Annotation of embedaddon/pcre/doc/html/pcreapi.html, revision 1.1
1.1 ! misho 1: <html>
! 2: <head>
! 3: <title>pcreapi specification</title>
! 4: </head>
! 5: <body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB">
! 6: <h1>pcreapi man page</h1>
! 7: <p>
! 8: Return to the <a href="index.html">PCRE index page</a>.
! 9: </p>
! 10: <p>
! 11: This page is part of the PCRE HTML documentation. It was generated automatically
! 12: from the original man page. If there is any nonsense in it, please consult the
! 13: man page, in case the conversion went wrong.
! 14: <br>
! 15: <ul>
! 16: <li><a name="TOC1" href="#SEC1">PCRE NATIVE API BASIC FUNCTIONS</a>
! 17: <li><a name="TOC2" href="#SEC2">PCRE NATIVE API AUXILIARY FUNCTIONS</a>
! 18: <li><a name="TOC3" href="#SEC3">PCRE NATIVE API INDIRECTED FUNCTIONS</a>
! 19: <li><a name="TOC4" href="#SEC4">PCRE API OVERVIEW</a>
! 20: <li><a name="TOC5" href="#SEC5">NEWLINES</a>
! 21: <li><a name="TOC6" href="#SEC6">MULTITHREADING</a>
! 22: <li><a name="TOC7" href="#SEC7">SAVING PRECOMPILED PATTERNS FOR LATER USE</a>
! 23: <li><a name="TOC8" href="#SEC8">CHECKING BUILD-TIME OPTIONS</a>
! 24: <li><a name="TOC9" href="#SEC9">COMPILING A PATTERN</a>
! 25: <li><a name="TOC10" href="#SEC10">COMPILATION ERROR CODES</a>
! 26: <li><a name="TOC11" href="#SEC11">STUDYING A PATTERN</a>
! 27: <li><a name="TOC12" href="#SEC12">LOCALE SUPPORT</a>
! 28: <li><a name="TOC13" href="#SEC13">INFORMATION ABOUT A PATTERN</a>
! 29: <li><a name="TOC14" href="#SEC14">OBSOLETE INFO FUNCTION</a>
! 30: <li><a name="TOC15" href="#SEC15">REFERENCE COUNTS</a>
! 31: <li><a name="TOC16" href="#SEC16">MATCHING A PATTERN: THE TRADITIONAL FUNCTION</a>
! 32: <li><a name="TOC17" href="#SEC17">EXTRACTING CAPTURED SUBSTRINGS BY NUMBER</a>
! 33: <li><a name="TOC18" href="#SEC18">EXTRACTING CAPTURED SUBSTRINGS BY NAME</a>
! 34: <li><a name="TOC19" href="#SEC19">DUPLICATE SUBPATTERN NAMES</a>
! 35: <li><a name="TOC20" href="#SEC20">FINDING ALL POSSIBLE MATCHES</a>
! 36: <li><a name="TOC21" href="#SEC21">MATCHING A PATTERN: THE ALTERNATIVE FUNCTION</a>
! 37: <li><a name="TOC22" href="#SEC22">SEE ALSO</a>
! 38: <li><a name="TOC23" href="#SEC23">AUTHOR</a>
! 39: <li><a name="TOC24" href="#SEC24">REVISION</a>
! 40: </ul>
! 41: <br><a name="SEC1" href="#TOC1">PCRE NATIVE API BASIC FUNCTIONS</a><br>
! 42: <P>
! 43: <b>#include <pcre.h></b>
! 44: </P>
! 45: <P>
! 46: <b>pcre *pcre_compile(const char *<i>pattern</i>, int <i>options</i>,</b>
! 47: <b>const char **<i>errptr</i>, int *<i>erroffset</i>,</b>
! 48: <b>const unsigned char *<i>tableptr</i>);</b>
! 49: </P>
! 50: <P>
! 51: <b>pcre *pcre_compile2(const char *<i>pattern</i>, int <i>options</i>,</b>
! 52: <b>int *<i>errorcodeptr</i>,</b>
! 53: <b>const char **<i>errptr</i>, int *<i>erroffset</i>,</b>
! 54: <b>const unsigned char *<i>tableptr</i>);</b>
! 55: </P>
! 56: <P>
! 57: <b>pcre_extra *pcre_study(const pcre *<i>code</i>, int <i>options</i>,</b>
! 58: <b>const char **<i>errptr</i>);</b>
! 59: </P>
! 60: <P>
! 61: <b>void pcre_free_study(pcre_extra *<i>extra</i>);</b>
! 62: </P>
! 63: <P>
! 64: <b>int pcre_exec(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b>
! 65: <b>const char *<i>subject</i>, int <i>length</i>, int <i>startoffset</i>,</b>
! 66: <b>int <i>options</i>, int *<i>ovector</i>, int <i>ovecsize</i>);</b>
! 67: </P>
! 68: <br><a name="SEC2" href="#TOC1">PCRE NATIVE API AUXILIARY FUNCTIONS</a><br>
! 69: <P>
! 70: <b>pcre_jit_stack *pcre_jit_stack_alloc(int <i>startsize</i>, int <i>maxsize</i>);</b>
! 71: </P>
! 72: <P>
! 73: <b>void pcre_jit_stack_free(pcre_jit_stack *<i>stack</i>);</b>
! 74: </P>
! 75: <P>
! 76: <b>void pcre_assign_jit_stack(pcre_extra *<i>extra</i>,</b>
! 77: <b>pcre_jit_callback <i>callback</i>, void *<i>data</i>);</b>
! 78: </P>
! 79: <P>
! 80: <b>int pcre_dfa_exec(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b>
! 81: <b>const char *<i>subject</i>, int <i>length</i>, int <i>startoffset</i>,</b>
! 82: <b>int <i>options</i>, int *<i>ovector</i>, int <i>ovecsize</i>,</b>
! 83: <b>int *<i>workspace</i>, int <i>wscount</i>);</b>
! 84: </P>
! 85: <P>
! 86: <b>int pcre_copy_named_substring(const pcre *<i>code</i>,</b>
! 87: <b>const char *<i>subject</i>, int *<i>ovector</i>,</b>
! 88: <b>int <i>stringcount</i>, const char *<i>stringname</i>,</b>
! 89: <b>char *<i>buffer</i>, int <i>buffersize</i>);</b>
! 90: </P>
! 91: <P>
! 92: <b>int pcre_copy_substring(const char *<i>subject</i>, int *<i>ovector</i>,</b>
! 93: <b>int <i>stringcount</i>, int <i>stringnumber</i>, char *<i>buffer</i>,</b>
! 94: <b>int <i>buffersize</i>);</b>
! 95: </P>
! 96: <P>
! 97: <b>int pcre_get_named_substring(const pcre *<i>code</i>,</b>
! 98: <b>const char *<i>subject</i>, int *<i>ovector</i>,</b>
! 99: <b>int <i>stringcount</i>, const char *<i>stringname</i>,</b>
! 100: <b>const char **<i>stringptr</i>);</b>
! 101: </P>
! 102: <P>
! 103: <b>int pcre_get_stringnumber(const pcre *<i>code</i>,</b>
! 104: <b>const char *<i>name</i>);</b>
! 105: </P>
! 106: <P>
! 107: <b>int pcre_get_stringtable_entries(const pcre *<i>code</i>,</b>
! 108: <b>const char *<i>name</i>, char **<i>first</i>, char **<i>last</i>);</b>
! 109: </P>
! 110: <P>
! 111: <b>int pcre_get_substring(const char *<i>subject</i>, int *<i>ovector</i>,</b>
! 112: <b>int <i>stringcount</i>, int <i>stringnumber</i>,</b>
! 113: <b>const char **<i>stringptr</i>);</b>
! 114: </P>
! 115: <P>
! 116: <b>int pcre_get_substring_list(const char *<i>subject</i>,</b>
! 117: <b>int *<i>ovector</i>, int <i>stringcount</i>, const char ***<i>listptr</i>);</b>
! 118: </P>
! 119: <P>
! 120: <b>void pcre_free_substring(const char *<i>stringptr</i>);</b>
! 121: </P>
! 122: <P>
! 123: <b>void pcre_free_substring_list(const char **<i>stringptr</i>);</b>
! 124: </P>
! 125: <P>
! 126: <b>const unsigned char *pcre_maketables(void);</b>
! 127: </P>
! 128: <P>
! 129: <b>int pcre_fullinfo(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b>
! 130: <b>int <i>what</i>, void *<i>where</i>);</b>
! 131: </P>
! 132: <P>
! 133: <b>int pcre_info(const pcre *<i>code</i>, int *<i>optptr</i>, int</b>
! 134: <b>*<i>firstcharptr</i>);</b>
! 135: </P>
! 136: <P>
! 137: <b>int pcre_refcount(pcre *<i>code</i>, int <i>adjust</i>);</b>
! 138: </P>
! 139: <P>
! 140: <b>int pcre_config(int <i>what</i>, void *<i>where</i>);</b>
! 141: </P>
! 142: <P>
! 143: <b>char *pcre_version(void);</b>
! 144: </P>
! 145: <br><a name="SEC3" href="#TOC1">PCRE NATIVE API INDIRECTED FUNCTIONS</a><br>
! 146: <P>
! 147: <b>void *(*pcre_malloc)(size_t);</b>
! 148: </P>
! 149: <P>
! 150: <b>void (*pcre_free)(void *);</b>
! 151: </P>
! 152: <P>
! 153: <b>void *(*pcre_stack_malloc)(size_t);</b>
! 154: </P>
! 155: <P>
! 156: <b>void (*pcre_stack_free)(void *);</b>
! 157: </P>
! 158: <P>
! 159: <b>int (*pcre_callout)(pcre_callout_block *);</b>
! 160: </P>
! 161: <br><a name="SEC4" href="#TOC1">PCRE API OVERVIEW</a><br>
! 162: <P>
! 163: PCRE has its own native API, which is described in this document. There are
! 164: also some wrapper functions that correspond to the POSIX regular expression
! 165: API, but they do not give access to all the functionality. They are described
! 166: in the
! 167: <a href="pcreposix.html"><b>pcreposix</b></a>
! 168: documentation. Both of these APIs define a set of C function calls. A C++
! 169: wrapper is also distributed with PCRE. It is documented in the
! 170: <a href="pcrecpp.html"><b>pcrecpp</b></a>
! 171: page.
! 172: </P>
! 173: <P>
! 174: The native API C function prototypes are defined in the header file
! 175: <b>pcre.h</b>, and on Unix systems the library itself is called <b>libpcre</b>.
! 176: It can normally be accessed by adding <b>-lpcre</b> to the command for linking
! 177: an application that uses PCRE. The header file defines the macros PCRE_MAJOR
! 178: and PCRE_MINOR to contain the major and minor release numbers for the library.
! 179: Applications can use these to include support for different releases of PCRE.
! 180: </P>
! 181: <P>
! 182: In a Windows environment, if you want to statically link an application program
! 183: against a non-dll <b>pcre.a</b> file, you must define PCRE_STATIC before
! 184: including <b>pcre.h</b> or <b>pcrecpp.h</b>, because otherwise the
! 185: <b>pcre_malloc()</b> and <b>pcre_free()</b> exported functions will be declared
! 186: <b>__declspec(dllimport)</b>, with unwanted results.
! 187: </P>
! 188: <P>
! 189: The functions <b>pcre_compile()</b>, <b>pcre_compile2()</b>, <b>pcre_study()</b>,
! 190: and <b>pcre_exec()</b> are used for compiling and matching regular expressions
! 191: in a Perl-compatible manner. A sample program that demonstrates the simplest
! 192: way of using them is provided in the file called <i>pcredemo.c</i> in the PCRE
! 193: source distribution. A listing of this program is given in the
! 194: <a href="pcredemo.html"><b>pcredemo</b></a>
! 195: documentation, and the
! 196: <a href="pcresample.html"><b>pcresample</b></a>
! 197: documentation describes how to compile and run it.
! 198: </P>
! 199: <P>
! 200: Just-in-time compiler support is an optional feature of PCRE that can be built
! 201: in appropriate hardware environments. It greatly speeds up the matching
! 202: performance of many patterns. Simple programs can easily request that it be
! 203: used if available, by setting an option that is ignored when it is not
! 204: relevant. More complicated programs might need to make use of the functions
! 205: <b>pcre_jit_stack_alloc()</b>, <b>pcre_jit_stack_free()</b>, and
! 206: <b>pcre_assign_jit_stack()</b> in order to control the JIT code's memory usage.
! 207: These functions are discussed in the
! 208: <a href="pcrejit.html"><b>pcrejit</b></a>
! 209: documentation.
! 210: </P>
! 211: <P>
! 212: A second matching function, <b>pcre_dfa_exec()</b>, which is not
! 213: Perl-compatible, is also provided. This uses a different algorithm for the
! 214: matching. The alternative algorithm finds all possible matches (at a given
! 215: point in the subject), and scans the subject just once (unless there are
! 216: lookbehind assertions). However, this algorithm does not return captured
! 217: substrings. A description of the two matching algorithms and their advantages
! 218: and disadvantages is given in the
! 219: <a href="pcrematching.html"><b>pcrematching</b></a>
! 220: documentation.
! 221: </P>
! 222: <P>
! 223: In addition to the main compiling and matching functions, there are convenience
! 224: functions for extracting captured substrings from a subject string that is
! 225: matched by <b>pcre_exec()</b>. They are:
! 226: <pre>
! 227: <b>pcre_copy_substring()</b>
! 228: <b>pcre_copy_named_substring()</b>
! 229: <b>pcre_get_substring()</b>
! 230: <b>pcre_get_named_substring()</b>
! 231: <b>pcre_get_substring_list()</b>
! 232: <b>pcre_get_stringnumber()</b>
! 233: <b>pcre_get_stringtable_entries()</b>
! 234: </pre>
! 235: <b>pcre_free_substring()</b> and <b>pcre_free_substring_list()</b> are also
! 236: provided, to free the memory used for extracted strings.
! 237: </P>
! 238: <P>
! 239: The function <b>pcre_maketables()</b> is used to build a set of character tables
! 240: in the current locale for passing to <b>pcre_compile()</b>, <b>pcre_exec()</b>,
! 241: or <b>pcre_dfa_exec()</b>. This is an optional facility that is provided for
! 242: specialist use. Most commonly, no special tables are passed, in which case
! 243: internal tables that are generated when PCRE is built are used.
! 244: </P>
! 245: <P>
! 246: The function <b>pcre_fullinfo()</b> is used to find out information about a
! 247: compiled pattern; <b>pcre_info()</b> is an obsolete version that returns only
! 248: some of the available information, but is retained for backwards compatibility.
! 249: The function <b>pcre_version()</b> returns a pointer to a string containing the
! 250: version of PCRE and its date of release.
! 251: </P>
! 252: <P>
! 253: The function <b>pcre_refcount()</b> maintains a reference count in a data block
! 254: containing a compiled pattern. This is provided for the benefit of
! 255: object-oriented applications.
! 256: </P>
! 257: <P>
! 258: The global variables <b>pcre_malloc</b> and <b>pcre_free</b> initially contain
! 259: the entry points of the standard <b>malloc()</b> and <b>free()</b> functions,
! 260: respectively. PCRE calls the memory management functions via these variables,
! 261: so a calling program can replace them if it wishes to intercept the calls. This
! 262: should be done before calling any PCRE functions.
! 263: </P>
! 264: <P>
! 265: The global variables <b>pcre_stack_malloc</b> and <b>pcre_stack_free</b> are also
! 266: indirections to memory management functions. These special functions are used
! 267: only when PCRE is compiled to use the heap for remembering data, instead of
! 268: recursive function calls, when running the <b>pcre_exec()</b> function. See the
! 269: <a href="pcrebuild.html"><b>pcrebuild</b></a>
! 270: documentation for details of how to do this. It is a non-standard way of
! 271: building PCRE, for use in environments that have limited stacks. Because of the
! 272: greater use of memory management, it runs more slowly. Separate functions are
! 273: provided so that special-purpose external code can be used for this case. When
! 274: used, these functions are always called in a stack-like manner (last obtained,
! 275: first freed), and always for memory blocks of the same size. There is a
! 276: discussion about PCRE's stack usage in the
! 277: <a href="pcrestack.html"><b>pcrestack</b></a>
! 278: documentation.
! 279: </P>
! 280: <P>
! 281: The global variable <b>pcre_callout</b> initially contains NULL. It can be set
! 282: by the caller to a "callout" function, which PCRE will then call at specified
! 283: points during a matching operation. Details are given in the
! 284: <a href="pcrecallout.html"><b>pcrecallout</b></a>
! 285: documentation.
! 286: <a name="newlines"></a></P>
! 287: <br><a name="SEC5" href="#TOC1">NEWLINES</a><br>
! 288: <P>
! 289: PCRE supports five different conventions for indicating line breaks in
! 290: strings: a single CR (carriage return) character, a single LF (linefeed)
! 291: character, the two-character sequence CRLF, any of the three preceding, or any
! 292: Unicode newline sequence. The Unicode newline sequences are the three just
! 293: mentioned, plus the single characters VT (vertical tab, U+000B), FF (formfeed,
! 294: U+000C), NEL (next line, U+0085), LS (line separator, U+2028), and PS
! 295: (paragraph separator, U+2029).
! 296: </P>
! 297: <P>
! 298: Each of the first three conventions is used by at least one operating system as
! 299: its standard newline sequence. When PCRE is built, a default can be specified.
! 300: The default default is LF, which is the Unix standard. When PCRE is run, the
! 301: default can be overridden, either when a pattern is compiled, or when it is
! 302: matched.
