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 unsigned char *<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 \fIreplacementzfP,</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 unsigned char *pcre2_maketables(pcre2_general_context *<i>gcontext</i>);</b> 313<br> 314<br> 315<b>int pcre2_pattern_info(const pcre2_code *<i>code</i>, uint32_t <i>what</i>,</b> 316<b> void *<i>where</i>);</b> 317<br> 318<br> 319<b>int pcre2_callout_enumerate(const pcre2_code *<i>code</i>,</b> 320<b> int (*<i>callback</i>)(pcre2_callout_enumerate_block *, void *),</b> 321<b> void *<i>user_data</i>);</b> 322<br> 323<br> 324<b>int pcre2_config(uint32_t <i>what</i>, void *<i>where</i>);</b> 325</P> 326<br><a name="SEC11" href="#TOC1">PCRE2 NATIVE API OBSOLETE FUNCTIONS</a><br> 327<P> 328<b>int pcre2_set_recursion_limit(pcre2_match_context *<i>mcontext</i>,</b> 329<b> uint32_t <i>value</i>);</b> 330<br> 331<br> 332<b>int pcre2_set_recursion_memory_management(</b> 333<b> pcre2_match_context *<i>mcontext</i>,</b> 334<b> void *(*<i>private_malloc</i>)(PCRE2_SIZE, void *),</b> 335<b> void (*<i>private_free</i>)(void *, void *), void *<i>memory_data</i>);</b> 336<br> 337<br> 338These functions became obsolete at release 10.30 and are retained only for 339backward compatibility. They should not be used in new code. The first is 340replaced by <b>pcre2_set_depth_limit()</b>; the second is no longer needed and 341has no effect (it always returns zero). 342</P> 343<br><a name="SEC12" href="#TOC1">PCRE2 EXPERIMENTAL PATTERN CONVERSION FUNCTIONS</a><br> 344<P> 345<b>pcre2_convert_context *pcre2_convert_context_create(</b> 346<b> pcre2_general_context *<i>gcontext</i>);</b> 347<br> 348<br> 349<b>pcre2_convert_context *pcre2_convert_context_copy(</b> 350<b> pcre2_convert_context *<i>cvcontext</i>);</b> 351<br> 352<br> 353<b>void pcre2_convert_context_free(pcre2_convert_context *<i>cvcontext</i>);</b> 354<br> 355<br> 356<b>int pcre2_set_glob_escape(pcre2_convert_context *<i>cvcontext</i>,</b> 357<b> uint32_t <i>escape_char</i>);</b> 358<br> 359<br> 360<b>int pcre2_set_glob_separator(pcre2_convert_context *<i>cvcontext</i>,</b> 361<b> uint32_t <i>separator_char</i>);</b> 362<br> 363<br> 364<b>int pcre2_pattern_convert(PCRE2_SPTR <i>pattern</i>, PCRE2_SIZE <i>length</i>,</b> 365<b> uint32_t <i>options</i>, PCRE2_UCHAR **<i>buffer</i>,</b> 366<b> PCRE2_SIZE *<i>blength</i>, pcre2_convert_context *<i>cvcontext</i>);</b> 367<br> 368<br> 369<b>void pcre2_converted_pattern_free(PCRE2_UCHAR *<i>converted_pattern</i>);</b> 370<br> 371<br> 372These functions provide a way of converting non-PCRE2 patterns into 373patterns that can be processed by <b>pcre2_compile()</b>. This facility is 374experimental and may be changed in future releases. At present, "globs" and 375POSIX basic and extended patterns can be converted. Details are given in the 376<a href="pcre2convert.html"><b>pcre2convert</b></a> 377documentation. 378</P> 379<br><a name="SEC13" href="#TOC1">PCRE2 8-BIT, 16-BIT, AND 32-BIT LIBRARIES</a><br> 380<P> 381There are three PCRE2 libraries, supporting 8-bit, 16-bit, and 32-bit code 382units, respectively. However, there is just one header file, <b>pcre2.h</b>. 383This contains the function prototypes and other definitions for all three 384libraries. One, two, or all three can be installed simultaneously. On Unix-like 385systems the libraries are called <b>libpcre2-8</b>, <b>libpcre2-16</b>, and 386<b>libpcre2-32</b>, and they can also co-exist with the original PCRE libraries. 387</P> 388<P> 389Character strings are passed to and from a PCRE2 library as a sequence of 390unsigned integers in code units of the appropriate width. Every PCRE2 function 391comes in three different forms, one for each library, for example: 392<pre> 393 <b>pcre2_compile_8()</b> 394 <b>pcre2_compile_16()</b> 395 <b>pcre2_compile_32()</b> 396</pre> 397There are also three different sets of data types: 398<pre> 399 <b>PCRE2_UCHAR8, PCRE2_UCHAR16, PCRE2_UCHAR32</b> 400 <b>PCRE2_SPTR8, PCRE2_SPTR16, PCRE2_SPTR32</b> 401</pre> 402The UCHAR types define unsigned code units of the appropriate widths. For 403example, PCRE2_UCHAR16 is usually defined as `uint16_t'. The SPTR types are 404constant pointers to the equivalent UCHAR types, that is, they are pointers to 405vectors of unsigned code units. 406</P> 407<P> 408Many applications use only one code unit width. For their convenience, macros 409are defined whose names are the generic forms such as <b>pcre2_compile()</b> and 410PCRE2_SPTR. These macros use the value of the macro PCRE2_CODE_UNIT_WIDTH to 411generate the appropriate width-specific function and macro names. 412PCRE2_CODE_UNIT_WIDTH is not defined by default. An application must define it 413to be 8, 16, or 32 before including <b>pcre2.h</b> in order to make use of the 414generic names. 415</P> 416<P> 417Applications that use more than one code unit width can be linked with more 418than one PCRE2 library, but must define PCRE2_CODE_UNIT_WIDTH to be 0 before 419including <b>pcre2.h</b>, and then use the real function names. Any code that is 420to be included in an environment where the value of PCRE2_CODE_UNIT_WIDTH is 421unknown should also use the real function names. (Unfortunately, it is not 422possible in C code to save and restore the value of a macro.) 423</P> 424<P> 425If PCRE2_CODE_UNIT_WIDTH is not defined before including <b>pcre2.h</b>, a 426compiler error occurs. 427</P> 428<P> 429When using multiple libraries in an application, you must take care when 430processing any particular pattern to use only functions from a single library. 431For example, if you want to run a match using a pattern that was compiled with 432<b>pcre2_compile_16()</b>, you must do so with <b>pcre2_match_16()</b>, not 433<b>pcre2_match_8()</b> or <b>pcre2_match_32()</b>. 434</P> 435<P> 436In the function summaries above, and in the rest of this document and other 437PCRE2 documents, functions and data types are described using their generic 438names, without the _8, _16, or _32 suffix. 439</P> 440<br><a name="SEC14" href="#TOC1">PCRE2 API OVERVIEW</a><br> 441<P> 442PCRE2 has its own native API, which is described in this document. There are 443also some wrapper functions for the 8-bit library that correspond to the 444POSIX regular expression API, but they do not give access to all the 445functionality of PCRE2. They are described in the 446<a href="pcre2posix.html"><b>pcre2posix</b></a> 447documentation. Both these APIs define a set of C function calls. 448</P> 449<P> 450The native API C data types, function prototypes, option values, and error 451codes are defined in the header file <b>pcre2.h</b>, which also contains 452definitions of PCRE2_MAJOR and PCRE2_MINOR, the major and minor release numbers 453for the library. Applications can use these to include support for different 454releases of PCRE2. 455</P> 456<P> 457In a Windows environment, if you want to statically link an application program 458against a non-dll PCRE2 library, you must define PCRE2_STATIC before including 459<b>pcre2.h</b>. 460</P> 461<P> 462The functions <b>pcre2_compile()</b> and <b>pcre2_match()</b> are used for 463compiling and matching regular expressions in a Perl-compatible manner. A 464sample program that demonstrates the simplest way of using them is provided in 465the file called <i>pcre2demo.c</i> in the PCRE2 source distribution. A listing 466of this program is given in the 467<a href="pcre2demo.html"><b>pcre2demo</b></a> 468documentation, and the 469<a href="pcre2sample.html"><b>pcre2sample</b></a> 470documentation describes how to compile and run it. 471</P> 472<P> 473The compiling and matching functions recognize various options that are passed 474as bits in an options argument. There are also some more complicated parameters 475such as custom memory management functions and resource limits that are passed 476in "contexts" (which are just memory blocks, described below). Simple 477applications do not need to make use of contexts. 478</P> 479<P> 480Just-in-time (JIT) compiler support is an optional feature of PCRE2 that can be 481built in appropriate hardware environments. It greatly speeds up the matching 482performance of many patterns. Programs can request that it be used if 483available by calling <b>pcre2_jit_compile()</b> after a pattern has been 484successfully compiled by <b>pcre2_compile()</b>. This does nothing if JIT 485support is not available. 486</P> 487<P> 488More complicated programs might need to make use of the specialist functions 489<b>pcre2_jit_stack_create()</b>, <b>pcre2_jit_stack_free()</b>, and 490<b>pcre2_jit_stack_assign()</b> in order to control the JIT code's memory usage. 491</P> 492<P> 493JIT matching is automatically used by <b>pcre2_match()</b> if it is available, 494unless the PCRE2_NO_JIT option is set. There is also a direct interface for JIT 495matching, which gives improved performance at the expense of less sanity 496checking. The JIT-specific functions are discussed in the 497<a href="pcre2jit.html"><b>pcre2jit</b></a> 498documentation. 499</P> 500<P> 501A second matching function, <b>pcre2_dfa_match()</b>, which is not 502Perl-compatible, is also provided. This uses a different algorithm for the 503matching. The alternative algorithm finds all possible matches (at a given 504point in the subject), and scans the subject just once (unless there are 505lookaround assertions). However, this algorithm does not return captured 506substrings. A description of the two matching algorithms and their advantages 507and disadvantages is given in the 508<a href="pcre2matching.html"><b>pcre2matching</b></a> 509documentation. There is no JIT support for <b>pcre2_dfa_match()</b>. 510</P> 511<P> 512In addition to the main compiling and matching functions, there are convenience 513functions for extracting captured substrings from a subject string that has 514been matched by <b>pcre2_match()</b>. They are: 515<pre> 516 <b>pcre2_substring_copy_byname()</b> 517 <b>pcre2_substring_copy_bynumber()</b> 518 <b>pcre2_substring_get_byname()</b> 519 <b>pcre2_substring_get_bynumber()</b> 520 <b>pcre2_substring_list_get()</b> 521 <b>pcre2_substring_length_byname()</b> 522 <b>pcre2_substring_length_bynumber()</b> 523 <b>pcre2_substring_nametable_scan()</b> 524 <b>pcre2_substring_number_from_name()</b> 525</pre> 526<b>pcre2_substring_free()</b> and <b>pcre2_substring_list_free()</b> are also 527provided, to free memory used for extracted strings. If either of these 528functions is called with a NULL argument, the function returns immediately 529without doing anything. 530</P> 531<P> 532The function <b>pcre2_substitute()</b> can be called to match a pattern and 533return a copy of the subject string with substitutions for parts that were 534matched. 535</P> 536<P> 537Functions whose names begin with <b>pcre2_serialize_</b> are used for saving 538compiled patterns on disc or elsewhere, and reloading them later. 539</P> 540<P> 541Finally, there are functions for finding out information about a compiled 542pattern (<b>pcre2_pattern_info()</b>) and about the configuration with which 543PCRE2 was built (<b>pcre2_config()</b>). 544</P> 545<P> 546Functions with names ending with <b>_free()</b> are used for freeing memory 547blocks of various sorts. In all cases, if one of these functions is called with 548a NULL argument, it does nothing. 549</P> 550<br><a name="SEC15" href="#TOC1">STRING LENGTHS AND OFFSETS</a><br> 551<P> 552The PCRE2 API uses string lengths and offsets into strings of code units in 553several places. These values are always of type PCRE2_SIZE, which is an 554unsigned integer type, currently always defined as <i>size_t</i>. The largest 555value that can be stored in such a type (that is ~(PCRE2_SIZE)0) is reserved 556as a special indicator for zero-terminated strings and unset offsets. 557Therefore, the longest string that can be handled is one less than this 558maximum. 559<a name="newlines"></a></P> 560<br><a name="SEC16" href="#TOC1">NEWLINES</a><br> 561<P> 562PCRE2 supports five different conventions for indicating line breaks in 563strings: a single CR (carriage return) character, a single LF (linefeed) 564character, the two-character sequence CRLF, any of the three preceding, or any 565Unicode newline sequence. The Unicode newline sequences are the three just 566mentioned, plus the single characters VT (vertical tab, U+000B), FF (form feed, 567U+000C), NEL (next line, U+0085), LS (line separator, U+2028), and PS 568(paragraph separator, U+2029). 569</P> 570<P> 571Each of the first three conventions is used by at least one operating system as 572its standard newline sequence. When PCRE2 is built, a default can be specified. 573If it is not, the default is set to LF, which is the Unix standard. However, 574the newline convention can be changed by an application when calling 575<b>pcre2_compile()</b>, or it can be specified by special text at the start of 576the pattern itself; this overrides any other settings. See the 577<a href="pcre2pattern.html"><b>pcre2pattern</b></a> 578page for details of the special character sequences. 579</P> 580<P> 581In the PCRE2 documentation the word "newline" is used to mean "the character or 582pair of characters that indicate a line break". The choice of newline 583convention affects the handling of the dot, circumflex, and dollar 584metacharacters, the handling of #-comments in /x mode, and, when CRLF is a 585recognized line ending sequence, the match position advancement for a 586non-anchored pattern. There is more detail about this in the 587<a href="#matchoptions">section on <b>pcre2_match()</b> options</a> 588below. 589</P> 590<P> 591The choice of newline convention does not affect the interpretation of 592the \n or \r escape sequences, nor does it affect what \R matches; this has 593its own separate convention. 594</P> 595<br><a name="SEC17" href="#TOC1">MULTITHREADING</a><br> 596<P> 597In a multithreaded application it is important to keep thread-specific data 598separate from data that can be shared between threads. The PCRE2 library code 599itself is thread-safe: it contains no static or global variables. The API is 600designed to be fairly simple for non-threaded applications while at the same 601time ensuring that multithreaded applications can use it. 602</P> 603<P> 604There are several different blocks of data that are used to pass information 605between the application and the PCRE2 libraries. 606</P> 607<br><b> 608The compiled pattern 609</b><br> 610<P> 611A pointer to the compiled form of a pattern is returned to the user when 612<b>pcre2_compile()</b> is successful. The data in the compiled pattern is fixed, 613and does not change when the pattern is matched. Therefore, it is thread-safe, 614that is, the same compiled pattern can be used by more than one thread 615simultaneously. For example, an application can compile all its patterns at the 616start, before forking off multiple threads that use them. However, if the 617just-in-time (JIT) optimization feature is being used, it needs separate memory 618stack areas for each thread. See the 619<a href="pcre2jit.html"><b>pcre2jit</b></a> 620documentation for more details. 621</P> 622<P> 623In a more complicated situation, where patterns are compiled only when they are 624first needed, but are still shared between threads, pointers to compiled 625patterns must be protected from simultaneous writing by multiple threads, at 626least until a pattern has been compiled. The logic can be something like this: 627<pre> 628 Get a read-only (shared) lock (mutex) for pointer 629 if (pointer == NULL) 630 { 631 Get a write (unique) lock for pointer 632 pointer = pcre2_compile(... 633 } 634 Release the lock 635 Use pointer in pcre2_match() 636</pre> 637Of course, testing for compilation errors should also be included in the code. 638</P> 639<P> 640If JIT is being used, but the JIT compilation is not being done immediately, 641(perhaps waiting to see if the pattern is used often enough) similar logic is 642required. JIT compilation updates a pointer within the compiled code block, so 643a thread must gain unique write access to the pointer before calling 644<b>pcre2_jit_compile()</b>. Alternatively, <b>pcre2_code_copy()</b> or 645<b>pcre2_code_copy_with_tables()</b> can be used to obtain a private copy of the 646compiled code before calling the JIT compiler. 647</P> 648<br><b> 649Context blocks 650</b><br> 651<P> 652The next main section below introduces the idea of "contexts" in which PCRE2 653functions are called. A context is nothing more than a collection of parameters 654that control the way PCRE2 operates. Grouping a number of parameters together 655in a context is a convenient way of passing them to a PCRE2 function without 656using lots of arguments. The parameters that are stored in contexts are in some 657sense "advanced features" of the API. Many straightforward applications will 658not need to use contexts. 659</P> 660<P> 661In a multithreaded application, if the parameters in a context are values that 662are never changed, the same context can be used by all the threads. However, if 663any thread needs to change any value in a context, it must make its own 664thread-specific copy. 665</P> 666<br><b> 667Match blocks 668</b><br> 669<P> 670The matching functions need a block of memory for storing the results of a 671match. This includes details of what was matched, as well as additional 672information such as the name of a (*MARK) setting. Each thread must provide its 673own copy of this memory. 674</P> 675<br><a name="SEC18" href="#TOC1">PCRE2 CONTEXTS</a><br> 676<P> 677Some PCRE2 functions have a lot of parameters, many of which are used only by 678specialist applications, for example, those that use custom memory management 679or non-standard character tables. To keep function argument lists at a 680reasonable size, and at the same time to keep the API extensible, "uncommon" 681parameters are passed to certain functions in a <b>context</b> instead of 682directly. A context is just a block of memory that holds the parameter values. 683Applications that do not need to adjust any of the context parameters can pass 684NULL when a context pointer is required. 685</P> 686<P> 687There are three different types of context: a general context that is relevant 688for several PCRE2 operations, a compile-time context, and a match-time context. 689</P> 690<br><b> 691The general context 692</b><br> 693<P> 694At present, this context just contains pointers to (and data for) external 695memory management functions that are called from several places in the PCRE2 696library. The context is named `general' rather than specifically `memory' 697because in future other fields may be added. If you do not want to supply your 698own custom memory management functions, you do not need to bother with a 699general context. A general context is created by: 700<br> 701<br> 702<b>pcre2_general_context *pcre2_general_context_create(</b> 703<b> void *(*<i>private_malloc</i>)(PCRE2_SIZE, void *),</b> 704<b> void (*<i>private_free</i>)(void *, void *), void *<i>memory_data</i>);</b> 705<br> 706<br> 707The two function pointers specify custom memory management functions, whose 708prototypes are: 709<pre> 710 <b>void *private_malloc(PCRE2_SIZE, void *);</b> 711 <b>void private_free(void *, void *);</b> 712</pre> 713Whenever code in PCRE2 calls these functions, the final argument is the value 714of <i>memory_data</i>. Either of the first two arguments of the creation 715function may be NULL, in which case the system memory management functions 716<i>malloc()</i> and <i>free()</i> are used. (This is not currently useful, as 717there are no other fields in a general context, but in future there might be.) 718The <i>private_malloc()</i> function is used (if supplied) to obtain memory for 719storing the context, and all three values are saved as part of the context. 720</P> 721<P> 722Whenever PCRE2 creates a data block of any kind, the block contains a pointer 723to the <i>free()</i> function that matches the <i>malloc()</i> function that was 724used. When the time comes to free the block, this function is called. 725</P> 726<P> 727A general context can be copied by calling: 728<br> 729<br> 730<b>pcre2_general_context *pcre2_general_context_copy(</b> 731<b> pcre2_general_context *<i>gcontext</i>);</b> 732<br> 733<br> 734The memory used for a general context should be freed by calling: 735<br> 736<br> 737<b>void pcre2_general_context_free(pcre2_general_context *<i>gcontext</i>);</b> 738<br> 739<br> 740If this function is passed a NULL argument, it returns immediately without 741doing anything. 742<a name="compilecontext"></a></P> 743<br><b> 744The compile context 745</b><br> 746<P> 747A compile context is required if you want to provide an external function for 748stack checking during compilation or to change the default values of any of the 749following compile-time parameters: 750<pre> 751 What \R matches (Unicode newlines or CR, LF, CRLF only) 752 PCRE2's character tables 753 The newline character sequence 754 The compile time nested parentheses limit 755 The maximum length of the pattern string 756 The extra options bits (none set by default) 757</pre> 758A compile context is also required if you are using custom memory management. 759If none of these apply, just pass NULL as the context argument of 760<i>pcre2_compile()</i>. 761</P> 762<P> 763A compile context is created, copied, and freed by the following functions: 764<br> 765<br> 766<b>pcre2_compile_context *pcre2_compile_context_create(</b> 767<b> pcre2_general_context *<i>gcontext</i>);</b> 768<br> 769<br> 770<b>pcre2_compile_context *pcre2_compile_context_copy(</b> 771<b> pcre2_compile_context *<i>ccontext</i>);</b> 772<br> 773<br> 774<b>void pcre2_compile_context_free(pcre2_compile_context *<i>ccontext</i>);</b> 775<br> 776<br> 777A compile context is created with default values for its parameters. These can 778be changed by calling the following functions, which return 0 on success, or 779PCRE2_ERROR_BADDATA if invalid data is detected. 