@@ -28,10 +29,40 @@ support for one or two .NET and Oniguruma syntax items for requesting some minor changes that give better JavaScript compatibility.
+Starting with release 8.30, it is possible to compile two separate PCRE +libraries: the original, which supports 8-bit character strings (including +UTF-8 strings), and a second library that supports 16-bit character strings +(including UTF-16 strings). The build process allows either one or both to be +built. The majority of the work to make this possible was done by Zoltan +Herczeg. +
++Starting with release 8.32 it is possible to compile a third separate PCRE +library that supports 32-bit character strings (including UTF-32 strings). The +build process allows any combination of the 8-, 16- and 32-bit libraries. The +work to make this possible was done by Christian Persch. +
++The three libraries contain identical sets of functions, except that the names +in the 16-bit library start with pcre16_ instead of pcre_, and the +names in the 32-bit library start with pcre32_ instead of pcre_. To +avoid over-complication and reduce the documentation maintenance load, most of +the documentation describes the 8-bit library, with the differences for the +16-bit and 32-bit libraries described separately in the +pcre16 +and +pcre32 +pages. References to functions or structures of the form pcre[16|32]_xxx +should be read as meaning "pcre_xxx when using the 8-bit library, +pcre16_xxx when using the 16-bit library, or pcre32_xxx when using +the 32-bit library". +
+The current implementation of PCRE corresponds approximately with Perl 5.12, -including support for UTF-8 encoded strings and Unicode general category -properties. However, UTF-8 and Unicode support has to be explicitly enabled; it -is not the default. The Unicode tables correspond to Unicode release 6.0.0. +including support for UTF-8/16/32 encoded strings and Unicode general category +properties. However, UTF-8/16/32 and Unicode support has to be explicitly +enabled; it is not the default. The Unicode tables correspond to Unicode +release 6.3.0.
In addition to the Perl-compatible matching function, PCRE contains an @@ -44,8 +75,8 @@ page.
PCRE is written in C and released as a C library. A number of people have written wrappers and interfaces of various kinds. In particular, Google Inc. -have provided a comprehensive C++ wrapper. This is now included as part of the -PCRE distribution. The +have provided a comprehensive C++ wrapper for the 8-bit library. This is now +included as part of the PCRE distribution. The pcrecpp page has details of this interface. Other people's contributions can be found in the Contrib directory at the primary FTP site, which is: @@ -69,20 +100,57 @@ function makes it possible for a client to discover wh available. The features themselves are described in the pcrebuild page. Documentation about building PCRE for various operating systems can be -found in the README and NON-UNIX-USE files in the source -distribution. +found in the +README +and +NON-AUTOTOOLS_BUILD +files in the source distribution.
-The library contains a number of undocumented internal functions and data +The libraries contains a number of undocumented internal functions and data tables that are used by more than one of the exported external functions, but which are not intended for use by external callers. Their names all begin with -"_pcre_", which hopefully will not provoke any name clashes. In some -environments, it is possible to control which external symbols are exported -when a shared library is built, and in these cases the undocumented symbols are -not exported. +"_pcre_" or "_pcre16_" or "_pcre32_", which hopefully will not provoke any name +clashes. In some environments, it is possible to control which external symbols +are exported when a shared library is built, and in these cases the +undocumented symbols are not exported.
-+If you are using PCRE in a non-UTF application that permits users to supply +arbitrary patterns for compilation, you should be aware of a feature that +allows users to turn on UTF support from within a pattern, provided that PCRE +was built with UTF support. For example, an 8-bit pattern that begins with +"(*UTF8)" or "(*UTF)" turns on UTF-8 mode, which interprets patterns and +subjects as strings of UTF-8 characters instead of individual 8-bit characters. +This causes both the pattern and any data against which it is matched to be +checked for UTF-8 validity. If the data string is very long, such a check might +use sufficiently many resources as to cause your application to lose +performance. +
++One way of guarding against this possibility is to use the +pcre_fullinfo() function to check the compiled pattern's options for UTF. +Alternatively, from release 8.33, you can set the PCRE_NEVER_UTF option at +compile time. This causes an compile time error if a pattern contains a +UTF-setting sequence. +
++If your application is one that supports UTF, be aware that validity checking +can take time. If the same data string is to be matched many times, you can use +the PCRE_NO_UTF[8|16|32]_CHECK option for the second and subsequent matches to +save redundant checks. +
++Another way that performance can be hit is by running a pattern that has a very +large search tree against a string that will never match. Nested unlimited +repeats in a pattern are a common example. PCRE provides some protection +against this: see the PCRE_EXTRA_MATCH_LIMIT feature in the +pcreapi +page. +
+The user documentation for PCRE comprises a number of different sections. In the "man" format, each of these is a separate "man page". In the HTML format, each is a separate page, linked from the index page. In the plain text format, @@ -91,31 +159,33 @@ of searching. The sections are as follows:
pcre this document pcre-config show PCRE installation configuration information + pcre16 details of the 16-bit library + pcre32 details of the 32-bit library pcreapi details of PCRE's native C API - pcrebuild options for building PCRE + pcrebuild building PCRE pcrecallout details of the callout feature pcrecompat discussion of Perl compatibility - pcrecpp details of the C++ wrapper + pcrecpp details of the C++ wrapper for the 8-bit library pcredemo a demonstration C program that uses PCRE - pcregrep description of the pcregrep command + pcregrep description of the pcregrep command (8-bit only) pcrejit discussion of the just-in-time optimization support pcrelimits details of size and other limits pcrematching discussion of the two matching algorithms pcrepartial details of the partial matching facility pcrepattern syntax and semantics of supported regular expressions pcreperform discussion of performance issues - pcreposix the POSIX-compatible C API + pcreposix the POSIX-compatible C API for the 8-bit library pcreprecompile details of saving and re-using precompiled patterns pcresample discussion of the pcredemo program pcrestack discussion of stack usage pcresyntax quick syntax reference pcretest description of the pcretest testing command - pcreunicode discussion of Unicode and UTF-8 support + pcreunicode discussion of Unicode and UTF-8/16/32 supportIn addition, in the "man" and HTML formats, there is a short page for each C library function, listing its arguments and results. -
Philip Hazel
@@ -129,11 +199,11 @@ Putting an actual email address here seems to have bee
taken it away. If you want to email me, use my two initials, followed by the
two digits 10, at the domain cam.ac.uk.
-Last updated: 24 August 2011
+Last updated: 13 May 2013
-Copyright © 1997-2011 University of Cambridge.
+Copyright © 1997-2013 University of Cambridge.
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