! 303: </P>
! 304: <P>
! 305: At compile time, the newline convention can be specified by the <i>options</i>
! 306: argument of <b>pcre_compile()</b>, or it can be specified by special text at the
! 307: start of the pattern itself; this overrides any other settings. See the
! 308: <a href="pcrepattern.html"><b>pcrepattern</b></a>
! 309: page for details of the special character sequences.
! 310: </P>
! 311: <P>
! 312: In the PCRE documentation the word "newline" is used to mean "the character or
! 313: pair of characters that indicate a line break". The choice of newline
! 314: convention affects the handling of the dot, circumflex, and dollar
! 315: metacharacters, the handling of #-comments in /x mode, and, when CRLF is a
! 316: recognized line ending sequence, the match position advancement for a
! 317: non-anchored pattern. There is more detail about this in the
! 318: <a href="#execoptions">section on <b>pcre_exec()</b> options</a>
! 319: below.
! 320: </P>
! 321: <P>
! 322: The choice of newline convention does not affect the interpretation of
! 323: the \n or \r escape sequences, nor does it affect what \R matches, which is
! 324: controlled in a similar way, but by separate options.
! 325: </P>
! 326: <br><a name="SEC6" href="#TOC1">MULTITHREADING</a><br>
! 327: <P>
! 328: The PCRE functions can be used in multi-threading applications, with the
! 329: proviso that the memory management functions pointed to by <b>pcre_malloc</b>,
! 330: <b>pcre_free</b>, <b>pcre_stack_malloc</b>, and <b>pcre_stack_free</b>, and the
! 331: callout function pointed to by <b>pcre_callout</b>, are shared by all threads.
! 332: </P>
! 333: <P>
! 334: The compiled form of a regular expression is not altered during matching, so
! 335: the same compiled pattern can safely be used by several threads at once.
! 336: </P>
! 337: <P>
! 338: If the just-in-time optimization feature is being used, it needs separate
! 339: memory stack areas for each thread. See the
! 340: <a href="pcrejit.html"><b>pcrejit</b></a>
! 341: documentation for more details.
! 342: </P>
! 343: <br><a name="SEC7" href="#TOC1">SAVING PRECOMPILED PATTERNS FOR LATER USE</a><br>
! 344: <P>
! 345: The compiled form of a regular expression can be saved and re-used at a later
! 346: time, possibly by a different program, and even on a host other than the one on
! 347: which it was compiled. Details are given in the
! 348: <a href="pcreprecompile.html"><b>pcreprecompile</b></a>
! 349: documentation. However, compiling a regular expression with one version of PCRE
! 350: for use with a different version is not guaranteed to work and may cause
! 351: crashes.
! 352: </P>
! 353: <br><a name="SEC8" href="#TOC1">CHECKING BUILD-TIME OPTIONS</a><br>
! 354: <P>
! 355: <b>int pcre_config(int <i>what</i>, void *<i>where</i>);</b>
! 356: </P>
! 357: <P>
! 358: The function <b>pcre_config()</b> makes it possible for a PCRE client to
! 359: discover which optional features have been compiled into the PCRE library. The
! 360: <a href="pcrebuild.html"><b>pcrebuild</b></a>
! 361: documentation has more details about these optional features.
! 362: </P>
! 363: <P>
! 364: The first argument for <b>pcre_config()</b> is an integer, specifying which
! 365: information is required; the second argument is a pointer to a variable into
! 366: which the information is placed. The following information is available:
! 367: <pre>
! 368: PCRE_CONFIG_UTF8
! 369: </pre>
! 370: The output is an integer that is set to one if UTF-8 support is available;
! 371: otherwise it is set to zero.
! 372: <pre>
! 373: PCRE_CONFIG_UNICODE_PROPERTIES
! 374: </pre>
! 375: The output is an integer that is set to one if support for Unicode character
! 376: properties is available; otherwise it is set to zero.
! 377: <pre>
! 378: PCRE_CONFIG_JIT
! 379: </pre>
! 380: The output is an integer that is set to one if support for just-in-time
! 381: compiling is available; otherwise it is set to zero.
! 382: <pre>
! 383: PCRE_CONFIG_NEWLINE
! 384: </pre>
! 385: The output is an integer whose value specifies the default character sequence
! 386: that is recognized as meaning "newline". The four values that are supported
! 387: are: 10 for LF, 13 for CR, 3338 for CRLF, -2 for ANYCRLF, and -1 for ANY.
! 388: Though they are derived from ASCII, the same values are returned in EBCDIC
! 389: environments. The default should normally correspond to the standard sequence
! 390: for your operating system.
! 391: <pre>
! 392: PCRE_CONFIG_BSR
! 393: </pre>
! 394: The output is an integer whose value indicates what character sequences the \R
! 395: escape sequence matches by default. A value of 0 means that \R matches any
! 396: Unicode line ending sequence; a value of 1 means that \R matches only CR, LF,
! 397: or CRLF. The default can be overridden when a pattern is compiled or matched.
! 398: <pre>
! 399: PCRE_CONFIG_LINK_SIZE
! 400: </pre>
! 401: The output is an integer that contains the number of bytes used for internal
! 402: linkage in compiled regular expressions. The value is 2, 3, or 4. Larger values
! 403: allow larger regular expressions to be compiled, at the expense of slower
! 404: matching. The default value of 2 is sufficient for all but the most massive
! 405: patterns, since it allows the compiled pattern to be up to 64K in size.
! 406: <pre>
! 407: PCRE_CONFIG_POSIX_MALLOC_THRESHOLD
! 408: </pre>
! 409: The output is an integer that contains the threshold above which the POSIX
! 410: interface uses <b>malloc()</b> for output vectors. Further details are given in
! 411: the
! 412: <a href="pcreposix.html"><b>pcreposix</b></a>
! 413: documentation.
! 414: <pre>
! 415: PCRE_CONFIG_MATCH_LIMIT
! 416: </pre>
! 417: The output is a long integer that gives the default limit for the number of
! 418: internal matching function calls in a <b>pcre_exec()</b> execution. Further
! 419: details are given with <b>pcre_exec()</b> below.
! 420: <pre>
! 421: PCRE_CONFIG_MATCH_LIMIT_RECURSION
! 422: </pre>
! 423: The output is a long integer that gives the default limit for the depth of
! 424: recursion when calling the internal matching function in a <b>pcre_exec()</b>
! 425: execution. Further details are given with <b>pcre_exec()</b> below.
! 426: <pre>
! 427: PCRE_CONFIG_STACKRECURSE
! 428: </pre>
! 429: The output is an integer that is set to one if internal recursion when running
! 430: <b>pcre_exec()</b> is implemented by recursive function calls that use the stack
! 431: to remember their state. This is the usual way that PCRE is compiled. The
! 432: output is zero if PCRE was compiled to use blocks of data on the heap instead
! 433: of recursive function calls. In this case, <b>pcre_stack_malloc</b> and
! 434: <b>pcre_stack_free</b> are called to manage memory blocks on the heap, thus
! 435: avoiding the use of the stack.
! 436: </P>
! 437: <br><a name="SEC9" href="#TOC1">COMPILING A PATTERN</a><br>
! 438: <P>
! 439: <b>pcre *pcre_compile(const char *<i>pattern</i>, int <i>options</i>,</b>
! 440: <b>const char **<i>errptr</i>, int *<i>erroffset</i>,</b>
! 441: <b>const unsigned char *<i>tableptr</i>);</b>
! 442: <b>pcre *pcre_compile2(const char *<i>pattern</i>, int <i>options</i>,</b>
! 443: <b>int *<i>errorcodeptr</i>,</b>
! 444: <b>const char **<i>errptr</i>, int *<i>erroffset</i>,</b>
! 445: <b>const unsigned char *<i>tableptr</i>);</b>
! 446: </P>
! 447: <P>
! 448: Either of the functions <b>pcre_compile()</b> or <b>pcre_compile2()</b> can be
! 449: called to compile a pattern into an internal form. The only difference between
! 450: the two interfaces is that <b>pcre_compile2()</b> has an additional argument,
! 451: <i>errorcodeptr</i>, via which a numerical error code can be returned. To avoid
! 452: too much repetition, we refer just to <b>pcre_compile()</b> below, but the
! 453: information applies equally to <b>pcre_compile2()</b>.
! 454: </P>
! 455: <P>
! 456: The pattern is a C string terminated by a binary zero, and is passed in the
! 457: <i>pattern</i> argument. A pointer to a single block of memory that is obtained
! 458: via <b>pcre_malloc</b> is returned. This contains the compiled code and related
! 459: data. The <b>pcre</b> type is defined for the returned block; this is a typedef
! 460: for a structure whose contents are not externally defined. It is up to the
! 461: caller to free the memory (via <b>pcre_free</b>) when it is no longer required.
! 462: </P>
! 463: <P>
! 464: Although the compiled code of a PCRE regex is relocatable, that is, it does not
! 465: depend on memory location, the complete <b>pcre</b> data block is not
! 466: fully relocatable, because it may contain a copy of the <i>tableptr</i>
! 467: argument, which is an address (see below).
! 468: </P>
! 469: <P>
! 470: The <i>options</i> argument contains various bit settings that affect the
! 471: compilation. It should be zero if no options are required. The available
! 472: options are described below. Some of them (in particular, those that are
! 473: compatible with Perl, but some others as well) can also be set and unset from
! 474: within the pattern (see the detailed description in the
! 475: <a href="pcrepattern.html"><b>pcrepattern</b></a>
! 476: documentation). For those options that can be different in different parts of
! 477: the pattern, the contents of the <i>options</i> argument specifies their
! 478: settings at the start of compilation and execution. The PCRE_ANCHORED,
! 479: PCRE_BSR_<i>xxx</i>, PCRE_NEWLINE_<i>xxx</i>, PCRE_NO_UTF8_CHECK, and
! 480: PCRE_NO_START_OPT options can be set at the time of matching as well as at
! 481: compile time.
! 482: </P>
! 483: <P>
! 484: If <i>errptr</i> is NULL, <b>pcre_compile()</b> returns NULL immediately.
! 485: Otherwise, if compilation of a pattern fails, <b>pcre_compile()</b> returns
! 486: NULL, and sets the variable pointed to by <i>errptr</i> to point to a textual
! 487: error message. This is a static string that is part of the library. You must
! 488: not try to free it. Normally, the offset from the start of the pattern to the
! 489: byte that was being processed when the error was discovered is placed in the
! 490: variable pointed to by <i>erroffset</i>, which must not be NULL (if it is, an
! 491: immediate error is given). However, for an invalid UTF-8 string, the offset is
! 492: that of the first byte of the failing character. Also, some errors are not
! 493: detected until checks are carried out when the whole pattern has been scanned;
! 494: in these cases the offset passed back is the length of the pattern.
! 495: </P>
! 496: <P>
! 497: Note that the offset is in bytes, not characters, even in UTF-8 mode. It may
! 498: sometimes point into the middle of a UTF-8 character.
! 499: </P>
! 500: <P>
! 501: If <b>pcre_compile2()</b> is used instead of <b>pcre_compile()</b>, and the
! 502: <i>errorcodeptr</i> argument is not NULL, a non-zero error code number is
! 503: returned via this argument in the event of an error. This is in addition to the
! 504: textual error message. Error codes and messages are listed below.
! 505: </P>
! 506: <P>
! 507: If the final argument, <i>tableptr</i>, is NULL, PCRE uses a default set of
! 508: character tables that are built when PCRE is compiled, using the default C
! 509: locale. Otherwise, <i>tableptr</i> must be an address that is the result of a
! 510: call to <b>pcre_maketables()</b>. This value is stored with the compiled
! 511: pattern, and used again by <b>pcre_exec()</b>, unless another table pointer is
! 512: passed to it. For more discussion, see the section on locale support below.
! 513: </P>
! 514: <P>
! 515: This code fragment shows a typical straightforward call to <b>pcre_compile()</b>:
! 516: <pre>
! 517: pcre *re;
! 518: const char *error;
! 519: int erroffset;
! 520: re = pcre_compile(
! 521: "^A.*Z", /* the pattern */
! 522: 0, /* default options */
! 523: &error, /* for error message */
! 524: &erroffset, /* for error offset */
! 525: NULL); /* use default character tables */
! 526: </pre>
! 527: The following names for option bits are defined in the <b>pcre.h</b> header
! 528: file:
! 529: <pre>
! 530: PCRE_ANCHORED
! 531: </pre>
! 532: If this bit is set, the pattern is forced to be "anchored", that is, it is
! 533: constrained to match only at the first matching point in the string that is
! 534: being searched (the "subject string"). This effect can also be achieved by
! 535: appropriate constructs in the pattern itself, which is the only way to do it in
! 536: Perl.
! 537: <pre>
! 538: PCRE_AUTO_CALLOUT
! 539: </pre>
! 540: If this bit is set, <b>pcre_compile()</b> automatically inserts callout items,
! 541: all with number 255, before each pattern item. For discussion of the callout
! 542: facility, see the
! 543: <a href="pcrecallout.html"><b>pcrecallout</b></a>
! 544: documentation.
! 545: <pre>
! 546: PCRE_BSR_ANYCRLF
! 547: PCRE_BSR_UNICODE
! 548: </pre>
! 549: These options (which are mutually exclusive) control what the \R escape
! 550: sequence matches. The choice is either to match only CR, LF, or CRLF, or to
! 551: match any Unicode newline sequence. The default is specified when PCRE is
! 552: built. It can be overridden from within the pattern, or by setting an option
! 553: when a compiled pattern is matched.
! 554: <pre>
! 555: PCRE_CASELESS
! 556: </pre>
! 557: If this bit is set, letters in the pattern match both upper and lower case
! 558: letters. It is equivalent to Perl's /i option, and it can be changed within a
! 559: pattern by a (?i) option setting. In UTF-8 mode, PCRE always understands the
! 560: concept of case for characters whose values are less than 128, so caseless
! 561: matching is always possible. For characters with higher values, the concept of
! 562: case is supported if PCRE is compiled with Unicode property support, but not
! 563: otherwise. If you want to use caseless matching for characters 128 and above,
! 564: you must ensure that PCRE is compiled with Unicode property support as well as
! 565: with UTF-8 support.
! 566: <pre>
! 567: PCRE_DOLLAR_ENDONLY
! 568: </pre>
! 569: If this bit is set, a dollar metacharacter in the pattern matches only at the
! 570: end of the subject string. Without this option, a dollar also matches
! 571: immediately before a newline at the end of the string (but not before any other
! 572: newlines). The PCRE_DOLLAR_ENDONLY option is ignored if PCRE_MULTILINE is set.
! 573: There is no equivalent to this option in Perl, and no way to set it within a
! 574: pattern.
! 575: <pre>
! 576: PCRE_DOTALL
! 577: </pre>
! 578: If this bit is set, a dot metacharacter in the pattern matches a character of
! 579: any value, including one that indicates a newline. However, it only ever
! 580: matches one character, even if newlines are coded as CRLF. Without this option,
! 581: a dot does not match when the current position is at a newline. This option is
! 582: equivalent to Perl's /s option, and it can be changed within a pattern by a
! 583: (?s) option setting. A negative class such as [^a] always matches newline
! 584: characters, independent of the setting of this option.
! 585: <pre>
! 586: PCRE_DUPNAMES
! 587: </pre>
! 588: If this bit is set, names used to identify capturing subpatterns need not be
! 589: unique. This can be helpful for certain types of pattern when it is known that
! 590: only one instance of the named subpattern can ever be matched. There are more
! 591: details of named subpatterns below; see also the
! 592: <a href="pcrepattern.html"><b>pcrepattern</b></a>
! 593: documentation.
! 594: <pre>
! 595: PCRE_EXTENDED
! 596: </pre>
! 597: If this bit is set, whitespace data characters in the pattern are totally
! 598: ignored except when escaped or inside a character class. Whitespace does not
! 599: include the VT character (code 11). In addition, characters between an
! 600: unescaped # outside a character class and the next newline, inclusive, are also
! 601: ignored. This is equivalent to Perl's /x option, and it can be changed within a
! 602: pattern by a (?x) option setting.
! 603: </P>
! 604: <P>
! 605: Which characters are interpreted as newlines is controlled by the options
! 606: passed to <b>pcre_compile()</b> or by a special sequence at the start of the
! 607: pattern, as described in the section entitled
! 608: <a href="pcrepattern.html#newlines">"Newline conventions"</a>
! 609: in the <b>pcrepattern</b> documentation. Note that the end of this type of
! 610: comment is a literal newline sequence in the pattern; escape sequences that
! 611: happen to represent a newline do not count.
! 612: </P>
! 613: <P>
! 614: This option makes it possible to include comments inside complicated patterns.
! 615: Note, however, that this applies only to data characters. Whitespace characters
! 616: may never appear within special character sequences in a pattern, for example
! 617: within the sequence (?( that introduces a conditional subpattern.
! 618: <pre>
! 619: PCRE_EXTRA
! 620: </pre>
! 621: This option was invented in order to turn on additional functionality of PCRE
! 622: that is incompatible with Perl, but it is currently of very little use. When
! 623: set, any backslash in a pattern that is followed by a letter that has no
! 624: special meaning causes an error, thus reserving these combinations for future
! 625: expansion. By default, as in Perl, a backslash followed by a letter with no
! 626: special meaning is treated as a literal. (Perl can, however, be persuaded to
! 627: give an error for this, by running it with the -w option.) There are at present
! 628: no other features controlled by this option. It can also be set by a (?X)
! 629: option setting within a pattern.