780<br> 781<br> 782<b>int pcre2_set_bsr(pcre2_compile_context *<i>ccontext</i>,</b> 783<b> uint32_t <i>value</i>);</b> 784<br> 785<br> 786The value must be PCRE2_BSR_ANYCRLF, to specify that \R matches only CR, LF, 787or CRLF, or PCRE2_BSR_UNICODE, to specify that \R matches any Unicode line 788ending sequence. The value is used by the JIT compiler and by the two 789interpreted matching functions, <i>pcre2_match()</i> and 790<i>pcre2_dfa_match()</i>. 791<br> 792<br> 793<b>int pcre2_set_character_tables(pcre2_compile_context *<i>ccontext</i>,</b> 794<b> const unsigned char *<i>tables</i>);</b> 795<br> 796<br> 797The value must be the result of a call to <i>pcre2_maketables()</i>, whose only 798argument is a general context. This function builds a set of character tables 799in the current locale. 800<br> 801<br> 802<b>int pcre2_set_compile_extra_options(pcre2_compile_context *<i>ccontext</i>,</b> 803<b> uint32_t <i>extra_options</i>);</b> 804<br> 805<br> 806As PCRE2 has developed, almost all the 32 option bits that are available in 807the <i>options</i> argument of <b>pcre2_compile()</b> have been used up. To avoid 808running out, the compile context contains a set of extra option bits which are 809used for some newer, assumed rarer, options. This function sets those bits. It 810always sets all the bits (either on or off). It does not modify any existing 811setting. The available options are defined in the section entitled "Extra 812compile options" 813<a href="#extracompileoptions">below.</a> 814<br> 815<br> 816<b>int pcre2_set_max_pattern_length(pcre2_compile_context *<i>ccontext</i>,</b> 817<b> PCRE2_SIZE <i>value</i>);</b> 818<br> 819<br> 820This sets a maximum length, in code units, for any pattern string that is 821compiled with this context. If the pattern is longer, an error is generated. 822This facility is provided so that applications that accept patterns from 823external sources can limit their size. The default is the largest number that a 824PCRE2_SIZE variable can hold, which is effectively unlimited. 825<br> 826<br> 827<b>int pcre2_set_newline(pcre2_compile_context *<i>ccontext</i>,</b> 828<b> uint32_t <i>value</i>);</b> 829<br> 830<br> 831This specifies which characters or character sequences are to be recognized as 832newlines. The value must be one of PCRE2_NEWLINE_CR (carriage return only), 833PCRE2_NEWLINE_LF (linefeed only), PCRE2_NEWLINE_CRLF (the two-character 834sequence CR followed by LF), PCRE2_NEWLINE_ANYCRLF (any of the above), 835PCRE2_NEWLINE_ANY (any Unicode newline sequence), or PCRE2_NEWLINE_NUL (the 836NUL character, that is a binary zero). 837</P> 838<P> 839A pattern can override the value set in the compile context by starting with a 840sequence such as (*CRLF). See the 841<a href="pcre2pattern.html"><b>pcre2pattern</b></a> 842page for details. 843</P> 844<P> 845When a pattern is compiled with the PCRE2_EXTENDED or PCRE2_EXTENDED_MORE 846option, the newline convention affects the recognition of the end of internal 847comments starting with #. The value is saved with the compiled pattern for 848subsequent use by the JIT compiler and by the two interpreted matching 849functions, <i>pcre2_match()</i> and <i>pcre2_dfa_match()</i>. 850<br> 851<br> 852<b>int pcre2_set_parens_nest_limit(pcre2_compile_context *<i>ccontext</i>,</b> 853<b> uint32_t <i>value</i>);</b> 854<br> 855<br> 856This parameter adjusts the limit, set when PCRE2 is built (default 250), on the 857depth of parenthesis nesting in a pattern. This limit stops rogue patterns 858using up too much system stack when being compiled. The limit applies to 859parentheses of all kinds, not just capturing parentheses. 860<br> 861<br> 862<b>int pcre2_set_compile_recursion_guard(pcre2_compile_context *<i>ccontext</i>,</b> 863<b> int (*<i>guard_function</i>)(uint32_t, void *), void *<i>user_data</i>);</b> 864<br> 865<br> 866There is at least one application that runs PCRE2 in threads with very limited 867system stack, where running out of stack is to be avoided at all costs. The 868parenthesis limit above cannot take account of how much stack is actually 869available during compilation. For a finer control, you can supply a function 870that is called whenever <b>pcre2_compile()</b> starts to compile a parenthesized 871part of a pattern. This function can check the actual stack size (or anything 872else that it wants to, of course). 873</P> 874<P> 875The first argument to the callout function gives the current depth of 876nesting, and the second is user data that is set up by the last argument of 877<b>pcre2_set_compile_recursion_guard()</b>. The callout function should return 878zero if all is well, or non-zero to force an error. 879<a name="matchcontext"></a></P> 880<br><b> 881The match context 882</b><br> 883<P> 884A match context is required if you want to: 885<pre> 886 Set up a callout function 887 Set an offset limit for matching an unanchored pattern 888 Change the limit on the amount of heap used when matching 889 Change the backtracking match limit 890 Change the backtracking depth limit 891 Set custom memory management specifically for the match 892</pre> 893If none of these apply, just pass NULL as the context argument of 894<b>pcre2_match()</b>, <b>pcre2_dfa_match()</b>, or <b>pcre2_jit_match()</b>. 895</P> 896<P> 897A match context is created, copied, and freed by the following functions: 898<br> 899<br> 900<b>pcre2_match_context *pcre2_match_context_create(</b> 901<b> pcre2_general_context *<i>gcontext</i>);</b> 902<br> 903<br> 904<b>pcre2_match_context *pcre2_match_context_copy(</b> 905<b> pcre2_match_context *<i>mcontext</i>);</b> 906<br> 907<br> 908<b>void pcre2_match_context_free(pcre2_match_context *<i>mcontext</i>);</b> 909<br> 910<br> 911A match context is created with default values for its parameters. These can 912be changed by calling the following functions, which return 0 on success, or 913PCRE2_ERROR_BADDATA if invalid data is detected. 914<br> 915<br> 916<b>int pcre2_set_callout(pcre2_match_context *<i>mcontext</i>,</b> 917<b> int (*<i>callout_function</i>)(pcre2_callout_block *, void *),</b> 918<b> void *<i>callout_data</i>);</b> 919<br> 920<br> 921This sets up a callout function for PCRE2 to call at specified points 922during a matching operation. Details are given in the 923<a href="pcre2callout.html"><b>pcre2callout</b></a> 924documentation. 925<br> 926<br> 927<b>int pcre2_set_substitute_callout(pcre2_match_context *<i>mcontext</i>,</b> 928<b> int (*<i>callout_function</i>)(pcre2_substitute_callout_block *, void *),</b> 929<b> void *<i>callout_data</i>);</b> 930<br> 931<br> 932This sets up a callout function for PCRE2 to call after each substitution 933made by <b>pcre2_substitute()</b>. Details are given in the section entitled 934"Creating a new string with substitutions" 935<a href="#substitutions">below.</a> 936<br> 937<br> 938<b>int pcre2_set_offset_limit(pcre2_match_context *<i>mcontext</i>,</b> 939<b> PCRE2_SIZE <i>value</i>);</b> 940<br> 941<br> 942The <i>offset_limit</i> parameter limits how far an unanchored search can 943advance in the subject string. The default value is PCRE2_UNSET. The 944<b>pcre2_match()</b> and <b>pcre2_dfa_match()</b> functions return 945PCRE2_ERROR_NOMATCH if a match with a starting point before or at the given 946offset is not found. The <b>pcre2_substitute()</b> function makes no more 947substitutions. 948</P> 949<P> 950For example, if the pattern /abc/ is matched against "123abc" with an offset 951limit less than 3, the result is PCRE2_ERROR_NOMATCH. A match can never be 952found if the <i>startoffset</i> argument of <b>pcre2_match()</b>, 953<b>pcre2_dfa_match()</b>, or <b>pcre2_substitute()</b> is greater than the offset 954limit set in the match context. 955</P> 956<P> 957When using this facility, you must set the PCRE2_USE_OFFSET_LIMIT option when 958calling <b>pcre2_compile()</b> so that when JIT is in use, different code can be 959compiled. If a match is started with a non-default match limit when 960PCRE2_USE_OFFSET_LIMIT is not set, an error is generated. 961</P> 962<P> 963The offset limit facility can be used to track progress when searching large 964subject strings or to limit the extent of global substitutions. See also the 965PCRE2_FIRSTLINE option, which requires a match to start before or at the first 966newline that follows the start of matching in the subject. If this is set with 967an offset limit, a match must occur in the first line and also within the 968offset limit. In other words, whichever limit comes first is used. 969<br> 970<br> 971<b>int pcre2_set_heap_limit(pcre2_match_context *<i>mcontext</i>,</b> 972<b> uint32_t <i>value</i>);</b> 973<br> 974<br> 975The <i>heap_limit</i> parameter specifies, in units of kibibytes (1024 bytes), 976the maximum amount of heap memory that <b>pcre2_match()</b> may use to hold 977backtracking information when running an interpretive match. This limit also 978applies to <b>pcre2_dfa_match()</b>, which may use the heap when processing 979patterns with a lot of nested pattern recursion or lookarounds or atomic 980groups. This limit does not apply to matching with the JIT optimization, which 981has its own memory control arrangements (see the 982<a href="pcre2jit.html"><b>pcre2jit</b></a> 983documentation for more details). If the limit is reached, the negative error 984code PCRE2_ERROR_HEAPLIMIT is returned. The default limit can be set when PCRE2 985is built; if it is not, the default is set very large and is essentially 986"unlimited". 987</P> 988<P> 989A value for the heap limit may also be supplied by an item at the start of a 990pattern of the form 991<pre> 992 (*LIMIT_HEAP=ddd) 993</pre> 994where ddd is a decimal number. However, such a setting is ignored unless ddd is 995less than the limit set by the caller of <b>pcre2_match()</b> or, if no such 996limit is set, less than the default. 997</P> 998<P> 999The <b>pcre2_match()</b> function starts out using a 20KiB vector on the system 1000stack for recording backtracking points. The more nested backtracking points 1001there are (that is, the deeper the search tree), the more memory is needed. 1002Heap memory is used only if the initial vector is too small. If the heap limit 1003is set to a value less than 21 (in particular, zero) no heap memory will be 1004used. In this case, only patterns that do not have a lot of nested backtracking 1005can be successfully processed. 1006</P> 1007<P> 1008Similarly, for <b>pcre2_dfa_match()</b>, a vector on the system stack is used 1009when processing pattern recursions, lookarounds, or atomic groups, and only if 1010this is not big enough is heap memory used. In this case, too, setting a value 1011of zero disables the use of the heap. 1012<br> 1013<br> 1014<b>int pcre2_set_match_limit(pcre2_match_context *<i>mcontext</i>,</b> 1015<b> uint32_t <i>value</i>);</b> 1016<br> 1017<br> 1018The <i>match_limit</i> parameter provides a means of preventing PCRE2 from using 1019up too many computing resources when processing patterns that are not going to 1020match, but which have a very large number of possibilities in their search 1021trees. The classic example is a pattern that uses nested unlimited repeats. 1022</P> 1023<P> 1024There is an internal counter in <b>pcre2_match()</b> that is incremented each 1025time round its main matching loop. If this value reaches the match limit, 1026<b>pcre2_match()</b> returns the negative value PCRE2_ERROR_MATCHLIMIT. This has 1027the effect of limiting the amount of backtracking that can take place. For 1028patterns that are not anchored, the count restarts from zero for each position 1029in the subject string. This limit also applies to <b>pcre2_dfa_match()</b>, 1030though the counting is done in a different way. 1031</P> 1032<P> 1033When <b>pcre2_match()</b> is called with a pattern that was successfully 1034processed by <b>pcre2_jit_compile()</b>, the way in which matching is executed 1035is entirely different. However, there is still the possibility of runaway 1036matching that goes on for a very long time, and so the <i>match_limit</i> value 1037is also used in this case (but in a different way) to limit how long the 1038matching can continue. 1039</P> 1040<P> 1041The default value for the limit can be set when PCRE2 is built; the default 1042default is 10 million, which handles all but the most extreme cases. A value 1043for the match limit may also be supplied by an item at the start of a pattern 1044of the form 1045<pre> 1046 (*LIMIT_MATCH=ddd) 1047</pre> 1048where ddd is a decimal number. However, such a setting is ignored unless ddd is 1049less than the limit set by the caller of <b>pcre2_match()</b> or 1050<b>pcre2_dfa_match()</b> or, if no such limit is set, less than the default. 1051<br> 1052<br> 1053<b>int pcre2_set_depth_limit(pcre2_match_context *<i>mcontext</i>,</b> 1054<b> uint32_t <i>value</i>);</b> 1055<br> 1056<br> 1057This parameter limits the depth of nested backtracking in <b>pcre2_match()</b>. 1058Each time a nested backtracking point is passed, a new memory "frame" is used 1059to remember the state of matching at that point. Thus, this parameter 1060indirectly limits the amount of memory that is used in a match. However, 1061because the size of each memory "frame" depends on the number of capturing 1062parentheses, the actual memory limit varies from pattern to pattern. This limit 1063was more useful in versions before 10.30, where function recursion was used for 1064backtracking. 1065</P> 1066<P> 1067The depth limit is not relevant, and is ignored, when matching is done using 1068JIT compiled code. However, it is supported by <b>pcre2_dfa_match()</b>, which 1069uses it to limit the depth of nested internal recursive function calls that 1070implement atomic groups, lookaround assertions, and pattern recursions. This 1071limits, indirectly, the amount of system stack that is used. It was more useful 1072in versions before 10.32, when stack memory was used for local workspace 1073vectors for recursive function calls. From version 10.32, only local variables 1074are allocated on the stack and as each call uses only a few hundred bytes, even 1075a small stack can support quite a lot of recursion. 1076</P> 1077<P> 1078If the depth of internal recursive function calls is great enough, local 1079workspace vectors are allocated on the heap from version 10.32 onwards, so the 1080depth limit also indirectly limits the amount of heap memory that is used. A 1081recursive pattern such as /(.(?2))((?1)|)/, when matched to a very long string 1082using <b>pcre2_dfa_match()</b>, can use a great deal of memory. However, it is 1083probably better to limit heap usage directly by calling 1084<b>pcre2_set_heap_limit()</b>. 1085</P> 1086<P> 1087The default value for the depth limit can be set when PCRE2 is built; if it is 1088not, the default is set to the same value as the default for the match limit. 1089If the limit is exceeded, <b>pcre2_match()</b> or <b>pcre2_dfa_match()</b> 1090returns PCRE2_ERROR_DEPTHLIMIT. A value for the depth limit may also be 1091supplied by an item at the start of a pattern of the form 1092<pre> 1093 (*LIMIT_DEPTH=ddd) 1094</pre> 1095where ddd is a decimal number. However, such a setting is ignored unless ddd is 1096less than the limit set by the caller of <b>pcre2_match()</b> or 1097<b>pcre2_dfa_match()</b> or, if no such limit is set, less than the default. 1098</P> 1099<br><a name="SEC19" href="#TOC1">CHECKING BUILD-TIME OPTIONS</a><br> 1100<P> 1101<b>int pcre2_config(uint32_t <i>what</i>, void *<i>where</i>);</b> 1102</P> 1103<P> 1104The function <b>pcre2_config()</b> makes it possible for a PCRE2 client to 1105discover which optional features have been compiled into the PCRE2 library. The 1106<a href="pcre2build.html"><b>pcre2build</b></a> 1107documentation has more details about these optional features. 1108</P> 1109<P> 1110The first argument for <b>pcre2_config()</b> specifies which information is 1111required. The second argument is a pointer to memory into which the information 1112is placed. If NULL is passed, the function returns the amount of memory that is 1113needed for the requested information. For calls that return numerical values, 1114the value is in bytes; when requesting these values, <i>where</i> should point 1115to appropriately aligned memory. For calls that return strings, the required 1116length is given in code units, not counting the terminating zero. 1117</P> 1118<P> 1119When requesting information, the returned value from <b>pcre2_config()</b> is 1120non-negative on success, or the negative error code PCRE2_ERROR_BADOPTION if 1121the value in the first argument is not recognized. The following information is 1122available: 1123<pre> 1124 PCRE2_CONFIG_BSR 1125</pre> 1126The output is a uint32_t integer whose value indicates what character 1127sequences the \R escape sequence matches by default. A value of 1128PCRE2_BSR_UNICODE means that \R matches any Unicode line ending sequence; a 1129value of PCRE2_BSR_ANYCRLF means that \R matches only CR, LF, or CRLF. The 1130default can be overridden when a pattern is compiled. 1131<pre> 1132 PCRE2_CONFIG_COMPILED_WIDTHS 1133</pre> 1134The output is a uint32_t integer whose lower bits indicate which code unit 1135widths were selected when PCRE2 was built. The 1-bit indicates 8-bit support, 1136and the 2-bit and 4-bit indicate 16-bit and 32-bit support, respectively. 1137<pre> 1138 PCRE2_CONFIG_DEPTHLIMIT 1139</pre> 1140The output is a uint32_t integer that gives the default limit for the depth of 1141nested backtracking in <b>pcre2_match()</b> or the depth of nested recursions, 1142lookarounds, and atomic groups in <b>pcre2_dfa_match()</b>. Further details are 1143given with <b>pcre2_set_depth_limit()</b> above. 1144<pre> 1145 PCRE2_CONFIG_HEAPLIMIT 1146</pre> 1147The output is a uint32_t integer that gives, in kibibytes, the default limit 1148for the amount of heap memory used by <b>pcre2_match()</b> or 1149<b>pcre2_dfa_match()</b>. Further details are given with 1150<b>pcre2_set_heap_limit()</b> above. 1151<pre> 1152 PCRE2_CONFIG_JIT 1153</pre> 1154The output is a uint32_t integer that is set to one if support for just-in-time 1155compiling is available; otherwise it is set to zero. 1156<pre> 1157 PCRE2_CONFIG_JITTARGET 1158</pre> 1159The <i>where</i> argument should point to a buffer that is at least 48 code 1160units long. (The exact length required can be found by calling 1161<b>pcre2_config()</b> with <b>where</b> set to NULL.) The buffer is filled with a 1162string that contains the name of the architecture for which the JIT compiler is 1163configured, for example "x86 32bit (little endian + unaligned)". If JIT support 1164is not available, PCRE2_ERROR_BADOPTION is returned, otherwise the number of 1165code units used is returned. This is the length of the string, plus one unit 1166for the terminating zero. 1167<pre> 1168 PCRE2_CONFIG_LINKSIZE 1169</pre> 1170The output is a uint32_t integer that contains the number of bytes used for 1171internal linkage in compiled regular expressions. When PCRE2 is configured, the 1172value can be set to 2, 3, or 4, with the default being 2. This is the value 1173that is returned by <b>pcre2_config()</b>. However, when the 16-bit library is 1174compiled, a value of 3 is rounded up to 4, and when the 32-bit library is 1175compiled, internal linkages always use 4 bytes, so the configured value is not 1176relevant. 1177</P> 1178<P> 1179The default value of 2 for the 8-bit and 16-bit libraries is sufficient for all 1180but the most massive patterns, since it allows the size of the compiled pattern 1181to be up to 65535 code units. Larger values allow larger regular expressions to 1182be compiled by those two libraries, but at the expense of slower matching. 1183<pre> 1184 PCRE2_CONFIG_MATCHLIMIT 1185</pre> 1186The output is a uint32_t integer that gives the default match limit for 1187<b>pcre2_match()</b>. Further details are given with 1188<b>pcre2_set_match_limit()</b> above. 1189<pre> 1190 PCRE2_CONFIG_NEWLINE 1191</pre> 1192The output is a uint32_t integer whose value specifies the default character 1193sequence that is recognized as meaning "newline". The values are: 1194<pre> 1195 PCRE2_NEWLINE_CR Carriage return (CR) 1196 PCRE2_NEWLINE_LF Linefeed (LF) 1197 PCRE2_NEWLINE_CRLF Carriage return, linefeed (CRLF) 1198 PCRE2_NEWLINE_ANY Any Unicode line ending 1199 PCRE2_NEWLINE_ANYCRLF Any of CR, LF, or CRLF 1200 PCRE2_NEWLINE_NUL The NUL character (binary zero) 1201</pre> 1202The default should normally correspond to the standard sequence for your 1203operating system. 1204<pre> 1205 PCRE2_CONFIG_NEVER_BACKSLASH_C 1206</pre> 1207The output is a uint32_t integer that is set to one if the use of \C was 1208permanently disabled when PCRE2 was built; otherwise it is set to zero. 1209<pre> 1210 PCRE2_CONFIG_PARENSLIMIT 1211</pre> 1212The output is a uint32_t integer that gives the maximum depth of nesting 1213of parentheses (of any kind) in a pattern. This limit is imposed to cap the 1214amount of system stack used when a pattern is compiled. It is specified when 1215PCRE2 is built; the default is 250. This limit does not take into account the 1216stack that may already be used by the calling application. For finer control 1217over compilation stack usage, see <b>pcre2_set_compile_recursion_guard()</b>. 1218<pre> 1219 PCRE2_CONFIG_STACKRECURSE 1220</pre> 1221This parameter is obsolete and should not be used in new code. The output is a 1222uint32_t integer that is always set to zero. 1223<pre> 1224 PCRE2_CONFIG_UNICODE_VERSION 1225</pre> 1226The <i>where</i> argument should point to a buffer that is at least 24 code 1227units long. (The exact length required can be found by calling 1228<b>pcre2_config()</b> with <b>where</b> set to NULL.) If PCRE2 has been compiled 1229without Unicode support, the buffer is filled with the text "Unicode not 1230supported". Otherwise, the Unicode version string (for example, "8.0.0") is 1231inserted. The number of code units used is returned. This is the length of the 1232string plus one unit for the terminating zero. 1233<pre> 1234 PCRE2_CONFIG_UNICODE 1235</pre> 1236The output is a uint32_t integer that is set to one if Unicode support is 1237available; otherwise it is set to zero. Unicode support implies UTF support. 