2_CONFIG_TABLES_LENGTH 1258</pre> 1259The output is a uint32_t integer that gives the length of PCRE2's character 1260processing tables in bytes. For details of these tables see the 1261<a href="#localesupport">section on locale support</a> 1262below. 1263<pre> 1264 PCRE2_CONFIG_UNICODE_VERSION 1265</pre> 1266The <i>where</i> argument should point to a buffer that is at least 24 code 1267units long. (The exact length required can be found by calling 1268<b>pcre2_config()</b> with <b>where</b> set to NULL.) If PCRE2 has been compiled 1269without Unicode support, the buffer is filled with the text "Unicode not 1270supported". Otherwise, the Unicode version string (for example, "8.0.0") is 1271inserted. The number of code units used is returned. This is the length of the 1272string plus one unit for the terminating zero. 1273<pre> 1274 PCRE2_CONFIG_UNICODE 1275</pre> 1276The output is a uint32_t integer that is set to one if Unicode support is 1277available; otherwise it is set to zero. Unicode support implies UTF support. 1278<pre> 1279 PCRE2_CONFIG_VERSION 1280</pre> 1281The <i>where</i> argument should point to a buffer that is at least 24 code 1282units long. (The exact length required can be found by calling 1283<b>pcre2_config()</b> with <b>where</b> set to NULL.) The buffer is filled with 1284the PCRE2 version string, zero-terminated. The number of code units used is 1285returned. This is the length of the string plus one unit for the terminating 1286zero. 1287<a name="compiling"></a></P> 1288<br><a name="SEC20" href="#TOC1">COMPILING A PATTERN</a><br> 1289<P> 1290<b>pcre2_code *pcre2_compile(PCRE2_SPTR <i>pattern</i>, PCRE2_SIZE <i>length</i>,</b> 1291<b> uint32_t <i>options</i>, int *<i>errorcode</i>, PCRE2_SIZE *<i>erroroffset,</i></b> 1292<b> pcre2_compile_context *<i>ccontext</i>);</b> 1293<br> 1294<br> 1295<b>void pcre2_code_free(pcre2_code *<i>code</i>);</b> 1296<br> 1297<br> 1298<b>pcre2_code *pcre2_code_copy(const pcre2_code *<i>code</i>);</b> 1299<br> 1300<br> 1301<b>pcre2_code *pcre2_code_copy_with_tables(const pcre2_code *<i>code</i>);</b> 1302</P> 1303<P> 1304The <b>pcre2_compile()</b> function compiles a pattern into an internal form. 1305The pattern is defined by a pointer to a string of code units and a length (in 1306code units). If the pattern is zero-terminated, the length can be specified as 1307PCRE2_ZERO_TERMINATED. The function returns a pointer to a block of memory that 1308contains the compiled pattern and related data, or NULL if an error occurred. 1309</P> 1310<P> 1311If the compile context argument <i>ccontext</i> is NULL, memory for the compiled 1312pattern is obtained by calling <b>malloc()</b>. Otherwise, it is obtained from 1313the same memory function that was used for the compile context. The caller must 1314free the memory by calling <b>pcre2_code_free()</b> when it is no longer needed. 1315If <b>pcre2_code_free()</b> is called with a NULL argument, it returns 1316immediately, without doing anything. 1317</P> 1318<P> 1319The function <b>pcre2_code_copy()</b> makes a copy of the compiled code in new 1320memory, using the same memory allocator as was used for the original. However, 1321if the code has been processed by the JIT compiler (see 1322<a href="#jitcompiling">below),</a> 1323the JIT information cannot be copied (because it is position-dependent). 1324The new copy can initially be used only for non-JIT matching, though it can be 1325passed to <b>pcre2_jit_compile()</b> if required. If <b>pcre2_code_copy()</b> is 1326called with a NULL argument, it returns NULL. 1327</P> 1328<P> 1329The <b>pcre2_code_copy()</b> function provides a way for individual threads in a 1330multithreaded application to acquire a private copy of shared compiled code. 1331However, it does not make a copy of the character tables used by the compiled 1332pattern; the new pattern code points to the same tables as the original code. 1333(See 1334<a href="#jitcompiling">"Locale Support"</a> 1335below for details of these character tables.) In many applications the same 1336tables are used throughout, so this behaviour is appropriate. Nevertheless, 1337there are occasions when a copy of a compiled pattern and the relevant tables 1338are needed. The <b>pcre2_code_copy_with_tables()</b> provides this facility. 1339Copies of both the code and the tables are made, with the new code pointing to 1340the new tables. The memory for the new tables is automatically freed when 1341<b>pcre2_code_free()</b> is called for the new copy of the compiled code. If 1342<b>pcre2_code_copy_with_tables()</b> is called with a NULL argument, it returns 1343NULL. 1344</P> 1345<P> 1346NOTE: When one of the matching functions is called, pointers to the compiled 1347pattern and the subject string are set in the match data block so that they can 1348be referenced by the substring extraction functions after a successful match. 1349After running a match, you must not free a compiled pattern or a subject string 1350until after all operations on the 1351<a href="#matchdatablock">match data block</a> 1352have taken place, unless, in the case of the subject string, you have used the 1353PCRE2_COPY_MATCHED_SUBJECT option, which is described in the section entitled 1354"Option bits for <b>pcre2_match()</b>" 1355<a href="#matchoptions>">below.</a> 1356</P> 1357<P> 1358The <i>options</i> argument for <b>pcre2_compile()</b> contains various bit 1359settings that affect the compilation. It should be zero if none of them are 1360required. The available options are described below. Some of them (in 1361particular, those that are compatible with Perl, but some others as well) can 1362also be set and unset from within the pattern (see the detailed description in 1363the 1364<a href="pcre2pattern.html"><b>pcre2pattern</b></a> 1365documentation). 1366</P> 1367<P> 1368For those options that can be different in different parts of the pattern, the 1369contents of the <i>options</i> argument specifies their settings at the start of 1370compilation. The PCRE2_ANCHORED, PCRE2_ENDANCHORED, and PCRE2_NO_UTF_CHECK 1371options can be set at the time of matching as well as at compile time. 1372</P> 1373<P> 1374Some additional options and less frequently required compile-time parameters 1375(for example, the newline setting) can be provided in a compile context (as 1376described 1377<a href="#compilecontext">above).</a> 1378</P> 1379<P> 1380If <i>errorcode</i> or <i>erroroffset</i> is NULL, <b>pcre2_compile()</b> returns 1381NULL immediately. Otherwise, the variables to which these point are set to an 1382error code and an offset (number of code units) within the pattern, 1383respectively, when <b>pcre2_compile()</b> returns NULL because a compilation 1384error has occurred. 1385</P> 1386<P> 1387There are nearly 100 positive error codes that <b>pcre2_compile()</b> may return 1388if it finds an error in the pattern. There are also some negative error codes 1389that are used for invalid UTF strings when validity checking is in force. These 1390are the same as given by <b>pcre2_match()</b> and <b>pcre2_dfa_match()</b>, and 1391are described in the 1392<a href="pcre2unicode.html"><b>pcre2unicode</b></a> 1393documentation. There is no separate documentation for the positive error codes, 1394because the textual error messages that are obtained by calling the 1395<b>pcre2_get_error_message()</b> function (see "Obtaining a textual error 1396message" 1397<a href="#geterrormessage">below)</a> 1398should be self-explanatory. Macro names starting with PCRE2_ERROR_ are defined 1399for both positive and negative error codes in <b>pcre2.h</b>. When compilation 1400is successful <i>errorcode</i> is set to a value that returns the message "no 1401error" if passed to <b>pcre2_get_error_message()</b>. 1402</P> 1403<P> 1404The value returned in <i>erroroffset</i> is an indication of where in the 1405pattern an error occurred. When there is no error, zero is returned. A non-zero 1406value is not necessarily the furthest point in the pattern that was read. For 1407example, after the error "lookbehind assertion is not fixed length", the error 1408offset points to the start of the failing assertion. For an invalid UTF-8 or 1409UTF-16 string, the offset is that of the first code unit of the failing 1410character. 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>. The maximum number of pairs is 65535; if the the first 2547argument of <b>pcre2_match_data_create()</b> is greater than this, 65535 is 2548used. 2549</P> 2550<P> 2551The second argument of <b>pcre2_match_data_create()</b> is a pointer to a 2552general context, which can specify custom memory management for obtaining the 2553memory for the match data block. If you are not using custom memory management, 2554pass NULL, which causes <b>malloc()</b> to be used. 2555</P> 2556<P> 2557For <b>pcre2_match_data_create_from_pattern()</b>, the first argument is a 2558pointer to a compiled pattern. The ovector is created to be exactly the right 2559size to hold all the substrings a pattern might capture when matched using 2560<b>pcre2_match()</b>. You should not use this call when matching with 2561<b>pcre2_dfa_match()</b>. The second argument is again a pointer to a general 2562context, but in this case if NULL is passed, the memory is obtained using the 2563same allocator that was used for the compiled pattern (custom or default). 2564</P> 2565<P> 2566A match data block can be used many times, with the same or different compiled 2567patterns. You can extract information from a match data block after a match 2568operation has finished, using functions that are described in the sections on 2569<a href="#matchedstrings">matched strings</a> 2570and 2571<a href="#matchotherdata">other match data</a> 2572below. 2573</P> 2574<P> 2575When a call of <b>pcre2_match()</b> fails, valid data is available in the match 2576block only when the error is PCRE2_ERROR_NOMATCH, PCRE2_ERROR_PARTIAL, or one 2577of the error codes for an invalid UTF string. Exactly what is available depends 2578on the error, and is detailed below. 2579</P> 2580<P> 2581When one of the matching functions is called, pointers to the compiled pattern 2582and the subject string are set in the match data block so that they can be 2583referenced by the extraction functions after a successful match. After running 2584a match, you must not free a compiled pattern or a subject string until after 2585all operations on the match data block (for that match) have taken place, 2586unless, in the case of the subject string, you have used the 2587PCRE2_COPY_MATCHED_SUBJECT option, which is described in the section entitled 2588"Option bits for <b>pcre2_match()</b>" 2589<a href="#matchoptions>">below.