! 630: <pre>
! 631: PCRE_FIRSTLINE
! 632: </pre>
! 633: If this option is set, an unanchored pattern is required to match before or at
! 634: the first newline in the subject string, though the matched text may continue
! 635: over the newline.
! 636: <pre>
! 637: PCRE_JAVASCRIPT_COMPAT
! 638: </pre>
! 639: If this option is set, PCRE's behaviour is changed in some ways so that it is
! 640: compatible with JavaScript rather than Perl. The changes are as follows:
! 641: </P>
! 642: <P>
! 643: (1) A lone closing square bracket in a pattern causes a compile-time error,
! 644: because this is illegal in JavaScript (by default it is treated as a data
! 645: character). Thus, the pattern AB]CD becomes illegal when this option is set.
! 646: </P>
! 647: <P>
! 648: (2) At run time, a back reference to an unset subpattern group matches an empty
! 649: string (by default this causes the current matching alternative to fail). A
! 650: pattern such as (\1)(a) succeeds when this option is set (assuming it can find
! 651: an "a" in the subject), whereas it fails by default, for Perl compatibility.
! 652: </P>
! 653: <P>
! 654: (3) \U matches an upper case "U" character; by default \U causes a compile
! 655: time error (Perl uses \U to upper case subsequent characters).
! 656: </P>
! 657: <P>
! 658: (4) \u matches a lower case "u" character unless it is followed by four
! 659: hexadecimal digits, in which case the hexadecimal number defines the code point
! 660: to match. By default, \u causes a compile time error (Perl uses it to upper
! 661: case the following character).
! 662: </P>
! 663: <P>
! 664: (5) \x matches a lower case "x" character unless it is followed by two
! 665: hexadecimal digits, in which case the hexadecimal number defines the code point
! 666: to match. By default, as in Perl, a hexadecimal number is always expected after
! 667: \x, but it may have zero, one, or two digits (so, for example, \xz matches a
! 668: binary zero character followed by z).
! 669: <pre>
! 670: PCRE_MULTILINE
! 671: </pre>
! 672: By default, PCRE treats the subject string as consisting of a single line of
! 673: characters (even if it actually contains newlines). The "start of line"
! 674: metacharacter (^) matches only at the start of the string, while the "end of
! 675: line" metacharacter ($) matches only at the end of the string, or before a
! 676: terminating newline (unless PCRE_DOLLAR_ENDONLY is set). This is the same as
! 677: Perl.
! 678: </P>
! 679: <P>
! 680: When PCRE_MULTILINE it is set, the "start of line" and "end of line" constructs
! 681: match immediately following or immediately before internal newlines in the
! 682: subject string, respectively, as well as at the very start and end. This is
! 683: equivalent to Perl's /m option, and it can be changed within a pattern by a
! 684: (?m) option setting. If there are no newlines in a subject string, or no
! 685: occurrences of ^ or $ in a pattern, setting PCRE_MULTILINE has no effect.
! 686: <pre>
! 687: PCRE_NEWLINE_CR
! 688: PCRE_NEWLINE_LF
! 689: PCRE_NEWLINE_CRLF
! 690: PCRE_NEWLINE_ANYCRLF
! 691: PCRE_NEWLINE_ANY
! 692: </pre>
! 693: These options override the default newline definition that was chosen when PCRE
! 694: was built. Setting the first or the second specifies that a newline is
! 695: indicated by a single character (CR or LF, respectively). Setting
! 696: PCRE_NEWLINE_CRLF specifies that a newline is indicated by the two-character
! 697: CRLF sequence. Setting PCRE_NEWLINE_ANYCRLF specifies that any of the three
! 698: preceding sequences should be recognized. Setting PCRE_NEWLINE_ANY specifies
! 699: that any Unicode newline sequence should be recognized. The Unicode newline
! 700: sequences are the three just mentioned, plus the single characters VT (vertical
! 701: tab, U+000B), FF (formfeed, U+000C), NEL (next line, U+0085), LS (line
! 702: separator, U+2028), and PS (paragraph separator, U+2029). The last two are
! 703: recognized only in UTF-8 mode.
! 704: </P>
! 705: <P>
! 706: The newline setting in the options word uses three bits that are treated
! 707: as a number, giving eight possibilities. Currently only six are used (default
! 708: plus the five values above). This means that if you set more than one newline
! 709: option, the combination may or may not be sensible. For example,
! 710: PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to PCRE_NEWLINE_CRLF, but
! 711: other combinations may yield unused numbers and cause an error.
! 712: </P>
! 713: <P>
! 714: The only time that a line break in a pattern is specially recognized when
! 715: compiling is when PCRE_EXTENDED is set. CR and LF are whitespace characters,
! 716: and so are ignored in this mode. Also, an unescaped # outside a character class
! 717: indicates a comment that lasts until after the next line break sequence. In
! 718: other circumstances, line break sequences in patterns are treated as literal
! 719: data.
! 720: </P>
! 721: <P>
! 722: The newline option that is set at compile time becomes the default that is used
! 723: for <b>pcre_exec()</b> and <b>pcre_dfa_exec()</b>, but it can be overridden.
! 724: <pre>
! 725: PCRE_NO_AUTO_CAPTURE
! 726: </pre>
! 727: If this option is set, it disables the use of numbered capturing parentheses in
! 728: the pattern. Any opening parenthesis that is not followed by ? behaves as if it
! 729: were followed by ?: but named parentheses can still be used for capturing (and
! 730: they acquire numbers in the usual way). There is no equivalent of this option
! 731: in Perl.
! 732: <pre>
! 733: NO_START_OPTIMIZE
! 734: </pre>
! 735: This is an option that acts at matching time; that is, it is really an option
! 736: for <b>pcre_exec()</b> or <b>pcre_dfa_exec()</b>. If it is set at compile time,
! 737: it is remembered with the compiled pattern and assumed at matching time. For
! 738: details see the discussion of PCRE_NO_START_OPTIMIZE
! 739: <a href="#execoptions">below.</a>
! 740: <pre>
! 741: PCRE_UCP
! 742: </pre>
! 743: This option changes the way PCRE processes \B, \b, \D, \d, \S, \s, \W,
! 744: \w, and some of the POSIX character classes. By default, only ASCII characters
! 745: are recognized, but if PCRE_UCP is set, Unicode properties are used instead to
! 746: classify characters. More details are given in the section on
! 747: <a href="pcre.html#genericchartypes">generic character types</a>
! 748: in the
! 749: <a href="pcrepattern.html"><b>pcrepattern</b></a>
! 750: page. If you set PCRE_UCP, matching one of the items it affects takes much
! 751: longer. The option is available only if PCRE has been compiled with Unicode
! 752: property support.
! 753: <pre>
! 754: PCRE_UNGREEDY
! 755: </pre>
! 756: This option inverts the "greediness" of the quantifiers so that they are not
! 757: greedy by default, but become greedy if followed by "?". It is not compatible
! 758: with Perl. It can also be set by a (?U) option setting within the pattern.
! 759: <pre>
! 760: PCRE_UTF8
! 761: </pre>
! 762: This option causes PCRE to regard both the pattern and the subject as strings
! 763: of UTF-8 characters instead of single-byte character strings. However, it is
! 764: available only when PCRE is built to include UTF-8 support. If not, the use
! 765: of this option provokes an error. Details of how this option changes the
! 766: behaviour of PCRE are given in the
! 767: <a href="pcreunicode.html"><b>pcreunicode</b></a>
! 768: page.
! 769: <pre>
! 770: PCRE_NO_UTF8_CHECK
! 771: </pre>
! 772: When PCRE_UTF8 is set, the validity of the pattern as a UTF-8 string is
! 773: automatically checked. There is a discussion about the
! 774: <a href="pcre.html#utf8strings">validity of UTF-8 strings</a>
! 775: in the main
! 776: <a href="pcre.html"><b>pcre</b></a>
! 777: page. If an invalid UTF-8 sequence of bytes is found, <b>pcre_compile()</b>
! 778: returns an error. If you already know that your pattern is valid, and you want
! 779: to skip this check for performance reasons, you can set the PCRE_NO_UTF8_CHECK
! 780: option. When it is set, the effect of passing an invalid UTF-8 string as a
! 781: pattern is undefined. It may cause your program to crash. Note that this option
! 782: can also be passed to <b>pcre_exec()</b> and <b>pcre_dfa_exec()</b>, to suppress
! 783: the UTF-8 validity checking of subject strings.
! 784: </P>
! 785: <br><a name="SEC10" href="#TOC1">COMPILATION ERROR CODES</a><br>
! 786: <P>
! 787: The following table lists the error codes than may be returned by
! 788: <b>pcre_compile2()</b>, along with the error messages that may be returned by
! 789: both compiling functions. As PCRE has developed, some error codes have fallen
! 790: out of use. To avoid confusion, they have not been re-used.
! 791: <pre>
! 792: 0 no error
! 793: 1 \ at end of pattern
! 794: 2 \c at end of pattern
! 795: 3 unrecognized character follows \
! 796: 4 numbers out of order in {} quantifier
! 797: 5 number too big in {} quantifier
! 798: 6 missing terminating ] for character class
! 799: 7 invalid escape sequence in character class
! 800: 8 range out of order in character class
! 801: 9 nothing to repeat
! 802: 10 [this code is not in use]
! 803: 11 internal error: unexpected repeat
! 804: 12 unrecognized character after (? or (?-
! 805: 13 POSIX named classes are supported only within a class
! 806: 14 missing )
! 807: 15 reference to non-existent subpattern
! 808: 16 erroffset passed as NULL
! 809: 17 unknown option bit(s) set
! 810: 18 missing ) after comment
! 811: 19 [this code is not in use]
! 812: 20 regular expression is too large
! 813: 21 failed to get memory
! 814: 22 unmatched parentheses
! 815: 23 internal error: code overflow
! 816: 24 unrecognized character after (?<
! 817: 25 lookbehind assertion is not fixed length
! 818: 26 malformed number or name after (?(
! 819: 27 conditional group contains more than two branches
! 820: 28 assertion expected after (?(
! 821: 29 (?R or (?[+-]digits must be followed by )
! 822: 30 unknown POSIX class name
! 823: 31 POSIX collating elements are not supported
! 824: 32 this version of PCRE is not compiled with PCRE_UTF8 support
! 825: 33 [this code is not in use]
! 826: 34 character value in \x{...} sequence is too large
! 827: 35 invalid condition (?(0)
! 828: 36 \C not allowed in lookbehind assertion
! 829: 37 PCRE does not support \L, \l, \N{name}, \U, or \u
! 830: 38 number after (?C is > 255
! 831: 39 closing ) for (?C expected
! 832: 40 recursive call could loop indefinitely
! 833: 41 unrecognized character after (?P
! 834: 42 syntax error in subpattern name (missing terminator)
! 835: 43 two named subpatterns have the same name
! 836: 44 invalid UTF-8 string
! 837: 45 support for \P, \p, and \X has not been compiled
! 838: 46 malformed \P or \p sequence
! 839: 47 unknown property name after \P or \p
! 840: 48 subpattern name is too long (maximum 32 characters)
! 841: 49 too many named subpatterns (maximum 10000)
! 842: 50 [this code is not in use]
! 843: 51 octal value is greater than \377 (not in UTF-8 mode)
! 844: 52 internal error: overran compiling workspace
! 845: 53 internal error: previously-checked referenced subpattern
! 846: not found
! 847: 54 DEFINE group contains more than one branch
! 848: 55 repeating a DEFINE group is not allowed
! 849: 56 inconsistent NEWLINE options
! 850: 57 \g is not followed by a braced, angle-bracketed, or quoted
! 851: name/number or by a plain number
! 852: 58 a numbered reference must not be zero
! 853: 59 an argument is not allowed for (*ACCEPT), (*FAIL), or (*COMMIT)
! 854: 60 (*VERB) not recognized
! 855: 61 number is too big
! 856: 62 subpattern name expected
! 857: 63 digit expected after (?+
! 858: 64 ] is an invalid data character in JavaScript compatibility mode
! 859: 65 different names for subpatterns of the same number are
! 860: not allowed
! 861: 66 (*MARK) must have an argument
! 862: 67 this version of PCRE is not compiled with PCRE_UCP support
! 863: 68 \c must be followed by an ASCII character
! 864: 69 \k is not followed by a braced, angle-bracketed, or quoted name
! 865: </pre>
! 866: The numbers 32 and 10000 in errors 48 and 49 are defaults; different values may
! 867: be used if the limits were changed when PCRE was built.
! 868: <a name="studyingapattern"></a></P>
! 869: <br><a name="SEC11" href="#TOC1">STUDYING A PATTERN</a><br>
! 870: <P>
! 871: <b>pcre_extra *pcre_study(const pcre *<i>code</i>, int <i>options</i></b>
! 872: <b>const char **<i>errptr</i>);</b>
! 873: </P>
! 874: <P>
! 875: If a compiled pattern is going to be used several times, it is worth spending
! 876: more time analyzing it in order to speed up the time taken for matching. The
! 877: function <b>pcre_study()</b> takes a pointer to a compiled pattern as its first
! 878: argument. If studying the pattern produces additional information that will
! 879: help speed up matching, <b>pcre_study()</b> returns a pointer to a
! 880: <b>pcre_extra</b> block, in which the <i>study_data</i> field points to the
! 881: results of the study.
! 882: </P>
! 883: <P>
! 884: The returned value from <b>pcre_study()</b> can be passed directly to
! 885: <b>pcre_exec()</b> or <b>pcre_dfa_exec()</b>. However, a <b>pcre_extra</b> block
! 886: also contains other fields that can be set by the caller before the block is
! 887: passed; these are described
! 888: <a href="#extradata">below</a>
! 889: in the section on matching a pattern.
! 890: </P>
! 891: <P>
! 892: If studying the pattern does not produce any useful information,
! 893: <b>pcre_study()</b> returns NULL. In that circumstance, if the calling program
! 894: wants to pass any of the other fields to <b>pcre_exec()</b> or
! 895: <b>pcre_dfa_exec()</b>, it must set up its own <b>pcre_extra</b> block.
! 896: </P>
! 897: <P>
! 898: The second argument of <b>pcre_study()</b> contains option bits. There is only
! 899: one option: PCRE_STUDY_JIT_COMPILE. If this is set, and the just-in-time
! 900: compiler is available, the pattern is further compiled into machine code that
! 901: executes much faster than the <b>pcre_exec()</b> matching function. If
! 902: the just-in-time compiler is not available, this option is ignored. All other
! 903: bits in the <i>options</i> argument must be zero.
! 904: </P>
! 905: <P>
! 906: JIT compilation is a heavyweight optimization. It can take some time for
! 907: patterns to be analyzed, and for one-off matches and simple patterns the
! 908: benefit of faster execution might be offset by a much slower study time.
! 909: Not all patterns can be optimized by the JIT compiler. For those that cannot be
! 910: handled, matching automatically falls back to the <b>pcre_exec()</b>
! 911: interpreter. For more details, see the
! 912: <a href="pcrejit.html"><b>pcrejit</b></a>
! 913: documentation.
! 914: </P>
! 915: <P>
! 916: The third argument for <b>pcre_study()</b> is a pointer for an error message. If
! 917: studying succeeds (even if no data is returned), the variable it points to is
! 918: set to NULL. Otherwise it is set to point to a textual error message. This is a
! 919: static string that is part of the library. You must not try to free it. You
! 920: should test the error pointer for NULL after calling <b>pcre_study()</b>, to be
! 921: sure that it has run successfully.
! 922: </P>
! 923: <P>
! 924: When you are finished with a pattern, you can free the memory used for the
! 925: study data by calling <b>pcre_free_study()</b>. This function was added to the
! 926: API for release 8.20. For earlier versions, the memory could be freed with
! 927: <b>pcre_free()</b>, just like the pattern itself. This will still work in cases
! 928: where PCRE_STUDY_JIT_COMPILE is not used, but it is advisable to change to the
! 929: new function when convenient.
! 930: </P>
! 931: <P>
! 932: This is a typical way in which <b>pcre_study</b>() is used (except that in a
! 933: real application there should be tests for errors):
! 934: <pre>
! 935: int rc;
! 936: pcre *re;
! 937: pcre_extra *sd;
! 938: re = pcre_compile("pattern", 0, &error, &erroroffset, NULL);
! 939: sd = pcre_study(
! 940: re, /* result of pcre_compile() */
! 941: 0, /* no options */
! 942: &error); /* set to NULL or points to a message */
! 943: rc = pcre_exec( /* see below for details of pcre_exec() options */
! 944: re, sd, "subject", 7, 0, 0, ovector, 30);
! 945: ...
! 946: pcre_free_study(sd);
! 947: pcre_free(re);
! 948: </pre>
! 949: Studying a pattern does two things: first, a lower bound for the length of
! 950: subject string that is needed to match the pattern is computed. This does not
! 951: mean that there are any strings of that length that match, but it does
! 952: guarantee that no shorter strings match. The value is used by
! 953: <b>pcre_exec()</b> and <b>pcre_dfa_exec()</b> to avoid wasting time by trying to
! 954: match strings that are shorter than the lower bound. You can find out the value
! 955: in a calling program via the <b>pcre_fullinfo()</b> function.
! 956: </P>
! 957: <P>
! 958: Studying a pattern is also useful for non-anchored patterns that do not have a
! 959: single fixed starting character. A bitmap of possible starting bytes is
! 960: created. This speeds up finding a position in the subject at which to start
! 961: matching.
