pcreposix specification

From 582b500cd996c96054615870fd13d6ab0ea77428 Mon Sep 17 00:00:00 2001 From: Jay Berkenbilt Date: Sat, 10 Oct 2009 15:10:05 +0000 Subject: start integrating windows port git-svn-id: svn+q:///qpdf/trunk@757 71b93d88-0707-0410-a8cf-f5a4172ac649 --- external-libs/pcre/doc/html/pcreposix.html | 237 +++++++++++++++++++++++++++++ 1 file changed, 237 insertions(+) create mode 100644 external-libs/pcre/doc/html/pcreposix.html (limited to 'external-libs/pcre/doc/html/pcreposix.html') diff --git a/external-libs/pcre/doc/html/pcreposix.html b/external-libs/pcre/doc/html/pcreposix.html new file mode 100644 index 00000000..d0a5e127 --- /dev/null +++ b/external-libs/pcre/doc/html/pcreposix.html @@ -0,0 +1,237 @@ + + +pcreposix specification + + +This HTML document has been generated automatically from the original man page. +If there is any nonsense in it, please consult the man page, in case the +conversion went wrong.
+

SYNOPSIS OF POSIX API +
DESCRIPTION +
COMPILING A PATTERN +
MATCHING NEWLINE CHARACTERS +
MATCHING A PATTERN +
ERROR MESSAGES +
STORAGE +
AUTHOR +

+
SYNOPSIS OF POSIX API
+

+#include <pcreposix.h> +

+int regcomp(regex_t *preg, const char *pattern, +int cflags); +

+int regexec(regex_t *preg, const char *string, +size_t nmatch, regmatch_t pmatch[], int eflags); +

+size_t regerror(int errcode, const regex_t *preg, +char *errbuf, size_t errbuf_size); +

+void regfree(regex_t *preg); +

+
DESCRIPTION
+

+This set of functions provides a POSIX-style API to the PCRE regular expression +package. See the +pcreapi +documentation for a description of the native API, which contains additional +functionality. +

+The functions described here are just wrapper functions that ultimately call +the PCRE native API. Their prototypes are defined in the pcreposix.h +header file, and on Unix systems the library itself is called +pcreposix.a, so can be accessed by adding -lpcreposix to the +command for linking an application which uses them. Because the POSIX functions +call the native ones, it is also necessary to add \fR-lpcre\fR. +

+I have implemented only those option bits that can be reasonably mapped to PCRE +native options. In addition, the options REG_EXTENDED and REG_NOSUB are defined +with the value zero. They have no effect, but since programs that are written +to the POSIX interface often use them, this makes it easier to slot in PCRE as +a replacement library. Other POSIX options are not even defined. +

+When PCRE is called via these functions, it is only the API that is POSIX-like +in style. The syntax and semantics of the regular expressions themselves are +still those of Perl, subject to the setting of various PCRE options, as +described below. "POSIX-like in style" means that the API approximates to the +POSIX definition; it is not fully POSIX-compatible, and in multi-byte encoding +domains it is probably even less compatible. +

+The header for these functions is supplied as pcreposix.h to avoid any +potential clash with other POSIX libraries. It can, of course, be renamed or +aliased as regex.h, which is the "correct" name. It provides two +structure types, regex_t for compiled internal forms, and +regmatch_t for returning captured substrings. It also defines some +constants whose names start with "REG_"; these are used for setting options and +identifying error codes. +

+
COMPILING A PATTERN
+

+The function regcomp() is called to compile a pattern into an +internal form. The pattern is a C string terminated by a binary zero, and +is passed in the argument pattern. The preg argument is a pointer +to a regex_t structure which is used as a base for storing information about +the compiled expression. +

+The argument cflags is either zero, or contains one or more of the bits +defined by the following macros: +

+  REG_ICASE
+

+The PCRE_CASELESS option is set when the expression is passed for compilation +to the native function. +