1238<pre> 1239 PCRE2_CONFIG_VERSION 1240</pre> 1241The <i>where</i> argument should point to a buffer that is at least 24 code 1242units long. (The exact length required can be found by calling 1243<b>pcre2_config()</b> with <b>where</b> set to NULL.) The buffer is filled with 1244the PCRE2 version string, zero-terminated. The number of code units used is 1245returned. This is the length of the string plus one unit for the terminating 1246zero. 1247<a name="compiling"></a></P> 1248<br><a name="SEC20" href="#TOC1">COMPILING A PATTERN</a><br> 1249<P> 1250<b>pcre2_code *pcre2_compile(PCRE2_SPTR <i>pattern</i>, PCRE2_SIZE <i>length</i>,</b> 1251<b> uint32_t <i>options</i>, int *<i>errorcode</i>, PCRE2_SIZE *<i>erroroffset,</i></b> 1252<b> pcre2_compile_context *<i>ccontext</i>);</b> 1253<br> 1254<br> 1255<b>void pcre2_code_free(pcre2_code *<i>code</i>);</b> 1256<br> 1257<br> 1258<b>pcre2_code *pcre2_code_copy(const pcre2_code *<i>code</i>);</b> 1259<br> 1260<br> 1261<b>pcre2_code *pcre2_code_copy_with_tables(const pcre2_code *<i>code</i>);</b> 1262</P> 1263<P> 1264The <b>pcre2_compile()</b> function compiles a pattern into an internal form. 1265The pattern is defined by a pointer to a string of code units and a length (in 1266code units). If the pattern is zero-terminated, the length can be specified as 1267PCRE2_ZERO_TERMINATED. The function returns a pointer to a block of memory that 1268contains the compiled pattern and related data, or NULL if an error occurred. 1269</P> 1270<P> 1271If the compile context argument <i>ccontext</i> is NULL, memory for the compiled 1272pattern is obtained by calling <b>malloc()</b>. Otherwise, it is obtained from 1273the same memory function that was used for the compile context. The caller must 1274free the memory by calling <b>pcre2_code_free()</b> when it is no longer needed. 1275If <b>pcre2_code_free()</b> is called with a NULL argument, it returns 1276immediately, without doing anything. 1277</P> 1278<P> 1279The function <b>pcre2_code_copy()</b> makes a copy of the compiled code in new 1280memory, using the same memory allocator as was used for the original. However, 1281if the code has been processed by the JIT compiler (see 1282<a href="#jitcompiling">below),</a> 1283the JIT information cannot be copied (because it is position-dependent). 1284The new copy can initially be used only for non-JIT matching, though it can be 1285passed to <b>pcre2_jit_compile()</b> if required. If <b>pcre2_code_copy()</b> is 1286called with a NULL argument, it returns NULL. 1287</P> 1288<P> 1289The <b>pcre2_code_copy()</b> function provides a way for individual threads in a 1290multithreaded application to acquire a private copy of shared compiled code. 1291However, it does not make a copy of the character tables used by the compiled 1292pattern; the new pattern code points to the same tables as the original code. 1293(See 1294<a href="#jitcompiling">"Locale Support"</a> 1295below for details of these character tables.) In many applications the same 1296tables are used throughout, so this behaviour is appropriate. Nevertheless, 1297there are occasions when a copy of a compiled pattern and the relevant tables 1298are needed. The <b>pcre2_code_copy_with_tables()</b> provides this facility. 1299Copies of both the code and the tables are made, with the new code pointing to 1300the new tables. The memory for the new tables is automatically freed when 1301<b>pcre2_code_free()</b> is called for the new copy of the compiled code. If 1302<b>pcre2_code_copy_with_tables()</b> is called with a NULL argument, it returns 1303NULL. 1304</P> 1305<P> 1306NOTE: When one of the matching functions is called, pointers to the compiled 1307pattern and the subject string are set in the match data block so that they can 1308be referenced by the substring extraction functions after a successful match. 1309After running a match, you must not free a compiled pattern or a subject string 1310until after all operations on the 1311<a href="#matchdatablock">match data block</a> 1312have taken place, unless, in the case of the subject string, you have used the 1313PCRE2_COPY_MATCHED_SUBJECT option, which is described in the section entitled 1314"Option bits for <b>pcre2_match()</b>" 1315<a href="#matchoptions>">below.</a> 1316</P> 1317<P> 1318The <i>options</i> argument for <b>pcre2_compile()</b> contains various bit 1319settings that affect the compilation. It should be zero if none of them are 1320required. The available options are described below. Some of them (in 1321particular, those that are compatible with Perl, but some others as well) can 1322also be set and unset from within the pattern (see the detailed description in 1323the 1324<a href="pcre2pattern.html"><b>pcre2pattern</b></a> 1325documentation). 1326</P> 1327<P> 1328For those options that can be different in different parts of the pattern, the 1329contents of the <i>options</i> argument specifies their settings at the start of 1330compilation. The PCRE2_ANCHORED, PCRE2_ENDANCHORED, and PCRE2_NO_UTF_CHECK 1331options can be set at the time of matching as well as at compile time. 1332</P> 1333<P> 1334Some additional options and less frequently required compile-time parameters 1335(for example, the newline setting) can be provided in a compile context (as 1336described 1337<a href="#compilecontext">above).</a> 1338</P> 1339<P> 1340If <i>errorcode</i> or <i>erroroffset</i> is NULL, <b>pcre2_compile()</b> returns 1341NULL immediately. Otherwise, the variables to which these point are set to an 1342error code and an offset (number of code units) within the pattern, 1343respectively, when <b>pcre2_compile()</b> returns NULL because a compilation 1344error has occurred. The values are not defined when compilation is successful 1345and <b>pcre2_compile()</b> returns a non-NULL value. 1346</P> 1347<P> 1348There are nearly 100 positive error codes that <b>pcre2_compile()</b> may return 1349if it finds an error in the pattern. There are also some negative error codes 1350that are used for invalid UTF strings. These are the same as given by 1351<b>pcre2_match()</b> and <b>pcre2_dfa_match()</b>, and are described in the 1352<a href="pcre2unicode.html"><b>pcre2unicode</b></a> 1353page. There is no separate documentation for the positive error codes, because 1354the textual error messages that are obtained by calling the 1355<b>pcre2_get_error_message()</b> function (see "Obtaining a textual error 1356message" 1357<a href="#geterrormessage">below)</a> 1358should be self-explanatory. Macro names starting with PCRE2_ERROR_ are defined 1359for both positive and negative error codes in <b>pcre2.h</b>. 1360</P> 1361<P> 1362The value returned in <i>erroroffset</i> is an indication of where in the 1363pattern the error occurred. It is not necessarily the furthest point in the 1364pattern that was read. For example, after the error "lookbehind assertion is 1365not fixed length", the error offset points to the start of the failing 1366assertion. For an invalid UTF-8 or UTF-16 string, the offset is that of the 1367first code unit of the failing character. 1368</P> 1369<P> 1370Some errors are not detected until the whole pattern has been scanned; in these 1371cases, the offset passed back is the length of the pattern. Note that the 1372offset is in code units, not characters, even in a UTF mode. It may sometimes 1373point into the middle of a UTF-8 or UTF-16 character. 1374</P> 1375<P> 1376This code fragment shows a typical straightforward call to 1377<b>pcre2_compile()</b>: 1378<pre> 1379 pcre2_code *re; 1380 PCRE2_SIZE erroffset; 1381 int errorcode; 1382 re = pcre2_compile( 1383 "^A.*Z", /* the pattern */ 1384 PCRE2_ZERO_TERMINATED, /* the pattern is zero-terminated */ 1385 0, /* default options */ 1386 &errorcode, /* for error code */ 1387 &erroffset, /* for error offset */ 1388 NULL); /* no compile context */ 1389 1390</PRE> 1391</P> 1392<br><b> 1393Main compile options 1394</b><br> 1395<P> 1396The following names for option bits are defined in the <b>pcre2.h</b> header 1397file: 1398<pre> 1399 PCRE2_ANCHORED 1400</pre> 1401If this bit is set, the pattern is forced to be "anchored", that is, it is 1402constrained to match only at the first matching point in the string that is 1403being searched (the "subject string"). This effect can also be achieved by 1404appropriate constructs in the pattern itself, which is the only way to do it in 1405Perl. 1406<pre> 1407 PCRE2_ALLOW_EMPTY_CLASS 1408</pre> 1409By default, for compatibility with Perl, a closing square bracket that 1410immediately follows an opening one is treated as a data character for the 1411class. When PCRE2_ALLOW_EMPTY_CLASS is set, it terminates the class, which 1412therefore contains no characters and so can never match. 1413<pre> 1414 PCRE2_ALT_BSUX 1415</pre> 1416This option request alternative handling of three escape sequences, which 1417makes PCRE2's behaviour more like ECMAscript (aka JavaScript). When it is set: 1418</P> 1419<P> 1420(1) \U matches an upper case "U" character; by default \U causes a compile 1421time error (Perl uses \U to upper case subsequent characters). 1422</P> 1423<P> 1424(2) \u matches a lower case "u" character unless it is followed by four 1425hexadecimal digits, in which case the hexadecimal number defines the code point 1426to match. By default, \u causes a compile time error (Perl uses it to upper 1427case the following character). 1428</P> 1429<P> 1430(3) \x matches a lower case "x" character unless it is followed by two 1431hexadecimal digits, in which case the hexadecimal number defines the code point 1432to match. By default, as in Perl, a hexadecimal number is always expected after 1433\x, but it may have zero, one, or two digits (so, for example, \xz matches a 1434binary zero character followed by z). 1435</P> 1436<P> 1437ECMAscript 6 added additional functionality to \u. This can be accessed using 1438the PCRE2_EXTRA_ALT_BSUX extra option (see "Extra compile options" 1439<a href="#extracompileoptions">below).</a> 1440Note that this alternative escape handling applies only to patterns. Neither of 1441these options affects the processing of replacement strings passed to 1442<b>pcre2_substitute()</b>. 1443<pre> 1444 PCRE2_ALT_CIRCUMFLEX 1445</pre> 1446In multiline mode (when PCRE2_MULTILINE is set), the circumflex metacharacter 1447matches at the start of the subject (unless PCRE2_NOTBOL is set), and also 1448after any internal newline. However, it does not match after a newline at the 1449end of the subject, for compatibility with Perl. If you want a multiline 1450circumflex also to match after a terminating newline, you must set 1451PCRE2_ALT_CIRCUMFLEX. 1452<pre> 1453 PCRE2_ALT_VERBNAMES 1454</pre> 1455By default, for compatibility with Perl, the name in any verb sequence such as 1456(*MARK:NAME) is any sequence of characters that does not include a closing 1457parenthesis. The name is not processed in any way, and it is not possible to 1458include a closing parenthesis in the name. However, if the PCRE2_ALT_VERBNAMES 1459option is set, normal backslash processing is applied to verb names and only an 1460unescaped closing parenthesis terminates the name. A closing parenthesis can be 1461included in a name either as \) or between \Q and \E. If the PCRE2_EXTENDED 1462or PCRE2_EXTENDED_MORE option is set with PCRE2_ALT_VERBNAMES, unescaped 1463whitespace in verb names is skipped and #-comments are recognized, exactly as 1464in the rest of the pattern. 1465<pre> 1466 PCRE2_AUTO_CALLOUT 1467</pre> 1468If this bit is set, <b>pcre2_compile()</b> automatically inserts callout items, 1469all with number 255, before each pattern item, except immediately before or 1470after an explicit callout in the pattern. For discussion of the callout 1471facility, see the 1472<a href="pcre2callout.html"><b>pcre2callout</b></a> 1473documentation. 1474<pre> 1475 PCRE2_CASELESS 1476</pre> 1477If this bit is set, letters in the pattern match both upper and lower case 1478letters in the subject. It is equivalent to Perl's /i option, and it can be 1479changed within a pattern by a (?i) option setting. If PCRE2_UTF is set, Unicode 1480properties are used for all characters with more than one other case, and for 1481all characters whose code points are greater than U+007F. For lower valued 1482characters with only one other case, a lookup table is used for speed. When 1483PCRE2_UTF is not set, a lookup table is used for all code points less than 256, 1484and higher code points (available only in 16-bit or 32-bit mode) are treated as 1485not having another case. 1486<pre> 1487 PCRE2_DOLLAR_ENDONLY 1488</pre> 1489If this bit is set, a dollar metacharacter in the pattern matches only at the 1490end of the subject string. Without this option, a dollar also matches 1491immediately before a newline at the end of the string (but not before any other 1492newlines). The PCRE2_DOLLAR_ENDONLY option is ignored if PCRE2_MULTILINE is 1493set. There is no equivalent to this option in Perl, and no way to set it within 1494a pattern. 1495<pre> 1496 PCRE2_DOTALL 1497</pre> 1498If this bit is set, a dot metacharacter in the pattern matches any character, 1499including one that indicates a newline. However, it only ever matches one 1500character, even if newlines are coded as CRLF. Without this option, a dot does 1501not match when the current position in the subject is at a newline. This option 1502is equivalent to Perl's /s option, and it can be changed within a pattern by a 1503(?s) option setting. A negative class such as [^a] always matches newline 1504characters, and the \N escape sequence always matches a non-newline character, 1505independent of the setting of PCRE2_DOTALL. 1506<pre> 1507 PCRE2_DUPNAMES 1508</pre> 1509If this bit is set, names used to identify capture groups need not be unique. 1510This can be helpful for certain types of pattern when it is known that only one 1511instance of the named group can ever be matched. There are more details of 1512named capture groups below; see also the 1513<a href="pcre2pattern.html"><b>pcre2pattern</b></a> 1514documentation. 1515<pre> 1516 PCRE2_ENDANCHORED 1517</pre> 1518If this bit is set, the end of any pattern match must be right at the end of 1519the string being searched (the "subject string"). If the pattern match 1520succeeds by reaching (*ACCEPT), but does not reach the end of the subject, the 1521match fails at the current starting point. For unanchored patterns, a new match 1522is then tried at the next starting point. However, if the match succeeds by 1523reaching the end of the pattern, but not the end of the subject, backtracking 1524occurs and an alternative match may be found. Consider these two patterns: 1525<pre> 1526 .(*ACCEPT)|.. 1527 .|.. 1528</pre> 1529If matched against "abc" with PCRE2_ENDANCHORED set, the first matches "c" 1530whereas the second matches "bc". The effect of PCRE2_ENDANCHORED can also be 1531achieved by appropriate constructs in the pattern itself, which is the only way 1532to do it in Perl. 1533</P> 1534<P> 1535For DFA matching with <b>pcre2_dfa_match()</b>, PCRE2_ENDANCHORED applies only 1536to the first (that is, the longest) matched string. Other parallel matches, 1537which are necessarily substrings of the first one, must obviously end before 1538the end of the subject. 1539<pre> 1540 PCRE2_EXTENDED 1541</pre> 1542If this bit is set, most white space characters in the pattern are totally 1543ignored except when escaped or inside a character class. However, white space 1544is not allowed within sequences such as (?> that introduce various 1545parenthesized groups, nor within numerical quantifiers such as {1,3}. Ignorable 1546white space is permitted between an item and a following quantifier and between 1547a quantifier and a following + that indicates possessiveness. PCRE2_EXTENDED is 1548equivalent to Perl's /x option, and it can be changed within a pattern by a 1549(?x) option setting. 1550</P> 1551<P> 1552When PCRE2 is compiled without Unicode support, PCRE2_EXTENDED recognizes as 1553white space only those characters with code points less than 256 that are 1554flagged as white space in its low-character table. The table is normally 1555created by 1556<a href="pcre2_maketables.html"><b>pcre2_maketables()</b>,</a> 1557which uses the <b>isspace()</b> function to identify space characters. In most 1558ASCII environments, the relevant characters are those with code points 0x0009 1559(tab), 0x000A (linefeed), 0x000B (vertical tab), 0x000C (formfeed), 0x000D 1560(carriage return), and 0x0020 (space). 1561</P> 1562<P> 1563When PCRE2 is compiled with Unicode support, in addition to these characters, 1564five more Unicode "Pattern White Space" characters are recognized by 1565PCRE2_EXTENDED. These are U+0085 (next line), U+200E (left-to-right mark), 1566U+200F (right-to-left mark), U+2028 (line separator), and U+2029 (paragraph 1567separator). This set of characters is the same as recognized by Perl's /x 1568option. Note that the horizontal and vertical space characters that are matched 1569by the \h and \v escapes in patterns are a much bigger set. 1570</P> 1571<P> 1572As well as ignoring most white space, PCRE2_EXTENDED also causes characters 1573between an unescaped # outside a character class and the next newline, 1574inclusive, to be ignored, which makes it possible to include comments inside 1575complicated patterns. Note that the end of this type of comment is a literal 1576newline sequence in the pattern; escape sequences that happen to represent a 1577newline do not count. 1578</P> 1579<P> 1580Which characters are interpreted as newlines can be specified by a setting in 1581the compile context that is passed to <b>pcre2_compile()</b> or by a special 1582sequence at the start of the pattern, as described in the section entitled 1583<a href="pcre2pattern.html#newlines">"Newline conventions"</a> 1584in the <b>pcre2pattern</b> documentation. A default is defined when PCRE2 is 1585built. 1586<pre> 1587 PCRE2_EXTENDED_MORE 1588</pre> 1589This option has the effect of PCRE2_EXTENDED, but, in addition, unescaped space 1590and horizontal tab characters are ignored inside a character class. Note: only 1591these two characters are ignored, not the full set of pattern white space 1592characters that are ignored outside a character class. PCRE2_EXTENDED_MORE is 1593equivalent to Perl's /xx option, and it can be changed within a pattern by a 1594(?xx) option setting. 1595<pre> 1596 PCRE2_FIRSTLINE 1597</pre> 1598If this option is set, the start of an unanchored pattern match must be before 1599or at the first newline in the subject string following the start of matching, 1600though the matched text may continue over the newline. If <i>startoffset</i> is 1601non-zero, the limiting newline is not necessarily the first newline in the 1602subject. For example, if the subject string is "abc\nxyz" (where \n 1603represents a single-character newline) a pattern match for "yz" succeeds with 1604PCRE2_FIRSTLINE if <i>startoffset</i> is greater than 3. See also 1605PCRE2_USE_OFFSET_LIMIT, which provides a more general limiting facility. If 1606PCRE2_FIRSTLINE is set with an offset limit, a match must occur in the first 1607line and also within the offset limit. In other words, whichever limit comes 1608first is used. 1609<pre> 1610 PCRE2_LITERAL 1611</pre> 1612If this option is set, all meta-characters in the pattern are disabled, and it 1613is treated as a literal string. Matching literal strings with a regular 1614expression engine is not the most efficient way of doing it. If you are doing a 1615lot of literal matching and are worried about efficiency, you should consider 1616using other approaches. The only other main options that are allowed with 1617PCRE2_LITERAL are: PCRE2_ANCHORED, PCRE2_ENDANCHORED, PCRE2_AUTO_CALLOUT, 1618PCRE2_CASELESS, PCRE2_FIRSTLINE, PCRE2_NO_START_OPTIMIZE, PCRE2_NO_UTF_CHECK, 1619PCRE2_UTF, and PCRE2_USE_OFFSET_LIMIT. The extra options PCRE2_EXTRA_MATCH_LINE 1620and PCRE2_EXTRA_MATCH_WORD are also supported. Any other options cause an 1621error. 1622<pre> 1623 PCRE2_MATCH_UNSET_BACKREF 1624</pre> 1625If this option is set, a backreference to an unset capture group matches an 1626empty string (by default this causes the current matching alternative to fail). 1627A pattern such as (\1)(a) succeeds when this option is set (assuming it can 1628find an "a" in the subject), whereas it fails by default, for Perl 1629compatibility. Setting this option makes PCRE2 behave more like ECMAscript (aka 1630JavaScript). 1631<pre> 1632 PCRE2_MULTILINE 1633</pre> 1634By default, for the purposes of matching "start of line" and "end of line", 1635PCRE2 treats the subject string as consisting of a single line of characters, 1636even if it actually contains newlines. The "start of line" metacharacter (^) 1637matches only at the start of the string, and the "end of line" metacharacter 1638($) matches only at the end of the string, or before a terminating newline 1639(except when PCRE2_DOLLAR_ENDONLY is set). Note, however, that unless 1640PCRE2_DOTALL is set, the "any character" metacharacter (.) does not match at a 1641newline. This behaviour (for ^, $, and dot) is the same as Perl. 1642</P> 1643<P> 1644When PCRE2_MULTILINE it is set, the "start of line" and "end of line" 1645constructs match immediately following or immediately before internal newlines 1646in the subject string, respectively, as well as at the very start and end. This 1647is equivalent to Perl's /m option, and it can be changed within a pattern by a 1648(?m) option setting. Note that the "start of line" metacharacter does not match 1649after a newline at the end of the subject, for compatibility with Perl. 1650However, you can change this by setting the PCRE2_ALT_CIRCUMFLEX option. If 1651there are no newlines in a subject string, or no occurrences of ^ or $ in a 1652pattern, setting PCRE2_MULTILINE has no effect. 1653<pre> 1654 PCRE2_NEVER_BACKSLASH_C 1655</pre> 1656This option locks out the use of \C in the pattern that is being compiled. 