</a> 2590</P> 2591<P> 2592When a match data block itself is no longer needed, it should be freed by 2593calling <b>pcre2_match_data_free()</b>. If this function is called with a NULL 2594argument, it returns immediately, without doing anything. 2595</P> 2596<br><a name="SEC27" href="#TOC1">MATCHING A PATTERN: THE TRADITIONAL FUNCTION</a><br> 2597<P> 2598<b>int pcre2_match(const pcre2_code *<i>code</i>, PCRE2_SPTR <i>subject</i>,</b> 2599<b> PCRE2_SIZE <i>length</i>, PCRE2_SIZE <i>startoffset</i>,</b> 2600<b> uint32_t <i>options</i>, pcre2_match_data *<i>match_data</i>,</b> 2601<b> pcre2_match_context *<i>mcontext</i>);</b> 2602</P> 2603<P> 2604The function <b>pcre2_match()</b> is called to match a subject string against a 2605compiled pattern, which is passed in the <i>code</i> argument. You can call 2606<b>pcre2_match()</b> with the same <i>code</i> argument as many times as you 2607like, in order to find multiple matches in the subject string or to match 2608different subject strings with the same pattern. 2609</P> 2610<P> 2611This function is the main matching facility of the library, and it operates in 2612a Perl-like manner. For specialist use there is also an alternative matching 2613function, which is described 2614<a href="#dfamatch">below</a> 2615in the section about the <b>pcre2_dfa_match()</b> function. 2616</P> 2617<P> 2618Here is an example of a simple call to <b>pcre2_match()</b>: 2619<pre> 2620 pcre2_match_data *md = pcre2_match_data_create(4, NULL); 2621 int rc = pcre2_match( 2622 re, /* result of pcre2_compile() */ 2623 "some string", /* the subject string */ 2624 11, /* the length of the subject string */ 2625 0, /* start at offset 0 in the subject */ 2626 0, /* default options */ 2627 md, /* the match data block */ 2628 NULL); /* a match context; NULL means use defaults */ 2629</pre> 2630If the subject string is zero-terminated, the length can be given as 2631PCRE2_ZERO_TERMINATED. A match context must be provided if certain less common 2632matching parameters are to be changed. For details, see the section on 2633<a href="#matchcontext">the match context</a> 2634above. 2635</P> 2636<br><b> 2637The string to be matched by <b>pcre2_match()</b> 2638</b><br> 2639<P> 2640The subject string is passed to <b>pcre2_match()</b> as a pointer in 2641<i>subject</i>, a length in <i>length</i>, and a starting offset in 2642<i>startoffset</i>. The length and offset are in code units, not characters. 2643That is, they are in bytes for the 8-bit library, 16-bit code units for the 264416-bit library, and 32-bit code units for the 32-bit library, whether or not 2645UTF processing is enabled. As a special case, if <i>subject</i> is NULL and 2646<i>length</i> is zero, the subject is assumed to be an empty string. If 2647<i>length</i> is non-zero, an error occurs if <i>subject</i> is NULL. 2648</P> 2649<P> 2650If <i>startoffset</i> is greater than the length of the subject, 2651<b>pcre2_match()</b> returns PCRE2_ERROR_BADOFFSET. When the starting offset is 2652zero, the search for a match starts at the beginning of the subject, and this 2653is by far the most common case. In UTF-8 or UTF-16 mode, the starting offset 2654must point to the start of a character, or to the end of the subject (in UTF-32 2655mode, one code unit equals one character, so all offsets are valid). Like the 2656pattern string, the subject may contain binary zeros. 2657</P> 2658<P> 2659A non-zero starting offset is useful when searching for another match in the 2660same subject by calling <b>pcre2_match()</b> again after a previous success. 2661Setting <i>startoffset</i> differs from passing over a shortened string and 2662setting PCRE2_NOTBOL in the case of a pattern that begins with any kind of 2663lookbehind. For example, consider the pattern 2664<pre> 2665 \Biss\B 2666</pre> 2667which finds occurrences of "iss" in the middle of words. (\B matches only if 2668the current position in the subject is not a word boundary.) When applied to 2669the string "Mississippi" the first call to <b>pcre2_match()</b> finds the first 2670occurrence. If <b>pcre2_match()</b> is called again with just the remainder of 2671the subject, namely "issippi", it does not match, because \B is always false 2672at the start of the subject, which is deemed to be a word boundary. However, if 2673<b>pcre2_match()</b> is passed the entire string again, but with 2674<i>startoffset</i> set to 4, it finds the second occurrence of "iss" because it 2675is able to look behind the starting point to discover that it is preceded by a 2676letter. 2677</P> 2678<P> 2679Finding all the matches in a subject is tricky when the pattern can match an 2680empty string. It is possible to emulate Perl's /g behaviour by first trying the 2681match again at the same offset, with the PCRE2_NOTEMPTY_ATSTART and 2682PCRE2_ANCHORED options, and then if that fails, advancing the starting offset 2683and trying an ordinary match again. There is some code that demonstrates how to 2684do this in the 2685<a href="pcre2demo.html"><b>pcre2demo</b></a> 2686sample program. In the most general case, you have to check to see if the 2687newline convention recognizes CRLF as a newline, and if so, and the current 2688character is CR followed by LF, advance the starting offset by two characters 2689instead of one. 2690</P> 2691<P> 2692If a non-zero starting offset is passed when the pattern is anchored, a single 2693attempt to match at the given offset is made. This can only succeed if the 2694pattern does not require the match to be at the start of the subject. In other 2695words, the anchoring must be the result of setting the PCRE2_ANCHORED option or 2696the use of .* with PCRE2_DOTALL, not by starting the pattern with ^ or \A. 2697<a name="matchoptions"></a></P> 2698<br><b> 2699Option bits for <b>pcre2_match()</b> 2700</b><br> 2701<P> 2702The unused bits of the <i>options</i> argument for <b>pcre2_match()</b> must be 2703zero. The only bits that may be set are PCRE2_ANCHORED, 2704PCRE2_COPY_MATCHED_SUBJECT, PCRE2_ENDANCHORED, PCRE2_NOTBOL, PCRE2_NOTEOL, 2705PCRE2_NOTEMPTY, PCRE2_NOTEMPTY_ATSTART, PCRE2_NO_JIT, PCRE2_NO_UTF_CHECK, 2706PCRE2_PARTIAL_HARD, and PCRE2_PARTIAL_SOFT. Their action is described below. 2707</P> 2708<P> 2709Setting PCRE2_ANCHORED or PCRE2_ENDANCHORED at match time is not supported by 2710the just-in-time (JIT) compiler. If it is set, JIT matching is disabled and the 2711interpretive code in <b>pcre2_match()</b> is run. Apart from PCRE2_NO_JIT 2712(obviously), the remaining options are supported for JIT matching. 2713<pre> 2714 PCRE2_ANCHORED 2715</pre> 2716The PCRE2_ANCHORED option limits <b>pcre2_match()</b> to matching at the first 2717matching position. If a pattern was compiled with PCRE2_ANCHORED, or turned out 2718to be anchored by virtue of its contents, it cannot be made unachored at 2719matching time. Note that setting the option at match time disables JIT 2720matching. 2721<pre> 2722 PCRE2_COPY_MATCHED_SUBJECT 2723</pre> 2724By default, a pointer to the subject is remembered in the match data block so 2725that, after a successful match, it can be referenced by the substring 2726extraction functions. This means that the subject's memory must not be freed 2727until all such operations are complete. For some applications where the 2728lifetime of the subject string is not guaranteed, it may be necessary to make a 2729copy of the subject string, but it is wasteful to do this unless the match is 2730successful. After a successful match, if PCRE2_COPY_MATCHED_SUBJECT is set, the 2731subject is copied and the new pointer is remembered in the match data block 2732instead of the original subject pointer. The memory allocator that was used for 2733the match block itself is used. The copy is automatically freed when 2734<b>pcre2_match_data_free()</b> is called to free the match data block. It is also 2735automatically freed if the match data block is re-used for another match 2736operation. 2737<pre> 2738 PCRE2_ENDANCHORED 2739</pre> 2740If the PCRE2_ENDANCHORED option is set, any string that <b>pcre2_match()</b> 2741matches must be right at the end of the subject string. Note that setting the 2742option at match time disables JIT matching. 2743<pre> 2744 PCRE2_NOTBOL 2745</pre> 2746This option specifies that first character of the subject string is not the 2747beginning of a line, so the circumflex metacharacter should not match before 2748it. Setting this without having set PCRE2_MULTILINE at compile time causes 2749circumflex never to match. This option affects only the behaviour of the 2750circumflex metacharacter. It does not affect \A. 2751<pre> 2752 PCRE2_NOTEOL 2753</pre> 2754This option specifies that the end of the subject string is not the end of a 2755line, so the dollar metacharacter should not match it nor (except in multiline 2756mode) a newline immediately before it. Setting this without having set 2757PCRE2_MULTILINE at compile time causes dollar never to match. This option 2758affects only the behaviour of the dollar metacharacter. It does not affect \Z 2759or \z. 2760<pre> 2761 PCRE2_NOTEMPTY 2762</pre> 2763An empty string is not considered to be a valid match if this option is set. If 2764there are alternatives in the pattern, they are tried. If all the alternatives 2765match the empty string, the entire match fails. For example, if the pattern 2766<pre> 2767 a?b? 2768</pre> 2769is applied to a string not beginning with "a" or "b", it matches an empty 2770string at the start of the subject. With PCRE2_NOTEMPTY set, this match is not 2771valid, so <b>pcre2_match()</b> searches further into the string for occurrences 2772of "a" or "b". 2773<pre> 2774 PCRE2_NOTEMPTY_ATSTART 2775</pre> 2776This is like PCRE2_NOTEMPTY, except that it locks out an empty string match 2777only at the first matching position, that is, at the start of the subject plus 2778the starting offset. An empty string match later in the subject is permitted. 2779If the pattern is anchored, such a match can occur only if the pattern contains 2780\K. 2781<pre> 2782 PCRE2_NO_JIT 2783</pre> 2784By default, if a pattern has been successfully processed by 2785<b>pcre2_jit_compile()</b>, JIT is automatically used when <b>pcre2_match()</b> 2786is called with options that JIT supports. Setting PCRE2_NO_JIT disables the use 2787of JIT; it forces matching to be done by the interpreter. 