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   pcrejit    ( 3 )

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SIMPLE USE OF JIT

You have to do two things to make use of the JIT support in the simplest way:

(1) Call pcre_study() with the PCRE_STUDY_JIT_COMPILE option for each compiled pattern, and pass the resulting pcre_extra block to pcre_exec().

(2) Use pcre_free_study() to free the pcre_extra block when it is no longer needed, instead of just freeing it yourself. This ensures that any JIT data is also freed.

For a program that may be linked with pre-8.20 versions of PCRE, you can insert

#ifndef PCRE_STUDY_JIT_COMPILE #define PCRE_STUDY_JIT_COMPILE 0 #endif

so that no option is passed to pcre_study(), and then use something like this to free the study data:

#ifdef PCRE_CONFIG_JIT pcre_free_study(study_ptr); #else pcre_free(study_ptr); #endif

PCRE_STUDY_JIT_COMPILE requests the JIT compiler to generate code for complete matches. If you want to run partial matches using the PCRE_PARTIAL_HARD or PCRE_PARTIAL_SOFT options of pcre_exec(), you should set one or both of the following options in addition to, or instead of, PCRE_STUDY_JIT_COMPILE when you call pcre_study():

PCRE_STUDY_JIT_PARTIAL_HARD_COMPILE PCRE_STUDY_JIT_PARTIAL_SOFT_COMPILE

If using pcre_jit_exec() and supporting a pre-8.32 version of PCRE, you can insert:

#if PCRE_MAJOR >= 8 && PCRE_MINOR >= 32 pcre_jit_exec(...); #else pcre_exec(...) #endif

but as described in the "JIT FAST PATH API" section below this assumes version 8.32 and later are compiled with --enable-jit, which may break.

The JIT compiler generates different optimized code for each of the three modes (normal, soft partial, hard partial). When pcre_exec() is called, the appropriate code is run if it is available. Otherwise, the pattern is matched using interpretive code.

In some circumstances you may need to call additional functions. These are described in the section entitled "Controlling the JIT stack" below.

If JIT support is not available, PCRE_STUDY_JIT_COMPILE etc. are ignored, and no JIT data is created. Otherwise, the compiled pattern is passed to the JIT compiler, which turns it into machine code that executes much faster than the normal interpretive code. When pcre_exec() is passed a pcre_extra block containing a pointer to JIT code of the appropriate mode (normal or hard/soft partial), it obeys that code instead of running the interpreter. The result is identical, but the compiled JIT code runs much faster.

There are some pcre_exec() options that are not supported for JIT execution. There are also some pattern items that JIT cannot handle. Details are given below. In both cases, execution automatically falls back to the interpretive code. If you want to know whether JIT was actually used for a particular match, you should arrange for a JIT callback function to be set up as described in the section entitled "Controlling the JIT stack" below, even if you do not need to supply a non-default JIT stack. Such a callback function is called whenever JIT code is about to be obeyed. If the execution options are not right for JIT execution, the callback function is not obeyed.

If the JIT compiler finds an unsupported item, no JIT data is generated. You can find out if JIT execution is available after studying a pattern by calling pcre_fullinfo() with the PCRE_INFO_JIT option. A result of 1 means that JIT compilation was successful. A result of 0 means that JIT support is not available, or the pattern was not studied with PCRE_STUDY_JIT_COMPILE etc., or the JIT compiler was not able to handle the pattern.

Once a pattern has been studied, with or without JIT, it can be used as many times as you like for matching different subject strings.