1657This escape can cause unpredictable behaviour in UTF-8 or UTF-16 modes, because 1658it may leave the current matching point in the middle of a multi-code-unit 1659character. This option may be useful in applications that process patterns from 1660external sources. Note that there is also a build-time option that permanently 1661locks out the use of \C. 1662<pre> 1663 PCRE2_NEVER_UCP 1664</pre> 1665This option locks out the use of Unicode properties for handling \B, \b, \D, 1666\d, \S, \s, \W, \w, and some of the POSIX character classes, as described 1667for the PCRE2_UCP option below. In particular, it prevents the creator of the 1668pattern from enabling this facility by starting the pattern with (*UCP). This 1669option may be useful in applications that process patterns from external 1670sources. The option combination PCRE_UCP and PCRE_NEVER_UCP causes an error. 1671<pre> 1672 PCRE2_NEVER_UTF 1673</pre> 1674This option locks out interpretation of the pattern as UTF-8, UTF-16, or 1675UTF-32, depending on which library is in use. In particular, it prevents the 1676creator of the pattern from switching to UTF interpretation by starting the 1677pattern with (*UTF). This option may be useful in applications that process 1678patterns from external sources. The combination of PCRE2_UTF and 1679PCRE2_NEVER_UTF causes an error. 1680<pre> 1681 PCRE2_NO_AUTO_CAPTURE 1682</pre> 1683If this option is set, it disables the use of numbered capturing parentheses in 1684the pattern. Any opening parenthesis that is not followed by ? behaves as if it 1685were followed by ?: but named parentheses can still be used for capturing (and 1686they acquire numbers in the usual way). This is the same as Perl's /n option. 1687Note that, when this option is set, references to capture groups 1688(backreferences or recursion/subroutine calls) may only refer to named groups, 1689though the reference can be by name or by number. 1690<pre> 1691 PCRE2_NO_AUTO_POSSESS 1692</pre> 1693If this option is set, it disables "auto-possessification", which is an 1694optimization that, for example, turns a+b into a++b in order to avoid 1695backtracks into a+ that can never be successful. However, if callouts are in 1696use, auto-possessification means that some callouts are never taken. You can 1697set this option if you want the matching functions to do a full unoptimized 1698search and run all the callouts, but it is mainly provided for testing 1699purposes. 1700<pre> 1701 PCRE2_NO_DOTSTAR_ANCHOR 1702</pre> 1703If this option is set, it disables an optimization that is applied when .* is 1704the first significant item in a top-level branch of a pattern, and all the 1705other branches also start with .* or with \A or \G or ^. The optimization is 1706automatically disabled for .* if it is inside an atomic group or a capture 1707group that is the subject of a backreference, or if the pattern contains 1708(*PRUNE) or (*SKIP). When the optimization is not disabled, such a pattern is 1709automatically anchored if PCRE2_DOTALL is set for all the .* items and 1710PCRE2_MULTILINE is not set for any ^ items. Otherwise, the fact that any match 1711must start either at the start of the subject or following a newline is 1712remembered. Like other optimizations, this can cause callouts to be skipped. 1713<pre> 1714 PCRE2_NO_START_OPTIMIZE 1715</pre> 1716This is an option whose main effect is at matching time. It does not change 1717what <b>pcre2_compile()</b> generates, but it does affect the output of the JIT 1718compiler. 1719</P> 1720<P> 1721There are a number of optimizations that may occur at the start of a match, in 1722order to speed up the process. For example, if it is known that an unanchored 1723match must start with a specific code unit value, the matching code searches 1724the subject for that value, and fails immediately if it cannot find it, without 1725actually running the main matching function. This means that a special item 1726such as (*COMMIT) at the start of a pattern is not considered until after a 1727suitable starting point for the match has been found. Also, when callouts or 1728(*MARK) items are in use, these "start-up" optimizations can cause them to be 1729skipped if the pattern is never actually used. The start-up optimizations are 1730in effect a pre-scan of the subject that takes place before the pattern is run. 1731</P> 1732<P> 1733The PCRE2_NO_START_OPTIMIZE option disables the start-up optimizations, 1734possibly causing performance to suffer, but ensuring that in cases where the 1735result is "no match", the callouts do occur, and that items such as (*COMMIT) 1736and (*MARK) are considered at every possible starting position in the subject 1737string. 1738</P> 1739<P> 1740Setting PCRE2_NO_START_OPTIMIZE may change the outcome of a matching operation. 1741Consider the pattern 1742<pre> 1743 (*COMMIT)ABC 1744</pre> 1745When this is compiled, PCRE2 records the fact that a match must start with the 1746character "A". Suppose the subject string is "DEFABC". The start-up 1747optimization scans along the subject, finds "A" and runs the first match 1748attempt from there. The (*COMMIT) item means that the pattern must match the 1749current starting position, which in this case, it does. However, if the same 1750match is run with PCRE2_NO_START_OPTIMIZE set, the initial scan along the 1751subject string does not happen. The first match attempt is run starting from 1752"D" and when this fails, (*COMMIT) prevents any further matches being tried, so 1753the overall result is "no match". 1754</P> 1755<P> 1756There are also other start-up optimizations. For example, a minimum length for 1757the subject may be recorded. Consider the pattern 1758<pre> 1759 (*MARK:A)(X|Y) 1760</pre> 1761The minimum length for a match is one character. If the subject is "ABC", there 1762will be attempts to match "ABC", "BC", and "C". An attempt to match an empty 1763string at the end of the subject does not take place, because PCRE2 knows that 1764the subject is now too short, and so the (*MARK) is never encountered. In this 1765case, the optimization does not affect the overall match result, which is still 1766"no match", but it does affect the auxiliary information that is returned. 1767<pre> 1768 PCRE2_NO_UTF_CHECK 1769</pre> 1770When PCRE2_UTF is set, the validity of the pattern as a UTF string is 1771automatically checked. There are discussions about the validity of 1772<a href="pcre2unicode.html#utf8strings">UTF-8 strings,</a> 1773<a href="pcre2unicode.html#utf16strings">UTF-16 strings,</a> 1774and 1775<a href="pcre2unicode.html#utf32strings">UTF-32 strings</a> 1776in the 1777<a href="pcre2unicode.html"><b>pcre2unicode</b></a> 1778document. If an invalid UTF sequence is found, <b>pcre2_compile()</b> returns a 1779negative error code. 1780</P> 1781<P> 1782If you know that your pattern is a valid UTF string, and you want to skip this 1783check for performance reasons, you can set the PCRE2_NO_UTF_CHECK option. When 1784it is set, the effect of passing an invalid UTF string as a pattern is 1785undefined. It may cause your program to crash or loop. 1786</P> 1787<P> 1788Note that this option can also be passed to <b>pcre2_match()</b> and 1789<b>pcre_dfa_match()</b>, to suppress UTF validity checking of the subject 1790string. 1791</P> 1792<P> 1793Note also that setting PCRE2_NO_UTF_CHECK at compile time does not disable the 1794error that is given if an escape sequence for an invalid Unicode code point is 1795encountered in the pattern. In particular, the so-called "surrogate" code 1796points (0xd800 to 0xdfff) are invalid. If you want to allow escape sequences 1797such as \x{d800} you can set the PCRE2_EXTRA_ALLOW_SURROGATE_ESCAPES extra 1798option, as described in the section entitled "Extra compile options" 1799<a href="#extracompileoptions">below.</a> 1800However, this is possible only in UTF-8 and UTF-32 modes, because these values 1801are not representable in UTF-16. 1802<pre> 1803 PCRE2_UCP 1804</pre> 1805This option changes the way PCRE2 processes \B, \b, \D, \d, \S, \s, \W, 1806\w, and some of the POSIX character classes. By default, only ASCII characters 1807are recognized, but if PCRE2_UCP is set, Unicode properties are used instead to 1808classify characters. More details are given in the section on 1809<a href="pcre2pattern.html#genericchartypes">generic character types</a> 1810in the 1811<a href="pcre2pattern.html"><b>pcre2pattern</b></a> 1812page. If you set PCRE2_UCP, matching one of the items it affects takes much 1813longer. The option is available only if PCRE2 has been compiled with Unicode 1814support (which is the default). 1815<pre> 1816 PCRE2_UNGREEDY 1817</pre> 1818This option inverts the "greediness" of the quantifiers so that they are not 1819greedy by default, but become greedy if followed by "?". It is not compatible 1820with Perl. It can also be set by a (?U) option setting within the pattern. 1821<pre> 1822 PCRE2_USE_OFFSET_LIMIT 1823</pre> 1824This option must be set for <b>pcre2_compile()</b> if 1825<b>pcre2_set_offset_limit()</b> is going to be used to set a non-default offset 1826limit in a match context for matches that use this pattern. An error is 1827generated if an offset limit is set without this option. For more details, see 1828the description of <b>pcre2_set_offset_limit()</b> in the 1829<a href="#matchcontext">section</a> 1830that describes match contexts. See also the PCRE2_FIRSTLINE 1831option above. 1832<pre> 1833 PCRE2_UTF 1834</pre> 1835This option causes PCRE2 to regard both the pattern and the subject strings 1836that are subsequently processed as strings of UTF characters instead of 1837single-code-unit strings. It is available when PCRE2 is built to include 1838Unicode support (which is the default). If Unicode support is not available, 1839the use of this option provokes an error. Details of how PCRE2_UTF changes the 1840behaviour of PCRE2 are given in the 1841<a href="pcre2unicode.html"><b>pcre2unicode</b></a> 1842page. In particular, note that it changes the way PCRE2_CASELESS handles 1843characters with code points greater than 127. 1844<a name="extracompileoptions"></a></P> 1845<br><b> 1846Extra compile options 1847</b><br> 1848<P> 1849The option bits that can be set in a compile context by calling the 1850<b>pcre2_set_compile_extra_options()</b> function are as follows: 1851<pre> 1852 PCRE2_EXTRA_ALLOW_SURROGATE_ESCAPES 1853</pre> 1854This option applies when compiling a pattern in UTF-8 or UTF-32 mode. It is 1855forbidden in UTF-16 mode, and ignored in non-UTF modes. Unicode "surrogate" 1856code points in the range 0xd800 to 0xdfff are used in pairs in UTF-16 to encode 1857code points with values in the range 0x10000 to 0x10ffff. The surrogates cannot 1858therefore be represented in UTF-16. They can be represented in UTF-8 and 1859UTF-32, but are defined as invalid code points, and cause errors if encountered 1860in a UTF-8 or UTF-32 string that is being checked for validity by PCRE2. 1861</P> 1862<P> 1863These values also cause errors if encountered in escape sequences such as 1864\x{d912} within a pattern. However, it seems that some applications, when 1865using PCRE2 to check for unwanted characters in UTF-8 strings, explicitly test 1866for the surrogates using escape sequences. The PCRE2_NO_UTF_CHECK option does 1867not disable the error that occurs, because it applies only to the testing of 1868input strings for UTF validity. 1869</P> 1870<P> 1871If the extra option PCRE2_EXTRA_ALLOW_SURROGATE_ESCAPES is set, surrogate code 1872point values in UTF-8 and UTF-32 patterns no longer provoke errors and are 1873incorporated in the compiled pattern. However, they can only match subject 1874characters if the matching function is called with PCRE2_NO_UTF_CHECK set. 1875<pre> 1876 PCRE2_EXTRA_ALT_BSUX 1877</pre> 1878The original option PCRE2_ALT_BSUX causes PCRE2 to process \U, \u, and \x in 1879the way that ECMAscript (aka JavaScript) does. Additional functionality was 1880defined by ECMAscript 6; setting PCRE2_EXTRA_ALT_BSUX has the effect of 1881PCRE2_ALT_BSUX, but in addition it recognizes \u{hhh..} as a hexadecimal 1882character code, where hhh.. is any number of hexadecimal digits. 1883<pre> 1884 PCRE2_EXTRA_BAD_ESCAPE_IS_LITERAL 1885</pre> 1886This is a dangerous option. Use with care. By default, an unrecognized escape 1887such as \j or a malformed one such as \x{2z} causes a compile-time error when 1888detected by <b>pcre2_compile()</b>. Perl is somewhat inconsistent in handling 1889such items: for example, \j is treated as a literal "j", and non-hexadecimal 1890digits in \x{} are just ignored, though warnings are given in both cases if 1891Perl's warning switch is enabled. However, a malformed octal number after \o{ 1892always causes an error in Perl. 1893</P> 1894<P> 1895If the PCRE2_EXTRA_BAD_ESCAPE_IS_LITERAL extra option is passed to 1896<b>pcre2_compile()</b>, all unrecognized or malformed escape sequences are 1897treated as single-character escapes. For example, \j is a literal "j" and 1898\x{2z} is treated as the literal string "x{2z}". Setting this option means 1899that typos in patterns may go undetected and have unexpected results. Also note 1900that a sequence such as [\N{] is interpreted as a malformed attempt at 1901[\N{...}] and so is treated as [N{] whereas [\N] gives an error because an 1902unqualified \N is a valid escape sequence but is not supported in a character 1903class. To reiterate: this is a dangerous option. Use with great care. 1904<pre> 1905 PCRE2_EXTRA_ESCAPED_CR_IS_LF 1906</pre> 1907There are some legacy applications where the escape sequence \r in a pattern 1908is expected to match a newline. If this option is set, \r in a pattern is 1909converted to \n so that it matches a LF (linefeed) instead of a CR (carriage 1910return) character. The option does not affect a literal CR in the pattern, nor 1911does it affect CR specified as an explicit code point such as \x{0D}. 1912<pre> 1913 PCRE2_EXTRA_MATCH_LINE 1914</pre> 1915This option is provided for use by the <b>-x</b> option of <b>pcre2grep</b>. It 1916causes the pattern only to match complete lines. This is achieved by 1917automatically inserting the code for "^(?:" at the start of the compiled 1918pattern and ")$" at the end. Thus, when PCRE2_MULTILINE is set, the matched 1919line may be in the middle of the subject string. This option can be used with 1920PCRE2_LITERAL. 1921<pre> 1922 PCRE2_EXTRA_MATCH_WORD 1923</pre> 1924This option is provided for use by the <b>-w</b> option of <b>pcre2grep</b>. It 1925causes the pattern only to match strings that have a word boundary at the start 1926and the end. This is achieved by automatically inserting the code for "\b(?:" 1927at the start of the compiled pattern and ")\b" at the end. The option may be 1928used with PCRE2_LITERAL. However, it is ignored if PCRE2_EXTRA_MATCH_LINE is 1929also set. 1930<a name="jitcompiling"></a></P> 1931<br><a name="SEC21" href="#TOC1">JUST-IN-TIME (JIT) COMPILATION</a><br> 1932<P> 1933<b>int pcre2_jit_compile(pcre2_code *<i>code</i>, uint32_t <i>options</i>);</b> 1934<br> 1935<br> 1936<b>int pcre2_jit_match(const pcre2_code *<i>code</i>, PCRE2_SPTR <i>subject</i>,</b> 1937<b> PCRE2_SIZE <i>length</i>, PCRE2_SIZE <i>startoffset</i>,</b> 1938<b> uint32_t <i>options</i>, pcre2_match_data *<i>match_data</i>,</b> 1939<b> pcre2_match_context *<i>mcontext</i>);</b> 1940<br> 1941<br> 1942<b>void pcre2_jit_free_unused_memory(pcre2_general_context *<i>gcontext</i>);</b> 1943<br> 1944<br> 1945<b>pcre2_jit_stack *pcre2_jit_stack_create(PCRE2_SIZE <i>startsize</i>,</b> 1946<b> PCRE2_SIZE <i>maxsize</i>, pcre2_general_context *<i>gcontext</i>);</b> 1947<br> 1948<br> 1949<b>void pcre2_jit_stack_assign(pcre2_match_context *<i>mcontext</i>,</b> 1950<b> pcre2_jit_callback <i>callback_function</i>, void *<i>callback_data</i>);</b> 1951<br> 1952<br> 1953<b>void pcre2_jit_stack_free(pcre2_jit_stack *<i>jit_stack</i>);</b> 1954</P> 1955<P> 1956These functions provide support for JIT compilation, which, if the just-in-time 1957compiler is available, further processes a compiled pattern into machine code 1958that executes much faster than the <b>pcre2_match()</b> interpretive matching 1959function. Full details are given in the 1960<a href="pcre2jit.html"><b>pcre2jit</b></a> 1961documentation. 1962</P> 1963<P> 1964JIT compilation is a heavyweight optimization. It can take some time for 1965patterns to be analyzed, and for one-off matches and simple patterns the 1966benefit of faster execution might be offset by a much slower compilation time. 1967Most (but not all) patterns can be optimized by the JIT compiler. 1968<a name="localesupport"></a></P> 1969<br><a name="SEC22" href="#TOC1">LOCALE SUPPORT</a><br> 1970<P> 1971PCRE2 handles caseless matching, and determines whether characters are letters, 1972digits, or whatever, by reference to a set of tables, indexed by character code 1973point. This applies only to characters whose code points are less than 256. By 1974default, higher-valued code points never match escapes such as \w or \d. 1975However, if PCRE2 is built with Unicode support, all characters can be tested 1976with \p and \P, or, alternatively, the PCRE2_UCP option can be set when a 1977pattern is compiled; this causes \w and friends to use Unicode property 1978support instead of the built-in tables. 1979</P> 1980<P> 1981The use of locales with Unicode is discouraged. If you are handling characters 1982with code points greater than 128, you should either use Unicode support, or 1983use locales, but not try to mix the two. 1984</P> 1985<P> 1986PCRE2 contains an internal set of character tables that are used by default. 1987These are sufficient for many applications. Normally, the internal tables 1988recognize only ASCII characters. However, when PCRE2 is built, it is possible 1989to cause the internal tables to be rebuilt in the default "C" locale of the 1990local system, which may cause them to be different. 1991</P> 1992<P> 1993The internal tables can be overridden by tables supplied by the application 1994that calls PCRE2. These may be created in a different locale from the default. 1995As more and more applications change to using Unicode, the need for this locale 1996support is expected to die away. 1997</P> 1998<P> 1999External tables are built by calling the <b>pcre2_maketables()</b> function, in 2000the relevant locale. The result can be passed to <b>pcre2_compile()</b> as often 2001as necessary, by creating a compile context and calling 2002<b>pcre2_set_character_tables()</b> to set the tables pointer therein. For 2003example, to build and use tables that are appropriate for the French locale 2004(where accented characters with values greater than 128 are treated as 2005letters), the following code could be used: 2006<pre> 2007 setlocale(LC_CTYPE, "fr_FR"); 2008 tables = pcre2_maketables(NULL); 2009 ccontext = pcre2_compile_context_create(NULL); 2010 pcre2_set_character_tables(ccontext, tables); 2011 re = pcre2_compile(..., ccontext); 2012</pre> 2013The locale name "fr_FR" is used on Linux and other Unix-like systems; if you 2014are using Windows, the name for the French locale is "french". It is the 2015caller's responsibility to ensure that the memory containing the tables remains 2016available for as long as it is needed. 2017</P> 2018<P> 2019The pointer that is passed (via the compile context) to <b>pcre2_compile()</b> 2020is saved with the compiled pattern, and the same tables are used by 2021<b>pcre2_match()</b> and <b>pcre_dfa_match()</b>. Thus, for any single pattern, 2022compilation and matching both happen in the same locale, but different patterns 2023can be processed in different locales. 2024<a name="infoaboutpattern"></a></P> 2025<br><a name="SEC23" href="#TOC1">INFORMATION ABOUT A COMPILED PATTERN</a><br> 2026<P> 2027<b>int pcre2_pattern_info(const pcre2 *<i>code</i>, uint32_t <i>what</i>, void *<i>where</i>);</b> 2028</P> 2029<P> 2030The <b>pcre2_pattern_info()</b> function returns general information about a 2031compiled pattern. For information about callouts, see the 2032<a href="pcre2pattern.html#infoaboutcallouts">next section.</a> 2033The first argument for <b>pcre2_pattern_info()</b> is a pointer to the compiled 2034pattern. The second argument specifies which piece of information is required, 2035and the third argument is a pointer to a variable to receive the data. If the 2036third argument is NULL, the first argument is ignored, and the function returns 2037the size in bytes of the variable that is required for the information 2038requested. Otherwise, the yield of the function is zero for success, or one of 2039the following negative numbers: 2040<pre> 2041 PCRE2_ERROR_NULL the argument <i>code</i> was NULL 2042 PCRE2_ERROR_BADMAGIC the "magic number" was not found 2043 PCRE2_ERROR_BADOPTION the value of <i>what</i> was invalid 2044 PCRE2_ERROR_UNSET the requested field is not set 2045</pre> 2046The "magic number" is placed at the start of each compiled pattern as an simple 2047check against passing an arbitrary memory pointer. Here is a typical call of 2048<b>pcre2_pattern_info()</b>, to obtain the length of the compiled pattern: 2049<pre> 2050 int rc; 2051 size_t length; 2052 rc = pcre2_pattern_info( 2053 re, /* result of pcre2_compile() */ 2054 PCRE2_INFO_SIZE, /* what is required */ 2055 &length); /* where to put the data */ 2056</pre> 2057The possible values for the second argument are defined in <b>pcre2.h</b>, and 2058are as follows: 2059<pre> 2060 PCRE2_INFO_ALLOPTIONS 2061 PCRE2_INFO_ARGOPTIONS 2062 PCRE2_INFO_EXTRAOPTIONS 2063</pre> 2064Return copies of the pattern's options. The third argument should point to a 2065<b>uint32_t</b> variable. PCRE2_INFO_ARGOPTIONS returns exactly the options that 2066were passed to <b>pcre2_compile()</b>, whereas PCRE2_INFO_ALLOPTIONS returns 2067the compile options as modified by any top-level (*XXX) option settings such as 2068(*UTF) at the start of the pattern itself. PCRE2_INFO_EXTRAOPTIONS returns the 2069extra options that were set in the compile context by calling the 2070pcre2_set_compile_extra_options() function. 2071</P> 2072<P> 2073For example, if the pattern /(*UTF)abc/ is compiled with the PCRE2_EXTENDED 2074option, the result for PCRE2_INFO_ALLOPTIONS is PCRE2_EXTENDED and PCRE2_UTF. 2075Option settings such as (?i) that can change within a pattern do not affect the 2076result of PCRE2_INFO_ALLOPTIONS, even if they appear right at the start of the 2077pattern. (This was different in some earlier releases.) 