2788<pre> 2789 PCRE2_NO_UTF_CHECK 2790</pre> 2791When PCRE2_UTF is set at compile time, the validity of the subject as a UTF 2792string is checked unless PCRE2_NO_UTF_CHECK is passed to <b>pcre2_match()</b> or 2793PCRE2_MATCH_INVALID_UTF was passed to <b>pcre2_compile()</b>. The latter special 2794case is discussed in detail in the 2795<a href="pcre2unicode.html"><b>pcre2unicode</b></a> 2796documentation. 2797</P> 2798<P> 2799In the default case, if a non-zero starting offset is given, the check is 2800applied only to that part of the subject that could be inspected during 2801matching, and there is a check that the starting offset points to the first 2802code unit of a character or to the end of the subject. If there are no 2803lookbehind assertions in the pattern, the check starts at the starting offset. 2804Otherwise, it starts at the length of the longest lookbehind before the 2805starting offset, or at the start of the subject if there are not that many 2806characters before the starting offset. Note that the sequences \b and \B are 2807one-character lookbehinds. 2808</P> 2809<P> 2810The check is carried out before any other processing takes place, and a 2811negative error code is returned if the check fails. There are several UTF error 2812codes for each code unit width, corresponding to different problems with the 2813code unit sequence. There are discussions about the validity of 2814<a href="pcre2unicode.html#utf8strings">UTF-8 strings,</a> 2815<a href="pcre2unicode.html#utf16strings">UTF-16 strings,</a> 2816and 2817<a href="pcre2unicode.html#utf32strings">UTF-32 strings</a> 2818in the 2819<a href="pcre2unicode.html"><b>pcre2unicode</b></a> 2820documentation. 2821</P> 2822<P> 2823If you know that your subject is valid, and you want to skip this check for 2824performance reasons, you can set the PCRE2_NO_UTF_CHECK option when calling 2825<b>pcre2_match()</b>. You might want to do this for the second and subsequent 2826calls to <b>pcre2_match()</b> if you are making repeated calls to find multiple 2827matches in the same subject string. 2828</P> 2829<P> 2830<b>Warning:</b> Unless PCRE2_MATCH_INVALID_UTF was set at compile time, when 2831PCRE2_NO_UTF_CHECK is set at match time the effect of passing an invalid 2832string as a subject, or an invalid value of <i>startoffset</i>, is undefined. 2833Your program may crash or loop indefinitely or give wrong results. 2834<pre> 2835 PCRE2_PARTIAL_HARD 2836 PCRE2_PARTIAL_SOFT 2837</pre> 2838These options turn on the partial matching feature. A partial match occurs if 2839the end of the subject string is reached successfully, but there are not enough 2840subject characters to complete the match. In addition, either at least one 2841character must have been inspected or the pattern must contain a lookbehind, or 2842the pattern must be one that could match an empty string. 2843</P> 2844<P> 2845If this situation arises when PCRE2_PARTIAL_SOFT (but not PCRE2_PARTIAL_HARD) 2846is set, matching continues by testing any remaining alternatives. Only if no 2847complete match can be found is PCRE2_ERROR_PARTIAL returned instead of 2848PCRE2_ERROR_NOMATCH. In other words, PCRE2_PARTIAL_SOFT specifies that the 2849caller is prepared to handle a partial match, but only if no complete match can 2850be found. 2851</P> 2852<P> 2853If PCRE2_PARTIAL_HARD is set, it overrides PCRE2_PARTIAL_SOFT. In this case, if 2854a partial match is found, <b>pcre2_match()</b> immediately returns 2855PCRE2_ERROR_PARTIAL, without considering any other alternatives. In other 2856words, when PCRE2_PARTIAL_HARD is set, a partial match is considered to be more 2857important that an alternative complete match. 2858</P> 2859<P> 2860There is a more detailed discussion of partial and multi-segment matching, with 2861examples, in the 2862<a href="pcre2partial.html"><b>pcre2partial</b></a> 2863documentation. 2864</P> 2865<br><a name="SEC28" href="#TOC1">NEWLINE HANDLING WHEN MATCHING</a><br> 2866<P> 2867When PCRE2 is built, a default newline convention is set; this is usually the 2868standard convention for the operating system. The default can be overridden in 2869a 2870<a href="#compilecontext">compile context</a> 2871by calling <b>pcre2_set_newline()</b>. It can also be overridden by starting a 2872pattern string with, for example, (*CRLF), as described in the 2873<a href="pcre2pattern.html#newlines">section on newline conventions</a> 2874in the 2875<a href="pcre2pattern.html"><b>pcre2pattern</b></a> 2876page. During matching, the newline choice affects the behaviour of the dot, 2877circumflex, and dollar metacharacters. It may also alter the way the match 2878starting position is advanced after a match failure for an unanchored pattern. 2879</P> 2880<P> 2881When PCRE2_NEWLINE_CRLF, PCRE2_NEWLINE_ANYCRLF, or PCRE2_NEWLINE_ANY is set as 2882the newline convention, and a match attempt for an unanchored pattern fails 2883when the current starting position is at a CRLF sequence, and the pattern 2884contains no explicit matches for CR or LF characters, the match position is 2885advanced by two characters instead of one, in other words, to after the CRLF. 2886</P> 2887<P> 2888The above rule is a compromise that makes the most common cases work as 2889expected. For example, if the pattern is .+A (and the PCRE2_DOTALL option is 2890not set), it does not match the string "\r\nA" because, after failing at the 2891start, it skips both the CR and the LF before retrying. However, the pattern 2892[\r\n]A does match that string, because it contains an explicit CR or LF 2893reference, and so advances only by one character after the first failure. 2894</P> 2895<P> 2896An explicit match for CR of LF is either a literal appearance of one of those 2897characters in the pattern, or one of the \r or \n or equivalent octal or 2898hexadecimal escape sequences. Implicit matches such as [^X] do not count, nor 2899does \s, even though it includes CR and LF in the characters that it matches. 2900</P> 2901<P> 2902Notwithstanding the above, anomalous effects may still occur when CRLF is a 2903valid newline sequence and explicit \r or \n escapes appear in the pattern. 2904<a name="matchedstrings"></a></P> 2905<br><a name="SEC29" href="#TOC1">HOW PCRE2_MATCH() RETURNS A STRING AND CAPTURED SUBSTRINGS</a><br> 2906<P> 2907<b>uint32_t pcre2_get_ovector_count(pcre2_match_data *<i>match_data</i>);</b> 2908<br> 2909<br> 2910<b>PCRE2_SIZE *pcre2_get_ovector_pointer(pcre2_match_data *<i>match_data</i>);</b> 2911</P> 2912<P> 2913In general, a pattern matches a certain portion of the subject, and in 2914addition, further substrings from the subject may be picked out by 2915parenthesized parts of the pattern. Following the usage in Jeffrey Friedl's 2916book, this is called "capturing" in what follows, and the phrase "capture 2917group" (Perl terminology) is used for a fragment of a pattern that picks out a 2918substring. PCRE2 supports several other kinds of parenthesized group that do 2919not cause substrings to be captured. The <b>pcre2_pattern_info()</b> function 2920can be used to find out how many capture groups there are in a compiled 2921pattern. 2922</P> 2923<P> 2924You can use auxiliary functions for accessing captured substrings 2925<a href="#extractbynumber">by number</a> 2926or 2927<a href="#extractbyname">by name,</a> 2928as described in sections below. 2929</P> 2930<P> 2931Alternatively, you can make direct use of the vector of PCRE2_SIZE values, 2932called the <b>ovector</b>, which contains the offsets of captured strings. It is 2933part of the 2934<a href="#matchdatablock">match data block.</a> 2935The function <b>pcre2_get_ovector_pointer()</b> returns the address of the 2936ovector, and <b>pcre2_get_ovector_count()</b> returns the number of pairs of 2937values it contains. 2938</P> 2939<P> 2940Within the ovector, the first in each pair of values is set to the offset of 2941the first code unit of a substring, and the second is set to the offset of the 2942first code unit after the end of a substring. These values are always code unit 2943offsets, not character offsets. That is, they are byte offsets in the 8-bit 2944library, 16-bit offsets in the 16-bit library, and 32-bit offsets in the 32-bit 2945library. 2946</P> 2947<P> 2948After a partial match (error return PCRE2_ERROR_PARTIAL), only the first pair 2949of offsets (that is, <i>ovector[0]</i> and <i>ovector[1]</i>) are set. They 2950identify the part of the subject that was partially matched. See the 2951<a href="pcre2partial.html"><b>pcre2partial</b></a> 2952documentation for details of partial matching. 2953</P> 2954<P> 2955After a fully successful match, the first pair of offsets identifies the 2956portion of the subject string that was matched by the entire pattern. The next 2957pair is used for the first captured substring, and so on. The value returned by 2958<b>pcre2_match()</b> is one more than the highest numbered pair that has been 2959set. For example, if two substrings have been captured, the returned value is 29603. If there are no captured substrings, the return value from a successful 2961match is 1, indicating that just the first pair of offsets has been set. 2962</P> 2963<P> 2964If a pattern uses the \K escape sequence within a positive assertion, the 2965reported start of a successful match can be greater than the end of the match. 2966For example, if the pattern (?=ab\K) is matched against "ab", the start and 2967end offset values for the match are 2 and 0. 2968</P> 2969<P> 2970If a capture group is matched repeatedly within a single match operation, it is 2971the last portion of the subject that it matched that is returned. 2972</P> 2973<P> 2974If the ovector is too small to hold all the captured substring offsets, as much 2975as possible is filled in, and the function returns a value of zero. If captured 2976substrings are not of interest, <b>pcre2_match()</b> may be called with a match 2977data block whose ovector is of minimum length (that is, one pair). 2978</P> 2979<P> 2980It is possible for capture group number <i>n+1</i> to match some part of the 2981subject when group <i>n</i> has not been used at all. For example, if the string 2982"abc" is matched against the pattern (a|(z))(bc) the return from the function 2983is 4, and groups 1 and 3 are matched, but 2 is not. When this happens, both 2984values in the offset pairs corresponding to unused groups are set to 2985PCRE2_UNSET. 