! 962: </P>
! 963: <P>
! 964: These two optimizations apply to both <b>pcre_exec()</b> and
! 965: <b>pcre_dfa_exec()</b>. However, they are not used by <b>pcre_exec()</b> if
! 966: <b>pcre_study()</b> is called with the PCRE_STUDY_JIT_COMPILE option, and
! 967: just-in-time compiling is successful. The optimizations can be disabled by
! 968: setting the PCRE_NO_START_OPTIMIZE option when calling <b>pcre_exec()</b> or
! 969: <b>pcre_dfa_exec()</b>. You might want to do this if your pattern contains
! 970: callouts or (*MARK) (which cannot be handled by the JIT compiler), and you want
! 971: to make use of these facilities in cases where matching fails. See the
! 972: discussion of PCRE_NO_START_OPTIMIZE
! 973: <a href="#execoptions">below.</a>
! 974: <a name="localesupport"></a></P>
! 975: <br><a name="SEC12" href="#TOC1">LOCALE SUPPORT</a><br>
! 976: <P>
! 977: PCRE handles caseless matching, and determines whether characters are letters,
! 978: digits, or whatever, by reference to a set of tables, indexed by character
! 979: value. When running in UTF-8 mode, this applies only to characters with codes
! 980: less than 128. By default, higher-valued codes never match escapes such as \w
! 981: or \d, but they can be tested with \p if PCRE is built with Unicode character
! 982: property support. Alternatively, the PCRE_UCP option can be set at compile
! 983: time; this causes \w and friends to use Unicode property support instead of
! 984: built-in tables. The use of locales with Unicode is discouraged. If you are
! 985: handling characters with codes greater than 128, you should either use UTF-8
! 986: and Unicode, or use locales, but not try to mix the two.
! 987: </P>
! 988: <P>
! 989: PCRE contains an internal set of tables that are used when the final argument
! 990: of <b>pcre_compile()</b> is NULL. These are sufficient for many applications.
! 991: Normally, the internal tables recognize only ASCII characters. However, when
! 992: PCRE is built, it is possible to cause the internal tables to be rebuilt in the
! 993: default "C" locale of the local system, which may cause them to be different.
! 994: </P>
! 995: <P>
! 996: The internal tables can always be overridden by tables supplied by the
! 997: application that calls PCRE. These may be created in a different locale from
! 998: the default. As more and more applications change to using Unicode, the need
! 999: for this locale support is expected to die away.
! 1000: </P>
! 1001: <P>
! 1002: External tables are built by calling the <b>pcre_maketables()</b> function,
! 1003: which has no arguments, in the relevant locale. The result can then be passed
! 1004: to <b>pcre_compile()</b> or <b>pcre_exec()</b> as often as necessary. For
! 1005: example, to build and use tables that are appropriate for the French locale
! 1006: (where accented characters with values greater than 128 are treated as letters),
! 1007: the following code could be used:
! 1008: <pre>
! 1009: setlocale(LC_CTYPE, "fr_FR");
! 1010: tables = pcre_maketables();
! 1011: re = pcre_compile(..., tables);
! 1012: </pre>
! 1013: The locale name "fr_FR" is used on Linux and other Unix-like systems; if you
! 1014: are using Windows, the name for the French locale is "french".
! 1015: </P>
! 1016: <P>
! 1017: When <b>pcre_maketables()</b> runs, the tables are built in memory that is
! 1018: obtained via <b>pcre_malloc</b>. It is the caller's responsibility to ensure
! 1019: that the memory containing the tables remains available for as long as it is
! 1020: needed.
! 1021: </P>
! 1022: <P>
! 1023: The pointer that is passed to <b>pcre_compile()</b> is saved with the compiled
! 1024: pattern, and the same tables are used via this pointer by <b>pcre_study()</b>
! 1025: and normally also by <b>pcre_exec()</b>. Thus, by default, for any single
! 1026: pattern, compilation, studying and matching all happen in the same locale, but
! 1027: different patterns can be compiled in different locales.
! 1028: </P>
! 1029: <P>
! 1030: It is possible to pass a table pointer or NULL (indicating the use of the
! 1031: internal tables) to <b>pcre_exec()</b>. Although not intended for this purpose,
! 1032: this facility could be used to match a pattern in a different locale from the
! 1033: one in which it was compiled. Passing table pointers at run time is discussed
! 1034: below in the section on matching a pattern.
! 1035: <a name="infoaboutpattern"></a></P>
! 1036: <br><a name="SEC13" href="#TOC1">INFORMATION ABOUT A PATTERN</a><br>
! 1037: <P>
! 1038: <b>int pcre_fullinfo(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b>
! 1039: <b>int <i>what</i>, void *<i>where</i>);</b>
! 1040: </P>
! 1041: <P>
! 1042: The <b>pcre_fullinfo()</b> function returns information about a compiled
! 1043: pattern. It replaces the obsolete <b>pcre_info()</b> function, which is
! 1044: nevertheless retained for backwards compability (and is documented below).
! 1045: </P>
! 1046: <P>
! 1047: The first argument for <b>pcre_fullinfo()</b> is a pointer to the compiled
! 1048: pattern. The second argument is the result of <b>pcre_study()</b>, or NULL if
! 1049: the pattern was not studied. The third argument specifies which piece of
! 1050: information is required, and the fourth argument is a pointer to a variable
! 1051: to receive the data. The yield of the function is zero for success, or one of
! 1052: the following negative numbers:
! 1053: <pre>
! 1054: PCRE_ERROR_NULL the argument <i>code</i> was NULL
! 1055: the argument <i>where</i> was NULL
! 1056: PCRE_ERROR_BADMAGIC the "magic number" was not found
! 1057: PCRE_ERROR_BADOPTION the value of <i>what</i> was invalid
! 1058: </pre>
! 1059: The "magic number" is placed at the start of each compiled pattern as an simple
! 1060: check against passing an arbitrary memory pointer. Here is a typical call of
! 1061: <b>pcre_fullinfo()</b>, to obtain the length of the compiled pattern:
! 1062: <pre>
! 1063: int rc;
! 1064: size_t length;
! 1065: rc = pcre_fullinfo(
! 1066: re, /* result of pcre_compile() */
! 1067: sd, /* result of pcre_study(), or NULL */
! 1068: PCRE_INFO_SIZE, /* what is required */
! 1069: &length); /* where to put the data */
! 1070: </pre>
! 1071: The possible values for the third argument are defined in <b>pcre.h</b>, and are
! 1072: as follows:
! 1073: <pre>
! 1074: PCRE_INFO_BACKREFMAX
! 1075: </pre>
! 1076: Return the number of the highest back reference in the pattern. The fourth
! 1077: argument should point to an <b>int</b> variable. Zero is returned if there are
! 1078: no back references.
! 1079: <pre>
! 1080: PCRE_INFO_CAPTURECOUNT
! 1081: </pre>
! 1082: Return the number of capturing subpatterns in the pattern. The fourth argument
! 1083: should point to an <b>int</b> variable.
! 1084: <pre>
! 1085: PCRE_INFO_DEFAULT_TABLES
! 1086: </pre>
! 1087: Return a pointer to the internal default character tables within PCRE. The
! 1088: fourth argument should point to an <b>unsigned char *</b> variable. This
! 1089: information call is provided for internal use by the <b>pcre_study()</b>
! 1090: function. External callers can cause PCRE to use its internal tables by passing
! 1091: a NULL table pointer.
! 1092: <pre>
! 1093: PCRE_INFO_FIRSTBYTE
! 1094: </pre>
! 1095: Return information about the first byte of any matched string, for a
! 1096: non-anchored pattern. The fourth argument should point to an <b>int</b>
! 1097: variable. (This option used to be called PCRE_INFO_FIRSTCHAR; the old name is
! 1098: still recognized for backwards compatibility.)
! 1099: </P>
! 1100: <P>
! 1101: If there is a fixed first byte, for example, from a pattern such as
! 1102: (cat|cow|coyote), its value is returned. Otherwise, if either
! 1103: <br>
! 1104: <br>
! 1105: (a) the pattern was compiled with the PCRE_MULTILINE option, and every branch
! 1106: starts with "^", or
! 1107: <br>
! 1108: <br>
! 1109: (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not set
! 1110: (if it were set, the pattern would be anchored),
! 1111: <br>
! 1112: <br>
! 1113: -1 is returned, indicating that the pattern matches only at the start of a
! 1114: subject string or after any newline within the string. Otherwise -2 is
! 1115: returned. For anchored patterns, -2 is returned.
! 1116: <pre>
! 1117: PCRE_INFO_FIRSTTABLE
! 1118: </pre>
! 1119: If the pattern was studied, and this resulted in the construction of a 256-bit
! 1120: table indicating a fixed set of bytes for the first byte in any matching
! 1121: string, a pointer to the table is returned. Otherwise NULL is returned. The
! 1122: fourth argument should point to an <b>unsigned char *</b> variable.
! 1123: <pre>
! 1124: PCRE_INFO_HASCRORLF
! 1125: </pre>
! 1126: Return 1 if the pattern contains any explicit matches for CR or LF characters,
! 1127: otherwise 0. The fourth argument should point to an <b>int</b> variable. An
! 1128: explicit match is either a literal CR or LF character, or \r or \n.
! 1129: <pre>
! 1130: PCRE_INFO_JCHANGED
! 1131: </pre>
! 1132: Return 1 if the (?J) or (?-J) option setting is used in the pattern, otherwise
! 1133: 0. The fourth argument should point to an <b>int</b> variable. (?J) and
! 1134: (?-J) set and unset the local PCRE_DUPNAMES option, respectively.
! 1135: <pre>
! 1136: PCRE_INFO_JIT
! 1137: </pre>
! 1138: Return 1 if the pattern was studied with the PCRE_STUDY_JIT_COMPILE option, and
! 1139: just-in-time compiling was successful. The fourth argument should point to an
! 1140: <b>int</b> variable. A return value of 0 means that JIT support is not available
! 1141: in this version of PCRE, or that the pattern was not studied with the
! 1142: PCRE_STUDY_JIT_COMPILE option, or that the JIT compiler could not handle this
! 1143: particular pattern. See the
! 1144: <a href="pcrejit.html"><b>pcrejit</b></a>
! 1145: documentation for details of what can and cannot be handled.
! 1146: <pre>
! 1147: PCRE_INFO_JITSIZE
! 1148: </pre>
! 1149: If the pattern was successfully studied with the PCRE_STUDY_JIT_COMPILE option,
! 1150: return the size of the JIT compiled code, otherwise return zero. The fourth
! 1151: argument should point to a <b>size_t</b> variable.
! 1152: <pre>
! 1153: PCRE_INFO_LASTLITERAL
! 1154: </pre>
! 1155: Return the value of the rightmost literal byte that must exist in any matched
! 1156: string, other than at its start, if such a byte has been recorded. The fourth
! 1157: argument should point to an <b>int</b> variable. If there is no such byte, -1 is
! 1158: returned. For anchored patterns, a last literal byte is recorded only if it
! 1159: follows something of variable length. For example, for the pattern
! 1160: /^a\d+z\d+/ the returned value is "z", but for /^a\dz\d/ the returned value
! 1161: is -1.
! 1162: <pre>
! 1163: PCRE_INFO_MINLENGTH
! 1164: </pre>
! 1165: If the pattern was studied and a minimum length for matching subject strings
! 1166: was computed, its value is returned. Otherwise the returned value is -1. The
! 1167: value is a number of characters, not bytes (this may be relevant in UTF-8
! 1168: mode). The fourth argument should point to an <b>int</b> variable. A
! 1169: non-negative value is a lower bound to the length of any matching string. There
! 1170: may not be any strings of that length that do actually match, but every string
! 1171: that does match is at least that long.
! 1172: <pre>
! 1173: PCRE_INFO_NAMECOUNT
! 1174: PCRE_INFO_NAMEENTRYSIZE
! 1175: PCRE_INFO_NAMETABLE
! 1176: </pre>
! 1177: PCRE supports the use of named as well as numbered capturing parentheses. The
! 1178: names are just an additional way of identifying the parentheses, which still
! 1179: acquire numbers. Several convenience functions such as
! 1180: <b>pcre_get_named_substring()</b> are provided for extracting captured
! 1181: substrings by name. It is also possible to extract the data directly, by first
! 1182: converting the name to a number in order to access the correct pointers in the
! 1183: output vector (described with <b>pcre_exec()</b> below). To do the conversion,
! 1184: you need to use the name-to-number map, which is described by these three
! 1185: values.
! 1186: </P>
! 1187: <P>
! 1188: The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT gives
! 1189: the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size of each
! 1190: entry; both of these return an <b>int</b> value. The entry size depends on the
! 1191: length of the longest name. PCRE_INFO_NAMETABLE returns a pointer to the first
! 1192: entry of the table (a pointer to <b>char</b>). The first two bytes of each entry
! 1193: are the number of the capturing parenthesis, most significant byte first. The
! 1194: rest of the entry is the corresponding name, zero terminated.
! 1195: </P>
! 1196: <P>
! 1197: The names are in alphabetical order. Duplicate names may appear if (?| is used
! 1198: to create multiple groups with the same number, as described in the
! 1199: <a href="pcrepattern.html#dupsubpatternnumber">section on duplicate subpattern numbers</a>
! 1200: in the
! 1201: <a href="pcrepattern.html"><b>pcrepattern</b></a>
! 1202: page. Duplicate names for subpatterns with different numbers are permitted only
! 1203: if PCRE_DUPNAMES is set. In all cases of duplicate names, they appear in the
! 1204: table in the order in which they were found in the pattern. In the absence of
! 1205: (?| this is the order of increasing number; when (?| is used this is not
! 1206: necessarily the case because later subpatterns may have lower numbers.
! 1207: </P>
! 1208: <P>
! 1209: As a simple example of the name/number table, consider the following pattern
! 1210: (assume PCRE_EXTENDED is set, so white space - including newlines - is
! 1211: ignored):
! 1212: <pre>
! 1213: (?<date> (?<year>(\d\d)?\d\d) - (?<month>\d\d) - (?<day>\d\d) )
! 1214: </pre>
! 1215: There are four named subpatterns, so the table has four entries, and each entry
! 1216: in the table is eight bytes long. The table is as follows, with non-printing
! 1217: bytes shows in hexadecimal, and undefined bytes shown as ??:
! 1218: <pre>
! 1219: 00 01 d a t e 00 ??
! 1220: 00 05 d a y 00 ?? ??
! 1221: 00 04 m o n t h 00
! 1222: 00 02 y e a r 00 ??
! 1223: </pre>
! 1224: When writing code to extract data from named subpatterns using the
! 1225: name-to-number map, remember that the length of the entries is likely to be
! 1226: different for each compiled pattern.
! 1227: <pre>
! 1228: PCRE_INFO_OKPARTIAL
! 1229: </pre>
! 1230: Return 1 if the pattern can be used for partial matching with
! 1231: <b>pcre_exec()</b>, otherwise 0. The fourth argument should point to an
! 1232: <b>int</b> variable. From release 8.00, this always returns 1, because the
! 1233: restrictions that previously applied to partial matching have been lifted. The
! 1234: <a href="pcrepartial.html"><b>pcrepartial</b></a>
! 1235: documentation gives details of partial matching.
! 1236: <pre>
! 1237: PCRE_INFO_OPTIONS
! 1238: </pre>
! 1239: Return a copy of the options with which the pattern was compiled. The fourth
! 1240: argument should point to an <b>unsigned long int</b> variable. These option bits
! 1241: are those specified in the call to <b>pcre_compile()</b>, modified by any
! 1242: top-level option settings at the start of the pattern itself. In other words,
! 1243: they are the options that will be in force when matching starts. For example,
! 1244: if the pattern /(?im)abc(?-i)d/ is compiled with the PCRE_EXTENDED option, the
! 1245: result is PCRE_CASELESS, PCRE_MULTILINE, and PCRE_EXTENDED.
! 1246: </P>
! 1247: <P>
! 1248: A pattern is automatically anchored by PCRE if all of its top-level
! 1249: alternatives begin with one of the following:
! 1250: <pre>
! 1251: ^ unless PCRE_MULTILINE is set
! 1252: \A always
! 1253: \G always
! 1254: .* if PCRE_DOTALL is set and there are no back references to the subpattern in which .* appears
! 1255: </pre>
! 1256: For such patterns, the PCRE_ANCHORED bit is set in the options returned by
! 1257: <b>pcre_fullinfo()</b>.
! 1258: <pre>
! 1259: PCRE_INFO_SIZE
! 1260: </pre>
! 1261: Return the size of the compiled pattern. The fourth argument should point to a
! 1262: <b>size_t</b> variable. This value does not include the size of the <b>pcre</b>
! 1263: structure that is returned by <b>pcre_compile()</b>. The value that is passed as
! 1264: the argument to <b>pcre_malloc()</b> when <b>pcre_compile()</b> is getting memory
! 1265: in which to place the compiled data is the value returned by this option plus
! 1266: the size of the <b>pcre</b> structure. Studying a compiled pattern, with or
! 1267: without JIT, does not alter the value returned by this option.
! 1268: <pre>
! 1269: PCRE_INFO_STUDYSIZE
! 1270: </pre>
! 1271: Return the size of the data block pointed to by the <i>study_data</i> field in a
! 1272: <b>pcre_extra</b> block. If <b>pcre_extra</b> is NULL, or there is no study data,
! 1273: zero is returned. The fourth argument should point to a <b>size_t</b> variable.
! 1274: The <i>study_data</i> field is set by <b>pcre_study()</b> to record information
! 1275: that will speed up matching (see the section entitled
! 1276: <a href="#studyingapattern">"Studying a pattern"</a>
! 1277: above). The format of the <i>study_data</i> block is private, but its length
! 1278: is made available via this option so that it can be saved and restored (see the
! 1279: <a href="pcreprecompile.html"><b>pcreprecompile</b></a>
! 1280: documentation for details).