2078</P> 2079<P> 2080A pattern compiled without PCRE2_ANCHORED is automatically anchored by PCRE2 if 2081the first significant item in every top-level branch is one of the following: 2082<pre> 2083 ^ unless PCRE2_MULTILINE is set 2084 \A always 2085 \G always 2086 .* sometimes - see below 2087</pre> 2088When .* is the first significant item, anchoring is possible only when all the 2089following are true: 2090<pre> 2091 .* is not in an atomic group 2092 .* is not in a capture group that is the subject of a backreference 2093 PCRE2_DOTALL is in force for .* 2094 Neither (*PRUNE) nor (*SKIP) appears in the pattern 2095 PCRE2_NO_DOTSTAR_ANCHOR is not set 2096</pre> 2097For patterns that are auto-anchored, the PCRE2_ANCHORED bit is set in the 2098options returned for PCRE2_INFO_ALLOPTIONS. 2099<pre> 2100 PCRE2_INFO_BACKREFMAX 2101</pre> 2102Return the number of the highest backreference in the pattern. The third 2103argument should point to an <b>uint32_t</b> variable. Named capture groups 2104acquire numbers as well as names, and these count towards the highest 2105backreference. Backreferences such as \4 or \g{12} match the captured 2106characters of the given group, but in addition, the check that a capture 2107group is set in a conditional group such as (?(3)a|b) is also a backreference. 2108Zero is returned if there are no backreferences. 2109<pre> 2110 PCRE2_INFO_BSR 2111</pre> 2112The output is a uint32_t integer whose value indicates what character sequences 2113the \R escape sequence matches. A value of PCRE2_BSR_UNICODE means that \R 2114matches any Unicode line ending sequence; a value of PCRE2_BSR_ANYCRLF means 2115that \R matches only CR, LF, or CRLF. 2116<pre> 2117 PCRE2_INFO_CAPTURECOUNT 2118</pre> 2119Return the highest capture group number in the pattern. In patterns where (?| 2120is not used, this is also the total number of capture groups. The third 2121argument should point to an <b>uint32_t</b> variable. 2122<pre> 2123 PCRE2_INFO_DEPTHLIMIT 2124</pre> 2125If the pattern set a backtracking depth limit by including an item of the form 2126(*LIMIT_DEPTH=nnnn) at the start, the value is returned. The third argument 2127should point to a uint32_t integer. If no such value has been set, the call to 2128<b>pcre2_pattern_info()</b> returns the error PCRE2_ERROR_UNSET. Note that this 2129limit will only be used during matching if it is less than the limit set or 2130defaulted by the caller of the match function. 2131<pre> 2132 PCRE2_INFO_FIRSTBITMAP 2133</pre> 2134In the absence of a single first code unit for a non-anchored pattern, 2135<b>pcre2_compile()</b> may construct a 256-bit table that defines a fixed set of 2136values for the first code unit in any match. For example, a pattern that starts 2137with [abc] results in a table with three bits set. When code unit values 2138greater than 255 are supported, the flag bit for 255 means "any code unit of 2139value 255 or above". If such a table was constructed, a pointer to it is 2140returned. Otherwise NULL is returned. The third argument should point to a 2141<b>const uint8_t *</b> variable. 2142<pre> 2143 PCRE2_INFO_FIRSTCODETYPE 2144</pre> 2145Return information about the first code unit of any matched string, for a 2146non-anchored pattern. The third argument should point to an <b>uint32_t</b> 2147variable. If there is a fixed first value, for example, the letter "c" from a 2148pattern such as (cat|cow|coyote), 1 is returned, and the value can be retrieved 2149using PCRE2_INFO_FIRSTCODEUNIT. If there is no fixed first value, but it is 2150known that a match can occur only at the start of the subject or following a 2151newline in the subject, 2 is returned. Otherwise, and for anchored patterns, 0 2152is returned. 2153<pre> 2154 PCRE2_INFO_FIRSTCODEUNIT 2155</pre> 2156Return the value of the first code unit of any matched string for a pattern 2157where PCRE2_INFO_FIRSTCODETYPE returns 1; otherwise return 0. The third 2158argument should point to an <b>uint32_t</b> variable. In the 8-bit library, the 2159value is always less than 256. In the 16-bit library the value can be up to 21600xffff. In the 32-bit library in UTF-32 mode the value can be up to 0x10ffff, 2161and up to 0xffffffff when not using UTF-32 mode. 2162<pre> 2163 PCRE2_INFO_FRAMESIZE 2164</pre> 2165Return the size (in bytes) of the data frames that are used to remember 2166backtracking positions when the pattern is processed by <b>pcre2_match()</b> 2167without the use of JIT. The third argument should point to a <b>size_t</b> 2168variable. The frame size depends on the number of capturing parentheses in the 2169pattern. Each additional capture group adds two PCRE2_SIZE variables. 2170<pre> 2171 PCRE2_INFO_HASBACKSLASHC 2172</pre> 2173Return 1 if the pattern contains any instances of \C, otherwise 0. The third 2174argument should point to an <b>uint32_t</b> variable. 2175<pre> 2176 PCRE2_INFO_HASCRORLF 2177</pre> 2178Return 1 if the pattern contains any explicit matches for CR or LF characters, 2179otherwise 0. The third argument should point to an <b>uint32_t</b> variable. An 2180explicit match is either a literal CR or LF character, or \r or \n or one of 2181the equivalent hexadecimal or octal escape sequences. 2182<pre> 2183 PCRE2_INFO_HEAPLIMIT 2184</pre> 2185If the pattern set a heap memory limit by including an item of the form 2186(*LIMIT_HEAP=nnnn) at the start, the value is returned. The third argument 2187should point to a uint32_t integer. If no such value has been set, the call to 2188<b>pcre2_pattern_info()</b> returns the error PCRE2_ERROR_UNSET. Note that this 2189limit will only be used during matching if it is less than the limit set or 2190defaulted by the caller of the match function. 2191<pre> 2192 PCRE2_INFO_JCHANGED 2193</pre> 2194Return 1 if the (?J) or (?-J) option setting is used in the pattern, otherwise 21950. The third argument should point to an <b>uint32_t</b> variable. (?J) and 2196(?-J) set and unset the local PCRE2_DUPNAMES option, respectively. 2197<pre> 2198 PCRE2_INFO_JITSIZE 2199</pre> 2200If the compiled pattern was successfully processed by 2201<b>pcre2_jit_compile()</b>, return the size of the JIT compiled code, otherwise 2202return zero. The third argument should point to a <b>size_t</b> variable. 2203<pre> 2204 PCRE2_INFO_LASTCODETYPE 2205</pre> 2206Returns 1 if there is a rightmost literal code unit that must exist in any 2207matched string, other than at its start. The third argument should point to an 2208<b>uint32_t</b> variable. If there is no such value, 0 is returned. When 1 is 2209returned, the code unit value itself can be retrieved using 2210PCRE2_INFO_LASTCODEUNIT. For anchored patterns, a last literal value is 2211recorded only if it follows something of variable length. For example, for the 2212pattern /^a\d+z\d+/ the returned value is 1 (with "z" returned from 2213PCRE2_INFO_LASTCODEUNIT), but for /^a\dz\d/ the returned value is 0. 2214<pre> 2215 PCRE2_INFO_LASTCODEUNIT 2216</pre> 2217Return the value of the rightmost literal code unit that must exist in any 2218matched string, other than at its start, for a pattern where 2219PCRE2_INFO_LASTCODETYPE returns 1. Otherwise, return 0. The third argument 2220should point to an <b>uint32_t</b> variable. 2221<pre> 2222 PCRE2_INFO_MATCHEMPTY 2223</pre> 2224Return 1 if the pattern might match an empty string, otherwise 0. The third 2225argument should point to an <b>uint32_t</b> variable. When a pattern contains 2226recursive subroutine calls it is not always possible to determine whether or 2227not it can match an empty string. PCRE2 takes a cautious approach and returns 1 2228in such cases. 2229<pre> 2230 PCRE2_INFO_MATCHLIMIT 2231</pre> 2232If the pattern set a match limit by including an item of the form 2233(*LIMIT_MATCH=nnnn) at the start, the value is returned. The third argument 2234should point to a uint32_t integer. If no such value has been set, the call to 2235<b>pcre2_pattern_info()</b> returns the error PCRE2_ERROR_UNSET. Note that this 2236limit will only be used during matching if it is less than the limit set or 2237defaulted by the caller of the match function. 2238<pre> 2239 PCRE2_INFO_MAXLOOKBEHIND 2240</pre> 2241Return the number of characters (not code units) in the longest lookbehind 2242assertion in the pattern. The third argument should point to a uint32_t 2243integer. This information is useful when doing multi-segment matching using the 2244partial matching facilities. Note that the simple assertions \b and \B 2245require a one-character lookbehind. \A also registers a one-character 2246lookbehind, though it does not actually inspect the previous character. This is 2247to ensure that at least one character from the old segment is retained when a 2248new segment is processed. Otherwise, if there are no lookbehinds in the 2249pattern, \A might match incorrectly at the start of a second or subsequent 2250segment. 2251<pre> 2252 PCRE2_INFO_MINLENGTH 2253</pre> 2254If a minimum length for matching subject strings was computed, its value is 2255returned. Otherwise the returned value is 0. The value is a number of 2256characters, which in UTF mode may be different from the number of code units. 2257The third argument should point to an <b>uint32_t</b> variable. The value is a 2258lower bound to the length of any matching string. There may not be any strings 2259of that length that do actually match, but every string that does match is at 2260least that long. 2261<pre> 2262 PCRE2_INFO_NAMECOUNT 2263 PCRE2_INFO_NAMEENTRYSIZE 2264 PCRE2_INFO_NAMETABLE 2265</pre> 2266PCRE2 supports the use of named as well as numbered capturing parentheses. The 2267names are just an additional way of identifying the parentheses, which still 2268acquire numbers. Several convenience functions such as 2269<b>pcre2_substring_get_byname()</b> are provided for extracting captured 2270substrings by name. It is also possible to extract the data directly, by first 2271converting the name to a number in order to access the correct pointers in the 2272output vector (described with <b>pcre2_match()</b> below). To do the conversion, 2273you need to use the name-to-number map, which is described by these three 2274values. 2275</P> 2276<P> 2277The map consists of a number of fixed-size entries. PCRE2_INFO_NAMECOUNT gives 2278the number of entries, and PCRE2_INFO_NAMEENTRYSIZE gives the size of each 2279entry in code units; both of these return a <b>uint32_t</b> value. The entry 2280size depends on the length of the longest name. 2281</P> 2282<P> 2283PCRE2_INFO_NAMETABLE returns a pointer to the first entry of the table. This is 2284a PCRE2_SPTR pointer to a block of code units. In the 8-bit library, the first 2285two bytes of each entry are the number of the capturing parenthesis, most 2286significant byte first. In the 16-bit library, the pointer points to 16-bit 2287code units, the first of which contains the parenthesis number. In the 32-bit 2288library, the pointer points to 32-bit code units, the first of which contains 2289the parenthesis number. The rest of the entry is the corresponding name, zero 2290terminated. 2291</P> 2292<P> 2293The names are in alphabetical order. If (?| is used to create multiple capture 2294groups with the same number, as described in the 2295<a href="pcre2pattern.html#dupgroupnumber">section on duplicate group numbers</a> 2296in the 2297<a href="pcre2pattern.html"><b>pcre2pattern</b></a> 2298page, the groups may be given the same name, but there is only one entry in the 2299table. Different names for groups of the same number are not permitted. 2300</P> 2301<P> 2302Duplicate names for capture groups with different numbers are permitted, but 2303only if PCRE2_DUPNAMES is set. They appear in the table in the order in which 2304they were found in the pattern. In the absence of (?| this is the order of 2305increasing number; when (?| is used this is not necessarily the case because 2306later capture groups may have lower numbers. 2307</P> 2308<P> 2309As a simple example of the name/number table, consider the following pattern 2310after compilation by the 8-bit library (assume PCRE2_EXTENDED is set, so white 2311space - including newlines - is ignored): 2312<pre> 2313 (?<date> (?<year>(\d\d)?\d\d) - (?<month>\d\d) - (?<day>\d\d) ) 2314</pre> 2315There are four named capture groups, so the table has four entries, and each 2316entry in the table is eight bytes long. The table is as follows, with 2317non-printing bytes shows in hexadecimal, and undefined bytes shown as ??: 2318<pre> 2319 00 01 d a t e 00 ?? 2320 00 05 d a y 00 ?? ?? 2321 00 04 m o n t h 00 2322 00 02 y e a r 00 ?? 2323</pre> 2324When writing code to extract data from named capture groups using the 2325name-to-number map, remember that the length of the entries is likely to be 2326different for each compiled pattern. 2327<pre> 2328 PCRE2_INFO_NEWLINE 2329</pre> 2330The output is one of the following <b>uint32_t</b> values: 2331<pre> 2332 PCRE2_NEWLINE_CR Carriage return (CR) 2333 PCRE2_NEWLINE_LF Linefeed (LF) 2334 PCRE2_NEWLINE_CRLF Carriage return, linefeed (CRLF) 2335 PCRE2_NEWLINE_ANY Any Unicode line ending 2336 PCRE2_NEWLINE_ANYCRLF Any of CR, LF, or CRLF 2337 PCRE2_NEWLINE_NUL The NUL character (binary zero) 2338</pre> 2339This identifies the character sequence that will be recognized as meaning 2340"newline" while matching. 2341<pre> 2342 PCRE2_INFO_SIZE 2343</pre> 2344Return the size of the compiled pattern in bytes (for all three libraries). The 2345third argument should point to a <b>size_t</b> variable. This value includes the 2346size of the general data block that precedes the code units of the compiled 2347pattern itself. The value that is used when <b>pcre2_compile()</b> is getting 2348memory in which to place the compiled pattern may be slightly larger than the 2349value returned by this option, because there are cases where the code that 2350calculates the size has to over-estimate. Processing a pattern with the JIT 2351compiler does not alter the value returned by this option. 2352<a name="infoaboutcallouts"></a></P> 2353<br><a name="SEC24" href="#TOC1">INFORMATION ABOUT A PATTERN'S CALLOUTS</a><br> 2354<P> 2355<b>int pcre2_callout_enumerate(const pcre2_code *<i>code</i>,</b> 2356<b> int (*<i>callback</i>)(pcre2_callout_enumerate_block *, void *),</b> 2357<b> void *<i>user_data</i>);</b> 2358<br> 2359<br> 2360A script language that supports the use of string arguments in callouts might 2361like to scan all the callouts in a pattern before running the match. This can 2362be done by calling <b>pcre2_callout_enumerate()</b>. The first argument is a 2363pointer to a compiled pattern, the second points to a callback function, and 2364the third is arbitrary user data. The callback function is called for every 2365callout in the pattern in the order in which they appear. Its first argument is 2366a pointer to a callout enumeration block, and its second argument is the 2367<i>user_data</i> value that was passed to <b>pcre2_callout_enumerate()</b>. The 2368contents of the callout enumeration block are described in the 2369<a href="pcre2callout.html"><b>pcre2callout</b></a> 2370documentation, which also gives further details about callouts. 2371</P> 2372<br><a name="SEC25" href="#TOC1">SERIALIZATION AND PRECOMPILING</a><br> 2373<P> 2374It is possible to save compiled patterns on disc or elsewhere, and reload them 2375later, subject to a number of restrictions. The host on which the patterns are 2376reloaded must be running the same version of PCRE2, with the same code unit 2377width, and must also have the same endianness, pointer width, and PCRE2_SIZE 2378type. Before compiled patterns can be saved, they must be converted to a 2379"serialized" form, which in the case of PCRE2 is really just a bytecode dump. 2380The functions whose names begin with <b>pcre2_serialize_</b> are used for 2381converting to and from the serialized form. They are described in the 2382<a href="pcre2serialize.html"><b>pcre2serialize</b></a> 2383documentation. Note that PCRE2 serialization does not convert compiled patterns 2384to an abstract format like Java or .NET serialization. 2385<a name="matchdatablock"></a></P> 2386<br><a name="SEC26" href="#TOC1">THE MATCH DATA BLOCK</a><br> 2387<P> 2388<b>pcre2_match_data *pcre2_match_data_create(uint32_t <i>ovecsize</i>,</b> 2389<b> pcre2_general_context *<i>gcontext</i>);</b> 2390<br> 2391<br> 2392<b>pcre2_match_data *pcre2_match_data_create_from_pattern(</b> 2393<b> const pcre2_code *<i>code</i>, pcre2_general_context *<i>gcontext</i>);</b> 2394<br> 2395<br> 2396<b>void pcre2_match_data_free(pcre2_match_data *<i>match_data</i>);</b> 2397</P> 2398<P> 2399Information about a successful or unsuccessful match is placed in a match 2400data block, which is an opaque structure that is accessed by function calls. In 2401particular, the match data block contains a vector of offsets into the subject 2402string that define the matched part of the subject and any substrings that were 2403captured. This is known as the <i>ovector</i>. 2404</P> 2405<P> 2406Before calling <b>pcre2_match()</b>, <b>pcre2_dfa_match()</b>, or 2407<b>pcre2_jit_match()</b> you must create a match data block by calling one of 2408the creation functions above. For <b>pcre2_match_data_create()</b>, the first 2409argument is the number of pairs of offsets in the <i>ovector</i>. One pair of 2410offsets is required to identify the string that matched the whole pattern, with 2411an additional pair for each captured substring. For example, a value of 4 2412creates enough space to record the matched portion of the subject plus three 2413captured substrings. A minimum of at least 1 pair is imposed by 2414<b>pcre2_match_data_create()</b>, so it is always possible to return the overall 2415matched string. 2416</P> 2417<P> 2418The second argument of <b>pcre2_match_data_create()</b> is a pointer to a 2419general context, which can specify custom memory management for obtaining the 2420memory for the match data block. If you are not using custom memory management, 2421pass NULL, which causes <b>malloc()</b> to be used. 2422</P> 2423<P> 2424For <b>pcre2_match_data_create_from_pattern()</b>, the first argument is a 2425pointer to a compiled pattern. The ovector is created to be exactly the right 2426size to hold all the substrings a pattern might capture. The second argument is 2427again a pointer to a general context, but in this case if NULL is passed, the 2428memory is obtained using the same allocator that was used for the compiled 2429pattern (custom or default). 2430</P> 2431<P> 2432A match data block can be used many times, with the same or different compiled 2433patterns. You can extract information from a match data block after a match 2434operation has finished, using functions that are described in the sections on 2435<a href="#matchedstrings">matched strings</a> 2436and 2437<a href="#matchotherdata">other match data</a> 2438below. 2439</P> 2440<P> 2441When a call of <b>pcre2_match()</b> fails, valid data is available in the match 2442block only when the error is PCRE2_ERROR_NOMATCH, PCRE2_ERROR_PARTIAL, or one 2443of the error codes for an invalid UTF string. Exactly what is available depends 2444on the error, and is detailed below. 2445</P> 2446<P> 2447When one of the matching functions is called, pointers to the compiled pattern 2448and the subject string are set in the match data block so that they can be 2449referenced by the extraction functions after a successful match. After running 2450a match, you must not free a compiled pattern or a subject string until after 2451all operations on the match data block (for that match) have taken place, 2452unless, in the case of the subject string, you have used the 2453PCRE2_COPY_MATCHED_SUBJECT option, which is described in the section entitled 2454"Option bits for <b>pcre2_match()</b>" 2455<a href="#matchoptions>">below.</a> 2456</P> 2457<P> 2458When a match data block itself is no longer needed, it should be freed by 2459calling <b>pcre2_match_data_free()</b>. If this function is called with a NULL 2460argument, it returns immediately, without doing anything. 2461</P> 2462<br><a name="SEC27" href="#TOC1">MATCHING A PATTERN: THE TRADITIONAL FUNCTION</a><br> 2463<P> 2464<b>int pcre2_match(const pcre2_code *<i>code</i>, PCRE2_SPTR <i>subject</i>,</b> 2465<b> PCRE2_SIZE <i>length</i>, PCRE2_SIZE <i>startoffset</i>,</b> 2466<b> uint32_t <i>options</i>, pcre2_match_data *<i>match_data</i>,</b> 2467<b> pcre2_match_context *<i>mcontext</i>);</b> 2468</P> 2469<P> 2470The function <b>pcre2_match()</b> is called to match a subject string against a 2471compiled pattern, which is passed in the <i>code</i> argument. You can call 2472<b>pcre2_match()</b> with the same <i>code</i> argument as many times as you 2473like, in order to find multiple matches in the subject string or to match 2474different subject strings with the same pattern. 2475</P> 2476<P> 2477This function is the main matching facility of the library, and it operates in 2478a Perl-like manner. For specialist use there is also an alternative matching 2479function, which is described 2480<a href="#dfamatch">below</a> 2481in the section about the <b>pcre2_dfa_match()</b> function. 2482</P> 2483<P> 2484Here is an example of a simple call to <b>pcre2_match()</b>: 2485<pre> 2486 pcre2_match_data *md = pcre2_match_data_create(4, NULL); 2487 int rc = pcre2_match( 2488 re, /* result of pcre2_compile() */ 2489 "some string", /* the subject string */ 2490 11, /* the length of the subject string */ 2491 0, /* start at offset 0 in the subject */ 2492 0, /* default options */ 2493 md, /* the match data block */ 2494 NULL); /* a match context; NULL means use defaults */ 2495</pre> 2496If the subject string is zero-terminated, the length can be given as 2497PCRE2_ZERO_TERMINATED. A match context must be provided if certain less common 2498matching parameters are to be changed. For details, see the section on 2499<a href="#matchcontext">the match context</a> 2500above. 2501</P> 2502<br><b> 2503The string to be matched by <b>pcre2_match()</b> 2504</b><br> 2505<P> 2506The subject string is passed to <b>pcre2_match()</b> as a pointer in 2507<i>subject</i>, a length in <i>length</i>, and a starting offset in 2508<i>startoffset</i>. The length and offset are in code units, not characters. 