2986</P> 2987<P> 2988Offset values that correspond to unused groups at the end of the expression are 2989also set to PCRE2_UNSET. For example, if the string "abc" is matched against 2990the pattern (abc)(x(yz)?)? groups 2 and 3 are not matched. The return from the 2991function is 2, because the highest used capture group number is 1. The offsets 2992for for the second and third capture groupss (assuming the vector is large 2993enough, of course) are set to PCRE2_UNSET. 2994</P> 2995<P> 2996Elements in the ovector that do not correspond to capturing parentheses in the 2997pattern are never changed. That is, if a pattern contains <i>n</i> capturing 2998parentheses, no more than <i>ovector[0]</i> to <i>ovector[2n+1]</i> are set by 2999<b>pcre2_match()</b>. The other elements retain whatever values they previously 3000had. After a failed match attempt, the contents of the ovector are unchanged. 3001<a name="matchotherdata"></a></P> 3002<br><a name="SEC30" href="#TOC1">OTHER INFORMATION ABOUT A MATCH</a><br> 3003<P> 3004<b>PCRE2_SPTR pcre2_get_mark(pcre2_match_data *<i>match_data</i>);</b> 3005<br> 3006<br> 3007<b>PCRE2_SIZE pcre2_get_startchar(pcre2_match_data *<i>match_data</i>);</b> 3008</P> 3009<P> 3010As well as the offsets in the ovector, other information about a match is 3011retained in the match data block and can be retrieved by the above functions in 3012appropriate circumstances. If they are called at other times, the result is 3013undefined. 3014</P> 3015<P> 3016After a successful match, a partial match (PCRE2_ERROR_PARTIAL), or a failure 3017to match (PCRE2_ERROR_NOMATCH), a mark name may be available. The function 3018<b>pcre2_get_mark()</b> can be called to access this name, which can be 3019specified in the pattern by any of the backtracking control verbs, not just 3020(*MARK). The same function applies to all the verbs. It returns a pointer to 3021the zero-terminated name, which is within the compiled pattern. If no name is 3022available, NULL is returned. The length of the name (excluding the terminating 3023zero) is stored in the code unit that precedes the name. You should use this 3024length instead of relying on the terminating zero if the name might contain a 3025binary zero. 3026</P> 3027<P> 3028After a successful match, the name that is returned is the last mark name 3029encountered on the matching path through the pattern. Instances of backtracking 3030verbs without names do not count. Thus, for example, if the matching path 3031contains (*MARK:A)(*PRUNE), the name "A" is returned. After a "no match" or a 3032partial match, the last encountered name is returned. For example, consider 3033this pattern: 3034<pre> 3035 ^(*MARK:A)((*MARK:B)a|b)c 3036</pre> 3037When it matches "bc", the returned name is A. The B mark is "seen" in the first 3038branch of the group, but it is not on the matching path. On the other hand, 3039when this pattern fails to match "bx", the returned name is B. 3040</P> 3041<P> 3042<b>Warning:</b> By default, certain start-of-match optimizations are used to 3043give a fast "no match" result in some situations. For example, if the anchoring 3044is removed from the pattern above, there is an initial check for the presence 3045of "c" in the subject before running the matching engine. This check fails for 3046"bx", causing a match failure without seeing any marks. You can disable the 3047start-of-match optimizations by setting the PCRE2_NO_START_OPTIMIZE option for 3048<b>pcre2_compile()</b> or by starting the pattern with (*NO_START_OPT). 3049</P> 3050<P> 3051After a successful match, a partial match, or one of the invalid UTF errors 3052(for example, PCRE2_ERROR_UTF8_ERR5), <b>pcre2_get_startchar()</b> can be 3053called. After a successful or partial match it returns the code unit offset of 3054the character at which the match started. For a non-partial match, this can be 3055different to the value of <i>ovector[0]</i> if the pattern contains the \K 3056escape sequence. After a partial match, however, this value is always the same 3057as <i>ovector[0]</i> because \K does not affect the result of a partial match. 3058</P> 3059<P> 3060After a UTF check failure, <b>pcre2_get_startchar()</b> can be used to obtain 3061the code unit offset of the invalid UTF character. Details are given in the 3062<a href="pcre2unicode.html"><b>pcre2unicode</b></a> 3063page. 3064<a name="errorlist"></a></P> 3065<br><a name="SEC31" href="#TOC1">ERROR RETURNS FROM <b>pcre2_match()</b></a><br> 3066<P> 3067If <b>pcre2_match()</b> fails, it returns a negative number. This can be 3068converted to a text string by calling the <b>pcre2_get_error_message()</b> 3069function (see "Obtaining a textual error message" 3070<a href="#geterrormessage">below).</a> 3071Negative error codes are also returned by other functions, and are documented 3072with them. The codes are given names in the header file. If UTF checking is in 3073force and an invalid UTF subject string is detected, one of a number of 3074UTF-specific negative error codes is returned. Details are given in the 3075<a href="pcre2unicode.html"><b>pcre2unicode</b></a> 3076page. The following are the other errors that may be returned by 3077<b>pcre2_match()</b>: 3078<pre> 3079 PCRE2_ERROR_NOMATCH 3080</pre> 3081The subject string did not match the pattern. 3082<pre> 3083 PCRE2_ERROR_PARTIAL 3084</pre> 3085The subject string did not match, but it did match partially. See the 3086<a href="pcre2partial.html"><b>pcre2partial</b></a> 3087documentation for details of partial matching. 3088<pre> 3089 PCRE2_ERROR_BADMAGIC 3090</pre> 3091PCRE2 stores a 4-byte "magic number" at the start of the compiled code, to 3092catch the case when it is passed a junk pointer. This is the error that is 3093returned when the magic number is not present. 3094<pre> 3095 PCRE2_ERROR_BADMODE 3096</pre> 3097This error is given when a compiled pattern is passed to a function in a 3098library of a different code unit width, for example, a pattern compiled by 3099the 8-bit library is passed to a 16-bit or 32-bit library function. 3100<pre> 3101 PCRE2_ERROR_BADOFFSET 3102</pre> 3103The value of <i>startoffset</i> was greater than the length of the subject. 3104<pre> 3105 PCRE2_ERROR_BADOPTION 3106</pre> 3107An unrecognized bit was set in the <i>options</i> argument. 3108<pre> 3109 PCRE2_ERROR_BADUTFOFFSET 3110</pre> 3111The UTF code unit sequence that was passed as a subject was checked and found 3112to be valid (the PCRE2_NO_UTF_CHECK option was not set), but the value of 3113<i>startoffset</i> did not point to the beginning of a UTF character or the end 3114of the subject. 3115<pre> 3116 PCRE2_ERROR_CALLOUT 3117</pre> 3118This error is never generated by <b>pcre2_match()</b> itself. It is provided for 3119use by callout functions that want to cause <b>pcre2_match()</b> or 3120<b>pcre2_callout_enumerate()</b> to return a distinctive error code. See the 3121<a href="pcre2callout.html"><b>pcre2callout</b></a> 3122documentation for details. 3123<pre> 3124 PCRE2_ERROR_DEPTHLIMIT 3125</pre> 3126The nested backtracking depth limit was reached. 3127<pre> 3128 PCRE2_ERROR_HEAPLIMIT 3129</pre> 3130The heap limit was reached. 3131<pre> 3132 PCRE2_ERROR_INTERNAL 3133</pre> 3134An unexpected internal error has occurred. This error could be caused by a bug 3135in PCRE2 or by overwriting of the compiled pattern. 3136<pre> 3137 PCRE2_ERROR_JIT_STACKLIMIT 3138</pre> 3139This error is returned when a pattern that was successfully studied using JIT 3140is being matched, but the memory available for the just-in-time processing 3141stack is not large enough. See the 3142<a href="pcre2jit.html"><b>pcre2jit</b></a> 3143documentation for more details. 3144<pre> 3145 PCRE2_ERROR_MATCHLIMIT 3146</pre> 3147The backtracking match limit was reached. 3148<pre> 3149 PCRE2_ERROR_NOMEMORY 3150</pre> 3151Heap memory is used to remember backgracking points. This error is given when 3152the memory allocation function (default or custom) fails. Note that a different 3153error, PCRE2_ERROR_HEAPLIMIT, is given if the amount of memory needed exceeds 3154the heap limit. PCRE2_ERROR_NOMEMORY is also returned if 3155PCRE2_COPY_MATCHED_SUBJECT is set and memory allocation fails. 3156<pre> 3157 PCRE2_ERROR_NULL 3158</pre> 3159Either the <i>code</i>, <i>subject</i>, or <i>match_data</i> argument was passed 3160as NULL. 3161<pre> 3162 PCRE2_ERROR_RECURSELOOP 3163</pre> 3164This error is returned when <b>pcre2_match()</b> detects a recursion loop within 3165the pattern. Specifically, it means that either the whole pattern or a 3166capture group has been called recursively for the second time at the same 3167position in the subject string. Some simple patterns that might do this are 3168detected and faulted at compile time, but more complicated cases, in particular 3169mutual recursions between two different groups, cannot be detected until 3170matching is attempted. 3171<a name="geterrormessage"></a></P> 3172<br><a name="SEC32" href="#TOC1">OBTAINING A TEXTUAL ERROR MESSAGE</a><br> 3173<P> 3174<b>int pcre2_get_error_message(int <i>errorcode</i>, PCRE2_UCHAR *<i>buffer</i>,</b> 3175<b> PCRE2_SIZE <i>bufflen</i>);</b> 3176</P> 3177<P> 3178A text message for an error code from any PCRE2 function (compile, match, or 3179auxiliary) can be obtained by calling <b>pcre2_get_error_message()</b>. The code 3180is passed as the first argument, with the remaining two arguments specifying a 3181code unit buffer and its length in code units, into which the text message is 3182placed. The message is returned in code units of the appropriate width for the 3183library that is being used. 3184</P> 3185<P> 3186The returned message is terminated with a trailing zero, and the function 3187returns the number of code units used, excluding the trailing zero. If the 3188error number is unknown, the negative error code PCRE2_ERROR_BADDATA is 3189returned. If the buffer is too small, the message is truncated (but still with 3190a trailing zero), and the negative error code PCRE2_ERROR_NOMEMORY is returned. 3191None of the messages are very long; a buffer size of 120 code units is ample. 