! 1281: </P>
! 1282: <br><a name="SEC14" href="#TOC1">OBSOLETE INFO FUNCTION</a><br>
! 1283: <P>
! 1284: <b>int pcre_info(const pcre *<i>code</i>, int *<i>optptr</i>, int</b>
! 1285: <b>*<i>firstcharptr</i>);</b>
! 1286: </P>
! 1287: <P>
! 1288: The <b>pcre_info()</b> function is now obsolete because its interface is too
! 1289: restrictive to return all the available data about a compiled pattern. New
! 1290: programs should use <b>pcre_fullinfo()</b> instead. The yield of
! 1291: <b>pcre_info()</b> is the number of capturing subpatterns, or one of the
! 1292: following negative numbers:
! 1293: <pre>
! 1294: PCRE_ERROR_NULL the argument <i>code</i> was NULL
! 1295: PCRE_ERROR_BADMAGIC the "magic number" was not found
! 1296: </pre>
! 1297: If the <i>optptr</i> argument is not NULL, a copy of the options with which the
! 1298: pattern was compiled is placed in the integer it points to (see
! 1299: PCRE_INFO_OPTIONS above).
! 1300: </P>
! 1301: <P>
! 1302: If the pattern is not anchored and the <i>firstcharptr</i> argument is not NULL,
! 1303: it is used to pass back information about the first character of any matched
! 1304: string (see PCRE_INFO_FIRSTBYTE above).
! 1305: </P>
! 1306: <br><a name="SEC15" href="#TOC1">REFERENCE COUNTS</a><br>
! 1307: <P>
! 1308: <b>int pcre_refcount(pcre *<i>code</i>, int <i>adjust</i>);</b>
! 1309: </P>
! 1310: <P>
! 1311: The <b>pcre_refcount()</b> function is used to maintain a reference count in the
! 1312: data block that contains a compiled pattern. It is provided for the benefit of
! 1313: applications that operate in an object-oriented manner, where different parts
! 1314: of the application may be using the same compiled pattern, but you want to free
! 1315: the block when they are all done.
! 1316: </P>
! 1317: <P>
! 1318: When a pattern is compiled, the reference count field is initialized to zero.
! 1319: It is changed only by calling this function, whose action is to add the
! 1320: <i>adjust</i> value (which may be positive or negative) to it. The yield of the
! 1321: function is the new value. However, the value of the count is constrained to
! 1322: lie between 0 and 65535, inclusive. If the new value is outside these limits,
! 1323: it is forced to the appropriate limit value.
! 1324: </P>
! 1325: <P>
! 1326: Except when it is zero, the reference count is not correctly preserved if a
! 1327: pattern is compiled on one host and then transferred to a host whose byte-order
! 1328: is different. (This seems a highly unlikely scenario.)
! 1329: </P>
! 1330: <br><a name="SEC16" href="#TOC1">MATCHING A PATTERN: THE TRADITIONAL FUNCTION</a><br>
! 1331: <P>
! 1332: <b>int pcre_exec(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b>
! 1333: <b>const char *<i>subject</i>, int <i>length</i>, int <i>startoffset</i>,</b>
! 1334: <b>int <i>options</i>, int *<i>ovector</i>, int <i>ovecsize</i>);</b>
! 1335: </P>
! 1336: <P>
! 1337: The function <b>pcre_exec()</b> is called to match a subject string against a
! 1338: compiled pattern, which is passed in the <i>code</i> argument. If the
! 1339: pattern was studied, the result of the study should be passed in the
! 1340: <i>extra</i> argument. You can call <b>pcre_exec()</b> with the same <i>code</i>
! 1341: and <i>extra</i> arguments as many times as you like, in order to match
! 1342: different subject strings with the same pattern.
! 1343: </P>
! 1344: <P>
! 1345: This function is the main matching facility of the library, and it operates in
! 1346: a Perl-like manner. For specialist use there is also an alternative matching
! 1347: function, which is described
! 1348: <a href="#dfamatch">below</a>
! 1349: in the section about the <b>pcre_dfa_exec()</b> function.
! 1350: </P>
! 1351: <P>
! 1352: In most applications, the pattern will have been compiled (and optionally
! 1353: studied) in the same process that calls <b>pcre_exec()</b>. However, it is
! 1354: possible to save compiled patterns and study data, and then use them later
! 1355: in different processes, possibly even on different hosts. For a discussion
! 1356: about this, see the
! 1357: <a href="pcreprecompile.html"><b>pcreprecompile</b></a>
! 1358: documentation.
! 1359: </P>
! 1360: <P>
! 1361: Here is an example of a simple call to <b>pcre_exec()</b>:
! 1362: <pre>
! 1363: int rc;
! 1364: int ovector[30];
! 1365: rc = pcre_exec(
! 1366: re, /* result of pcre_compile() */
! 1367: NULL, /* we didn't study the pattern */
! 1368: "some string", /* the subject string */
! 1369: 11, /* the length of the subject string */
! 1370: 0, /* start at offset 0 in the subject */
! 1371: 0, /* default options */
! 1372: ovector, /* vector of integers for substring information */
! 1373: 30); /* number of elements (NOT size in bytes) */
! 1374: <a name="extradata"></a></PRE>
! 1375: </P>
! 1376: <br><b>
! 1377: Extra data for <b>pcre_exec()</b>
! 1378: </b><br>
! 1379: <P>
! 1380: If the <i>extra</i> argument is not NULL, it must point to a <b>pcre_extra</b>
! 1381: data block. The <b>pcre_study()</b> function returns such a block (when it
! 1382: doesn't return NULL), but you can also create one for yourself, and pass
! 1383: additional information in it. The <b>pcre_extra</b> block contains the following
! 1384: fields (not necessarily in this order):
! 1385: <pre>
! 1386: unsigned long int <i>flags</i>;
! 1387: void *<i>study_data</i>;
! 1388: void *<i>executable_jit</i>;
! 1389: unsigned long int <i>match_limit</i>;
! 1390: unsigned long int <i>match_limit_recursion</i>;
! 1391: void *<i>callout_data</i>;
! 1392: const unsigned char *<i>tables</i>;
! 1393: unsigned char **<i>mark</i>;
! 1394: </pre>
! 1395: The <i>flags</i> field is a bitmap that specifies which of the other fields
! 1396: are set. The flag bits are:
! 1397: <pre>
! 1398: PCRE_EXTRA_STUDY_DATA
! 1399: PCRE_EXTRA_EXECUTABLE_JIT
! 1400: PCRE_EXTRA_MATCH_LIMIT
! 1401: PCRE_EXTRA_MATCH_LIMIT_RECURSION
! 1402: PCRE_EXTRA_CALLOUT_DATA
! 1403: PCRE_EXTRA_TABLES
! 1404: PCRE_EXTRA_MARK
! 1405: </pre>
! 1406: Other flag bits should be set to zero. The <i>study_data</i> field and sometimes
! 1407: the <i>executable_jit</i> field are set in the <b>pcre_extra</b> block that is
! 1408: returned by <b>pcre_study()</b>, together with the appropriate flag bits. You
! 1409: should not set these yourself, but you may add to the block by setting the
! 1410: other fields and their corresponding flag bits.
! 1411: </P>
! 1412: <P>
! 1413: The <i>match_limit</i> field provides a means of preventing PCRE from using up a
! 1414: vast amount of resources when running patterns that are not going to match,
! 1415: but which have a very large number of possibilities in their search trees. The
! 1416: classic example is a pattern that uses nested unlimited repeats.
! 1417: </P>
! 1418: <P>
! 1419: Internally, <b>pcre_exec()</b> uses a function called <b>match()</b>, which it
! 1420: calls repeatedly (sometimes recursively). The limit set by <i>match_limit</i> is
! 1421: imposed on the number of times this function is called during a match, which
! 1422: has the effect of limiting the amount of backtracking that can take place. For
! 1423: patterns that are not anchored, the count restarts from zero for each position
! 1424: in the subject string.
! 1425: </P>
! 1426: <P>
! 1427: When <b>pcre_exec()</b> is called with a pattern that was successfully studied
! 1428: with the PCRE_STUDY_JIT_COMPILE option, the way that the matching is executed
! 1429: is entirely different. However, there is still the possibility of runaway
! 1430: matching that goes on for a very long time, and so the <i>match_limit</i> value
! 1431: is also used in this case (but in a different way) to limit how long the
! 1432: matching can continue.
! 1433: </P>
! 1434: <P>
! 1435: The default value for the limit can be set when PCRE is built; the default
! 1436: default is 10 million, which handles all but the most extreme cases. You can
! 1437: override the default by suppling <b>pcre_exec()</b> with a <b>pcre_extra</b>
! 1438: block in which <i>match_limit</i> is set, and PCRE_EXTRA_MATCH_LIMIT is set in
! 1439: the <i>flags</i> field. If the limit is exceeded, <b>pcre_exec()</b> returns
! 1440: PCRE_ERROR_MATCHLIMIT.
! 1441: </P>
! 1442: <P>
! 1443: The <i>match_limit_recursion</i> field is similar to <i>match_limit</i>, but
! 1444: instead of limiting the total number of times that <b>match()</b> is called, it
! 1445: limits the depth of recursion. The recursion depth is a smaller number than the
! 1446: total number of calls, because not all calls to <b>match()</b> are recursive.
! 1447: This limit is of use only if it is set smaller than <i>match_limit</i>.
! 1448: </P>
! 1449: <P>
! 1450: Limiting the recursion depth limits the amount of machine stack that can be
! 1451: used, or, when PCRE has been compiled to use memory on the heap instead of the
! 1452: stack, the amount of heap memory that can be used. This limit is not relevant,
! 1453: and is ignored, if the pattern was successfully studied with
! 1454: PCRE_STUDY_JIT_COMPILE.
! 1455: </P>
! 1456: <P>
! 1457: The default value for <i>match_limit_recursion</i> can be set when PCRE is
! 1458: built; the default default is the same value as the default for
! 1459: <i>match_limit</i>. You can override the default by suppling <b>pcre_exec()</b>
! 1460: with a <b>pcre_extra</b> block in which <i>match_limit_recursion</i> is set, and
! 1461: PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in the <i>flags</i> field. If the limit
! 1462: is exceeded, <b>pcre_exec()</b> returns PCRE_ERROR_RECURSIONLIMIT.
! 1463: </P>
! 1464: <P>
! 1465: The <i>callout_data</i> field is used in conjunction with the "callout" feature,
! 1466: and is described in the
! 1467: <a href="pcrecallout.html"><b>pcrecallout</b></a>
! 1468: documentation.
! 1469: </P>
! 1470: <P>
! 1471: The <i>tables</i> field is used to pass a character tables pointer to
! 1472: <b>pcre_exec()</b>; this overrides the value that is stored with the compiled
! 1473: pattern. A non-NULL value is stored with the compiled pattern only if custom
! 1474: tables were supplied to <b>pcre_compile()</b> via its <i>tableptr</i> argument.
! 1475: If NULL is passed to <b>pcre_exec()</b> using this mechanism, it forces PCRE's
! 1476: internal tables to be used. This facility is helpful when re-using patterns
! 1477: that have been saved after compiling with an external set of tables, because
! 1478: the external tables might be at a different address when <b>pcre_exec()</b> is
! 1479: called. See the
! 1480: <a href="pcreprecompile.html"><b>pcreprecompile</b></a>
! 1481: documentation for a discussion of saving compiled patterns for later use.
! 1482: </P>
! 1483: <P>
! 1484: If PCRE_EXTRA_MARK is set in the <i>flags</i> field, the <i>mark</i> field must
! 1485: be set to point to a <b>char *</b> variable. If the pattern contains any
! 1486: backtracking control verbs such as (*MARK:NAME), and the execution ends up with
! 1487: a name to pass back, a pointer to the name string (zero terminated) is placed
! 1488: in the variable pointed to by the <i>mark</i> field. The names are within the
! 1489: compiled pattern; if you wish to retain such a name you must copy it before
! 1490: freeing the memory of a compiled pattern. If there is no name to pass back, the
! 1491: variable pointed to by the <i>mark</i> field set to NULL. For details of the
! 1492: backtracking control verbs, see the section entitled
! 1493: <a href="pcrepattern#backtrackcontrol">"Backtracking control"</a>
! 1494: in the
! 1495: <a href="pcrepattern.html"><b>pcrepattern</b></a>
! 1496: documentation.
! 1497: <a name="execoptions"></a></P>
! 1498: <br><b>
! 1499: Option bits for <b>pcre_exec()</b>
! 1500: </b><br>
! 1501: <P>
! 1502: The unused bits of the <i>options</i> argument for <b>pcre_exec()</b> must be
! 1503: zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_<i>xxx</i>,
! 1504: PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
! 1505: PCRE_NO_START_OPTIMIZE, PCRE_NO_UTF8_CHECK, PCRE_PARTIAL_SOFT, and
! 1506: PCRE_PARTIAL_HARD.
! 1507: </P>
! 1508: <P>
! 1509: If the pattern was successfully studied with the PCRE_STUDY_JIT_COMPILE option,
! 1510: the only supported options for JIT execution are PCRE_NO_UTF8_CHECK,
! 1511: PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, and PCRE_NOTEMPTY_ATSTART. Note in
! 1512: particular that partial matching is not supported. If an unsupported option is
! 1513: used, JIT execution is disabled and the normal interpretive code in
! 1514: <b>pcre_exec()</b> is run.
! 1515: <pre>
! 1516: PCRE_ANCHORED
! 1517: </pre>
! 1518: The PCRE_ANCHORED option limits <b>pcre_exec()</b> to matching at the first
! 1519: matching position. If a pattern was compiled with PCRE_ANCHORED, or turned out
! 1520: to be anchored by virtue of its contents, it cannot be made unachored at
! 1521: matching time.
! 1522: <pre>
! 1523: PCRE_BSR_ANYCRLF
! 1524: PCRE_BSR_UNICODE
! 1525: </pre>
! 1526: These options (which are mutually exclusive) control what the \R escape
! 1527: sequence matches. The choice is either to match only CR, LF, or CRLF, or to
! 1528: match any Unicode newline sequence. These options override the choice that was
! 1529: made or defaulted when the pattern was compiled.
! 1530: <pre>
! 1531: PCRE_NEWLINE_CR
! 1532: PCRE_NEWLINE_LF
! 1533: PCRE_NEWLINE_CRLF
! 1534: PCRE_NEWLINE_ANYCRLF
! 1535: PCRE_NEWLINE_ANY
! 1536: </pre>
! 1537: These options override the newline definition that was chosen or defaulted when
! 1538: the pattern was compiled. For details, see the description of
! 1539: <b>pcre_compile()</b> above. During matching, the newline choice affects the
! 1540: behaviour of the dot, circumflex, and dollar metacharacters. It may also alter
! 1541: the way the match position is advanced after a match failure for an unanchored
! 1542: pattern.
! 1543: </P>
! 1544: <P>
! 1545: When PCRE_NEWLINE_CRLF, PCRE_NEWLINE_ANYCRLF, or PCRE_NEWLINE_ANY is set, and a
! 1546: match attempt for an unanchored pattern fails when the current position is at a
! 1547: CRLF sequence, and the pattern contains no explicit matches for CR or LF
! 1548: characters, the match position is advanced by two characters instead of one, in
! 1549: other words, to after the CRLF.
! 1550: </P>
! 1551: <P>
! 1552: The above rule is a compromise that makes the most common cases work as
! 1553: expected. For example, if the pattern is .+A (and the PCRE_DOTALL option is not
! 1554: set), it does not match the string "\r\nA" because, after failing at the
! 1555: start, it skips both the CR and the LF before retrying. However, the pattern
! 1556: [\r\n]A does match that string, because it contains an explicit CR or LF
! 1557: reference, and so advances only by one character after the first failure.
! 1558: </P>
! 1559: <P>
! 1560: An explicit match for CR of LF is either a literal appearance of one of those
! 1561: characters, or one of the \r or \n escape sequences. Implicit matches such as
! 1562: [^X] do not count, nor does \s (which includes CR and LF in the characters
! 1563: that it matches).
! 1564: </P>
! 1565: <P>
! 1566: Notwithstanding the above, anomalous effects may still occur when CRLF is a
! 1567: valid newline sequence and explicit \r or \n escapes appear in the pattern.
! 1568: <pre>
! 1569: PCRE_NOTBOL
! 1570: </pre>
! 1571: This option specifies that first character of the subject string is not the
! 1572: beginning of a line, so the circumflex metacharacter should not match before
! 1573: it. Setting this without PCRE_MULTILINE (at compile time) causes circumflex
! 1574: never to match. This option affects only the behaviour of the circumflex
! 1575: metacharacter. It does not affect \A.
! 1576: <pre>
! 1577: PCRE_NOTEOL
! 1578: </pre>
! 1579: This option specifies that the end of the subject string is not the end of a
! 1580: line, so the dollar metacharacter should not match it nor (except in multiline
! 1581: mode) a newline immediately before it. Setting this without PCRE_MULTILINE (at
! 1582: compile time) causes dollar never to match. This option affects only the
! 1583: behaviour of the dollar metacharacter. It does not affect \Z or \z.
! 1584: <pre>
! 1585: PCRE_NOTEMPTY
! 1586: </pre>
! 1587: An empty string is not considered to be a valid match if this option is set. If
! 1588: there are alternatives in the pattern, they are tried. If all the alternatives
! 1589: match the empty string, the entire match fails. For example, if the pattern
! 1590: <pre>
! 1591: a?b?