2509That is, they are in bytes for the 8-bit library, 16-bit code units for the 251016-bit library, and 32-bit code units for the 32-bit library, whether or not 2511UTF processing is enabled. 2512</P> 2513<P> 2514If <i>startoffset</i> is greater than the length of the subject, 2515<b>pcre2_match()</b> returns PCRE2_ERROR_BADOFFSET. When the starting offset is 2516zero, the search for a match starts at the beginning of the subject, and this 2517is by far the most common case. In UTF-8 or UTF-16 mode, the starting offset 2518must point to the start of a character, or to the end of the subject (in UTF-32 2519mode, one code unit equals one character, so all offsets are valid). Like the 2520pattern string, the subject may contain binary zeros. 2521</P> 2522<P> 2523A non-zero starting offset is useful when searching for another match in the 2524same subject by calling <b>pcre2_match()</b> again after a previous success. 2525Setting <i>startoffset</i> differs from passing over a shortened string and 2526setting PCRE2_NOTBOL in the case of a pattern that begins with any kind of 2527lookbehind. For example, consider the pattern 2528<pre> 2529 \Biss\B 2530</pre> 2531which finds occurrences of "iss" in the middle of words. (\B matches only if 2532the current position in the subject is not a word boundary.) When applied to 2533the string "Mississipi" the first call to <b>pcre2_match()</b> finds the first 2534occurrence. If <b>pcre2_match()</b> is called again with just the remainder of 2535the subject, namely "issipi", it does not match, because \B is always false at 2536the start of the subject, which is deemed to be a word boundary. However, if 2537<b>pcre2_match()</b> is passed the entire string again, but with 2538<i>startoffset</i> set to 4, it finds the second occurrence of "iss" because it 2539is able to look behind the starting point to discover that it is preceded by a 2540letter. 2541</P> 2542<P> 2543Finding all the matches in a subject is tricky when the pattern can match an 2544empty string. It is possible to emulate Perl's /g behaviour by first trying the 2545match again at the same offset, with the PCRE2_NOTEMPTY_ATSTART and 2546PCRE2_ANCHORED options, and then if that fails, advancing the starting offset 2547and trying an ordinary match again. There is some code that demonstrates how to 2548do this in the 2549<a href="pcre2demo.html"><b>pcre2demo</b></a> 2550sample program. In the most general case, you have to check to see if the 2551newline convention recognizes CRLF as a newline, and if so, and the current 2552character is CR followed by LF, advance the starting offset by two characters 2553instead of one. 2554</P> 2555<P> 2556If a non-zero starting offset is passed when the pattern is anchored, a single 2557attempt to match at the given offset is made. This can only succeed if the 2558pattern does not require the match to be at the start of the subject. In other 2559words, the anchoring must be the result of setting the PCRE2_ANCHORED option or 2560the use of .* with PCRE2_DOTALL, not by starting the pattern with ^ or \A. 2561<a name="matchoptions"></a></P> 2562<br><b> 2563Option bits for <b>pcre2_match()</b> 2564</b><br> 2565<P> 2566The unused bits of the <i>options</i> argument for <b>pcre2_match()</b> must be 2567zero. The only bits that may be set are PCRE2_ANCHORED, 2568PCRE2_COPY_MATCHED_SUBJECT, PCRE2_ENDANCHORED, PCRE2_NOTBOL, PCRE2_NOTEOL, 2569PCRE2_NOTEMPTY, PCRE2_NOTEMPTY_ATSTART, PCRE2_NO_JIT, PCRE2_NO_UTF_CHECK, 2570PCRE2_PARTIAL_HARD, and PCRE2_PARTIAL_SOFT. Their action is described below. 2571</P> 2572<P> 2573Setting PCRE2_ANCHORED or PCRE2_ENDANCHORED at match time is not supported by 2574the just-in-time (JIT) compiler. If it is set, JIT matching is disabled and the 2575interpretive code in <b>pcre2_match()</b> is run. Apart from PCRE2_NO_JIT 2576(obviously), the remaining options are supported for JIT matching. 2577<pre> 2578 PCRE2_ANCHORED 2579</pre> 2580The PCRE2_ANCHORED option limits <b>pcre2_match()</b> to matching at the first 2581matching position. If a pattern was compiled with PCRE2_ANCHORED, or turned out 2582to be anchored by virtue of its contents, it cannot be made unachored at 2583matching time. Note that setting the option at match time disables JIT 2584matching. 2585<pre> 2586 PCRE2_COPY_MATCHED_SUBJECT 2587</pre> 2588By default, a pointer to the subject is remembered in the match data block so 2589that, after a successful match, it can be referenced by the substring 2590extraction functions. This means that the subject's memory must not be freed 2591until all such operations are complete. For some applications where the 2592lifetime of the subject string is not guaranteed, it may be necessary to make a 2593copy of the subject string, but it is wasteful to do this unless the match is 2594successful. After a successful match, if PCRE2_COPY_MATCHED_SUBJECT is set, the 2595subject is copied and the new pointer is remembered in the match data block 2596instead of the original subject pointer. The memory allocator that was used for 2597the match block itself is used. The copy is automatically freed when 2598<b>pcre2_match_data_free()</b> is called to free the match data block. It is also 2599automatically freed if the match data block is re-used for another match 2600operation. 2601<pre> 2602 PCRE2_ENDANCHORED 2603</pre> 2604If the PCRE2_ENDANCHORED option is set, any string that <b>pcre2_match()</b> 2605matches must be right at the end of the subject string. Note that setting the 2606option at match time disables JIT matching. 2607<pre> 2608 PCRE2_NOTBOL 2609</pre> 2610This option specifies that first character of the subject string is not the 2611beginning of a line, so the circumflex metacharacter should not match before 2612it. Setting this without having set PCRE2_MULTILINE at compile time causes 2613circumflex never to match. This option affects only the behaviour of the 2614circumflex metacharacter. It does not affect \A. 2615<pre> 2616 PCRE2_NOTEOL 2617</pre> 2618This option specifies that the end of the subject string is not the end of a 2619line, so the dollar metacharacter should not match it nor (except in multiline 2620mode) a newline immediately before it. Setting this without having set 2621PCRE2_MULTILINE at compile time causes dollar never to match. This option 2622affects only the behaviour of the dollar metacharacter. It does not affect \Z 2623or \z. 2624<pre> 2625 PCRE2_NOTEMPTY 2626</pre> 2627An empty string is not considered to be a valid match if this option is set. If 2628there are alternatives in the pattern, they are tried. If all the alternatives 2629match the empty string, the entire match fails. For example, if the pattern 2630<pre> 2631 a?b? 2632</pre> 2633is applied to a string not beginning with "a" or "b", it matches an empty 2634string at the start of the subject. With PCRE2_NOTEMPTY set, this match is not 2635valid, so <b>pcre2_match()</b> searches further into the string for occurrences 2636of "a" or "b". 2637<pre> 2638 PCRE2_NOTEMPTY_ATSTART 2639</pre> 2640This is like PCRE2_NOTEMPTY, except that it locks out an empty string match 2641only at the first matching position, that is, at the start of the subject plus 2642the starting offset. An empty string match later in the subject is permitted. 2643If the pattern is anchored, such a match can occur only if the pattern contains 2644\K. 2645<pre> 2646 PCRE2_NO_JIT 2647</pre> 2648By default, if a pattern has been successfully processed by 2649<b>pcre2_jit_compile()</b>, JIT is automatically used when <b>pcre2_match()</b> 2650is called with options that JIT supports. Setting PCRE2_NO_JIT disables the use 2651of JIT; it forces matching to be done by the interpreter. 2652<pre> 2653 PCRE2_NO_UTF_CHECK 2654</pre> 2655When PCRE2_UTF is set at compile time, the validity of the subject as a UTF 2656string is checked by default when <b>pcre2_match()</b> is subsequently called. 2657If a non-zero starting offset is given, the check is applied only to that part 2658of the subject that could be inspected during matching, and there is a check 2659that the starting offset points to the first code unit of a character or to the 2660end of the subject. If there are no lookbehind assertions in the pattern, the 2661check starts at the starting offset. Otherwise, it starts at the length of the 2662longest lookbehind before the starting offset, or at the start of the subject 2663if there are not that many characters before the starting offset. Note that the 2664sequences \b and \B are one-character lookbehinds. 2665</P> 2666<P> 2667The check is carried out before any other processing takes place, and a 2668negative error code is returned if the check fails. There are several UTF error 2669codes for each code unit width, corresponding to different problems with the 2670code unit sequence. There are discussions about the validity of 2671<a href="pcre2unicode.html#utf8strings">UTF-8 strings,</a> 2672<a href="pcre2unicode.html#utf16strings">UTF-16 strings,</a> 2673and 2674<a href="pcre2unicode.html#utf32strings">UTF-32 strings</a> 2675in the 2676<a href="pcre2unicode.html"><b>pcre2unicode</b></a> 2677page. 2678</P> 2679<P> 2680If you know that your subject is valid, and you want to skip these checks for 2681performance reasons, you can set the PCRE2_NO_UTF_CHECK option when calling 2682<b>pcre2_match()</b>. You might want to do this for the second and subsequent 2683calls to <b>pcre2_match()</b> if you are making repeated calls to find other 2684matches in the same subject string. 2685</P> 2686<P> 2687<b>Warning:</b> When PCRE2_NO_UTF_CHECK is set, the effect of passing an invalid 2688string as a subject, or an invalid value of <i>startoffset</i>, is undefined. 2689Your program may crash or loop indefinitely. 2690<pre> 2691 PCRE2_PARTIAL_HARD 2692 PCRE2_PARTIAL_SOFT 2693</pre> 2694These options turn on the partial matching feature. A partial match occurs if 2695the end of the subject string is reached successfully, but there are not enough 2696subject characters to complete the match. If this happens when 2697PCRE2_PARTIAL_SOFT (but not PCRE2_PARTIAL_HARD) is set, matching continues by 2698testing any remaining alternatives. Only if no complete match can be found is 2699PCRE2_ERROR_PARTIAL returned instead of PCRE2_ERROR_NOMATCH. In other words, 2700PCRE2_PARTIAL_SOFT specifies that the caller is prepared to handle a partial 2701match, but only if no complete match can be found. 2702</P> 2703<P> 2704If PCRE2_PARTIAL_HARD is set, it overrides PCRE2_PARTIAL_SOFT. In this case, if 2705a partial match is found, <b>pcre2_match()</b> immediately returns 2706PCRE2_ERROR_PARTIAL, without considering any other alternatives. In other 2707words, when PCRE2_PARTIAL_HARD is set, a partial match is considered to be more 2708important that an alternative complete match. 2709</P> 2710<P> 2711There is a more detailed discussion of partial and multi-segment matching, with 2712examples, in the 2713<a href="pcre2partial.html"><b>pcre2partial</b></a> 2714documentation. 2715</P> 2716<br><a name="SEC28" href="#TOC1">NEWLINE HANDLING WHEN MATCHING</a><br> 2717<P> 2718When PCRE2 is built, a default newline convention is set; this is usually the 2719standard convention for the operating system. The default can be overridden in 2720a 2721<a href="#compilecontext">compile context</a> 2722by calling <b>pcre2_set_newline()</b>. It can also be overridden by starting a 2723pattern string with, for example, (*CRLF), as described in the 2724<a href="pcre2pattern.html#newlines">section on newline conventions</a> 2725in the 2726<a href="pcre2pattern.html"><b>pcre2pattern</b></a> 2727page. During matching, the newline choice affects the behaviour of the dot, 2728circumflex, and dollar metacharacters. It may also alter the way the match 2729starting position is advanced after a match failure for an unanchored pattern. 2730</P> 2731<P> 2732When PCRE2_NEWLINE_CRLF, PCRE2_NEWLINE_ANYCRLF, or PCRE2_NEWLINE_ANY is set as 2733the newline convention, and a match attempt for an unanchored pattern fails 2734when the current starting position is at a CRLF sequence, and the pattern 2735contains no explicit matches for CR or LF characters, the match position is 2736advanced by two characters instead of one, in other words, to after the CRLF. 2737</P> 2738<P> 2739The above rule is a compromise that makes the most common cases work as 2740expected. For example, if the pattern is .+A (and the PCRE2_DOTALL option is 2741not set), it does not match the string "\r\nA" because, after failing at the 2742start, it skips both the CR and the LF before retrying. However, the pattern 2743[\r\n]A does match that string, because it contains an explicit CR or LF 2744reference, and so advances only by one character after the first failure. 2745</P> 2746<P> 2747An explicit match for CR of LF is either a literal appearance of one of those 2748characters in the pattern, or one of the \r or \n or equivalent octal or 2749hexadecimal escape sequences. Implicit matches such as [^X] do not count, nor 2750does \s, even though it includes CR and LF in the characters that it matches. 2751</P> 2752<P> 2753Notwithstanding the above, anomalous effects may still occur when CRLF is a 2754valid newline sequence and explicit \r or \n escapes appear in the pattern. 2755<a name="matchedstrings"></a></P> 2756<br><a name="SEC29" href="#TOC1">HOW PCRE2_MATCH() RETURNS A STRING AND CAPTURED SUBSTRINGS</a><br> 2757<P> 2758<b>uint32_t pcre2_get_ovector_count(pcre2_match_data *<i>match_data</i>);</b> 2759<br> 2760<br> 2761<b>PCRE2_SIZE *pcre2_get_ovector_pointer(pcre2_match_data *<i>match_data</i>);</b> 2762</P> 2763<P> 2764In general, a pattern matches a certain portion of the subject, and in 2765addition, further substrings from the subject may be picked out by 2766parenthesized parts of the pattern. Following the usage in Jeffrey Friedl's 2767book, this is called "capturing" in what follows, and the phrase "capture 2768group" (Perl terminology) is used for a fragment of a pattern that picks out a 2769substring. PCRE2 supports several other kinds of parenthesized group that do 2770not cause substrings to be captured. The <b>pcre2_pattern_info()</b> function 2771can be used to find out how many capture groups there are in a compiled 2772pattern. 2773</P> 2774<P> 2775You can use auxiliary functions for accessing captured substrings 2776<a href="#extractbynumber">by number</a> 2777or 2778<a href="#extractbyname">by name,</a> 2779as described in sections below. 2780</P> 2781<P> 2782Alternatively, you can make direct use of the vector of PCRE2_SIZE values, 2783called the <b>ovector</b>, which contains the offsets of captured strings. It is 2784part of the 2785<a href="#matchdatablock">match data block.</a> 2786The function <b>pcre2_get_ovector_pointer()</b> returns the address of the 2787ovector, and <b>pcre2_get_ovector_count()</b> returns the number of pairs of 2788values it contains. 2789</P> 2790<P> 2791Within the ovector, the first in each pair of values is set to the offset of 2792the first code unit of a substring, and the second is set to the offset of the 2793first code unit after the end of a substring. These values are always code unit 2794offsets, not character offsets. That is, they are byte offsets in the 8-bit 2795library, 16-bit offsets in the 16-bit library, and 32-bit offsets in the 32-bit 2796library. 2797</P> 2798<P> 2799After a partial match (error return PCRE2_ERROR_PARTIAL), only the first pair 2800of offsets (that is, <i>ovector[0]</i> and <i>ovector[1]</i>) are set. They 2801identify the part of the subject that was partially matched. See the 2802<a href="pcre2partial.html"><b>pcre2partial</b></a> 2803documentation for details of partial matching. 2804</P> 2805<P> 2806After a fully successful match, the first pair of offsets identifies the 2807portion of the subject string that was matched by the entire pattern. The next 2808pair is used for the first captured substring, and so on. The value returned by 2809<b>pcre2_match()</b> is one more than the highest numbered pair that has been 2810set. For example, if two substrings have been captured, the returned value is 28113. If there are no captured substrings, the return value from a successful 2812match is 1, indicating that just the first pair of offsets has been set. 2813</P> 2814<P> 2815If a pattern uses the \K escape sequence within a positive assertion, the 2816reported start of a successful match can be greater than the end of the match. 2817For example, if the pattern (?=ab\K) is matched against "ab", the start and 2818end offset values for the match are 2 and 0. 2819</P> 2820<P> 2821If a capture group is matched repeatedly within a single match operation, it is 2822the last portion of the subject that it matched that is returned. 2823</P> 2824<P> 2825If the ovector is too small to hold all the captured substring offsets, as much 2826as possible is filled in, and the function returns a value of zero. If captured 2827substrings are not of interest, <b>pcre2_match()</b> may be called with a match 2828data block whose ovector is of minimum length (that is, one pair). 2829</P> 2830<P> 2831It is possible for capture group number <i>n+1</i> to match some part of the 2832subject when group <i>n</i> has not been used at all. For example, if the string 2833"abc" is matched against the pattern (a|(z))(bc) the return from the function 2834is 4, and groups 1 and 3 are matched, but 2 is not. When this happens, both 2835values in the offset pairs corresponding to unused groups are set to 2836PCRE2_UNSET. 2837</P> 2838<P> 2839Offset values that correspond to unused groups at the end of the expression are 2840also set to PCRE2_UNSET. For example, if the string "abc" is matched against 2841the pattern (abc)(x(yz)?)? groups 2 and 3 are not matched. The return from the 2842function is 2, because the highest used capture group number is 1. The offsets 2843for for the second and third capture groupss (assuming the vector is large 2844enough, of course) are set to PCRE2_UNSET. 2845</P> 2846<P> 2847Elements in the ovector that do not correspond to capturing parentheses in the 2848pattern are never changed. That is, if a pattern contains <i>n</i> capturing 2849parentheses, no more than <i>ovector[0]</i> to <i>ovector[2n+1]</i> are set by 2850<b>pcre2_match()</b>. The other elements retain whatever values they previously 2851had. After a failed match attempt, the contents of the ovector are unchanged. 2852<a name="matchotherdata"></a></P> 2853<br><a name="SEC30" href="#TOC1">OTHER INFORMATION ABOUT A MATCH</a><br> 2854<P> 2855<b>PCRE2_SPTR pcre2_get_mark(pcre2_match_data *<i>match_data</i>);</b> 2856<br> 2857<br> 2858<b>PCRE2_SIZE pcre2_get_startchar(pcre2_match_data *<i>match_data</i>);</b> 2859</P> 2860<P> 2861As well as the offsets in the ovector, other information about a match is 2862retained in the match data block and can be retrieved by the above functions in 2863appropriate circumstances. If they are called at other times, the result is 2864undefined. 2865</P> 2866<P> 2867After a successful match, a partial match (PCRE2_ERROR_PARTIAL), or a failure 2868to match (PCRE2_ERROR_NOMATCH), a mark name may be available. The function 2869<b>pcre2_get_mark()</b> can be called to access this name, which can be 2870specified in the pattern by any of the backtracking control verbs, not just 2871(*MARK). The same function applies to all the verbs. It returns a pointer to 2872the zero-terminated name, which is within the compiled pattern. If no name is 2873available, NULL is returned. The length of the name (excluding the terminating 2874zero) is stored in the code unit that precedes the name. You should use this 2875length instead of relying on the terminating zero if the name might contain a 2876binary zero. 2877</P> 2878<P> 2879After a successful match, the name that is returned is the last mark name 2880encountered on the matching path through the pattern. Instances of backtracking 2881verbs without names do not count. Thus, for example, if the matching path 2882contains (*MARK:A)(*PRUNE), the name "A" is returned. After a "no match" or a 2883partial match, the last encountered name is returned. For example, consider 2884this pattern: 2885<pre> 2886 ^(*MARK:A)((*MARK:B)a|b)c 2887</pre> 2888When it matches "bc", the returned name is A. The B mark is "seen" in the first 2889branch of the group, but it is not on the matching path. On the other hand, 2890when this pattern fails to match "bx", the returned name is B. 2891</P> 2892<P> 2893<b>Warning:</b> By default, certain start-of-match optimizations are used to 2894give a fast "no match" result in some situations. For example, if the anchoring 2895is removed from the pattern above, there is an initial check for the presence 2896of "c" in the subject before running the matching engine. This check fails for 2897"bx", causing a match failure without seeing any marks. You can disable the 2898start-of-match optimizations by setting the PCRE2_NO_START_OPTIMIZE option for 2899<b>pcre2_compile()</b> or by starting the pattern with (*NO_START_OPT). 2900</P> 2901<P> 2902After a successful match, a partial match, or one of the invalid UTF errors 2903(for example, PCRE2_ERROR_UTF8_ERR5), <b>pcre2_get_startchar()</b> can be 2904called. After a successful or partial match it returns the code unit offset of 2905the character at which the match started. For a non-partial match, this can be 2906different to the value of <i>ovector[0]</i> if the pattern contains the \K 2907escape sequence. After a partial match, however, this value is always the same 2908as <i>ovector[0]</i> because \K does not affect the result of a partial match. 2909</P> 2910<P> 2911After a UTF check failure, <b>pcre2_get_startchar()</b> can be used to obtain 2912the code unit offset of the invalid UTF character. Details are given in the 2913<a href="pcre2unicode.html"><b>pcre2unicode</b></a> 2914page. 2915<a name="errorlist"></a></P> 2916<br><a name="SEC31" href="#TOC1">ERROR RETURNS FROM <b>pcre2_match()</b></a><br> 2917<P> 2918If <b>pcre2_match()</b> fails, it returns a negative number. This can be 2919converted to a text string by calling the <b>pcre2_get_error_message()</b> 2920function (see "Obtaining a textual error message" 2921<a href="#geterrormessage">below).