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+<title>pcreprecompile specification</title>
+<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB">
+<h1>pcreprecompile man page</h1>
+Return to the <a href="index.html">PCRE index page</a>.
+This page is part of the PCRE HTML documentation. It was 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.
+<li><a name="TOC2" href="#SEC2">SAVING A COMPILED PATTERN</a>
+<li><a name="TOC3" href="#SEC3">RE-USING A PRECOMPILED PATTERN</a>
+<li><a name="TOC5" href="#SEC5">AUTHOR</a>
+<li><a name="TOC6" href="#SEC6">REVISION</a>
+If you are running an application that uses a large number of regular
+expression patterns, it may be useful to store them in a precompiled form
+instead of having to compile them every time the application is run.
+If you are not using any private character tables (see the
+<a href="pcre_maketables.html"><b>pcre_maketables()</b></a>
+documentation), this is relatively straightforward. If you are using private
+tables, it is a little bit more complicated. However, if you are using the
+just-in-time optimization feature, it is not possible to save and reload the
+JIT data.
+If you save compiled patterns to a file, you can copy them to a different host
+and run them there. If the two hosts have different endianness (byte order),
+you should run the <b>pcre[16|32]_pattern_to_host_byte_order()</b> function on the
+new host before trying to match the pattern. The matching functions return
+PCRE_ERROR_BADENDIANNESS if they detect a pattern with the wrong endianness.
+Compiling regular expressions with one version of PCRE for use with a different
+version is not guaranteed to work and may cause crashes, and saving and
+restoring a compiled pattern loses any JIT optimization data.
+<br><a name="SEC2" href="#TOC1">SAVING A COMPILED PATTERN</a><br>
+The value returned by <b>pcre[16|32]_compile()</b> points to a single block of
+memory that holds the compiled pattern and associated data. You can find the
+length of this block in bytes by calling <b>pcre[16|32]_fullinfo()</b> with an
+argument of PCRE_INFO_SIZE. You can then save the data in any appropriate
+manner. Here is sample code for the 8-bit library that compiles a pattern and
+writes it to a file. It assumes that the variable <i>fd</i> refers to a file
+that is open for output:
+ int erroroffset, rc, size;
+ char *error;
+ pcre *re;
+ re = pcre_compile("my pattern", 0, &error, &erroroffset, NULL);
+ if (re == NULL) { ... handle errors ... }
+ rc = pcre_fullinfo(re, NULL, PCRE_INFO_SIZE, &size);
+ if (rc &#60; 0) { ... handle errors ... }
+ rc = fwrite(re, 1, size, fd);
+ if (rc != size) { ... handle errors ... }
+In this example, the bytes that comprise the compiled pattern are copied
+exactly. Note that this is binary data that may contain any of the 256 possible
+byte values. On systems that make a distinction between binary and non-binary
+data, be sure that the file is opened for binary output.
+If you want to write more than one pattern to a file, you will have to devise a
+way of separating them. For binary data, preceding each pattern with its length
+is probably the most straightforward approach. Another possibility is to write
+out the data in hexadecimal instead of binary, one pattern to a line.
+Saving compiled patterns in a file is only one possible way of storing them for
+later use. They could equally well be saved in a database, or in the memory of
+some daemon process that passes them via sockets to the processes that want
+If the pattern has been studied, it is also possible to save the normal study
+data in a similar way to the compiled pattern itself. However, if the
+PCRE_STUDY_JIT_COMPILE was used, the just-in-time data that is created cannot
+be saved because it is too dependent on the current environment. When studying
+generates additional information, <b>pcre[16|32]_study()</b> returns a pointer to a
+<b>pcre[16|32]_extra</b> data block. Its format is defined in the
+<a href="pcreapi.html#extradata">section on matching a pattern</a>
+in the
+<a href="pcreapi.html"><b>pcreapi</b></a>
+documentation. The <i>study_data</i> field points to the binary study data, and
+this is what you must save (not the <b>pcre[16|32]_extra</b> block itself). The
+length of the study data can be obtained by calling <b>pcre[16|32]_fullinfo()</b>
+with an argument of PCRE_INFO_STUDYSIZE. Remember to check that
+<b>pcre[16|32]_study()</b> did return a non-NULL value before trying to save the
+study data.
+<br><a name="SEC3" href="#TOC1">RE-USING A PRECOMPILED PATTERN</a><br>
+Re-using a precompiled pattern is straightforward. Having reloaded it into main
+memory, called <b>pcre[16|32]_pattern_to_host_byte_order()</b> if necessary, you
+pass its pointer to <b>pcre[16|32]_exec()</b> or <b>pcre[16|32]_dfa_exec()</b> in
+the usual way.
+However, if you passed a pointer to custom character tables when the pattern
+was compiled (the <i>tableptr</i> argument of <b>pcre[16|32]_compile()</b>), you
+must now pass a similar pointer to <b>pcre[16|32]_exec()</b> or
+<b>pcre[16|32]_dfa_exec()</b>, because the value saved with the compiled pattern
+will obviously be nonsense. A field in a <b>pcre[16|32]_extra()</b> block is used
+to pass this data, as described in the
+<a href="pcreapi.html#extradata">section on matching a pattern</a>
+in the
+<a href="pcreapi.html"><b>pcreapi</b></a>
+<b>Warning:</b> The tables that <b>pcre_exec()</b> and <b>pcre_dfa_exec()</b> use
+must be the same as those that were used when the pattern was compiled. If this
+is not the case, the behaviour is undefined.
+If you did not provide custom character tables when the pattern was compiled,
+the pointer in the compiled pattern is NULL, which causes the matching
+functions to use PCRE's internal tables. Thus, you do not need to take any
+special action at run time in this case.
+If you saved study data with the compiled pattern, you need to create your own
+<b>pcre[16|32]_extra</b> data block and set the <i>study_data</i> field to point
+to the reloaded study data. You must also set the PCRE_EXTRA_STUDY_DATA bit in
+the <i>flags</i> field to indicate that study data is present. Then pass the
+<b>pcre[16|32]_extra</b> block to the matching function in the usual way. If the
+pattern was studied for just-in-time optimization, that data cannot be saved,
+and so is lost by a save/restore cycle.
+In general, it is safest to recompile all saved patterns when you update to a
+new PCRE release, though not all updates actually require this.
+<br><a name="SEC5" href="#TOC1">AUTHOR</a><br>
+Philip Hazel
+University Computing Service
+Cambridge CB2 3QH, England.
+<br><a name="SEC6" href="#TOC1">REVISION</a><br>
+Last updated: 12 November 2013
+Copyright &copy; 1997-2013 University of Cambridge.
+Return to the <a href="index.html">PCRE index page</a>.