! 1592: </pre>
! 1593: is applied to a string not beginning with "a" or "b", it matches an empty
! 1594: string at the start of the subject. With PCRE_NOTEMPTY set, this match is not
! 1595: valid, so PCRE searches further into the string for occurrences of "a" or "b".
! 1596: <pre>
! 1597: PCRE_NOTEMPTY_ATSTART
! 1598: </pre>
! 1599: This is like PCRE_NOTEMPTY, except that an empty string match that is not at
! 1600: the start of the subject is permitted. If the pattern is anchored, such a match
! 1601: can occur only if the pattern contains \K.
! 1602: </P>
! 1603: <P>
! 1604: Perl has no direct equivalent of PCRE_NOTEMPTY or PCRE_NOTEMPTY_ATSTART, but it
! 1605: does make a special case of a pattern match of the empty string within its
! 1606: <b>split()</b> function, and when using the /g modifier. It is possible to
! 1607: emulate Perl's behaviour after matching a null string by first trying the match
! 1608: again at the same offset with PCRE_NOTEMPTY_ATSTART and PCRE_ANCHORED, and then
! 1609: if that fails, by advancing the starting offset (see below) and trying an
! 1610: ordinary match again. There is some code that demonstrates how to do this in
! 1611: the
! 1612: <a href="pcredemo.html"><b>pcredemo</b></a>
! 1613: sample program. In the most general case, you have to check to see if the
! 1614: newline convention recognizes CRLF as a newline, and if so, and the current
! 1615: character is CR followed by LF, advance the starting offset by two characters
! 1616: instead of one.
! 1617: <pre>
! 1618: PCRE_NO_START_OPTIMIZE
! 1619: </pre>
! 1620: There are a number of optimizations that <b>pcre_exec()</b> uses at the start of
! 1621: a match, in order to speed up the process. For example, if it is known that an
! 1622: unanchored match must start with a specific character, it searches the subject
! 1623: for that character, and fails immediately if it cannot find it, without
! 1624: actually running the main matching function. This means that a special item
! 1625: such as (*COMMIT) at the start of a pattern is not considered until after a
! 1626: suitable starting point for the match has been found. When callouts or (*MARK)
! 1627: items are in use, these "start-up" optimizations can cause them to be skipped
! 1628: if the pattern is never actually used. The start-up optimizations are in effect
! 1629: a pre-scan of the subject that takes place before the pattern is run.
! 1630: </P>
! 1631: <P>
! 1632: The PCRE_NO_START_OPTIMIZE option disables the start-up optimizations, possibly
! 1633: causing performance to suffer, but ensuring that in cases where the result is
! 1634: "no match", the callouts do occur, and that items such as (*COMMIT) and (*MARK)
! 1635: are considered at every possible starting position in the subject string. If
! 1636: PCRE_NO_START_OPTIMIZE is set at compile time, it cannot be unset at matching
! 1637: time.
! 1638: </P>
! 1639: <P>
! 1640: Setting PCRE_NO_START_OPTIMIZE can change the outcome of a matching operation.
! 1641: Consider the pattern
! 1642: <pre>
! 1643: (*COMMIT)ABC
! 1644: </pre>
! 1645: When this is compiled, PCRE records the fact that a match must start with the
! 1646: character "A". Suppose the subject string is "DEFABC". The start-up
! 1647: optimization scans along the subject, finds "A" and runs the first match
! 1648: attempt from there. The (*COMMIT) item means that the pattern must match the
! 1649: current starting position, which in this case, it does. However, if the same
! 1650: match is run with PCRE_NO_START_OPTIMIZE set, the initial scan along the
! 1651: subject string does not happen. The first match attempt is run starting from
! 1652: "D" and when this fails, (*COMMIT) prevents any further matches being tried, so
! 1653: the overall result is "no match". If the pattern is studied, more start-up
! 1654: optimizations may be used. For example, a minimum length for the subject may be
! 1655: recorded. Consider the pattern
! 1656: <pre>
! 1657: (*MARK:A)(X|Y)
! 1658: </pre>
! 1659: The minimum length for a match is one character. If the subject is "ABC", there
! 1660: will be attempts to match "ABC", "BC", "C", and then finally an empty string.
! 1661: If the pattern is studied, the final attempt does not take place, because PCRE
! 1662: knows that the subject is too short, and so the (*MARK) is never encountered.
! 1663: In this case, studying the pattern does not affect the overall match result,
! 1664: which is still "no match", but it does affect the auxiliary information that is
! 1665: returned.
! 1666: <pre>
! 1667: PCRE_NO_UTF8_CHECK
! 1668: </pre>
! 1669: When PCRE_UTF8 is set at compile time, the validity of the subject as a UTF-8
! 1670: string is automatically checked when <b>pcre_exec()</b> is subsequently called.
! 1671: The value of <i>startoffset</i> is also checked to ensure that it points to the
! 1672: start of a UTF-8 character. There is a discussion about the validity of UTF-8
! 1673: strings in the
! 1674: <a href="pcre.html#utf8strings">section on UTF-8 support</a>
! 1675: in the main
! 1676: <a href="pcre.html"><b>pcre</b></a>
! 1677: page. If an invalid UTF-8 sequence of bytes is found, <b>pcre_exec()</b> returns
! 1678: the error PCRE_ERROR_BADUTF8 or, if PCRE_PARTIAL_HARD is set and the problem is
! 1679: a truncated UTF-8 character at the end of the subject, PCRE_ERROR_SHORTUTF8. In
! 1680: both cases, information about the precise nature of the error may also be
! 1681: returned (see the descriptions of these errors in the section entitled \fIError
! 1682: return values from\fP <b>pcre_exec()</b>
! 1683: <a href="#errorlist">below).</a>
! 1684: If <i>startoffset</i> contains a value that does not point to the start of a
! 1685: UTF-8 character (or to the end of the subject), PCRE_ERROR_BADUTF8_OFFSET is
! 1686: returned.
! 1687: </P>
! 1688: <P>
! 1689: If you already know that your subject is valid, and you want to skip these
! 1690: checks for performance reasons, you can set the PCRE_NO_UTF8_CHECK option when
! 1691: calling <b>pcre_exec()</b>. You might want to do this for the second and
! 1692: subsequent calls to <b>pcre_exec()</b> if you are making repeated calls to find
! 1693: all the matches in a single subject string. However, you should be sure that
! 1694: the value of <i>startoffset</i> points to the start of a UTF-8 character (or the
! 1695: end of the subject). When PCRE_NO_UTF8_CHECK is set, the effect of passing an
! 1696: invalid UTF-8 string as a subject or an invalid value of <i>startoffset</i> is
! 1697: undefined. Your program may crash.
! 1698: <pre>
! 1699: PCRE_PARTIAL_HARD
! 1700: PCRE_PARTIAL_SOFT
! 1701: </pre>
! 1702: These options turn on the partial matching feature. For backwards
! 1703: compatibility, PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A partial match
! 1704: occurs if the end of the subject string is reached successfully, but there are
! 1705: not enough subject characters to complete the match. If this happens when
! 1706: PCRE_PARTIAL_SOFT (but not PCRE_PARTIAL_HARD) is set, matching continues by
! 1707: testing any remaining alternatives. Only if no complete match can be found is
! 1708: PCRE_ERROR_PARTIAL returned instead of PCRE_ERROR_NOMATCH. In other words,
! 1709: PCRE_PARTIAL_SOFT says that the caller is prepared to handle a partial match,
! 1710: but only if no complete match can be found.
! 1711: </P>
! 1712: <P>
! 1713: If PCRE_PARTIAL_HARD is set, it overrides PCRE_PARTIAL_SOFT. In this case, if a
! 1714: partial match is found, <b>pcre_exec()</b> immediately returns
! 1715: PCRE_ERROR_PARTIAL, without considering any other alternatives. In other words,
! 1716: when PCRE_PARTIAL_HARD is set, a partial match is considered to be more
! 1717: important that an alternative complete match.
! 1718: </P>
! 1719: <P>
! 1720: In both cases, the portion of the string that was inspected when the partial
! 1721: match was found is set as the first matching string. There is a more detailed
! 1722: discussion of partial and multi-segment matching, with examples, in the
! 1723: <a href="pcrepartial.html"><b>pcrepartial</b></a>
! 1724: documentation.
! 1725: </P>
! 1726: <br><b>
! 1727: The string to be matched by <b>pcre_exec()</b>
! 1728: </b><br>
! 1729: <P>
! 1730: The subject string is passed to <b>pcre_exec()</b> as a pointer in
! 1731: <i>subject</i>, a length (in bytes) in <i>length</i>, and a starting byte offset
! 1732: in <i>startoffset</i>. If this is negative or greater than the length of the
! 1733: subject, <b>pcre_exec()</b> returns PCRE_ERROR_BADOFFSET. When the starting
! 1734: offset is zero, the search for a match starts at the beginning of the subject,
! 1735: and this is by far the most common case. In UTF-8 mode, the byte offset must
! 1736: point to the start of a UTF-8 character (or the end of the subject). Unlike the
! 1737: pattern string, the subject may contain binary zero bytes.
! 1738: </P>
! 1739: <P>
! 1740: A non-zero starting offset is useful when searching for another match in the
! 1741: same subject by calling <b>pcre_exec()</b> again after a previous success.
! 1742: Setting <i>startoffset</i> differs from just passing over a shortened string and
! 1743: setting PCRE_NOTBOL in the case of a pattern that begins with any kind of
! 1744: lookbehind. For example, consider the pattern
! 1745: <pre>
! 1746: \Biss\B
! 1747: </pre>
! 1748: which finds occurrences of "iss" in the middle of words. (\B matches only if
! 1749: the current position in the subject is not a word boundary.) When applied to
! 1750: the string "Mississipi" the first call to <b>pcre_exec()</b> finds the first
! 1751: occurrence. If <b>pcre_exec()</b> is called again with just the remainder of the
! 1752: subject, namely "issipi", it does not match, because \B is always false at the
! 1753: start of the subject, which is deemed to be a word boundary. However, if
! 1754: <b>pcre_exec()</b> is passed the entire string again, but with <i>startoffset</i>
! 1755: set to 4, it finds the second occurrence of "iss" because it is able to look
! 1756: behind the starting point to discover that it is preceded by a letter.
! 1757: </P>
! 1758: <P>
! 1759: Finding all the matches in a subject is tricky when the pattern can match an
! 1760: empty string. It is possible to emulate Perl's /g behaviour by first trying the
! 1761: match again at the same offset, with the PCRE_NOTEMPTY_ATSTART and
! 1762: PCRE_ANCHORED options, and then if that fails, advancing the starting offset
! 1763: and trying an ordinary match again. There is some code that demonstrates how to
! 1764: do this in the
! 1765: <a href="pcredemo.html"><b>pcredemo</b></a>
! 1766: sample program. In the most general case, you have to check to see if the
! 1767: newline convention recognizes CRLF as a newline, and if so, and the current
! 1768: character is CR followed by LF, advance the starting offset by two characters
! 1769: instead of one.
! 1770: </P>
! 1771: <P>
! 1772: If a non-zero starting offset is passed when the pattern is anchored, one
! 1773: attempt to match at the given offset is made. This can only succeed if the
! 1774: pattern does not require the match to be at the start of the subject.
! 1775: </P>
! 1776: <br><b>
! 1777: How <b>pcre_exec()</b> returns captured substrings
! 1778: </b><br>
! 1779: <P>
! 1780: In general, a pattern matches a certain portion of the subject, and in
! 1781: addition, further substrings from the subject may be picked out by parts of the
! 1782: pattern. Following the usage in Jeffrey Friedl's book, this is called
! 1783: "capturing" in what follows, and the phrase "capturing subpattern" is used for
! 1784: a fragment of a pattern that picks out a substring. PCRE supports several other
! 1785: kinds of parenthesized subpattern that do not cause substrings to be captured.
! 1786: </P>
! 1787: <P>
! 1788: Captured substrings are returned to the caller via a vector of integers whose
! 1789: address is passed in <i>ovector</i>. The number of elements in the vector is
! 1790: passed in <i>ovecsize</i>, which must be a non-negative number. <b>Note</b>: this
! 1791: argument is NOT the size of <i>ovector</i> in bytes.
! 1792: </P>
! 1793: <P>
! 1794: The first two-thirds of the vector is used to pass back captured substrings,
! 1795: each substring using a pair of integers. The remaining third of the vector is
! 1796: used as workspace by <b>pcre_exec()</b> while matching capturing subpatterns,
! 1797: and is not available for passing back information. The number passed in
! 1798: <i>ovecsize</i> should always be a multiple of three. If it is not, it is
! 1799: rounded down.
! 1800: </P>
! 1801: <P>
! 1802: When a match is successful, information about captured substrings is returned
! 1803: in pairs of integers, starting at the beginning of <i>ovector</i>, and
! 1804: continuing up to two-thirds of its length at the most. The first element of
! 1805: each pair is set to the byte offset of the first character in a substring, and
! 1806: the second is set to the byte offset of the first character after the end of a
! 1807: substring. <b>Note</b>: these values are always byte offsets, even in UTF-8
! 1808: mode. They are not character counts.
! 1809: </P>
! 1810: <P>
! 1811: The first pair of integers, <i>ovector[0]</i> and <i>ovector[1]</i>, identify the
! 1812: portion of the subject string matched by the entire pattern. The next pair is
! 1813: used for the first capturing subpattern, and so on. The value returned by
! 1814: <b>pcre_exec()</b> is one more than the highest numbered pair that has been set.
! 1815: For example, if two substrings have been captured, the returned value is 3. If
! 1816: there are no capturing subpatterns, the return value from a successful match is
! 1817: 1, indicating that just the first pair of offsets has been set.
! 1818: </P>
! 1819: <P>
! 1820: If a capturing subpattern is matched repeatedly, it is the last portion of the
! 1821: string that it matched that is returned.
! 1822: </P>
! 1823: <P>
! 1824: If the vector is too small to hold all the captured substring offsets, it is
! 1825: used as far as possible (up to two-thirds of its length), and the function
! 1826: returns a value of zero. If neither the actual string matched not any captured
! 1827: substrings are of interest, <b>pcre_exec()</b> may be called with <i>ovector</i>
! 1828: passed as NULL and <i>ovecsize</i> as zero. However, if the pattern contains
! 1829: back references and the <i>ovector</i> is not big enough to remember the related
! 1830: substrings, PCRE has to get additional memory for use during matching. Thus it
! 1831: is usually advisable to supply an <i>ovector</i> of reasonable size.
! 1832: </P>
! 1833: <P>
! 1834: There are some cases where zero is returned (indicating vector overflow) when
! 1835: in fact the vector is exactly the right size for the final match. For example,
! 1836: consider the pattern
! 1837: <pre>
! 1838: (a)(?:(b)c|bd)
! 1839: </pre>
! 1840: If a vector of 6 elements (allowing for only 1 captured substring) is given
! 1841: with subject string "abd", <b>pcre_exec()</b> will try to set the second
! 1842: captured string, thereby recording a vector overflow, before failing to match
! 1843: "c" and backing up to try the second alternative. The zero return, however,
! 1844: does correctly indicate that the maximum number of slots (namely 2) have been
! 1845: filled. In similar cases where there is temporary overflow, but the final
! 1846: number of used slots is actually less than the maximum, a non-zero value is
! 1847: returned.
! 1848: </P>
! 1849: <P>
! 1850: The <b>pcre_fullinfo()</b> function can be used to find out how many capturing
! 1851: subpatterns there are in a compiled pattern. The smallest size for
! 1852: <i>ovector</i> that will allow for <i>n</i> captured substrings, in addition to
! 1853: the offsets of the substring matched by the whole pattern, is (<i>n</i>+1)*3.
! 1854: </P>
! 1855: <P>
! 1856: It is possible for capturing subpattern number <i>n+1</i> to match some part of
! 1857: the subject when subpattern <i>n</i> has not been used at all. For example, if
! 1858: the string "abc" is matched against the pattern (a|(z))(bc) the return from the
! 1859: function is 4, and subpatterns 1 and 3 are matched, but 2 is not. When this
! 1860: happens, both values in the offset pairs corresponding to unused subpatterns
! 1861: are set to -1.
! 1862: </P>
! 1863: <P>
! 1864: Offset values that correspond to unused subpatterns at the end of the
! 1865: expression are also set to -1. For example, if the string "abc" is matched
! 1866: against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are not matched. The
! 1867: return from the function is 2, because the highest used capturing subpattern
! 1868: number is 1, and the offsets for for the second and third capturing subpatterns
! 1869: (assuming the vector is large enough, of course) are set to -1.
! 1870: </P>
! 1871: <P>
! 1872: <b>Note</b>: Elements in the first two-thirds of <i>ovector</i> that do not
! 1873: correspond to capturing parentheses in the pattern are never changed. That is,
! 1874: if a pattern contains <i>n</i> capturing parentheses, no more than
! 1875: <i>ovector[0]</i> to <i>ovector[2n+1]</i> are set by <b>pcre_exec()</b>. The other
! 1876: elements (in the first two-thirds) retain whatever values they previously had.
! 1877: </P>
! 1878: <P>
! 1879: Some convenience functions are provided for extracting the captured substrings
! 1880: as separate strings. These are described below.
! 1881: <a name="errorlist"></a></P>
! 1882: <br><b>
! 1883: Error return values from <b>pcre_exec()</b>
! 1884: </b><br>
! 1885: <P>
! 1886: If <b>pcre_exec()</b> fails, it returns a negative number. The following are
! 1887: defined in the header file:
! 1888: <pre>
! 1889: PCRE_ERROR_NOMATCH (-1)
! 1890: </pre>
! 1891: The subject string did not match the pattern.