</a> 2922Negative error codes are also returned by other functions, and are documented 2923with them. The codes are given names in the header file. If UTF checking is in 2924force and an invalid UTF subject string is detected, one of a number of 2925UTF-specific negative error codes is returned. Details are given in the 2926<a href="pcre2unicode.html"><b>pcre2unicode</b></a> 2927page. The following are the other errors that may be returned by 2928<b>pcre2_match()</b>: 2929<pre> 2930 PCRE2_ERROR_NOMATCH 2931</pre> 2932The subject string did not match the pattern. 2933<pre> 2934 PCRE2_ERROR_PARTIAL 2935</pre> 2936The subject string did not match, but it did match partially. See the 2937<a href="pcre2partial.html"><b>pcre2partial</b></a> 2938documentation for details of partial matching. 2939<pre> 2940 PCRE2_ERROR_BADMAGIC 2941</pre> 2942PCRE2 stores a 4-byte "magic number" at the start of the compiled code, to 2943catch the case when it is passed a junk pointer. This is the error that is 2944returned when the magic number is not present. 2945<pre> 2946 PCRE2_ERROR_BADMODE 2947</pre> 2948This error is given when a compiled pattern is passed to a function in a 2949library of a different code unit width, for example, a pattern compiled by 2950the 8-bit library is passed to a 16-bit or 32-bit library function. 2951<pre> 2952 PCRE2_ERROR_BADOFFSET 2953</pre> 2954The value of <i>startoffset</i> was greater than the length of the subject. 2955<pre> 2956 PCRE2_ERROR_BADOPTION 2957</pre> 2958An unrecognized bit was set in the <i>options</i> argument. 2959<pre> 2960 PCRE2_ERROR_BADUTFOFFSET 2961</pre> 2962The UTF code unit sequence that was passed as a subject was checked and found 2963to be valid (the PCRE2_NO_UTF_CHECK option was not set), but the value of 2964<i>startoffset</i> did not point to the beginning of a UTF character or the end 2965of the subject. 2966<pre> 2967 PCRE2_ERROR_CALLOUT 2968</pre> 2969This error is never generated by <b>pcre2_match()</b> itself. It is provided for 2970use by callout functions that want to cause <b>pcre2_match()</b> or 2971<b>pcre2_callout_enumerate()</b> to return a distinctive error code. See the 2972<a href="pcre2callout.html"><b>pcre2callout</b></a> 2973documentation for details. 2974<pre> 2975 PCRE2_ERROR_DEPTHLIMIT 2976</pre> 2977The nested backtracking depth limit was reached. 2978<pre> 2979 PCRE2_ERROR_HEAPLIMIT 2980</pre> 2981The heap limit was reached. 2982<pre> 2983 PCRE2_ERROR_INTERNAL 2984</pre> 2985An unexpected internal error has occurred. This error could be caused by a bug 2986in PCRE2 or by overwriting of the compiled pattern. 2987<pre> 2988 PCRE2_ERROR_JIT_STACKLIMIT 2989</pre> 2990This error is returned when a pattern that was successfully studied using JIT 2991is being matched, but the memory available for the just-in-time processing 2992stack is not large enough. See the 2993<a href="pcre2jit.html"><b>pcre2jit</b></a> 2994documentation for more details. 2995<pre> 2996 PCRE2_ERROR_MATCHLIMIT 2997</pre> 2998The backtracking match limit was reached. 2999<pre> 3000 PCRE2_ERROR_NOMEMORY 3001</pre> 3002If a pattern contains many nested backtracking points, heap memory is used to 3003remember them. This error is given when the memory allocation function (default 3004or custom) fails. Note that a different error, PCRE2_ERROR_HEAPLIMIT, is given 3005if the amount of memory needed exceeds the heap limit. PCRE2_ERROR_NOMEMORY is 3006also returned if PCRE2_COPY_MATCHED_SUBJECT is set and memory allocation fails. 3007<pre> 3008 PCRE2_ERROR_NULL 3009</pre> 3010Either the <i>code</i>, <i>subject</i>, or <i>match_data</i> argument was passed 3011as NULL. 3012<pre> 3013 PCRE2_ERROR_RECURSELOOP 3014</pre> 3015This error is returned when <b>pcre2_match()</b> detects a recursion loop within 3016the pattern. Specifically, it means that either the whole pattern or a 3017capture group has been called recursively for the second time at the same 3018position in the subject string. Some simple patterns that might do this are 3019detected and faulted at compile time, but more complicated cases, in particular 3020mutual recursions between two different groups, cannot be detected until 3021matching is attempted. 3022<a name="geterrormessage"></a></P> 3023<br><a name="SEC32" href="#TOC1">OBTAINING A TEXTUAL ERROR MESSAGE</a><br> 3024<P> 3025<b>int pcre2_get_error_message(int <i>errorcode</i>, PCRE2_UCHAR *<i>buffer</i>,</b> 3026<b> PCRE2_SIZE <i>bufflen</i>);</b> 3027</P> 3028<P> 3029A text message for an error code from any PCRE2 function (compile, match, or 3030auxiliary) can be obtained by calling <b>pcre2_get_error_message()</b>. The code 3031is passed as the first argument, with the remaining two arguments specifying a 3032code unit buffer and its length in code units, into which the text message is 3033placed. The message is returned in code units of the appropriate width for the 3034library that is being used. 3035</P> 3036<P> 3037The returned message is terminated with a trailing zero, and the function 3038returns the number of code units used, excluding the trailing zero. If the 3039error number is unknown, the negative error code PCRE2_ERROR_BADDATA is 3040returned. If the buffer is too small, the message is truncated (but still with 3041a trailing zero), and the negative error code PCRE2_ERROR_NOMEMORY is returned. 3042None of the messages are very long; a buffer size of 120 code units is ample. 3043<a name="extractbynumber"></a></P> 3044<br><a name="SEC33" href="#TOC1">EXTRACTING CAPTURED SUBSTRINGS BY NUMBER</a><br> 3045<P> 3046<b>int pcre2_substring_length_bynumber(pcre2_match_data *<i>match_data</i>,</b> 3047<b> uint32_t <i>number</i>, PCRE2_SIZE *<i>length</i>);</b> 3048<br> 3049<br> 3050<b>int pcre2_substring_copy_bynumber(pcre2_match_data *<i>match_data</i>,</b> 3051<b> uint32_t <i>number</i>, PCRE2_UCHAR *<i>buffer</i>,</b> 3052<b> PCRE2_SIZE *<i>bufflen</i>);</b> 3053<br> 3054<br> 3055<b>int pcre2_substring_get_bynumber(pcre2_match_data *<i>match_data</i>,</b> 3056<b> uint32_t <i>number</i>, PCRE2_UCHAR **<i>bufferptr</i>,</b> 3057<b> PCRE2_SIZE *<i>bufflen</i>);</b> 3058<br> 3059<br> 3060<b>void pcre2_substring_free(PCRE2_UCHAR *<i>buffer</i>);</b> 3061</P> 3062<P> 3063Captured substrings can be accessed directly by using the ovector as described 3064<a href="#matchedstrings">above.</a> 3065For convenience, auxiliary functions are provided for extracting captured 3066substrings as new, separate, zero-terminated strings. A substring that contains 3067a binary zero is correctly extracted and has a further zero added on the end, 3068but the result is not, of course, a C string. 3069</P> 3070<P> 3071The functions in this section identify substrings by number. The number zero 3072refers to the entire matched substring, with higher numbers referring to 3073substrings captured by parenthesized groups. After a partial match, only 3074substring zero is available. An attempt to extract any other substring gives 3075the error PCRE2_ERROR_PARTIAL. The next section describes similar functions for 3076extracting captured substrings by name. 3077</P> 3078<P> 3079If a pattern uses the \K escape sequence within a positive assertion, the 3080reported start of a successful match can be greater than the end of the match. 3081For example, if the pattern (?=ab\K) is matched against "ab", the start and 3082end offset values for the match are 2 and 0. In this situation, calling these 3083functions with a zero substring number extracts a zero-length empty string. 3084</P> 3085<P> 3086You can find the length in code units of a captured substring without 3087extracting it by calling <b>pcre2_substring_length_bynumber()</b>. The first 3088argument is a pointer to the match data block, the second is the group number, 3089and the third is a pointer to a variable into which the length is placed. If 3090you just want to know whether or not the substring has been captured, you can 3091pass the third argument as NULL. 3092</P> 3093<P> 3094The <b>pcre2_substring_copy_bynumber()</b> function copies a captured substring 3095into a supplied buffer, whereas <b>pcre2_substring_get_bynumber()</b> copies it 3096into new memory, obtained using the same memory allocation function that was 3097used for the match data block. The first two arguments of these functions are a 3098pointer to the match data block and a capture group number. 3099</P> 3100<P> 3101The final arguments of <b>pcre2_substring_copy_bynumber()</b> are a pointer to 3102the buffer and a pointer to a variable that contains its length in code units. 3103This is updated to contain the actual number of code units used for the 3104extracted substring, excluding the terminating zero. 3105</P> 3106<P> 3107For <b>pcre2_substring_get_bynumber()</b> the third and fourth arguments point 3108to variables that are updated with a pointer to the new memory and the number 3109of code units that comprise the substring, again excluding the terminating 3110zero. When the substring is no longer needed, the memory should be freed by 3111calling <b>pcre2_substring_free()</b>. 3112</P> 3113<P> 3114The return value from all these functions is zero for success, or a negative 3115error code. If the pattern match failed, the match failure code is returned. 3116If a substring number greater than zero is used after a partial match, 3117PCRE2_ERROR_PARTIAL is returned. Other possible error codes are: 3118<pre> 3119 PCRE2_ERROR_NOMEMORY 3120</pre> 3121The buffer was too small for <b>pcre2_substring_copy_bynumber()</b>, or the 3122attempt to get memory failed for <b>pcre2_substring_get_bynumber()</b>. 3123<pre> 3124 PCRE2_ERROR_NOSUBSTRING 3125</pre> 3126There is no substring with that number in the pattern, that is, the number is 3127greater than the number of capturing parentheses. 3128<pre> 3129 PCRE2_ERROR_UNAVAILABLE 3130</pre> 3131The substring number, though not greater than the number of captures in the 3132pattern, is greater than the number of slots in the ovector, so the substring 3133could not be captured. 3134<pre> 3135 PCRE2_ERROR_UNSET 3136</pre> 3137The substring did not participate in the match. For example, if the pattern is 3138(abc)|(def) and the subject is "def", and the ovector contains at least two 3139capturing slots, substring number 1 is unset. 3140</P> 3141<br><a name="SEC34" href="#TOC1">EXTRACTING A LIST OF ALL CAPTURED SUBSTRINGS</a><br> 3142<P> 3143<b>int pcre2_substring_list_get(pcre2_match_data *<i>match_data</i>,</b> 3144<b>" PCRE2_UCHAR ***<i>listptr</i>, PCRE2_SIZE **<i>lengthsptr</i>);</b> 3145<br> 3146<br> 3147<b>void pcre2_substring_list_free(PCRE2_SPTR *<i>list</i>);</b> 3148</P> 3149<P> 3150The <b>pcre2_substring_list_get()</b> function extracts all available substrings 3151and builds a list of pointers to them. It also (optionally) builds a second 3152list that contains their lengths (in code units), excluding a terminating zero 3153that is added to each of them. All this is done in a single block of memory 3154that is obtained using the same memory allocation function that was used to get 3155the match data block. 3156</P> 3157<P> 3158This function must be called only after a successful match. If called after a 3159partial match, the error code PCRE2_ERROR_PARTIAL is returned. 3160</P> 3161<P> 3162The address of the memory block is returned via <i>listptr</i>, which is also 3163the start of the list of string pointers. The end of the list is marked by a 3164NULL pointer. The address of the list of lengths is returned via 3165<i>lengthsptr</i>. If your strings do not contain binary zeros and you do not 3166therefore need the lengths, you may supply NULL as the <b>lengthsptr</b> 3167argument to disable the creation of a list of lengths. The yield of the 3168function is zero if all went well, or PCRE2_ERROR_NOMEMORY if the memory block 3169could not be obtained. When the list is no longer needed, it should be freed by 3170calling <b>pcre2_substring_list_free()</b>. 3171</P> 3172<P> 3173If this function encounters a substring that is unset, which can happen when 3174capture group number <i>n+1</i> matches some part of the subject, but group 3175<i>n</i> has not been used at all, it returns an empty string. This can be 3176distinguished from a genuine zero-length substring by inspecting the 3177appropriate offset in the ovector, which contain PCRE2_UNSET for unset 3178substrings, or by calling <b>pcre2_substring_length_bynumber()</b>. 3179<a name="extractbyname"></a></P> 3180<br><a name="SEC35" href="#TOC1">EXTRACTING CAPTURED SUBSTRINGS BY NAME</a><br> 3181<P> 3182<b>int pcre2_substring_number_from_name(const pcre2_code *<i>code</i>,</b> 3183<b> PCRE2_SPTR <i>name</i>);</b> 3184<br> 3185<br> 3186<b>int pcre2_substring_length_byname(pcre2_match_data *<i>match_data</i>,</b> 3187<b> PCRE2_SPTR <i>name</i>, PCRE2_SIZE *<i>length</i>);</b> 3188<br> 3189<br> 3190<b>int pcre2_substring_copy_byname(pcre2_match_data *<i>match_data</i>,</b> 3191<b> PCRE2_SPTR <i>name</i>, PCRE2_UCHAR *<i>buffer</i>, PCRE2_SIZE *<i>bufflen</i>);</b> 3192<br> 3193<br> 3194<b>int pcre2_substring_get_byname(pcre2_match_data *<i>match_data</i>,</b> 3195<b> PCRE2_SPTR <i>name</i>, PCRE2_UCHAR **<i>bufferptr</i>, PCRE2_SIZE *<i>bufflen</i>);</b> 3196<br> 3197<br> 3198<b>void pcre2_substring_free(PCRE2_UCHAR *<i>buffer</i>);</b> 3199</P> 3200<P> 3201To extract a substring by name, you first have to find associated number. 3202For example, for this pattern: 3203<pre> 3204 (a+)b(?<xxx>\d+)... 3205</pre> 3206the number of the capture group called "xxx" is 2. If the name is known to be 3207unique (PCRE2_DUPNAMES was not set), you can find the number from the name by 3208calling <b>pcre2_substring_number_from_name()</b>. The first argument is the 3209compiled pattern, and the second is the name. The yield of the function is the 3210group number, PCRE2_ERROR_NOSUBSTRING if there is no group with that name, or 3211PCRE2_ERROR_NOUNIQUESUBSTRING if there is more than one group with that name. 3212Given the number, you can extract the substring directly from the ovector, or 3213use one of the "bynumber" functions described above. 3214</P> 3215<P> 3216For convenience, there are also "byname" functions that correspond to the 3217"bynumber" functions, the only difference being that the second argument is a 3218name instead of a number. If PCRE2_DUPNAMES is set and there are duplicate 3219names, these functions scan all the groups with the given name, and return the 3220captured substring from the first named group that is set. 3221</P> 3222<P> 3223If there are no groups with the given name, PCRE2_ERROR_NOSUBSTRING is 3224returned. If all groups with the name have numbers that are greater than the 3225number of slots in the ovector, PCRE2_ERROR_UNAVAILABLE is returned. If there 3226is at least one group with a slot in the ovector, but no group is found to be 3227set, PCRE2_ERROR_UNSET is returned. 3228</P> 3229<P> 3230<b>Warning:</b> If the pattern uses the (?| feature to set up multiple 3231capture groups with the same number, as described in the 3232<a href="pcre2pattern.html#dupgroupnumber">section on duplicate group numbers</a> 3233in the 3234<a href="pcre2pattern.html"><b>pcre2pattern</b></a> 3235page, you cannot use names to distinguish the different capture groups, because 3236names are not included in the compiled code. The matching process uses only 3237numbers. For this reason, the use of different names for groups with the 3238same number causes an error at compile time. 3239<a name="substitutions"></a></P> 3240<br><a name="SEC36" href="#TOC1">CREATING A NEW STRING WITH SUBSTITUTIONS</a><br> 3241<P> 3242<b>int pcre2_substitute(const pcre2_code *<i>code</i>, PCRE2_SPTR <i>subject</i>,</b> 3243<b> PCRE2_SIZE <i>length</i>, PCRE2_SIZE <i>startoffset</i>,</b> 3244<b> uint32_t <i>options</i>, pcre2_match_data *<i>match_data</i>,</b> 3245<b> pcre2_match_context *<i>mcontext</i>, PCRE2_SPTR <i>replacement</i>,</b> 3246<b> PCRE2_SIZE <i>rlength</i>, PCRE2_UCHAR *<i>outputbuffer</i>,</b> 3247<b> PCRE2_SIZE *<i>outlengthptr</i>);</b> 3248</P> 3249<P> 3250This function calls <b>pcre2_match()</b> and then makes a copy of the subject 3251string in <i>outputbuffer</i>, replacing one or more parts that were matched 3252with the <i>replacement</i> string, whose length is supplied in <b>rlength</b>. 3253This can be given as PCRE2_ZERO_TERMINATED for a zero-terminated string. 3254The default is to perform just one replacement, but there is an option that 3255requests multiple replacements (see PCRE2_SUBSTITUTE_GLOBAL below for details). 3256</P> 3257<P> 3258Matches in which a \K item in a lookahead in the pattern causes the match to 3259end before it starts are not supported, and give rise to an error return. For 3260global replacements, matches in which \K in a lookbehind causes the match to 3261start earlier than the point that was reached in the previous iteration are 3262also not supported. 3263</P> 3264<P> 3265The first seven arguments of <b>pcre2_substitute()</b> are the same as for 3266<b>pcre2_match()</b>, except that the partial matching options are not 3267permitted, and <i>match_data</i> may be passed as NULL, in which case a match 3268data block is obtained and freed within this function, using memory management 3269functions from the match context, if provided, or else those that were used to 3270allocate memory for the compiled code. 3271</P> 3272<P> 3273If an external <i>match_data</i> block is provided, its contents afterwards 3274are those set by the final call to <b>pcre2_match()</b>. For global changes, 3275this will have ended in a matching error. The contents of the ovector within 3276the match data block may or may not have been changed. 3277</P> 3278<P> 3279The <i>outlengthptr</i> argument must point to a variable that contains the 3280length, in code units, of the output buffer. If the function is successful, the 3281value is updated to contain the length of the new string, excluding the 3282trailing zero that is automatically added. 3283</P> 3284<P> 3285If the function is not successful, the value set via <i>outlengthptr</i> depends 3286on the type of error. For syntax errors in the replacement string, the value is 3287the offset in the replacement string where the error was detected. For other 3288errors, the value is PCRE2_UNSET by default. This includes the case of the 3289output buffer being too small, unless PCRE2_SUBSTITUTE_OVERFLOW_LENGTH is set 3290(see below), in which case the value is the minimum length needed, including 3291space for the trailing zero. Note that in order to compute the required length, 3292<b>pcre2_substitute()</b> has to simulate all the matching and copying, instead 3293of giving an error return as soon as the buffer overflows. Note also that the 3294length is in code units, not bytes. 3295</P> 3296<P> 3297In the replacement string, which is interpreted as a UTF string in UTF mode, 3298and is checked for UTF validity unless the PCRE2_NO_UTF_CHECK option is set, a 3299dollar character is an escape character that can specify the insertion of 3300characters from capture groups or names from (*MARK) or other control verbs 3301in the pattern. The following forms are always recognized: 3302<pre> 3303 $$ insert a dollar character 3304 $<n> or ${<n>} insert the contents of group <n> 3305 $*MARK or ${*MARK} insert a control verb name 3306</pre> 3307Either a group number or a group name can be given for <n>. Curly brackets are 3308required only if the following character would be interpreted as part of the 3309number or name. The number may be zero to include the entire matched string. 3310For example, if the pattern a(b)c is matched with "=abc=" and the replacement 3311string "+$1$0$1+", the result is "=+babcb+=". 3312</P> 3313<P> 3314$*MARK inserts the name from the last encountered backtracking control verb on 3315the matching path that has a name. (*MARK) must always include a name, but the 3316other verbs need not. For example, in the case of (*MARK:A)(*PRUNE) the name 3317inserted is "A", but for (*MARK:A)(*PRUNE:B) the relevant name is "B". This 3318facility can be used to perform simple simultaneous substitutions, as this 3319<b>pcre2test</b> example shows: 3320<pre> 3321 /(*MARK:pear)apple|(*MARK:orange)lemon/g,replace=${*MARK} 3322 apple lemon 3323 2: pear orange 3324</pre> 3325As well as the usual options for <b>pcre2_match()</b>, a number of additional 3326options can be set in the <i>options</i> argument of <b>pcre2_substitute()</b>. 3327</P> 3328<P> 3329PCRE2_SUBSTITUTE_GLOBAL causes the function to iterate over the subject string, 3330replacing every matching substring. If this option is not set, only the first 3331matching substring is replaced. The search for matches takes place in the 3332original subject string (that is, previous replacements do not affect it). 3333Iteration is implemented by advancing the <i>startoffset</i> value for each 3334search, which is always passed the entire subject string. If an offset limit is 3335set in the match context, searching stops when that limit is reached. 3336</P> 3337<P> 3338You can restrict the effect of a global substitution to a portion of the 3339subject string by setting either or both of <i>startoffset</i> and an offset 3340limit. Here is a \fPpcre2test\fP example: 3341<pre> 3342 /B/g,replace=!,use_offset_limit 3343 ABC ABC ABC ABC\=offset=3,offset_limit=12 3344 2: ABC A!C A!C ABC 3345</pre> 3346When continuing with global substitutions after matching a substring with zero 3347length, an attempt to find a non-empty match at the same offset is performed. 3348If this is not successful, the offset is advanced by one character except when 3349CRLF is a valid newline sequence and the next two characters are CR, LF. In 3350this case, the offset is advanced by two characters. 3351</P> 3352<P> 3353PCRE2_SUBSTITUTE_OVERFLOW_LENGTH changes what happens when the output buffer is 3354too small. The default action is to return PCRE2_ERROR_NOMEMORY immediately. If 3355this option is set, however, <b>pcre2_substitute()</b> continues to go through 3356the motions of matching and substituting (without, of course, writing anything) 3357in order to compute the size of buffer that is needed. This value is passed 3358back via the <i>outlengthptr</i> variable, with the result of the function still 3359being PCRE2_ERROR_NOMEMORY. 