176 lines
7.5 KiB
Groff
176 lines
7.5 KiB
Groff
.TH PCRE2SERIALIZE 3 "03 November 2015" "PCRE2 10.21"
|
|
.SH NAME
|
|
PCRE2 - Perl-compatible regular expressions (revised API)
|
|
.SH "SAVING AND RE-USING PRECOMPILED PCRE2 PATTERNS"
|
|
.rs
|
|
.sp
|
|
.nf
|
|
.B int32_t pcre2_serialize_decode(pcre2_code **\fIcodes\fP,
|
|
.B " int32_t \fInumber_of_codes\fP, const uint32_t *\fIbytes\fP,"
|
|
.B " pcre2_general_context *\fIgcontext\fP);"
|
|
.sp
|
|
.B int32_t pcre2_serialize_encode(pcre2_code **\fIcodes\fP,
|
|
.B " int32_t \fInumber_of_codes\fP, uint32_t **\fIserialized_bytes\fP,"
|
|
.B " PCRE2_SIZE *\fIserialized_size\fP, pcre2_general_context *\fIgcontext\fP);"
|
|
.sp
|
|
.B void pcre2_serialize_free(uint8_t *\fIbytes\fP);
|
|
.sp
|
|
.B int32_t pcre2_serialize_get_number_of_codes(const uint8_t *\fIbytes\fP);
|
|
.fi
|
|
.sp
|
|
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. However,
|
|
if you are using the just-in-time optimization feature, it is not possible to
|
|
save and reload the JIT data, because it is position-dependent. The host on
|
|
which the patterns are reloaded must be running the same version of PCRE2, with
|
|
the same code unit width, and must also have the same endianness, pointer width
|
|
and PCRE2_SIZE type. For example, patterns compiled on a 32-bit system using
|
|
PCRE2's 16-bit library cannot be reloaded on a 64-bit system, nor can they be
|
|
reloaded using the 8-bit library.
|
|
.
|
|
.
|
|
.SH "SAVING COMPILED PATTERNS"
|
|
.rs
|
|
.sp
|
|
Before compiled patterns can be saved they must be serialized, that is,
|
|
converted to a stream of bytes. A single byte stream may contain any number of
|
|
compiled patterns, but they must all use the same character tables. A single
|
|
copy of the tables is included in the byte stream (its size is 1088 bytes). For
|
|
more details of character tables, see the
|
|
.\" HTML <a href="pcre2api.html#localesupport">
|
|
.\" </a>
|
|
section on locale support
|
|
.\"
|
|
in the
|
|
.\" HREF
|
|
\fBpcre2api\fP
|
|
.\"
|
|
documentation.
|
|
.P
|
|
The function \fBpcre2_serialize_encode()\fP creates a serialized byte stream
|
|
from a list of compiled patterns. Its first two arguments specify the list,
|
|
being a pointer to a vector of pointers to compiled patterns, and the length of
|
|
the vector. The third and fourth arguments point to variables which are set to
|
|
point to the created byte stream and its length, respectively. The final
|
|
argument is a pointer to a general context, which can be used to specify custom
|
|
memory mangagement functions. If this argument is NULL, \fBmalloc()\fP is used
|
|
to obtain memory for the byte stream. The yield of the function is the number
|
|
of serialized patterns, or one of the following negative error codes:
|
|
.sp
|
|
PCRE2_ERROR_BADDATA the number of patterns is zero or less
|
|
PCRE2_ERROR_BADMAGIC mismatch of id bytes in one of the patterns
|
|
PCRE2_ERROR_MEMORY memory allocation failed
|
|
PCRE2_ERROR_MIXEDTABLES the patterns do not all use the same tables
|
|
PCRE2_ERROR_NULL the 1st, 3rd, or 4th argument is NULL
|
|
.sp
|
|
PCRE2_ERROR_BADMAGIC means either that a pattern's code has been corrupted, or
|
|
that a slot in the vector does not point to a compiled pattern.
|
|
.P
|
|
Once a set of patterns has been serialized you can save the data in any
|
|
appropriate manner. Here is sample code that compiles two patterns and writes
|
|
them to a file. It assumes that the variable \fIfd\fP refers to a file that is
|
|
open for output. The error checking that should be present in a real
|
|
application has been omitted for simplicity.