3192<a name="extractbynumber"></a></P> 3193<br><a name="SEC33" href="#TOC1">EXTRACTING CAPTURED SUBSTRINGS BY NUMBER</a><br> 3194<P> 3195<b>int pcre2_substring_length_bynumber(pcre2_match_data *<i>match_data</i>,</b> 3196<b> uint32_t <i>number</i>, PCRE2_SIZE *<i>length</i>);</b> 3197<br> 3198<br> 3199<b>int pcre2_substring_copy_bynumber(pcre2_match_data *<i>match_data</i>,</b> 3200<b> uint32_t <i>number</i>, PCRE2_UCHAR *<i>buffer</i>,</b> 3201<b> PCRE2_SIZE *<i>bufflen</i>);</b> 3202<br> 3203<br> 3204<b>int pcre2_substring_get_bynumber(pcre2_match_data *<i>match_data</i>,</b> 3205<b> uint32_t <i>number</i>, PCRE2_UCHAR **<i>bufferptr</i>,</b> 3206<b> PCRE2_SIZE *<i>bufflen</i>);</b> 3207<br> 3208<br> 3209<b>void pcre2_substring_free(PCRE2_UCHAR *<i>buffer</i>);</b> 3210</P> 3211<P> 3212Captured substrings can be accessed directly by using the ovector as described 3213<a href="#matchedstrings">above.</a> 3214For convenience, auxiliary functions are provided for extracting captured 3215substrings as new, separate, zero-terminated strings. A substring that contains 3216a binary zero is correctly extracted and has a further zero added on the end, 3217but the result is not, of course, a C string. 3218</P> 3219<P> 3220The functions in this section identify substrings by number. The number zero 3221refers to the entire matched substring, with higher numbers referring to 3222substrings captured by parenthesized groups. After a partial match, only 3223substring zero is available. An attempt to extract any other substring gives 3224the error PCRE2_ERROR_PARTIAL. The next section describes similar functions for 3225extracting captured substrings by name. 3226</P> 3227<P> 3228If a pattern uses the \K escape sequence within a positive assertion, the 3229reported start of a successful match can be greater than the end of the match. 3230For example, if the pattern (?=ab\K) is matched against "ab", the start and 3231end offset values for the match are 2 and 0. In this situation, calling these 3232functions with a zero substring number extracts a zero-length empty string. 3233</P> 3234<P> 3235You can find the length in code units of a captured substring without 3236extracting it by calling <b>pcre2_substring_length_bynumber()</b>. The first 3237argument is a pointer to the match data block, the second is the group number, 3238and the third is a pointer to a variable into which the length is placed. If 3239you just want to know whether or not the substring has been captured, you can 3240pass the third argument as NULL. 3241</P> 3242<P> 3243The <b>pcre2_substring_copy_bynumber()</b> function copies a captured substring 3244into a supplied buffer, whereas <b>pcre2_substring_get_bynumber()</b> copies it 3245into new memory, obtained using the same memory allocation function that was 3246used for the match data block. The first two arguments of these functions are a 3247pointer to the match data block and a capture group number. 3248</P> 3249<P> 3250The final arguments of <b>pcre2_substring_copy_bynumber()</b> are a pointer to 3251the buffer and a pointer to a variable that contains its length in code units. 3252This is updated to contain the actual number of code units used for the 3253extracted substring, excluding the terminating zero. 3254</P> 3255<P> 3256For <b>pcre2_substring_get_bynumber()</b> the third and fourth arguments point 3257to variables that are updated with a pointer to the new memory and the number 3258of code units that comprise the substring, again excluding the terminating 3259zero. When the substring is no longer needed, the memory should be freed by 3260calling <b>pcre2_substring_free()</b>. 3261</P> 3262<P> 3263The return value from all these functions is zero for success, or a negative 3264error code. If the pattern match failed, the match failure code is returned. 3265If a substring number greater than zero is used after a partial match, 3266PCRE2_ERROR_PARTIAL is returned. Other possible error codes are: 3267<pre> 3268 PCRE2_ERROR_NOMEMORY 3269</pre> 3270The buffer was too small for <b>pcre2_substring_copy_bynumber()</b>, or the 3271attempt to get memory failed for <b>pcre2_substring_get_bynumber()</b>. 3272<pre> 3273 PCRE2_ERROR_NOSUBSTRING 3274</pre> 3275There is no substring with that number in the pattern, that is, the number is 3276greater than the number of capturing parentheses. 3277<pre> 3278 PCRE2_ERROR_UNAVAILABLE 3279</pre> 3280The substring number, though not greater than the number of captures in the 3281pattern, is greater than the number of slots in the ovector, so the substring 3282could not be captured. 3283<pre> 3284 PCRE2_ERROR_UNSET 3285</pre> 3286The substring did not participate in the match. For example, if the pattern is 3287(abc)|(def) and the subject is "def", and the ovector contains at least two 3288capturing slots, substring number 1 is unset. 3289</P> 3290<br><a name="SEC34" href="#TOC1">EXTRACTING A LIST OF ALL CAPTURED SUBSTRINGS</a><br> 3291<P> 3292<b>int pcre2_substring_list_get(pcre2_match_data *<i>match_data</i>,</b> 3293<b>" PCRE2_UCHAR ***<i>listptr</i>, PCRE2_SIZE **<i>lengthsptr</i>);</b> 3294<br> 3295<br> 3296<b>void pcre2_substring_list_free(PCRE2_SPTR *<i>list</i>);</b> 3297</P> 3298<P> 3299The <b>pcre2_substring_list_get()</b> function extracts all available substrings 3300and builds a list of pointers to them. It also (optionally) builds a second 3301list that contains their lengths (in code units), excluding a terminating zero 3302that is added to each of them. All this is done in a single block of memory 3303that is obtained using the same memory allocation function that was used to get 3304the match data block. 3305</P> 3306<P> 3307This function must be called only after a successful match. If called after a 3308partial match, the error code PCRE2_ERROR_PARTIAL is returned. 3309</P> 3310<P> 3311The address of the memory block is returned via <i>listptr</i>, which is also 3312the start of the list of string pointers. The end of the list is marked by a 3313NULL pointer. The address of the list of lengths is returned via 3314<i>lengthsptr</i>. If your strings do not contain binary zeros and you do not 3315therefore need the lengths, you may supply NULL as the <b>lengthsptr</b> 3316argument to disable the creation of a list of lengths. The yield of the 3317function is zero if all went well, or PCRE2_ERROR_NOMEMORY if the memory block 3318could not be obtained. When the list is no longer needed, it should be freed by 3319calling <b>pcre2_substring_list_free()</b>. 3320</P> 3321<P> 3322If this function encounters a substring that is unset, which can happen when 3323capture group number <i>n+1</i> matches some part of the subject, but group 3324<i>n</i> has not been used at all, it returns an empty string. This can be 3325distinguished from a genuine zero-length substring by inspecting the 3326appropriate offset in the ovector, which contain PCRE2_UNSET for unset 3327substrings, or by calling <b>pcre2_substring_length_bynumber()</b>. 3328<a name="extractbyname"></a></P> 3329<br><a name="SEC35" href="#TOC1">EXTRACTING CAPTURED SUBSTRINGS BY NAME</a><br> 3330<P> 3331<b>int pcre2_substring_number_from_name(const pcre2_code *<i>code</i>,</b> 3332<b> PCRE2_SPTR <i>name</i>);</b> 3333<br> 3334<br> 3335<b>int pcre2_substring_length_byname(pcre2_match_data *<i>match_data</i>,</b> 3336<b> PCRE2_SPTR <i>name</i>, PCRE2_SIZE *<i>length</i>);</b> 3337<br> 3338<br> 3339<b>int pcre2_substring_copy_byname(pcre2_match_data *<i>match_data</i>,</b> 3340<b> PCRE2_SPTR <i>name</i>, PCRE2_UCHAR *<i>buffer</i>, PCRE2_SIZE *<i>bufflen</i>);</b> 3341<br> 3342<br> 3343<b>int pcre2_substring_get_byname(pcre2_match_data *<i>match_data</i>,</b> 3344<b> PCRE2_SPTR <i>name</i>, PCRE2_UCHAR **<i>bufferptr</i>, PCRE2_SIZE *<i>bufflen</i>);</b> 3345<br> 3346<br> 3347<b>void pcre2_substring_free(PCRE2_UCHAR *<i>buffer</i>);</b> 3348</P> 3349<P> 3350To extract a substring by name, you first have to find associated number. 3351For example, for this pattern: 3352<pre> 3353 (a+)b(?<xxx>\d+)... 3354</pre> 3355the number of the capture group called "xxx" is 2. If the name is known to be 3356unique (PCRE2_DUPNAMES was not set), you can find the number from the name by 3357calling <b>pcre2_substring_number_from_name()</b>. The first argument is the 3358compiled pattern, and the second is the name. The yield of the function is the 3359group number, PCRE2_ERROR_NOSUBSTRING if there is no group with that name, or 3360PCRE2_ERROR_NOUNIQUESUBSTRING if there is more than one group with that name. 3361Given the number, you can extract the substring directly from the ovector, or 3362use one of the "bynumber" functions described above. 3363</P> 3364<P> 3365For convenience, there are also "byname" functions that correspond to the 3366"bynumber" functions, the only difference being that the second argument is a 3367name instead of a number. If PCRE2_DUPNAMES is set and there are duplicate 3368names, these functions scan all the groups with the given name, and return the 3369captured substring from the first named group that is set. 3370</P> 3371<P> 3372If there are no groups with the given name, PCRE2_ERROR_NOSUBSTRING is 3373returned. If all groups with the name have numbers that are greater than the 3374number of slots in the ovector, PCRE2_ERROR_UNAVAILABLE is returned. If there 3375is at least one group with a slot in the ovector, but no group is found to be 3376set, PCRE2_ERROR_UNSET is returned. 3377</P> 3378<P> 3379<b>Warning:</b> If the pattern uses the (?| feature to set up multiple 3380capture groups with the same number, as described in the 3381<a href="pcre2pattern.html#dupgroupnumber">section on duplicate group numbers</a> 3382in the 3383<a href="pcre2pattern.html"><b>pcre2pattern</b></a> 3384page, you cannot use names to distinguish the different capture groups, because 3385names are not included in the compiled code. The matching process uses only 3386numbers. For this reason, the use of different names for groups with the 3387same number causes an error at compile time. 3388<a name="substitutions"></a></P> 3389<br><a name="SEC36" href="#TOC1">CREATING A NEW STRING WITH SUBSTITUTIONS</a><br> 3390<P> 3391<b>int pcre2_substitute(const pcre2_code *<i>code</i>, PCRE2_SPTR <i>subject</i>,</b> 3392<b> PCRE2_SIZE <i>length</i>, PCRE2_SIZE <i>startoffset</i>,</b> 3393<b> uint32_t <i>options</i>, pcre2_match_data *<i>match_data</i>,</b> 3394<b> pcre2_match_context *<i>mcontext</i>, PCRE2_SPTR <i>replacement</i>,</b> 3395<b> PCRE2_SIZE <i>rlength</i>, PCRE2_UCHAR *<i>outputbuffer</i>,</b> 3396<b> PCRE2_SIZE *<i>outlengthptr</i>);</b> 3397</P> 3398<P> 3399This function optionally calls <b>pcre2_match()</b> and then makes a copy of the 3400subject string in <i>outputbuffer</i>, replacing parts that were matched with 3401the <i>replacement</i> string, whose length is supplied in <b>rlength</b>, which 3402can be given as PCRE2_ZERO_TERMINATED for a zero-terminated string. As a 3403special case, if <i>replacement</i> is NULL and <i>rlength</i> is zero, the 3404replacement is assumed to be an empty string. If <i>rlength</i> is non-zero, an 3405error occurs if <i>replacement</i> is NULL. 3406</P> 3407<P> 3408There is an option (see PCRE2_SUBSTITUTE_REPLACEMENT_ONLY below) to return just 3409the replacement string(s). The default action is to perform just one 3410replacement if the pattern matches, but there is an option that requests 3411multiple replacements (see PCRE2_SUBSTITUTE_GLOBAL below). 