3360</P> 3361<P> 3362Passing a buffer size of zero is a permitted way of finding out how much memory 3363is needed for given substitution. However, this does mean that the entire 3364operation is carried out twice. Depending on the application, it may be more 3365efficient to allocate a large buffer and free the excess afterwards, instead of 3366using PCRE2_SUBSTITUTE_OVERFLOW_LENGTH. 3367</P> 3368<P> 3369PCRE2_SUBSTITUTE_UNKNOWN_UNSET causes references to capture groups that do 3370not appear in the pattern to be treated as unset groups. This option should be 3371used with care, because it means that a typo in a group name or number no 3372longer causes the PCRE2_ERROR_NOSUBSTRING error. 3373</P> 3374<P> 3375PCRE2_SUBSTITUTE_UNSET_EMPTY causes unset capture groups (including unknown 3376groups when PCRE2_SUBSTITUTE_UNKNOWN_UNSET is set) to be treated as empty 3377strings when inserted as described above. If this option is not set, an attempt 3378to insert an unset group causes the PCRE2_ERROR_UNSET error. This option does 3379not influence the extended substitution syntax described below. 3380</P> 3381<P> 3382PCRE2_SUBSTITUTE_EXTENDED causes extra processing to be applied to the 3383replacement string. Without this option, only the dollar character is special, 3384and only the group insertion forms listed above are valid. When 3385PCRE2_SUBSTITUTE_EXTENDED is set, two things change: 3386</P> 3387<P> 3388Firstly, backslash in a replacement string is interpreted as an escape 3389character. The usual forms such as \n or \x{ddd} can be used to specify 3390particular character codes, and backslash followed by any non-alphanumeric 3391character quotes that character. Extended quoting can be coded using \Q...\E, 3392exactly as in pattern strings. 3393</P> 3394<P> 3395There are also four escape sequences for forcing the case of inserted letters. 3396The insertion mechanism has three states: no case forcing, force upper case, 3397and force lower case. The escape sequences change the current state: \U and 3398\L change to upper or lower case forcing, respectively, and \E (when not 3399terminating a \Q quoted sequence) reverts to no case forcing. The sequences 3400\u and \l force the next character (if it is a letter) to upper or lower 3401case, respectively, and then the state automatically reverts to no case 3402forcing. Case forcing applies to all inserted characters, including those from 3403capture groups and letters within \Q...\E quoted sequences. 3404</P> 3405<P> 3406Note that case forcing sequences such as \U...\E do not nest. For example, 3407the result of processing "\Uaa\LBB\Ecc\E" is "AAbbcc"; the final \E has no 3408effect. Note also that the PCRE2_ALT_BSUX and PCRE2_EXTRA_ALT_BSUX options do 3409not apply to not apply to replacement strings. 3410</P> 3411<P> 3412The second effect of setting PCRE2_SUBSTITUTE_EXTENDED is to add more 3413flexibility to capture group substitution. The syntax is similar to that used 3414by Bash: 3415<pre> 3416 ${<n>:-<string>} 3417 ${<n>:+<string1>:<string2>} 3418</pre> 3419As before, <n> may be a group number or a name. The first form specifies a 3420default value. If group <n> is set, its value is inserted; if not, <string> is 3421expanded and the result inserted. The second form specifies strings that are 3422expanded and inserted when group <n> is set or unset, respectively. The first 3423form is just a convenient shorthand for 3424<pre> 3425 ${<n>:+${<n>}:<string>} 3426</pre> 3427Backslash can be used to escape colons and closing curly brackets in the 3428replacement strings. A change of the case forcing state within a replacement 3429string remains in force afterwards, as shown in this <b>pcre2test</b> example: 3430<pre> 3431 /(some)?(body)/substitute_extended,replace=${1:+\U:\L}HeLLo 3432 body 3433 1: hello 3434 somebody 3435 1: HELLO 3436</pre> 3437The PCRE2_SUBSTITUTE_UNSET_EMPTY option does not affect these extended 3438substitutions. However, PCRE2_SUBSTITUTE_UNKNOWN_UNSET does cause unknown 3439groups in the extended syntax forms to be treated as unset. 3440</P> 3441<P> 3442If successful, <b>pcre2_substitute()</b> returns the number of successful 3443matches. This may be zero if no matches were found, and is never greater than 1 3444unless PCRE2_SUBSTITUTE_GLOBAL is set. 3445</P> 3446<P> 3447In the event of an error, a negative error code is returned. Except for 3448PCRE2_ERROR_NOMATCH (which is never returned), errors from <b>pcre2_match()</b> 3449are passed straight back. 3450</P> 3451<P> 3452PCRE2_ERROR_NOSUBSTRING is returned for a non-existent substring insertion, 3453unless PCRE2_SUBSTITUTE_UNKNOWN_UNSET is set. 3454</P> 3455<P> 3456PCRE2_ERROR_UNSET is returned for an unset substring insertion (including an 3457unknown substring when PCRE2_SUBSTITUTE_UNKNOWN_UNSET is set) when the simple 3458(non-extended) syntax is used and PCRE2_SUBSTITUTE_UNSET_EMPTY is not set. 3459</P> 3460<P> 3461PCRE2_ERROR_NOMEMORY is returned if the output buffer is not big enough. If the 3462PCRE2_SUBSTITUTE_OVERFLOW_LENGTH option is set, the size of buffer that is 3463needed is returned via <i>outlengthptr</i>. Note that this does not happen by 3464default. 3465</P> 3466<P> 3467PCRE2_ERROR_BADREPLACEMENT is used for miscellaneous syntax errors in the 3468replacement string, with more particular errors being PCRE2_ERROR_BADREPESCAPE 3469(invalid escape sequence), PCRE2_ERROR_REPMISSINGBRACE (closing curly bracket 3470not found), PCRE2_ERROR_BADSUBSTITUTION (syntax error in extended group 3471substitution), and PCRE2_ERROR_BADSUBSPATTERN (the pattern match ended before 3472it started or the match started earlier than the current position in the 3473subject, which can happen if \K is used in an assertion). 3474</P> 3475<P> 3476As for all PCRE2 errors, a text message that describes the error can be 3477obtained by calling the <b>pcre2_get_error_message()</b> function (see 3478"Obtaining a textual error message" 3479<a href="#geterrormessage">above).</a> 3480</P> 3481<br><b> 3482Substitution callouts 3483</b><br> 3484<P> 3485<b>int pcre2_set_substitute_callout(pcre2_match_context *<i>mcontext</i>,</b> 3486<b> int (*<i>callout_function</i>)(pcre2_substitute_callout_block *, void *),</b> 3487<b> void *<i>callout_data</i>);</b> 3488<br> 3489<br> 3490The <b>pcre2_set_substitution_callout()</b> function can be used to specify a 3491callout function for <b>pcre2_substitute()</b>. This information is passed in 3492a match context. The callout function is called after each substitution has 3493been processed, but it can cause the replacement not to happen. The callout 3494function is not called for simulated substitutions that happen as a result of 3495the PCRE2_SUBSTITUTE_OVERFLOW_LENGTH option. 3496</P> 3497<P> 3498The first argument of the callout function is a pointer to a substitute callout 3499block structure, which contains the following fields, not necessarily in this 3500order: 3501<pre> 3502 uint32_t <i>version</i>; 3503 uint32_t <i>subscount</i>; 3504 PCRE2_SPTR <i>input</i>; 3505 PCRE2_SPTR <i>output</i>; 3506 PCRE2_SIZE <i>*ovector</i>; 3507 uint32_t <i>oveccount</i>; 3508 PCRE2_SIZE <i>output_offsets[2]</i>; 3509</pre> 3510The <i>version</i> field contains the version number of the block format. The 3511current version is 0. The version number will increase in future if more fields 3512are added, but the intention is never to remove any of the existing fields. 3513</P> 3514<P> 3515The <i>subscount</i> field is the number of the current match. It is 1 for the 3516first callout, 2 for the second, and so on. The <i>input</i> and <i>output</i> 3517pointers are copies of the values passed to <b>pcre2_substitute()</b>. 3518</P> 3519<P> 3520The <i>ovector</i> field points to the ovector, which contains the result of the 3521most recent match. The <i>oveccount</i> field contains the number of pairs that 3522are set in the ovector, and is always greater than zero. 3523</P> 3524<P> 3525The <i>output_offsets</i> vector contains the offsets of the replacement in the 3526output string. This has already been processed for dollar and (if requested) 3527backslash substitutions as described above. 3528</P> 3529<P> 3530The second argument of the callout function is the value passed as 3531<i>callout_data</i> when the function was registered. The value returned by the 3532callout function is interpreted as follows: 3533</P> 3534<P> 3535If the value is zero, the replacement is accepted, and, if 3536PCRE2_SUBSTITUTE_GLOBAL is set, processing continues with a search for the next 3537match. If the value is not zero, the current replacement is not accepted. If 3538the value is greater than zero, processing continues when 3539PCRE2_SUBSTITUTE_GLOBAL is set. Otherwise (the value is less than zero or 3540PCRE2_SUBSTITUTE_GLOBAL is not set), the the rest of the input is copied to the 3541output and the call to <b>pcre2_substitute()</b> exits, returning the number of 3542matches so far. 3543</P> 3544<br><a name="SEC37" href="#TOC1">DUPLICATE CAPTURE GROUP NAMES</a><br> 3545<P> 3546<b>int pcre2_substring_nametable_scan(const pcre2_code *<i>code</i>,</b> 3547<b> PCRE2_SPTR <i>name</i>, PCRE2_SPTR *<i>first</i>, PCRE2_SPTR *<i>last</i>);</b> 3548</P> 3549<P> 3550When a pattern is compiled with the PCRE2_DUPNAMES option, names for capture 3551groups are not required to be unique. Duplicate names are always allowed for 3552groups with the same number, created by using the (?| feature. Indeed, if such 3553groups are named, they are required to use the same names. 3554</P> 3555<P> 3556Normally, patterns that use duplicate names are such that in any one match, 3557only one of each set of identically-named groups participates. An example is 3558shown in the 3559<a href="pcre2pattern.html"><b>pcre2pattern</b></a> 3560documentation. 3561</P> 3562<P> 3563When duplicates are present, <b>pcre2_substring_copy_byname()</b> and 3564<b>pcre2_substring_get_byname()</b> return the first substring corresponding to 3565the given name that is set. Only if none are set is PCRE2_ERROR_UNSET is 3566returned. The <b>pcre2_substring_number_from_name()</b> function returns the 3567error PCRE2_ERROR_NOUNIQUESUBSTRING when there are duplicate names. 3568</P> 3569<P> 3570If you want to get full details of all captured substrings for a given name, 3571you must use the <b>pcre2_substring_nametable_scan()</b> function. The first 3572argument is the compiled pattern, and the second is the name. If the third and 3573fourth arguments are NULL, the function returns a group number for a unique 3574name, or PCRE2_ERROR_NOUNIQUESUBSTRING otherwise. 3575</P> 3576<P> 3577When the third and fourth arguments are not NULL, they must be pointers to 3578variables that are updated by the function. After it has run, they point to the 3579first and last entries in the name-to-number table for the given name, and the 3580function returns the length of each entry in code units. In both cases, 3581PCRE2_ERROR_NOSUBSTRING is returned if there are no entries for the given name. 3582</P> 3583<P> 3584The format of the name table is described 3585<a href="#infoaboutpattern">above</a> 3586in the section entitled <i>Information about a pattern</i>. Given all the 3587relevant entries for the name, you can extract each of their numbers, and hence 3588the captured data. 3589</P> 3590<br><a name="SEC38" href="#TOC1">FINDING ALL POSSIBLE MATCHES AT ONE POSITION</a><br> 3591<P> 3592The traditional matching function uses a similar algorithm to Perl, which stops 3593when it finds the first match at a given point in the subject. If you want to 3594find all possible matches, or the longest possible match at a given position, 3595consider using the alternative matching function (see below) instead. If you 3596cannot use the alternative function, you can kludge it up by making use of the 3597callout facility, which is described in the 3598<a href="pcre2callout.html"><b>pcre2callout</b></a> 3599documentation. 3600</P> 3601<P> 3602What you have to do is to insert a callout right at the end of the pattern. 3603When your callout function is called, extract and save the current matched 3604substring. Then return 1, which forces <b>pcre2_match()</b> to backtrack and try 3605other alternatives. Ultimately, when it runs out of matches, 3606<b>pcre2_match()</b> will yield PCRE2_ERROR_NOMATCH. 3607<a name="dfamatch"></a></P> 3608<br><a name="SEC39" href="#TOC1">MATCHING A PATTERN: THE ALTERNATIVE FUNCTION</a><br> 3609<P> 3610<b>int pcre2_dfa_match(const pcre2_code *<i>code</i>, PCRE2_SPTR <i>subject</i>,</b> 3611<b> PCRE2_SIZE <i>length</i>, PCRE2_SIZE <i>startoffset</i>,</b> 3612<b> uint32_t <i>options</i>, pcre2_match_data *<i>match_data</i>,</b> 3613<b> pcre2_match_context *<i>mcontext</i>,</b> 3614<b> int *<i>workspace</i>, PCRE2_SIZE <i>wscount</i>);</b> 3615</P> 3616<P> 3617The function <b>pcre2_dfa_match()</b> is called to match a subject string 3618against a compiled pattern, using a matching algorithm that scans the subject 3619string just once (not counting lookaround assertions), and does not backtrack. 3620This has different characteristics to the normal algorithm, and is not 3621compatible with Perl. Some of the features of PCRE2 patterns are not supported. 3622Nevertheless, there are times when this kind of matching can be useful. For a 3623discussion of the two matching algorithms, and a list of features that 3624<b>pcre2_dfa_match()</b> does not support, see the 3625<a href="pcre2matching.html"><b>pcre2matching</b></a> 3626documentation. 3627</P> 3628<P> 3629The arguments for the <b>pcre2_dfa_match()</b> function are the same as for 3630<b>pcre2_match()</b>, plus two extras. The ovector within the match data block 3631is used in a different way, and this is described below. The other common 3632arguments are used in the same way as for <b>pcre2_match()</b>, so their 3633description is not repeated here. 3634</P> 3635<P> 3636The two additional arguments provide workspace for the function. The workspace 3637vector should contain at least 20 elements. It is used for keeping track of 3638multiple paths through the pattern tree. More workspace is needed for patterns 3639and subjects where there are a lot of potential matches. 3640</P> 3641<P> 3642Here is an example of a simple call to <b>pcre2_dfa_match()</b>: 3643<pre> 3644 int wspace[20]; 3645 pcre2_match_data *md = pcre2_match_data_create(4, NULL); 3646 int rc = pcre2_dfa_match( 3647 re, /* result of pcre2_compile() */ 3648 "some string", /* the subject string */ 3649 11, /* the length of the subject string */ 3650 0, /* start at offset 0 in the subject */ 3651 0, /* default options */ 3652 md, /* the match data block */ 3653 NULL, /* a match context; NULL means use defaults */ 3654 wspace, /* working space vector */ 3655 20); /* number of elements (NOT size in bytes) */ 3656</PRE> 3657</P> 3658<br><b> 3659Option bits for <b>pcre_dfa_match()</b> 3660</b><br> 3661<P> 3662The unused bits of the <i>options</i> argument for <b>pcre2_dfa_match()</b> must 3663be zero. The only bits that may be set are PCRE2_ANCHORED, 3664PCRE2_COPY_MATCHED_SUBJECT, PCRE2_ENDANCHORED, PCRE2_NOTBOL, PCRE2_NOTEOL, 3665PCRE2_NOTEMPTY, PCRE2_NOTEMPTY_ATSTART, PCRE2_NO_UTF_CHECK, PCRE2_PARTIAL_HARD, 3666PCRE2_PARTIAL_SOFT, PCRE2_DFA_SHORTEST, and PCRE2_DFA_RESTART. All but the last 3667four of these are exactly the same as for <b>pcre2_match()</b>, so their 3668description is not repeated here. 3669<pre> 3670 PCRE2_PARTIAL_HARD 3671 PCRE2_PARTIAL_SOFT 3672</pre> 3673These have the same general effect as they do for <b>pcre2_match()</b>, but the 3674details are slightly different. When PCRE2_PARTIAL_HARD is set for 3675<b>pcre2_dfa_match()</b>, it returns PCRE2_ERROR_PARTIAL if the end of the 3676subject is reached and there is still at least one matching possibility that 3677requires additional characters. This happens even if some complete matches have 3678already been found. When PCRE2_PARTIAL_SOFT is set, the return code 3679PCRE2_ERROR_NOMATCH is converted into PCRE2_ERROR_PARTIAL if the end of the 3680subject is reached, there have been no complete matches, but there is still at 3681least one matching possibility. The portion of the string that was inspected 3682when the longest partial match was found is set as the first matching string in 3683both cases. There is a more detailed discussion of partial and multi-segment 3684matching, with examples, in the 3685<a href="pcre2partial.html"><b>pcre2partial</b></a> 3686documentation. 3687<pre> 3688 PCRE2_DFA_SHORTEST 3689</pre> 3690Setting the PCRE2_DFA_SHORTEST option causes the matching algorithm to stop as 3691soon as it has found one match. Because of the way the alternative algorithm 3692works, this is necessarily the shortest possible match at the first possible 3693matching point in the subject string. 3694<pre> 3695 PCRE2_DFA_RESTART 3696</pre> 3697When <b>pcre2_dfa_match()</b> returns a partial match, it is possible to call it 3698again, with additional subject characters, and have it continue with the same 3699match. The PCRE2_DFA_RESTART option requests this action; when it is set, the 3700<i>workspace</i> and <i>wscount</i> options must reference the same vector as 3701before because data about the match so far is left in them after a partial 3702match. There is more discussion of this facility in the 3703<a href="pcre2partial.html"><b>pcre2partial</b></a> 3704documentation. 3705</P> 3706<br><b> 3707Successful returns from <b>pcre2_dfa_match()</b> 3708</b><br> 3709<P> 3710When <b>pcre2_dfa_match()</b> succeeds, it may have matched more than one 3711substring in the subject. Note, however, that all the matches from one run of 3712the function start at the same point in the subject. The shorter matches are 3713all initial substrings of the longer matches. For example, if the pattern 3714<pre> 3715 <.*> 3716</pre> 3717is matched against the string 3718<pre> 3719 This is <something> <something else> <something further> no more 3720</pre> 3721the three matched strings are 3722<pre> 3723 <something> <something else> <something further> 3724 <something> <something else> 3725 <something> 3726</pre> 3727On success, the yield of the function is a number greater than zero, which is 3728the number of matched substrings. The offsets of the substrings are returned in 3729the ovector, and can be extracted by number in the same way as for 3730<b>pcre2_match()</b>, but the numbers bear no relation to any capture groups 3731that may exist in the pattern, because DFA matching does not support capturing. 3732</P> 3733<P> 3734Calls to the convenience functions that extract substrings by name 3735return the error PCRE2_ERROR_DFA_UFUNC (unsupported function) if used after a 3736DFA match. The convenience functions that extract substrings by number never 3737return PCRE2_ERROR_NOSUBSTRING. 3738</P> 3739<P> 3740The matched strings are stored in the ovector in reverse order of length; that 3741is, the longest matching string is first. If there were too many matches to fit 3742into the ovector, the yield of the function is zero, and the vector is filled 3743with the longest matches. 3744</P> 3745<P> 3746NOTE: PCRE2's "auto-possessification" optimization usually applies to character 3747repeats at the end of a pattern (as well as internally). For example, the 3748pattern "a\d+" is compiled as if it were "a\d++". For DFA matching, this 3749means that only one possible match is found. If you really do want multiple 3750matches in such cases, either use an ungreedy repeat such as "a\d+?" or set 3751the PCRE2_NO_AUTO_POSSESS option when compiling. 3752</P> 3753<br><b> 3754Error returns from <b>pcre2_dfa_match()</b> 3755</b><br> 3756<P> 3757The <b>pcre2_dfa_match()</b> function returns a negative number when it fails. 3758Many of the errors are the same as for <b>pcre2_match()</b>, as described 3759<a href="#errorlist">above.</a> 3760There are in addition the following errors that are specific to 3761<b>pcre2_dfa_match()</b>: 3762<pre> 3763 PCRE2_ERROR_DFA_UITEM 3764</pre> 3765This return is given if <b>pcre2_dfa_match()</b> encounters an item in the 3766pattern that it does not support, for instance, the use of \C in a UTF mode or 3767a backreference. 3768<pre> 3769 PCRE2_ERROR_DFA_UCOND 3770</pre> 3771This return is given if <b>pcre2_dfa_match()</b> encounters a condition item 3772that uses a backreference for the condition, or a test for recursion in a 3773specific capture group. These are not supported. 3774<pre> 3775 PCRE2_ERROR_DFA_WSSIZE 3776</pre> 3777This return is given if <b>pcre2_dfa_match()</b> runs out of space in the 3778<i>workspace</i> vector. 3779<pre> 3780 PCRE2_ERROR_DFA_RECURSE 3781</pre> 3782When a recursion or subroutine call is processed, the matching function calls 3783itself recursively, using private memory for the ovector and <i>workspace</i>. 3784This error is given if the internal ovector is not large enough. This should be 3785extremely rare, as a vector of size 1000 is used. 3786<pre> 3787 PCRE2_ERROR_DFA_BADRESTART 3788</pre> 3789When <b>pcre2_dfa_match()</b> is called with the <b>PCRE2_DFA_RESTART</b> option, 3790some plausibility checks are made on the contents of the workspace, which 3791should contain data about the previous partial match. If any of these checks 3792fail, this error is given. 3793</P> 3794<br><a name="SEC40" href="#TOC1">SEE ALSO</a><br> 3795<P> 3796<b>pcre2build</b>(3), <b>pcre2callout</b>(3), <b>pcre2demo(3)</b>, 3797<b>pcre2matching</b>(3), <b>pcre2partial</b>(3), <b>pcre2posix</b>(3), 3798<b>pcre2sample</b>(3), <b>pcre2unicode</b>(3). 3799</P> 3800<br><a name="SEC41" href="#TOC1">AUTHOR</a><br> 3801<P> 3802Philip Hazel 3803<br> 3804University Computing Service 3805<br> 3806Cambridge, England. 3807<br> 3808</P> 3809<br><a name="SEC42" href="#TOC1">REVISION</a><br> 3810<P> 3811Last updated: 14 February 2019 3812<br> 3813Copyright © 1997-2019 University of Cambridge. 3814<br> 3815<p> 3816Return to the <a href="index.html">PCRE2 index page</a>. 3817</p> 3818