Provided by: libpcre2-dev_10.21-1_amd64 bug


       PCRE2 - Perl-compatible regular expressions (revised API)


       int32_t pcre2_serialize_decode(pcre2_code **codes,
         int32_t number_of_codes, const uint32_t *bytes,
         pcre2_general_context *gcontext);

       int32_t pcre2_serialize_encode(pcre2_code **codes,
         int32_t number_of_codes, uint32_t **serialized_bytes,
         PCRE2_SIZE *serialized_size, pcre2_general_context *gcontext);

       void pcre2_serialize_free(uint8_t *bytes);

       int32_t pcre2_serialize_get_number_of_codes(const uint8_t *bytes);

       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.


       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
       section on locale support in the pcre2api documentation.

       The  function  pcre2_serialize_encode()  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, malloc() 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:

         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

       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.

       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 fd 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.

         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);

       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.

       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
       pcre2_code_free(). When you have finished with the byte stream, it too must  be  freed  by
       calling pcre2_serialize_free().


       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
       pcre2_serialize_get_number_of_codes() function to find out how many compiled patterns  are
       in the serialized data without actually decoding the patterns:

         uint8_t *bytes = <serialized data>;
         int32_t number_of_codes = pcre2_serialize_get_number_of_codes(bytes);

       The  pcre2_serialize_decode()  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, malloc() and free() are used. After deserialization, the byte stream is no longer
       needed and can be discarded.

         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);

       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:

         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

       PCRE2_ERROR_BADMAGIC  may  mean  that  the  data  is corrupt, or that it was compiled on a
       system with different endianness.

       Decoded patterns can be used for matching in the usual way, and must be freed  by  calling
       pcre2_code_free(). 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 pcre2_code_free() for these patterns in different threads, you  must  arrange
       your own locking, and ensure that pcre2_code_free() cannot be called by two threads at the
       same time.

       If a pattern was processed by pcre2_jit_compile() 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 pcre2_jit_compile() if you wish.


       Philip Hazel
       University Computing Service
       Cambridge, England.


       Last updated: 03 November 2015
       Copyright (c) 1997-2015 University of Cambridge.