+  REG_NEWLINE
+

+The PCRE_MULTILINE option is set when the expression is passed for compilation +to the native function. Note that this does not mimic the defined POSIX +behaviour for REG_NEWLINE (see the following section). +

+In the absence of these flags, no options are passed to the native function. +This means the the regex is compiled with PCRE default semantics. In +particular, the way it handles newline characters in the subject string is the +Perl way, not the POSIX way. Note that setting PCRE_MULTILINE has only +some of the effects specified for REG_NEWLINE. It does not affect the way +newlines are matched by . (they aren't) or by a negative class such as [^a] +(they are). +

+The yield of regcomp() is zero on success, and non-zero otherwise. The +preg structure is filled in on success, and one member of the structure +is public: re_nsub contains the number of capturing subpatterns in +the regular expression. Various error codes are defined in the header file. +

+
MATCHING NEWLINE CHARACTERS
+

+This area is not simple, because POSIX and Perl take different views of things. +It is not possible to get PCRE to obey POSIX semantics, but then PCRE was never +intended to be a POSIX engine. The following table lists the different +possibilities for matching newline characters in PCRE: +

+                          Default   Change with
+

+  . matches newline          no     PCRE_DOTALL
+  newline matches [^a]       yes    not changeable
+  $ matches \n at end        yes    PCRE_DOLLARENDONLY
+  $ matches \n in middle     no     PCRE_MULTILINE
+  ^ matches \n in middle     no     PCRE_MULTILINE
+

+This is the equivalent table for POSIX: +

+                          Default   Change with
+

+  . matches newline          yes      REG_NEWLINE
+  newline matches [^a]       yes      REG_NEWLINE
+  $ matches \n at end        no       REG_NEWLINE
+  $ matches \n in middle     no       REG_NEWLINE
+  ^ matches \n in middle     no       REG_NEWLINE
+

+PCRE's behaviour is the same as Perl's, except that there is no equivalent for +PCRE_DOLLARENDONLY in Perl. In both PCRE and Perl, there is no way to stop +newline from matching [^a]. +

+The default POSIX newline handling can be obtained by setting PCRE_DOTALL and +PCRE_DOLLARENDONLY, but there is no way to make PCRE behave exactly as for the +REG_NEWLINE action. +

+
MATCHING A PATTERN
+

+The function regexec() is called to match a pre-compiled pattern +preg against a given string, which is terminated by a zero byte, +subject to the options in eflags. These can be: +

+  REG_NOTBOL
+

+The PCRE_NOTBOL option is set when calling the underlying PCRE matching +function. +

+  REG_NOTEOL
+

+The PCRE_NOTEOL option is set when calling the underlying PCRE matching +function. +

+The portion of the string that was matched, and also any captured substrings, +are returned via the pmatch argument, which points to an array of +nmatch structures of type regmatch_t, containing the members +rm_so and rm_eo. These contain the offset to the first character of +each substring and the offset to the first character after the end of each +substring, respectively. The 0th element of the vector relates to the entire +portion of string that was matched; subsequent elements relate to the +capturing subpatterns of the regular expression. Unused entries in the array +have both structure members set to -1. +

+A successful match yields a zero return; various error codes are defined in the +header file, of which REG_NOMATCH is the "expected" failure code. +

+
ERROR MESSAGES
+

+The regerror() function maps a non-zero errorcode from either +regcomp() or regexec() to a printable message. If preg is not +NULL, the error should have arisen from the use of that structure. A message +terminated by a binary zero is placed in errbuf. The length of the +message, including the zero, is limited to errbuf_size. The yield of the +function is the size of buffer needed to hold the whole message. +

+
STORAGE
+

+Compiling a regular expression causes memory to be allocated and associated +with the preg structure. The function regfree() frees all such +memory, after which preg may no longer be used as a compiled expression. +

+
AUTHOR
+

+Philip Hazel <ph10@cam.ac.uk> +
+University Computing Service, +
+Cambridge CB2 3QG, England. +