|
|
.sp
|
|
int errorcode;
|
|
uint8_t *bytes;
|
|
PCRE2_SIZE erroroffset;
|
|
PCRE2_SIZE bytescount;
|
|
pcre2_code *list_of_codes[2];
|
|
list_of_codes[0] = pcre2_compile("first pattern",
|
|
PCRE2_ZERO_TERMINATED, 0, &errorcode, &erroroffset, NULL);
|
|
list_of_codes[1] = pcre2_compile("second pattern",
|
|
PCRE2_ZERO_TERMINATED, 0, &errorcode, &erroroffset, NULL);
|
|
errorcode = pcre2_serialize_encode(list_of_codes, 2, &bytes,
|
|
&bytescount, NULL);
|
|
errorcode = fwrite(bytes, 1, bytescount, fd);
|
|
.sp
|
|
Note that the serialized data 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.
|
|
.P
|
|
Serializing a set of patterns leaves the original data untouched, so they can
|
|
still be used for matching. Their memory must eventually be freed in the usual
|
|
way by calling \fBpcre2_code_free()\fP. When you have finished with the byte
|
|
stream, it too must be freed by calling \fBpcre2_serialize_free()\fP.
|
|
.
|
|
.
|
|
.SH "RE-USING PRECOMPILED PATTERNS"
|
|
.rs
|
|
.sp
|
|
In order to re-use a set of saved patterns you must first make the serialized
|
|
byte stream available in main memory (for example, by reading from a file). The
|
|
management of this memory block is up to the application. You can use the
|
|
\fBpcre2_serialize_get_number_of_codes()\fP function to find out how many
|
|
compiled patterns are in the serialized data without actually decoding the
|
|
patterns:
|
|
.sp
|
|
uint8_t *bytes = <serialized data>;
|
|
int32_t number_of_codes = pcre2_serialize_get_number_of_codes(bytes);
|
|
.sp
|
|
The \fBpcre2_serialize_decode()\fP function reads a byte stream and recreates
|
|
the compiled patterns in new memory blocks, setting pointers to them in a
|
|
vector. The first two arguments are a pointer to a suitable vector and its
|
|
length, and the third argument points to a byte stream. The final argument is a
|
|
pointer to a general context, which can be used to specify custom memory
|
|
mangagement functions for the decoded patterns. If this argument is NULL,
|
|
\fBmalloc()\fP and \fBfree()\fP are used. After deserialization, the byte
|
|
stream is no longer needed and can be discarded.
|
|
.sp
|
|
int32_t number_of_codes;
|
|
pcre2_code *list_of_codes[2];
|
|
uint8_t *bytes = <serialized data>;
|
|
int32_t number_of_codes =
|
|
pcre2_serialize_decode(list_of_codes, 2, bytes, NULL);
|
|
.sp
|
|
If the vector is not large enough for all the patterns in the byte stream, it
|
|
is filled with those that fit, and the remainder are ignored. The yield of the
|
|
function is the number of decoded patterns, or one of the following negative
|
|
error codes:
|
|
.sp
|
|
PCRE2_ERROR_BADDATA second argument is zero or less
|
|
PCRE2_ERROR_BADMAGIC mismatch of id bytes in the data
|
|
PCRE2_ERROR_BADMODE mismatch of variable unit size or PCRE2 version
|
|
PCRE2_ERROR_MEMORY memory allocation failed
|
|
PCRE2_ERROR_NULL first or third argument is NULL
|
|
.sp
|
|
PCRE2_ERROR_BADMAGIC may mean that the data is corrupt, or that it was compiled
|
|
on a system with different endianness.
|
|
.P
|
|
Decoded patterns can be used for matching in the usual way, and must be freed
|
|
by calling \fBpcre2_code_free()\fP. However, be aware that there is a potential
|
|
race issue if you are using multiple patterns that were decoded from a single
|
|
byte stream in a multithreaded application. A single copy of the character
|
|
tables is used by all the decoded patterns and a reference count is used to
|
|
arrange for its memory to be automatically freed when the last pattern is
|
|
freed, but there is no locking on this reference count. Therefore, if you want
|
|
to call \fBpcre2_code_free()\fP for these patterns in different threads, you
|
|
must arrange your own locking, and ensure that \fBpcre2_code_free()\fP cannot
|
|
be called by two threads at the same time.
|
|
.P
|
|
If a pattern was processed by \fBpcre2_jit_compile()\fP before being
|
|
serialized, the JIT data is discarded and so is no longer available after a
|
|
save/restore cycle. You can, however, process a restored pattern with
|
|
\fBpcre2_jit_compile()\fP if you wish.
|
|
.
|
|
.
|
|
.
|
|
.SH AUTHOR
|
|
.rs
|
|
.sp
|
|
.nf
|
|
Philip Hazel
|
|
University Computing Service
|
|
Cambridge, England.
|
|
.fi
|
|
.
|
|
.
|
|
.SH REVISION
|
|
.rs
|
|
.sp
|
|
.nf
|
|
Last updated: 03 November 2015
|
|
Copyright (c) 1997-2015 University of Cambridge.
|
|
.fi
|