3412</P> 3413<P> 3414If successful, <b>pcre2_substitute()</b> returns the number of substitutions 3415that were carried out. This may be zero if no match was found, and is never 3416greater than one unless PCRE2_SUBSTITUTE_GLOBAL is set. A negative value is 3417returned if an error is detected. 3418</P> 3419<P> 3420Matches in which a \K item in a lookahead in the pattern causes the match to 3421end before it starts are not supported, and give rise to an error return. For 3422global replacements, matches in which \K in a lookbehind causes the match to 3423start earlier than the point that was reached in the previous iteration are 3424also not supported. 3425</P> 3426<P> 3427The first seven arguments of <b>pcre2_substitute()</b> are the same as for 3428<b>pcre2_match()</b>, except that the partial matching options are not 3429permitted, and <i>match_data</i> may be passed as NULL, in which case a match 3430data block is obtained and freed within this function, using memory management 3431functions from the match context, if provided, or else those that were used to 3432allocate memory for the compiled code. 3433</P> 3434<P> 3435If <i>match_data</i> is not NULL and PCRE2_SUBSTITUTE_MATCHED is not set, the 3436provided block is used for all calls to <b>pcre2_match()</b>, and its contents 3437afterwards are the result of the final call. For global changes, this will 3438always be a no-match error. The contents of the ovector within the match data 3439block may or may not have been changed. 3440</P> 3441<P> 3442As well as the usual options for <b>pcre2_match()</b>, a number of additional 3443options can be set in the <i>options</i> argument of <b>pcre2_substitute()</b>. 3444One such option is PCRE2_SUBSTITUTE_MATCHED. When this is set, an external 3445<i>match_data</i> block must be provided, and it must have already been used for 3446an external call to <b>pcre2_match()</b> with the same pattern and subject 3447arguments. The data in the <i>match_data</i> block (return code, offset vector) 3448is then used for the first substitution instead of calling <b>pcre2_match()</b> 3449from within <b>pcre2_substitute()</b>. This allows an application to check for a 3450match before choosing to substitute, without having to repeat the match. 3451</P> 3452<P> 3453The contents of the externally supplied match data block are not changed when 3454PCRE2_SUBSTITUTE_MATCHED is set. If PCRE2_SUBSTITUTE_GLOBAL is also set, 3455<b>pcre2_match()</b> is called after the first substitution to check for further 3456matches, but this is done using an internally obtained match data block, thus 3457always leaving the external block unchanged. 3458</P> 3459<P> 3460The <i>code</i> argument is not used for matching before the first substitution 3461when PCRE2_SUBSTITUTE_MATCHED is set, but it must be provided, even when 3462PCRE2_SUBSTITUTE_GLOBAL is not set, because it contains information such as the 3463UTF setting and the number of capturing parentheses in the pattern. 3464</P> 3465<P> 3466The default action of <b>pcre2_substitute()</b> is to return a copy of the 3467subject string with matched substrings replaced. However, if 3468PCRE2_SUBSTITUTE_REPLACEMENT_ONLY is set, only the replacement substrings are 3469returned. In the global case, multiple replacements are concatenated in the 3470output buffer. Substitution callouts (see 3471<a href="#subcallouts">below)</a> 3472can be used to separate them if necessary. 3473</P> 3474<P> 3475The <i>outlengthptr</i> argument of <b>pcre2_substitute()</b> must point to a 3476variable that contains the length, in code units, of the output buffer. If the 3477function is successful, the value is updated to contain the length in code 3478units of the new string, excluding the trailing zero that is automatically 3479added. 3480</P> 3481<P> 3482If the function is not successful, the value set via <i>outlengthptr</i> depends 3483on the type of error. For syntax errors in the replacement string, the value is 3484the offset in the replacement string where the error was detected. For other 3485errors, the value is PCRE2_UNSET by default. This includes the case of the 3486output buffer being too small, unless PCRE2_SUBSTITUTE_OVERFLOW_LENGTH is set. 3487</P> 3488<P> 3489PCRE2_SUBSTITUTE_OVERFLOW_LENGTH changes what happens when the output buffer is 3490too small. The default action is to return PCRE2_ERROR_NOMEMORY immediately. If 3491this option is set, however, <b>pcre2_substitute()</b> continues to go through 3492the motions of matching and substituting (without, of course, writing anything) 3493in order to compute the size of buffer that is needed. This value is passed 3494back via the <i>outlengthptr</i> variable, with the result of the function still 3495being PCRE2_ERROR_NOMEMORY. 3496</P> 3497<P> 3498Passing a buffer size of zero is a permitted way of finding out how much memory 3499is needed for given substitution. However, this does mean that the entire 3500operation is carried out twice. Depending on the application, it may be more 3501efficient to allocate a large buffer and free the excess afterwards, instead of 3502using PCRE2_SUBSTITUTE_OVERFLOW_LENGTH. 3503</P> 3504<P> 3505The replacement string, which is interpreted as a UTF string in UTF mode, is 3506checked for UTF validity unless PCRE2_NO_UTF_CHECK is set. An invalid UTF 3507replacement string causes an immediate return with the relevant UTF error code. 3508</P> 3509<P> 3510If PCRE2_SUBSTITUTE_LITERAL is set, the replacement string is not interpreted 3511in any way. By default, however, a dollar character is an escape character that 3512can specify the insertion of characters from capture groups and names from 3513(*MARK) or other control verbs in the pattern. The following forms are always 3514recognized: 3515<pre> 3516 $$ insert a dollar character 3517 $<n> or ${<n>} insert the contents of group <n> 3518 $*MARK or ${*MARK} insert a control verb name 3519</pre> 3520Either a group number or a group name can be given for <n>. Curly brackets are 3521required only if the following character would be interpreted as part of the 3522number or name. The number may be zero to include the entire matched string. 3523For example, if the pattern a(b)c is matched with "=abc=" and the replacement 3524string "+$1$0$1+", the result is "=+babcb+=". 3525</P> 3526<P> 3527$*MARK inserts the name from the last encountered backtracking control verb on 3528the matching path that has a name. (*MARK) must always include a name, but the 3529other verbs need not. For example, in the case of (*MARK:A)(*PRUNE) the name 3530inserted is "A", but for (*MARK:A)(*PRUNE:B) the relevant name is "B". This 3531facility can be used to perform simple simultaneous substitutions, as this 3532<b>pcre2test</b> example shows: 3533<pre> 3534 /(*MARK:pear)apple|(*MARK:orange)lemon/g,replace=${*MARK} 3535 apple lemon 3536 2: pear orange 3537</pre> 3538PCRE2_SUBSTITUTE_GLOBAL causes the function to iterate over the subject string, 3539replacing every matching substring. If this option is not set, only the first 3540matching substring is replaced. The search for matches takes place in the 3541original subject string (that is, previous replacements do not affect it). 3542Iteration is implemented by advancing the <i>startoffset</i> value for each 3543search, which is always passed the entire subject string. If an offset limit is 3544set in the match context, searching stops when that limit is reached. 3545</P> 3546<P> 3547You can restrict the effect of a global substitution to a portion of the 3548subject string by setting either or both of <i>startoffset</i> and an offset 3549limit. Here is a <b>pcre2test</b> example: 3550<pre> 3551 /B/g,replace=!,use_offset_limit 3552 ABC ABC ABC ABC\=offset=3,offset_limit=12 3553 2: ABC A!C A!C ABC 3554</pre> 3555When continuing with global substitutions after matching a substring with zero 3556length, an attempt to find a non-empty match at the same offset is performed. 3557If this is not successful, the offset is advanced by one character except when 3558CRLF is a valid newline sequence and the next two characters are CR, LF. In 3559this case, the offset is advanced by two characters. 3560</P> 3561<P> 3562PCRE2_SUBSTITUTE_UNKNOWN_UNSET causes references to capture groups that do 3563not appear in the pattern to be treated as unset groups. This option should be 3564used with care, because it means that a typo in a group name or number no 3565longer causes the PCRE2_ERROR_NOSUBSTRING error. 3566</P> 3567<P> 3568PCRE2_SUBSTITUTE_UNSET_EMPTY causes unset capture groups (including unknown 3569groups when PCRE2_SUBSTITUTE_UNKNOWN_UNSET is set) to be treated as empty 3570strings when inserted as described above. If this option is not set, an attempt 3571to insert an unset group causes the PCRE2_ERROR_UNSET error. This option does 3572not influence the extended substitution syntax described below. 3573</P> 3574<P> 3575PCRE2_SUBSTITUTE_EXTENDED causes extra processing to be applied to the 3576replacement string. Without this option, only the dollar character is special, 3577and only the group insertion forms listed above are valid. When 3578PCRE2_SUBSTITUTE_EXTENDED is set, two things change: 3579</P> 3580<P> 3581Firstly, backslash in a replacement string is interpreted as an escape 3582character. The usual forms such as \n or \x{ddd} can be used to specify 3583particular character codes, and backslash followed by any non-alphanumeric 3584character quotes that character. Extended quoting can be coded using \Q...\E, 3585exactly as in pattern strings. 3586</P> 3587<P> 3588There are also four escape sequences for forcing the case of inserted letters. 