! 1892: <pre>
! 1893: PCRE_ERROR_NULL (-2)
! 1894: </pre>
! 1895: Either <i>code</i> or <i>subject</i> was passed as NULL, or <i>ovector</i> was
! 1896: NULL and <i>ovecsize</i> was not zero.
! 1897: <pre>
! 1898: PCRE_ERROR_BADOPTION (-3)
! 1899: </pre>
! 1900: An unrecognized bit was set in the <i>options</i> argument.
! 1901: <pre>
! 1902: PCRE_ERROR_BADMAGIC (-4)
! 1903: </pre>
! 1904: PCRE stores a 4-byte "magic number" at the start of the compiled code, to catch
! 1905: the case when it is passed a junk pointer and to detect when a pattern that was
! 1906: compiled in an environment of one endianness is run in an environment with the
! 1907: other endianness. This is the error that PCRE gives when the magic number is
! 1908: not present.
! 1909: <pre>
! 1910: PCRE_ERROR_UNKNOWN_OPCODE (-5)
! 1911: </pre>
! 1912: While running the pattern match, an unknown item was encountered in the
! 1913: compiled pattern. This error could be caused by a bug in PCRE or by overwriting
! 1914: of the compiled pattern.
! 1915: <pre>
! 1916: PCRE_ERROR_NOMEMORY (-6)
! 1917: </pre>
! 1918: If a pattern contains back references, but the <i>ovector</i> that is passed to
! 1919: <b>pcre_exec()</b> is not big enough to remember the referenced substrings, PCRE
! 1920: gets a block of memory at the start of matching to use for this purpose. If the
! 1921: call via <b>pcre_malloc()</b> fails, this error is given. The memory is
! 1922: automatically freed at the end of matching.
! 1923: </P>
! 1924: <P>
! 1925: This error is also given if <b>pcre_stack_malloc()</b> fails in
! 1926: <b>pcre_exec()</b>. This can happen only when PCRE has been compiled with
! 1927: <b>--disable-stack-for-recursion</b>.
! 1928: <pre>
! 1929: PCRE_ERROR_NOSUBSTRING (-7)
! 1930: </pre>
! 1931: This error is used by the <b>pcre_copy_substring()</b>,
! 1932: <b>pcre_get_substring()</b>, and <b>pcre_get_substring_list()</b> functions (see
! 1933: below). It is never returned by <b>pcre_exec()</b>.
! 1934: <pre>
! 1935: PCRE_ERROR_MATCHLIMIT (-8)
! 1936: </pre>
! 1937: The backtracking limit, as specified by the <i>match_limit</i> field in a
! 1938: <b>pcre_extra</b> structure (or defaulted) was reached. See the description
! 1939: above.
! 1940: <pre>
! 1941: PCRE_ERROR_CALLOUT (-9)
! 1942: </pre>
! 1943: This error is never generated by <b>pcre_exec()</b> itself. It is provided for
! 1944: use by callout functions that want to yield a distinctive error code. See the
! 1945: <a href="pcrecallout.html"><b>pcrecallout</b></a>
! 1946: documentation for details.
! 1947: <pre>
! 1948: PCRE_ERROR_BADUTF8 (-10)
! 1949: </pre>
! 1950: A string that contains an invalid UTF-8 byte sequence was passed as a subject,
! 1951: and the PCRE_NO_UTF8_CHECK option was not set. If the size of the output vector
! 1952: (<i>ovecsize</i>) is at least 2, the byte offset to the start of the the invalid
! 1953: UTF-8 character is placed in the first element, and a reason code is placed in
! 1954: the second element. The reason codes are listed in the
! 1955: <a href="#badutf8reasons">following section.</a>
! 1956: For backward compatibility, if PCRE_PARTIAL_HARD is set and the problem is a
! 1957: truncated UTF-8 character at the end of the subject (reason codes 1 to 5),
! 1958: PCRE_ERROR_SHORTUTF8 is returned instead of PCRE_ERROR_BADUTF8.
! 1959: <pre>
! 1960: PCRE_ERROR_BADUTF8_OFFSET (-11)
! 1961: </pre>
! 1962: The UTF-8 byte sequence that was passed as a subject was checked and found to
! 1963: be valid (the PCRE_NO_UTF8_CHECK option was not set), but the value of
! 1964: <i>startoffset</i> did not point to the beginning of a UTF-8 character or the
! 1965: end of the subject.
! 1966: <pre>
! 1967: PCRE_ERROR_PARTIAL (-12)
! 1968: </pre>
! 1969: The subject string did not match, but it did match partially. See the
! 1970: <a href="pcrepartial.html"><b>pcrepartial</b></a>
! 1971: documentation for details of partial matching.
! 1972: <pre>
! 1973: PCRE_ERROR_BADPARTIAL (-13)
! 1974: </pre>
! 1975: This code is no longer in use. It was formerly returned when the PCRE_PARTIAL
! 1976: option was used with a compiled pattern containing items that were not
! 1977: supported for partial matching. From release 8.00 onwards, there are no
! 1978: restrictions on partial matching.
! 1979: <pre>
! 1980: PCRE_ERROR_INTERNAL (-14)
! 1981: </pre>
! 1982: An unexpected internal error has occurred. This error could be caused by a bug
! 1983: in PCRE or by overwriting of the compiled pattern.
! 1984: <pre>
! 1985: PCRE_ERROR_BADCOUNT (-15)
! 1986: </pre>
! 1987: This error is given if the value of the <i>ovecsize</i> argument is negative.
! 1988: <pre>
! 1989: PCRE_ERROR_RECURSIONLIMIT (-21)
! 1990: </pre>
! 1991: The internal recursion limit, as specified by the <i>match_limit_recursion</i>
! 1992: field in a <b>pcre_extra</b> structure (or defaulted) was reached. See the
! 1993: description above.
! 1994: <pre>
! 1995: PCRE_ERROR_BADNEWLINE (-23)
! 1996: </pre>
! 1997: An invalid combination of PCRE_NEWLINE_<i>xxx</i> options was given.
! 1998: <pre>
! 1999: PCRE_ERROR_BADOFFSET (-24)
! 2000: </pre>
! 2001: The value of <i>startoffset</i> was negative or greater than the length of the
! 2002: subject, that is, the value in <i>length</i>.
! 2003: <pre>
! 2004: PCRE_ERROR_SHORTUTF8 (-25)
! 2005: </pre>
! 2006: This error is returned instead of PCRE_ERROR_BADUTF8 when the subject string
! 2007: ends with a truncated UTF-8 character and the PCRE_PARTIAL_HARD option is set.
! 2008: Information about the failure is returned as for PCRE_ERROR_BADUTF8. It is in
! 2009: fact sufficient to detect this case, but this special error code for
! 2010: PCRE_PARTIAL_HARD precedes the implementation of returned information; it is
! 2011: retained for backwards compatibility.
! 2012: <pre>
! 2013: PCRE_ERROR_RECURSELOOP (-26)
! 2014: </pre>
! 2015: This error is returned when <b>pcre_exec()</b> detects a recursion loop within
! 2016: the pattern. Specifically, it means that either the whole pattern or a
! 2017: subpattern has been called recursively for the second time at the same position
! 2018: in the subject string. Some simple patterns that might do this are detected and
! 2019: faulted at compile time, but more complicated cases, in particular mutual
! 2020: recursions between two different subpatterns, cannot be detected until run
! 2021: time.
! 2022: <pre>
! 2023: PCRE_ERROR_JIT_STACKLIMIT (-27)
! 2024: </pre>
! 2025: This error is returned when a pattern that was successfully studied using the
! 2026: PCRE_STUDY_JIT_COMPILE option is being matched, but the memory available for
! 2027: the just-in-time processing stack is not large enough. See the
! 2028: <a href="pcrejit.html"><b>pcrejit</b></a>
! 2029: documentation for more details.
! 2030: </P>
! 2031: <P>
! 2032: Error numbers -16 to -20 and -22 are not used by <b>pcre_exec()</b>.
! 2033: <a name="badutf8reasons"></a></P>
! 2034: <br><b>
! 2035: Reason codes for invalid UTF-8 strings
! 2036: </b><br>
! 2037: <P>
! 2038: When <b>pcre_exec()</b> returns either PCRE_ERROR_BADUTF8 or
! 2039: PCRE_ERROR_SHORTUTF8, and the size of the output vector (<i>ovecsize</i>) is at
! 2040: least 2, the offset of the start of the invalid UTF-8 character is placed in
! 2041: the first output vector element (<i>ovector[0]</i>) and a reason code is placed
! 2042: in the second element (<i>ovector[1]</i>). The reason codes are given names in
! 2043: the <b>pcre.h</b> header file:
! 2044: <pre>
! 2045: PCRE_UTF8_ERR1
! 2046: PCRE_UTF8_ERR2
! 2047: PCRE_UTF8_ERR3
! 2048: PCRE_UTF8_ERR4
! 2049: PCRE_UTF8_ERR5
! 2050: </pre>
! 2051: The string ends with a truncated UTF-8 character; the code specifies how many
! 2052: bytes are missing (1 to 5). Although RFC 3629 restricts UTF-8 characters to be
! 2053: no longer than 4 bytes, the encoding scheme (originally defined by RFC 2279)
! 2054: allows for up to 6 bytes, and this is checked first; hence the possibility of
! 2055: 4 or 5 missing bytes.
! 2056: <pre>
! 2057: PCRE_UTF8_ERR6
! 2058: PCRE_UTF8_ERR7
! 2059: PCRE_UTF8_ERR8
! 2060: PCRE_UTF8_ERR9
! 2061: PCRE_UTF8_ERR10
! 2062: </pre>
! 2063: The two most significant bits of the 2nd, 3rd, 4th, 5th, or 6th byte of the
! 2064: character do not have the binary value 0b10 (that is, either the most
! 2065: significant bit is 0, or the next bit is 1).
! 2066: <pre>
! 2067: PCRE_UTF8_ERR11
! 2068: PCRE_UTF8_ERR12
! 2069: </pre>
! 2070: A character that is valid by the RFC 2279 rules is either 5 or 6 bytes long;
! 2071: these code points are excluded by RFC 3629.
! 2072: <pre>
! 2073: PCRE_UTF8_ERR13
! 2074: </pre>
! 2075: A 4-byte character has a value greater than 0x10fff; these code points are
! 2076: excluded by RFC 3629.
! 2077: <pre>
! 2078: PCRE_UTF8_ERR14
! 2079: </pre>
! 2080: A 3-byte character has a value in the range 0xd800 to 0xdfff; this range of
! 2081: code points are reserved by RFC 3629 for use with UTF-16, and so are excluded
! 2082: from UTF-8.
! 2083: <pre>
! 2084: PCRE_UTF8_ERR15
! 2085: PCRE_UTF8_ERR16
! 2086: PCRE_UTF8_ERR17
! 2087: PCRE_UTF8_ERR18
! 2088: PCRE_UTF8_ERR19
! 2089: </pre>
! 2090: A 2-, 3-, 4-, 5-, or 6-byte character is "overlong", that is, it codes for a
! 2091: value that can be represented by fewer bytes, which is invalid. For example,
! 2092: the two bytes 0xc0, 0xae give the value 0x2e, whose correct coding uses just
! 2093: one byte.
! 2094: <pre>
! 2095: PCRE_UTF8_ERR20
! 2096: </pre>
! 2097: The two most significant bits of the first byte of a character have the binary
! 2098: value 0b10 (that is, the most significant bit is 1 and the second is 0). Such a
! 2099: byte can only validly occur as the second or subsequent byte of a multi-byte
! 2100: character.
! 2101: <pre>
! 2102: PCRE_UTF8_ERR21
! 2103: </pre>
! 2104: The first byte of a character has the value 0xfe or 0xff. These values can
! 2105: never occur in a valid UTF-8 string.
! 2106: </P>
! 2107: <br><a name="SEC17" href="#TOC1">EXTRACTING CAPTURED SUBSTRINGS BY NUMBER</a><br>
! 2108: <P>
! 2109: <b>int pcre_copy_substring(const char *<i>subject</i>, int *<i>ovector</i>,</b>
! 2110: <b>int <i>stringcount</i>, int <i>stringnumber</i>, char *<i>buffer</i>,</b>
! 2111: <b>int <i>buffersize</i>);</b>
! 2112: </P>
! 2113: <P>
! 2114: <b>int pcre_get_substring(const char *<i>subject</i>, int *<i>ovector</i>,</b>
! 2115: <b>int <i>stringcount</i>, int <i>stringnumber</i>,</b>
! 2116: <b>const char **<i>stringptr</i>);</b>
! 2117: </P>
! 2118: <P>
! 2119: <b>int pcre_get_substring_list(const char *<i>subject</i>,</b>
! 2120: <b>int *<i>ovector</i>, int <i>stringcount</i>, const char ***<i>listptr</i>);</b>
! 2121: </P>
! 2122: <P>
! 2123: Captured substrings can be accessed directly by using the offsets returned by
! 2124: <b>pcre_exec()</b> in <i>ovector</i>. For convenience, the functions
! 2125: <b>pcre_copy_substring()</b>, <b>pcre_get_substring()</b>, and
! 2126: <b>pcre_get_substring_list()</b> are provided for extracting captured substrings
! 2127: as new, separate, zero-terminated strings. These functions identify substrings
! 2128: by number. The next section describes functions for extracting named
! 2129: substrings.
! 2130: </P>
! 2131: <P>
! 2132: A substring that contains a binary zero is correctly extracted and has a
! 2133: further zero added on the end, but the result is not, of course, a C string.
! 2134: However, you can process such a string by referring to the length that is
! 2135: returned by <b>pcre_copy_substring()</b> and <b>pcre_get_substring()</b>.
! 2136: Unfortunately, the interface to <b>pcre_get_substring_list()</b> is not adequate
! 2137: for handling strings containing binary zeros, because the end of the final
! 2138: string is not independently indicated.
! 2139: </P>
! 2140: <P>
! 2141: The first three arguments are the same for all three of these functions:
! 2142: <i>subject</i> is the subject string that has just been successfully matched,
! 2143: <i>ovector</i> is a pointer to the vector of integer offsets that was passed to
! 2144: <b>pcre_exec()</b>, and <i>stringcount</i> is the number of substrings that were
! 2145: captured by the match, including the substring that matched the entire regular
! 2146: expression. This is the value returned by <b>pcre_exec()</b> if it is greater
! 2147: than zero. If <b>pcre_exec()</b> returned zero, indicating that it ran out of
! 2148: space in <i>ovector</i>, the value passed as <i>stringcount</i> should be the
! 2149: number of elements in the vector divided by three.
! 2150: </P>
! 2151: <P>
! 2152: The functions <b>pcre_copy_substring()</b> and <b>pcre_get_substring()</b>
! 2153: extract a single substring, whose number is given as <i>stringnumber</i>. A
! 2154: value of zero extracts the substring that matched the entire pattern, whereas
! 2155: higher values extract the captured substrings. For <b>pcre_copy_substring()</b>,
! 2156: the string is placed in <i>buffer</i>, whose length is given by
! 2157: <i>buffersize</i>, while for <b>pcre_get_substring()</b> a new block of memory is
! 2158: obtained via <b>pcre_malloc</b>, and its address is returned via
! 2159: <i>stringptr</i>. The yield of the function is the length of the string, not
! 2160: including the terminating zero, or one of these error codes:
! 2161: <pre>
! 2162: PCRE_ERROR_NOMEMORY (-6)
! 2163: </pre>
! 2164: The buffer was too small for <b>pcre_copy_substring()</b>, or the attempt to get
! 2165: memory failed for <b>pcre_get_substring()</b>.
! 2166: <pre>
! 2167: PCRE_ERROR_NOSUBSTRING (-7)
! 2168: </pre>
! 2169: There is no substring whose number is <i>stringnumber</i>.
! 2170: </P>
! 2171: <P>
! 2172: The <b>pcre_get_substring_list()</b> function extracts all available substrings
! 2173: and builds a list of pointers to them. All this is done in a single block of
! 2174: memory that is obtained via <b>pcre_malloc</b>. The address of the memory block
! 2175: is returned via <i>listptr</i>, which is also the start of the list of string
! 2176: pointers. The end of the list is marked by a NULL pointer. The yield of the
! 2177: function is zero if all went well, or the error code
! 2178: <pre>
! 2179: PCRE_ERROR_NOMEMORY (-6)
! 2180: </pre>
! 2181: if the attempt to get the memory block failed.
! 2182: </P>
! 2183: <P>
! 2184: When any of these functions encounter a substring that is unset, which can
! 2185: happen when capturing subpattern number <i>n+1</i> matches some part of the
! 2186: subject, but subpattern <i>n</i> has not been used at all, they return an empty
! 2187: string. This can be distinguished from a genuine zero-length substring by
! 2188: inspecting the appropriate offset in <i>ovector</i>, which is negative for unset
! 2189: substrings.
! 2190: </P>
! 2191: <P>
! 2192: The two convenience functions <b>pcre_free_substring()</b> and
! 2193: <b>pcre_free_substring_list()</b> can be used to free the memory returned by
! 2194: a previous call of <b>pcre_get_substring()</b> or
! 2195: <b>pcre_get_substring_list()</b>, respectively. They do nothing more than call
! 2196: the function pointed to by <b>pcre_free</b>, which of course could be called
! 2197: directly from a C program. However, PCRE is used in some situations where it is
! 2198: linked via a special interface to another programming language that cannot use
! 2199: <b>pcre_free</b> directly; it is for these cases that the functions are
! 2200: provided.