3589The insertion mechanism has three states: no case forcing, force upper case, 3590and force lower case. The escape sequences change the current state: \U and 3591\L change to upper or lower case forcing, respectively, and \E (when not 3592terminating a \Q quoted sequence) reverts to no case forcing. The sequences 3593\u and \l force the next character (if it is a letter) to upper or lower 3594case, respectively, and then the state automatically reverts to no case 3595forcing. Case forcing applies to all inserted characters, including those from 3596capture groups and letters within \Q...\E quoted sequences. If either 3597PCRE2_UTF or PCRE2_UCP was set when the pattern was compiled, Unicode 3598properties are used for case forcing characters whose code points are greater 3599than 127. 3600</P> 3601<P> 3602Note that case forcing sequences such as \U...\E do not nest. For example, 3603the result of processing "\Uaa\LBB\Ecc\E" is "AAbbcc"; the final \E has no 3604effect. Note also that the PCRE2_ALT_BSUX and PCRE2_EXTRA_ALT_BSUX options do 3605not apply to replacement strings. 3606</P> 3607<P> 3608The second effect of setting PCRE2_SUBSTITUTE_EXTENDED is to add more 3609flexibility to capture group substitution. The syntax is similar to that used 3610by Bash: 3611<pre> 3612 ${<n>:-<string>} 3613 ${<n>:+<string1>:<string2>} 3614</pre> 3615As before, <n> may be a group number or a name. The first form specifies a 3616default value. If group <n> is set, its value is inserted; if not, <string> is 3617expanded and the result inserted. The second form specifies strings that are 3618expanded and inserted when group <n> is set or unset, respectively. The first 3619form is just a convenient shorthand for 3620<pre> 3621 ${<n>:+${<n>}:<string>} 3622</pre> 3623Backslash can be used to escape colons and closing curly brackets in the 3624replacement strings. A change of the case forcing state within a replacement 3625string remains in force afterwards, as shown in this <b>pcre2test</b> example: 3626<pre> 3627 /(some)?(body)/substitute_extended,replace=${1:+\U:\L}HeLLo 3628 body 3629 1: hello 3630 somebody 3631 1: HELLO 3632</pre> 3633The PCRE2_SUBSTITUTE_UNSET_EMPTY option does not affect these extended 3634substitutions. However, PCRE2_SUBSTITUTE_UNKNOWN_UNSET does cause unknown 3635groups in the extended syntax forms to be treated as unset. 3636</P> 3637<P> 3638If PCRE2_SUBSTITUTE_LITERAL is set, PCRE2_SUBSTITUTE_UNKNOWN_UNSET, 3639PCRE2_SUBSTITUTE_UNSET_EMPTY, and PCRE2_SUBSTITUTE_EXTENDED are irrelevant and 3640are ignored. 3641</P> 3642<br><b> 3643Substitution errors 3644</b><br> 3645<P> 3646In the event of an error, <b>pcre2_substitute()</b> returns a negative error 3647code. Except for PCRE2_ERROR_NOMATCH (which is never returned), errors from 3648<b>pcre2_match()</b> are passed straight back. 3649</P> 3650<P> 3651PCRE2_ERROR_NOSUBSTRING is returned for a non-existent substring insertion, 3652unless PCRE2_SUBSTITUTE_UNKNOWN_UNSET is set. 3653</P> 3654<P> 3655PCRE2_ERROR_UNSET is returned for an unset substring insertion (including an 3656unknown substring when PCRE2_SUBSTITUTE_UNKNOWN_UNSET is set) when the simple 3657(non-extended) syntax is used and PCRE2_SUBSTITUTE_UNSET_EMPTY is not set. 3658</P> 3659<P> 3660PCRE2_ERROR_NOMEMORY is returned if the output buffer is not big enough. If the 3661PCRE2_SUBSTITUTE_OVERFLOW_LENGTH option is set, the size of buffer that is 3662needed is returned via <i>outlengthptr</i>. Note that this does not happen by 3663default. 3664</P> 3665<P> 3666PCRE2_ERROR_NULL is returned if PCRE2_SUBSTITUTE_MATCHED is set but the 3667<i>match_data</i> argument is NULL or if the <i>subject</i> or <i>replacement</i> 3668arguments are NULL. For backward compatibility reasons an exception is made for 3669the <i>replacement</i> argument if the <i>rlength</i> argument is also 0. 3670</P> 3671<P> 3672PCRE2_ERROR_BADREPLACEMENT is used for miscellaneous syntax errors in the 3673replacement string, with more particular errors being PCRE2_ERROR_BADREPESCAPE 3674(invalid escape sequence), PCRE2_ERROR_REPMISSINGBRACE (closing curly bracket 3675not found), PCRE2_ERROR_BADSUBSTITUTION (syntax error in extended group 3676substitution), and PCRE2_ERROR_BADSUBSPATTERN (the pattern match ended before 3677it started or the match started earlier than the current position in the 3678subject, which can happen if \K is used in an assertion). 3679</P> 3680<P> 3681As for all PCRE2 errors, a text message that describes the error can be 3682obtained by calling the <b>pcre2_get_error_message()</b> function (see 3683"Obtaining a textual error message" 3684<a href="#geterrormessage">above).</a> 3685<a name="subcallouts"></a></P> 3686<br><b> 3687Substitution callouts 3688</b><br> 3689<P> 3690<b>int pcre2_set_substitute_callout(pcre2_match_context *<i>mcontext</i>,</b> 3691<b> int (*<i>callout_function</i>)(pcre2_substitute_callout_block *, void *),</b> 3692<b> void *<i>callout_data</i>);</b> 3693<br> 3694<br> 3695The <b>pcre2_set_substitution_callout()</b> function can be used to specify a 3696callout function for <b>pcre2_substitute()</b>. This information is passed in 3697a match context. The callout function is called after each substitution has 3698been processed, but it can cause the replacement not to happen. The callout 3699function is not called for simulated substitutions that happen as a result of 3700the PCRE2_SUBSTITUTE_OVERFLOW_LENGTH option. 3701</P> 3702<P> 3703The first argument of the callout function is a pointer to a substitute callout 3704block structure, which contains the following fields, not necessarily in this 3705order: 3706<pre> 3707 uint32_t <i>version</i>; 3708 uint32_t <i>subscount</i>; 3709 PCRE2_SPTR <i>input</i>; 3710 PCRE2_SPTR <i>output</i>; 3711 PCRE2_SIZE <i>*ovector</i>; 3712 uint32_t <i>oveccount</i>; 3713 PCRE2_SIZE <i>output_offsets[2]</i>; 3714</pre> 3715The <i>version</i> field contains the version number of the block format. The 3716current version is 0. The version number will increase in future if more fields 3717are added, but the intention is never to remove any of the existing fields. 3718</P> 3719<P> 3720The <i>subscount</i> field is the number of the current match. It is 1 for the 3721first callout, 2 for the second, and so on. The <i>input</i> and <i>output</i> 3722pointers are copies of the values passed to <b>pcre2_substitute()</b>. 3723</P> 3724<P> 3725The <i>ovector</i> field points to the ovector, which contains the result of the 3726most recent match. The <i>oveccount</i> field contains the number of pairs that 3727are set in the ovector, and is always greater than zero. 3728</P> 3729<P> 3730The <i>output_offsets</i> vector contains the offsets of the replacement in the 3731output string. This has already been processed for dollar and (if requested) 3732backslash substitutions as described above. 3733</P> 3734<P> 3735The second argument of the callout function is the value passed as 3736<i>callout_data</i> when the function was registered. The value returned by the 3737callout function is interpreted as follows: 3738</P> 3739<P> 3740If the value is zero, the replacement is accepted, and, if 3741PCRE2_SUBSTITUTE_GLOBAL is set, processing continues with a search for the next 3742match. If the value is not zero, the current replacement is not accepted. If 3743the value is greater than zero, processing continues when 3744PCRE2_SUBSTITUTE_GLOBAL is set. Otherwise (the value is less than zero or 3745PCRE2_SUBSTITUTE_GLOBAL is not set), the the rest of the input is copied to the 3746output and the call to <b>pcre2_substitute()</b> exits, returning the number of 3747matches so far. 3748</P> 3749<br><a name="SEC37" href="#TOC1">DUPLICATE CAPTURE GROUP NAMES</a><br> 3750<P> 3751<b>int pcre2_substring_nametable_scan(const pcre2_code *<i>code</i>,</b> 3752<b> PCRE2_SPTR <i>name</i>, PCRE2_SPTR *<i>first</i>, PCRE2_SPTR *<i>last</i>);</b> 3753</P> 3754<P> 3755When a pattern is compiled with the PCRE2_DUPNAMES option, names for capture 3756groups are not required to be unique. Duplicate names are always allowed for 3757groups with the same number, created by using the (?| feature. Indeed, if such 3758groups are named, they are required to use the same names. 3759</P> 3760<P> 3761Normally, patterns that use duplicate names are such that in any one match, 3762only one of each set of identically-named groups participates. An example is 3763shown in the 3764<a href="pcre2pattern.html"><b>pcre2pattern</b></a> 3765documentation. 3766</P> 3767<P> 3768When duplicates are present, <b>pcre2_substring_copy_byname()</b> and 3769<b>pcre2_substring_get_byname()</b> return the first substring corresponding to 3770the given name that is set. Only if none are set is PCRE2_ERROR_UNSET is 3771returned. The <b>pcre2_substring_number_from_name()</b> function returns the 3772error PCRE2_ERROR_NOUNIQUESUBSTRING when there are duplicate names. 3773</P> 3774<P> 3775If you want to get full details of all captured substrings for a given name, 3776you must use the <b>pcre2_substring_nametable_scan()</b> function. The first 3777argument is the compiled pattern, and the second is the name. If the third and 3778fourth arguments are NULL, the function returns a group number for a unique 3779name, or PCRE2_ERROR_NOUNIQUESUBSTRING otherwise. 3780</P> 3781<P> 3782When the third and fourth arguments are not NULL, they must be pointers to 3783variables that are updated by the function. After it has run, they point to the 3784first and last entries in the name-to-number table for the given name, and the 3785function returns the length of each entry in code units. In both cases, 3786PCRE2_ERROR_NOSUBSTRING is returned if there are no entries for the given name. 3787</P> 3788<P> 3789The format of the name table is described 3790<a href="#infoaboutpattern">above</a> 3791in the section entitled <i>Information about a pattern</i>. Given all the 3792relevant entries for the name, you can extract each of their numbers, and hence 3793the captured data. 3794</P> 3795<br><a name="SEC38" href="#TOC1">FINDING ALL POSSIBLE MATCHES AT ONE POSITION</a><br> 3796<P> 3797The traditional matching function uses a similar algorithm to Perl, which stops 3798when it finds the first match at a given point in the subject. If you want to 3799find all possible matches, or the longest possible match at a given position, 3800consider using the alternative matching function (see below) instead. If you 3801cannot use the alternative function, you can kludge it up by making use of the 3802callout facility, which is described in the 3803<a href="pcre2callout.html"><b>pcre2callout</b></a> 3804documentation. 3805</P> 3806<P> 3807What you have to do is to insert a callout right at the end of the pattern. 3808When your callout function is called, extract and save the current matched 3809substring. Then return 1, which forces <b>pcre2_match()</b> to backtrack and try 3810other alternatives. Ultimately, when it runs out of matches, 3811<b>pcre2_match()</b> will yield PCRE2_ERROR_NOMATCH. 3812<a name="dfamatch"></a></P> 3813<br><a name="SEC39" href="#TOC1">MATCHING A PATTERN: THE ALTERNATIVE FUNCTION</a><br> 3814<P> 3815<b>int pcre2_dfa_match(const pcre2_code *<i>code</i>, PCRE2_SPTR <i>subject</i>,</b> 3816<b> PCRE2_SIZE <i>length</i>, PCRE2_SIZE <i>startoffset</i>,</b> 3817<b> uint32_t <i>options</i>, pcre2_match_data *<i>match_data</i>,</b> 3818<b> pcre2_match_context *<i>mcontext</i>,</b> 3819<b> int *<i>workspace</i>, PCRE2_SIZE <i>wscount</i>);</b> 3820</P> 3821<P> 3822The function <b>pcre2_dfa_match()</b> is called to match a subject string 3823against a compiled pattern, using a matching algorithm that scans the subject 3824string just once (not counting lookaround assertions), and does not backtrack 3825(except when processing lookaround assertions). This has different 3826characteristics to the normal algorithm, and is not compatible with Perl. Some 3827of the features of PCRE2 patterns are not supported. Nevertheless, there are 3828times when this kind of matching can be useful. For a discussion of the two 3829matching algorithms, and a list of features that <b>pcre2_dfa_match()</b> does 3830not support, see the 3831<a href="pcre2matching.html"><b>pcre2matching</b></a> 3832documentation. 3833</P> 3834<P> 3835The arguments for the <b>pcre2_dfa_match()</b> function are the same as for 3836<b>pcre2_match()</b>, plus two extras. The ovector within the match data block 3837is used in a different way, and this is described below. The other common 3838arguments are used in the same way as for <b>pcre2_match()</b>, so their 3839description is not repeated here. 3840</P> 3841<P> 3842The two additional arguments provide workspace for the function. The workspace 3843vector should contain at least 20 elements. It is used for keeping track of 3844multiple paths through the pattern tree. More workspace is needed for patterns 3845and subjects where there are a lot of potential matches. 3846</P> 3847<P> 3848Here is an example of a simple call to <b>pcre2_dfa_match()</b>: 3849<pre> 3850 int wspace[20]; 3851 pcre2_match_data *md = pcre2_match_data_create(4, NULL); 3852 int rc = pcre2_dfa_match( 3853 re, /* result of pcre2_compile() */ 3854 "some string", /* the subject string */ 3855 11, /* the length of the subject string */ 3856 0, /* start at offset 0 in the subject */ 3857 0, /* default options */ 3858 md, /* the match data block */ 3859 NULL, /* a match context; NULL means use defaults */ 3860 wspace, /* working space vector */ 3861 20); /* number of elements (NOT size in bytes) */ 3862</PRE> 3863</P> 3864<br><b> 3865Option bits for <b>pcre2_dfa_match()</b> 3866</b><br> 3867<P> 3868The unused bits of the <i>options</i> argument for <b>pcre2_dfa_match()</b> must 3869be zero. The only bits that may be set are PCRE2_ANCHORED, 3870PCRE2_COPY_MATCHED_SUBJECT, PCRE2_ENDANCHORED, PCRE2_NOTBOL, PCRE2_NOTEOL, 3871PCRE2_NOTEMPTY, PCRE2_NOTEMPTY_ATSTART, PCRE2_NO_UTF_CHECK, PCRE2_PARTIAL_HARD, 3872PCRE2_PARTIAL_SOFT, PCRE2_DFA_SHORTEST, and PCRE2_DFA_RESTART. All but the last 3873four of these are exactly the same as for <b>pcre2_match()</b>, so their 3874description is not repeated here. 3875<pre> 3876 PCRE2_PARTIAL_HARD 3877 PCRE2_PARTIAL_SOFT 3878</pre> 3879These have the same general effect as they do for <b>pcre2_match()</b>, but the 3880details are slightly different. When PCRE2_PARTIAL_HARD is set for 3881<b>pcre2_dfa_match()</b>, it returns PCRE2_ERROR_PARTIAL if the end of the 3882subject is reached and there is still at least one matching possibility that 3883requires additional characters. This happens even if some complete matches have 3884already been found. When PCRE2_PARTIAL_SOFT is set, the return code 3885PCRE2_ERROR_NOMATCH is converted into PCRE2_ERROR_PARTIAL if the end of the 3886subject is reached, there have been no complete matches, but there is still at 3887least one matching possibility. The portion of the string that was inspected 3888when the longest partial match was found is set as the first matching string in 3889both cases. There is a more detailed discussion of partial and multi-segment 3890matching, with examples, in the 3891<a href="pcre2partial.html"><b>pcre2partial</b></a> 3892documentation. 3893<pre> 3894 PCRE2_DFA_SHORTEST 3895</pre> 3896Setting the PCRE2_DFA_SHORTEST option causes the matching algorithm to stop as 3897soon as it has found one match. Because of the way the alternative algorithm 3898works, this is necessarily the shortest possible match at the first possible 3899matching point in the subject string. 3900<pre> 3901 PCRE2_DFA_RESTART 3902</pre> 3903When <b>pcre2_dfa_match()</b> returns a partial match, it is possible to call it 3904again, with additional subject characters, and have it continue with the same 3905match. The PCRE2_DFA_RESTART option requests this action; when it is set, the 3906<i>workspace</i> and <i>wscount</i> options must reference the same vector as 3907before because data about the match so far is left in them after a partial 3908match. There is more discussion of this facility in the 3909<a href="pcre2partial.html"><b>pcre2partial</b></a> 3910documentation. 3911</P> 3912<br><b> 3913Successful returns from <b>pcre2_dfa_match()</b> 3914</b><br> 3915<P> 3916When <b>pcre2_dfa_match()</b> succeeds, it may have matched more than one 3917substring in the subject. Note, however, that all the matches from one run of 3918the function start at the same point in the subject. The shorter matches are 3919all initial substrings of the longer matches. For example, if the pattern 3920<pre> 3921 <.*> 3922</pre> 3923is matched against the string 3924<pre> 3925 This is <something> <something else> <something further> no more 3926</pre> 3927the three matched strings are 3928<pre> 3929 <something> <something else> <something further> 3930 <something> <something else> 3931 <something> 3932</pre> 3933On success, the yield of the function is a number greater than zero, which is 3934the number of matched substrings. The offsets of the substrings are returned in 3935the ovector, and can be extracted by number in the same way as for 3936<b>pcre2_match()</b>, but the numbers bear no relation to any capture groups 3937that may exist in the pattern, because DFA matching does not support capturing. 3938</P> 3939<P> 3940Calls to the convenience functions that extract substrings by name 3941return the error PCRE2_ERROR_DFA_UFUNC (unsupported function) if used after a 3942DFA match. The convenience functions that extract substrings by number never 3943return PCRE2_ERROR_NOSUBSTRING. 3944</P> 3945<P> 3946The matched strings are stored in the ovector in reverse order of length; that 3947is, the longest matching string is first. If there were too many matches to fit 3948into the ovector, the yield of the function is zero, and the vector is filled 3949with the longest matches. 3950</P> 3951<P> 3952NOTE: PCRE2's "auto-possessification" optimization usually applies to character 3953repeats at the end of a pattern (as well as internally). For example, the 3954pattern "a\d+" is compiled as if it were "a\d++". For DFA matching, this 3955means that only one possible match is found. If you really do want multiple 3956matches in such cases, either use an ungreedy repeat such as "a\d+?" or set 3957the PCRE2_NO_AUTO_POSSESS option when compiling. 3958</P> 3959<br><b> 3960Error returns from <b>pcre2_dfa_match()</b> 3961</b><br> 3962<P> 3963The <b>pcre2_dfa_match()</b> function returns a negative number when it fails. 3964Many of the errors are the same as for <b>pcre2_match()</b>, as described 3965<a href="#errorlist">above.</a> 3966There are in addition the following errors that are specific to 3967<b>pcre2_dfa_match()</b>: 3968<pre> 3969 PCRE2_ERROR_DFA_UITEM 3970</pre> 3971This return is given if <b>pcre2_dfa_match()</b> encounters an item in the 3972pattern that it does not support, for instance, the use of \C in a UTF mode or 3973a backreference. 3974<pre> 3975 PCRE2_ERROR_DFA_UCOND 3976</pre> 3977This return is given if <b>pcre2_dfa_match()</b> encounters a condition item 3978that uses a backreference for the condition, or a test for recursion in a 3979specific capture group. These are not supported. 3980<pre> 3981 PCRE2_ERROR_DFA_UINVALID_UTF 3982</pre> 3983This return is given if <b>pcre2_dfa_match()</b> is called for a pattern that 3984was compiled with PCRE2_MATCH_INVALID_UTF. This is not supported for DFA 3985matching. 3986<pre> 3987 PCRE2_ERROR_DFA_WSSIZE 3988</pre> 3989This return is given if <b>pcre2_dfa_match()</b> runs out of space in the 3990<i>workspace</i> vector. 3991<pre> 3992 PCRE2_ERROR_DFA_RECURSE 3993</pre> 3994When a recursion or subroutine call is processed, the matching function calls 3995itself recursively, using private memory for the ovector and <i>workspace</i>. 3996This error is given if the internal ovector is not large enough. This should be 3997extremely rare, as a vector of size 1000 is used. 3998<pre> 3999 PCRE2_ERROR_DFA_BADRESTART 4000</pre> 4001When <b>pcre2_dfa_match()</b> is called with the <b>PCRE2_DFA_RESTART</b> option, 4002some plausibility checks are made on the contents of the workspace, which 4003should contain data about the previous partial match. If any of these checks 4004fail, this error is given. 4005</P> 4006<br><a name="SEC40" href="#TOC1">SEE ALSO</a><br> 4007<P> 4008<b>pcre2build</b>(3), <b>pcre2callout</b>(3), <b>pcre2demo(3)</b>, 4009<b>pcre2matching</b>(3), <b>pcre2partial</b>(3), <b>pcre2posix</b>(3), 4010<b>pcre2sample</b>(3), <b>pcre2unicode</b>(3). 4011</P> 4012<br><a name="SEC41" href="#TOC1">AUTHOR</a><br> 4013<P> 4014Philip Hazel 4015<br> 4016Retired from University Computing Service 4017<br> 4018Cambridge, England. 4019<br> 4020</P> 4021<br><a name="SEC42" href="#TOC1">REVISION</a><br> 4022<P> 4023Last updated: 27 July 2022 4024<br> 4025Copyright © 1997-2022 University of Cambridge. 4026<br> 4027<p> 4028Return to the <a href="index.html">PCRE2 index page</a>. 4029</p> 4030