! 2201: </P>
! 2202: <br><a name="SEC18" href="#TOC1">EXTRACTING CAPTURED SUBSTRINGS BY NAME</a><br>
! 2203: <P>
! 2204: <b>int pcre_get_stringnumber(const pcre *<i>code</i>,</b>
! 2205: <b>const char *<i>name</i>);</b>
! 2206: </P>
! 2207: <P>
! 2208: <b>int pcre_copy_named_substring(const pcre *<i>code</i>,</b>
! 2209: <b>const char *<i>subject</i>, int *<i>ovector</i>,</b>
! 2210: <b>int <i>stringcount</i>, const char *<i>stringname</i>,</b>
! 2211: <b>char *<i>buffer</i>, int <i>buffersize</i>);</b>
! 2212: </P>
! 2213: <P>
! 2214: <b>int pcre_get_named_substring(const pcre *<i>code</i>,</b>
! 2215: <b>const char *<i>subject</i>, int *<i>ovector</i>,</b>
! 2216: <b>int <i>stringcount</i>, const char *<i>stringname</i>,</b>
! 2217: <b>const char **<i>stringptr</i>);</b>
! 2218: </P>
! 2219: <P>
! 2220: To extract a substring by name, you first have to find associated number.
! 2221: For example, for this pattern
! 2222: <pre>
! 2223: (a+)b(?<xxx>\d+)...
! 2224: </pre>
! 2225: the number of the subpattern called "xxx" is 2. If the name is known to be
! 2226: unique (PCRE_DUPNAMES was not set), you can find the number from the name by
! 2227: calling <b>pcre_get_stringnumber()</b>. The first argument is the compiled
! 2228: pattern, and the second is the name. The yield of the function is the
! 2229: subpattern number, or PCRE_ERROR_NOSUBSTRING (-7) if there is no subpattern of
! 2230: that name.
! 2231: </P>
! 2232: <P>
! 2233: Given the number, you can extract the substring directly, or use one of the
! 2234: functions described in the previous section. For convenience, there are also
! 2235: two functions that do the whole job.
! 2236: </P>
! 2237: <P>
! 2238: Most of the arguments of <b>pcre_copy_named_substring()</b> and
! 2239: <b>pcre_get_named_substring()</b> are the same as those for the similarly named
! 2240: functions that extract by number. As these are described in the previous
! 2241: section, they are not re-described here. There are just two differences:
! 2242: </P>
! 2243: <P>
! 2244: First, instead of a substring number, a substring name is given. Second, there
! 2245: is an extra argument, given at the start, which is a pointer to the compiled
! 2246: pattern. This is needed in order to gain access to the name-to-number
! 2247: translation table.
! 2248: </P>
! 2249: <P>
! 2250: These functions call <b>pcre_get_stringnumber()</b>, and if it succeeds, they
! 2251: then call <b>pcre_copy_substring()</b> or <b>pcre_get_substring()</b>, as
! 2252: appropriate. <b>NOTE:</b> If PCRE_DUPNAMES is set and there are duplicate names,
! 2253: the behaviour may not be what you want (see the next section).
! 2254: </P>
! 2255: <P>
! 2256: <b>Warning:</b> If the pattern uses the (?| feature to set up multiple
! 2257: subpatterns with the same number, as described in the
! 2258: <a href="pcrepattern.html#dupsubpatternnumber">section on duplicate subpattern numbers</a>
! 2259: in the
! 2260: <a href="pcrepattern.html"><b>pcrepattern</b></a>
! 2261: page, you cannot use names to distinguish the different subpatterns, because
! 2262: names are not included in the compiled code. The matching process uses only
! 2263: numbers. For this reason, the use of different names for subpatterns of the
! 2264: same number causes an error at compile time.
! 2265: </P>
! 2266: <br><a name="SEC19" href="#TOC1">DUPLICATE SUBPATTERN NAMES</a><br>
! 2267: <P>
! 2268: <b>int pcre_get_stringtable_entries(const pcre *<i>code</i>,</b>
! 2269: <b>const char *<i>name</i>, char **<i>first</i>, char **<i>last</i>);</b>
! 2270: </P>
! 2271: <P>
! 2272: When a pattern is compiled with the PCRE_DUPNAMES option, names for subpatterns
! 2273: are not required to be unique. (Duplicate names are always allowed for
! 2274: subpatterns with the same number, created by using the (?| feature. Indeed, if
! 2275: such subpatterns are named, they are required to use the same names.)
! 2276: </P>
! 2277: <P>
! 2278: Normally, patterns with duplicate names are such that in any one match, only
! 2279: one of the named subpatterns participates. An example is shown in the
! 2280: <a href="pcrepattern.html"><b>pcrepattern</b></a>
! 2281: documentation.
! 2282: </P>
! 2283: <P>
! 2284: When duplicates are present, <b>pcre_copy_named_substring()</b> and
! 2285: <b>pcre_get_named_substring()</b> return the first substring corresponding to
! 2286: the given name that is set. If none are set, PCRE_ERROR_NOSUBSTRING (-7) is
! 2287: returned; no data is returned. The <b>pcre_get_stringnumber()</b> function
! 2288: returns one of the numbers that are associated with the name, but it is not
! 2289: defined which it is.
! 2290: </P>
! 2291: <P>
! 2292: If you want to get full details of all captured substrings for a given name,
! 2293: you must use the <b>pcre_get_stringtable_entries()</b> function. The first
! 2294: argument is the compiled pattern, and the second is the name. The third and
! 2295: fourth are pointers to variables which are updated by the function. After it
! 2296: has run, they point to the first and last entries in the name-to-number table
! 2297: for the given name. The function itself returns the length of each entry, or
! 2298: PCRE_ERROR_NOSUBSTRING (-7) if there are none. The format of the table is
! 2299: described above in the section entitled <i>Information about a pattern</i>
! 2300: <a href="#infoaboutpattern">above.</a>
! 2301: Given all the relevant entries for the name, you can extract each of their
! 2302: numbers, and hence the captured data, if any.
! 2303: </P>
! 2304: <br><a name="SEC20" href="#TOC1">FINDING ALL POSSIBLE MATCHES</a><br>
! 2305: <P>
! 2306: The traditional matching function uses a similar algorithm to Perl, which stops
! 2307: when it finds the first match, starting at a given point in the subject. If you
! 2308: want to find all possible matches, or the longest possible match, consider
! 2309: using the alternative matching function (see below) instead. If you cannot use
! 2310: the alternative function, but still need to find all possible matches, you
! 2311: can kludge it up by making use of the callout facility, which is described in
! 2312: the
! 2313: <a href="pcrecallout.html"><b>pcrecallout</b></a>
! 2314: documentation.
! 2315: </P>
! 2316: <P>
! 2317: What you have to do is to insert a callout right at the end of the pattern.
! 2318: When your callout function is called, extract and save the current matched
! 2319: substring. Then return 1, which forces <b>pcre_exec()</b> to backtrack and try
! 2320: other alternatives. Ultimately, when it runs out of matches, <b>pcre_exec()</b>
! 2321: will yield PCRE_ERROR_NOMATCH.
! 2322: <a name="dfamatch"></a></P>
! 2323: <br><a name="SEC21" href="#TOC1">MATCHING A PATTERN: THE ALTERNATIVE FUNCTION</a><br>
! 2324: <P>
! 2325: <b>int pcre_dfa_exec(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b>
! 2326: <b>const char *<i>subject</i>, int <i>length</i>, int <i>startoffset</i>,</b>
! 2327: <b>int <i>options</i>, int *<i>ovector</i>, int <i>ovecsize</i>,</b>
! 2328: <b>int *<i>workspace</i>, int <i>wscount</i>);</b>
! 2329: </P>
! 2330: <P>
! 2331: The function <b>pcre_dfa_exec()</b> is called to match a subject string against
! 2332: a compiled pattern, using a matching algorithm that scans the subject string
! 2333: just once, and does not backtrack. This has different characteristics to the
! 2334: normal algorithm, and is not compatible with Perl. Some of the features of PCRE
! 2335: patterns are not supported. Nevertheless, there are times when this kind of
! 2336: matching can be useful. For a discussion of the two matching algorithms, and a
! 2337: list of features that <b>pcre_dfa_exec()</b> does not support, see the
! 2338: <a href="pcrematching.html"><b>pcrematching</b></a>
! 2339: documentation.
! 2340: </P>
! 2341: <P>
! 2342: The arguments for the <b>pcre_dfa_exec()</b> function are the same as for
! 2343: <b>pcre_exec()</b>, plus two extras. The <i>ovector</i> argument is used in a
! 2344: different way, and this is described below. The other common arguments are used
! 2345: in the same way as for <b>pcre_exec()</b>, so their description is not repeated
! 2346: here.
! 2347: </P>
! 2348: <P>
! 2349: The two additional arguments provide workspace for the function. The workspace
! 2350: vector should contain at least 20 elements. It is used for keeping track of
! 2351: multiple paths through the pattern tree. More workspace will be needed for
! 2352: patterns and subjects where there are a lot of potential matches.
! 2353: </P>
! 2354: <P>
! 2355: Here is an example of a simple call to <b>pcre_dfa_exec()</b>:
! 2356: <pre>
! 2357: int rc;
! 2358: int ovector[10];
! 2359: int wspace[20];
! 2360: rc = pcre_dfa_exec(
! 2361: re, /* result of pcre_compile() */
! 2362: NULL, /* we didn't study the pattern */
! 2363: "some string", /* the subject string */
! 2364: 11, /* the length of the subject string */
! 2365: 0, /* start at offset 0 in the subject */
! 2366: 0, /* default options */
! 2367: ovector, /* vector of integers for substring information */
! 2368: 10, /* number of elements (NOT size in bytes) */
! 2369: wspace, /* working space vector */
! 2370: 20); /* number of elements (NOT size in bytes) */
! 2371: </PRE>
! 2372: </P>
! 2373: <br><b>
! 2374: Option bits for <b>pcre_dfa_exec()</b>
! 2375: </b><br>
! 2376: <P>
! 2377: The unused bits of the <i>options</i> argument for <b>pcre_dfa_exec()</b> must be
! 2378: zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_<i>xxx</i>,
! 2379: PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
! 2380: PCRE_NO_UTF8_CHECK, PCRE_BSR_ANYCRLF, PCRE_BSR_UNICODE, PCRE_NO_START_OPTIMIZE,
! 2381: PCRE_PARTIAL_HARD, PCRE_PARTIAL_SOFT, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART.
! 2382: All but the last four of these are exactly the same as for <b>pcre_exec()</b>,
! 2383: so their description is not repeated here.
! 2384: <pre>
! 2385: PCRE_PARTIAL_HARD
! 2386: PCRE_PARTIAL_SOFT
! 2387: </pre>
! 2388: These have the same general effect as they do for <b>pcre_exec()</b>, but the
! 2389: details are slightly different. When PCRE_PARTIAL_HARD is set for
! 2390: <b>pcre_dfa_exec()</b>, it returns PCRE_ERROR_PARTIAL if the end of the subject
! 2391: is reached and there is still at least one matching possibility that requires
! 2392: additional characters. This happens even if some complete matches have also
! 2393: been found. When PCRE_PARTIAL_SOFT is set, the return code PCRE_ERROR_NOMATCH
! 2394: is converted into PCRE_ERROR_PARTIAL if the end of the subject is reached,
! 2395: there have been no complete matches, but there is still at least one matching
! 2396: possibility. The portion of the string that was inspected when the longest
! 2397: partial match was found is set as the first matching string in both cases.
! 2398: There is a more detailed discussion of partial and multi-segment matching, with
! 2399: examples, in the
! 2400: <a href="pcrepartial.html"><b>pcrepartial</b></a>
! 2401: documentation.
! 2402: <pre>
! 2403: PCRE_DFA_SHORTEST
! 2404: </pre>
! 2405: Setting the PCRE_DFA_SHORTEST option causes the matching algorithm to stop as
! 2406: soon as it has found one match. Because of the way the alternative algorithm
! 2407: works, this is necessarily the shortest possible match at the first possible
! 2408: matching point in the subject string.
! 2409: <pre>
! 2410: PCRE_DFA_RESTART
! 2411: </pre>
! 2412: When <b>pcre_dfa_exec()</b> returns a partial match, it is possible to call it
! 2413: again, with additional subject characters, and have it continue with the same
! 2414: match. The PCRE_DFA_RESTART option requests this action; when it is set, the
! 2415: <i>workspace</i> and <i>wscount</i> options must reference the same vector as
! 2416: before because data about the match so far is left in them after a partial
! 2417: match. There is more discussion of this facility in the
! 2418: <a href="pcrepartial.html"><b>pcrepartial</b></a>
! 2419: documentation.
! 2420: </P>
! 2421: <br><b>
! 2422: Successful returns from <b>pcre_dfa_exec()</b>
! 2423: </b><br>
! 2424: <P>
! 2425: When <b>pcre_dfa_exec()</b> succeeds, it may have matched more than one
! 2426: substring in the subject. Note, however, that all the matches from one run of
! 2427: the function start at the same point in the subject. The shorter matches are
! 2428: all initial substrings of the longer matches. For example, if the pattern
! 2429: <pre>
! 2430: <.*>
! 2431: </pre>
! 2432: is matched against the string
! 2433: <pre>
! 2434: This is <something> <something else> <something further> no more
! 2435: </pre>
! 2436: the three matched strings are
! 2437: <pre>
! 2438: <something>
! 2439: <something> <something else>
! 2440: <something> <something else> <something further>
! 2441: </pre>
! 2442: On success, the yield of the function is a number greater than zero, which is
! 2443: the number of matched substrings. The substrings themselves are returned in
! 2444: <i>ovector</i>. Each string uses two elements; the first is the offset to the
! 2445: start, and the second is the offset to the end. In fact, all the strings have
! 2446: the same start offset. (Space could have been saved by giving this only once,
! 2447: but it was decided to retain some compatibility with the way <b>pcre_exec()</b>
! 2448: returns data, even though the meaning of the strings is different.)
! 2449: </P>
! 2450: <P>
! 2451: The strings are returned in reverse order of length; that is, the longest
! 2452: matching string is given first. If there were too many matches to fit into
! 2453: <i>ovector</i>, the yield of the function is zero, and the vector is filled with
! 2454: the longest matches. Unlike <b>pcre_exec()</b>, <b>pcre_dfa_exec()</b> can use
! 2455: the entire <i>ovector</i> for returning matched strings.
! 2456: </P>
! 2457: <br><b>
! 2458: Error returns from <b>pcre_dfa_exec()</b>
! 2459: </b><br>
! 2460: <P>
! 2461: The <b>pcre_dfa_exec()</b> function returns a negative number when it fails.
! 2462: Many of the errors are the same as for <b>pcre_exec()</b>, and these are
! 2463: described
! 2464: <a href="#errorlist">above.</a>
! 2465: There are in addition the following errors that are specific to
! 2466: <b>pcre_dfa_exec()</b>:
! 2467: <pre>
! 2468: PCRE_ERROR_DFA_UITEM (-16)
! 2469: </pre>
! 2470: This return is given if <b>pcre_dfa_exec()</b> encounters an item in the pattern
! 2471: that it does not support, for instance, the use of \C or a back reference.
! 2472: <pre>
! 2473: PCRE_ERROR_DFA_UCOND (-17)
! 2474: </pre>
! 2475: This return is given if <b>pcre_dfa_exec()</b> encounters a condition item that
! 2476: uses a back reference for the condition, or a test for recursion in a specific
! 2477: group. These are not supported.
! 2478: <pre>
! 2479: PCRE_ERROR_DFA_UMLIMIT (-18)
! 2480: </pre>
! 2481: This return is given if <b>pcre_dfa_exec()</b> is called with an <i>extra</i>
! 2482: block that contains a setting of the <i>match_limit</i> or
! 2483: <i>match_limit_recursion</i> fields. This is not supported (these fields are
! 2484: meaningless for DFA matching).
! 2485: <pre>
! 2486: PCRE_ERROR_DFA_WSSIZE (-19)
! 2487: </pre>
! 2488: This return is given if <b>pcre_dfa_exec()</b> runs out of space in the
! 2489: <i>workspace</i> vector.
! 2490: <pre>
! 2491: PCRE_ERROR_DFA_RECURSE (-20)
! 2492: </pre>
! 2493: When a recursive subpattern is processed, the matching function calls itself
! 2494: recursively, using private vectors for <i>ovector</i> and <i>workspace</i>. This
! 2495: error is given if the output vector is not large enough. This should be
! 2496: extremely rare, as a vector of size 1000 is used.
! 2497: </P>
! 2498: <br><a name="SEC22" href="#TOC1">SEE ALSO</a><br>
! 2499: <P>
! 2500: <b>pcrebuild</b>(3), <b>pcrecallout</b>(3), <b>pcrecpp(3)</b>(3),
! 2501: <b>pcrematching</b>(3), <b>pcrepartial</b>(3), <b>pcreposix</b>(3),
! 2502: <b>pcreprecompile</b>(3), <b>pcresample</b>(3), <b>pcrestack</b>(3).
! 2503: </P>
! 2504: <br><a name="SEC23" href="#TOC1">AUTHOR</a><br>
! 2505: <P>
! 2506: Philip Hazel
! 2507: <br>
! 2508: University Computing Service
! 2509: <br>
! 2510: Cambridge CB2 3QH, England.
! 2511: <br>
! 2512: </P>
! 2513: <br><a name="SEC24" href="#TOC1">REVISION</a><br>
! 2514: <P>
! 2515: Last updated: 02 December 2011
! 2516: <br>
! 2517: Copyright © 1997-2011 University of Cambridge.
! 2518: <br>
! 2519: <p>
! 2520: Return to the <a href="index.html">PCRE index page</a>.
! 2521: </p>
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