glib/pcre/pcre_try_flipped.c

   1 /*************************************************
   2 *      Perl-Compatible Regular Expressions       *
   3 *************************************************/
   4
   5 /* PCRE is a library of functions to support regular expressions whose syntax
   6 and semantics are as close as possible to those of the Perl 5 language.
   7
   8                        Written by Philip Hazel
   9            Copyright (c) 1997-2009 University of Cambridge
  10
  11 -----------------------------------------------------------------------------
  12 Redistribution and use in source and binary forms, with or without
  13 modification, are permitted provided that the following conditions are met:
  14
  15     * Redistributions of source code must retain the above copyright notice,
  16       this list of conditions and the following disclaimer.
  17
  18     * Redistributions in binary form must reproduce the above copyright
  19       notice, this list of conditions and the following disclaimer in the
  20       documentation and/or other materials provided with the distribution.
  21
  22     * Neither the name of the University of Cambridge nor the names of its
  23       contributors may be used to endorse or promote products derived from
  24       this software without specific prior written permission.
  25
  26 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
  27 AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  28 IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  29 ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
  30 LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  31 CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  32 SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  33 INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  34 CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  35 ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  36 POSSIBILITY OF SUCH DAMAGE.
  37 -----------------------------------------------------------------------------
  38 */
  39
  40
  41 /* This module contains an internal function that tests a compiled pattern to
  42 see if it was compiled with the opposite endianness. If so, it uses an
  43 auxiliary local function to flip the appropriate bytes. */
  44
  45
  46 #ifdef HAVE_CONFIG_H
  47 #include "config.h"
  48 #endif
  49
  50 #include "pcre_internal.h"
  51
  52
  53 /*************************************************
  54 *         Flip bytes in an integer               *
  55 *************************************************/
  56
  57 /* This function is called when the magic number in a regex doesn't match, in
  58 order to flip its bytes to see if we are dealing with a pattern that was
  59 compiled on a host of different endianness. If so, this function is used to
  60 flip other byte values.
  61
  62 Arguments:
  63   value        the number to flip
  64   n            the number of bytes to flip (assumed to be 2 or 4)
  65
  66 Returns:       the flipped value
  67 */
  68
  69 static unsigned long int
  70 byteflip(unsigned long int value, int n)
  71 {
  72 if (n == 2) return ((value & 0x00ff) << 8) | ((value & 0xff00) >> 8);
  73 return ((value & 0x000000ff) << 24) |
  74        ((value & 0x0000ff00) <<  8) |
  75        ((value & 0x00ff0000) >>  8) |
  76        ((value & 0xff000000) >> 24);
  77 }
  78
  79
  80
  81 /*************************************************
  82 *       Test for a byte-flipped compiled regex   *
  83 *************************************************/
  84
  85 /* This function is called from pcre_exec(), pcre_dfa_exec(), and also from
  86 pcre_fullinfo(). Its job is to test whether the regex is byte-flipped - that
  87 is, it was compiled on a system of opposite endianness. The function is called
  88 only when the native MAGIC_NUMBER test fails. If the regex is indeed flipped,
  89 we flip all the relevant values into a different data block, and return it.
  90
  91 Arguments:
  92   re               points to the regex
  93   study            points to study data, or NULL
  94   internal_re      points to a new regex block
  95   internal_study   points to a new study block
  96
  97 Returns:           the new block if is is indeed a byte-flipped regex
  98                    NULL if it is not
  99 */
 100
 101 real_pcre *
 102 _pcre_try_flipped(const real_pcre *re, real_pcre *internal_re,
 103   const pcre_study_data *study, pcre_study_data *internal_study)
 104 {
 105 if (byteflip(re->magic_number, sizeof(re->magic_number)) != MAGIC_NUMBER)
 106   return NULL;
 107
 108 *internal_re = *re;           /* To copy other fields */
 109 internal_re->size = byteflip(re->size, sizeof(re->size));
 110 internal_re->options = byteflip(re->options, sizeof(re->options));
 111 internal_re->flags = (pcre_uint16)byteflip(re->flags, sizeof(re->flags));
 112 internal_re->top_bracket =
 113   (pcre_uint16)byteflip(re->top_bracket, sizeof(re->top_bracket));
 114 internal_re->top_backref =
 115   (pcre_uint16)byteflip(re->top_backref, sizeof(re->top_backref));
 116 internal_re->first_byte =
 117   (pcre_uint16)byteflip(re->first_byte, sizeof(re->first_byte));
 118 internal_re->req_byte =
 119   (pcre_uint16)byteflip(re->req_byte, sizeof(re->req_byte));
 120 internal_re->name_table_offset =
 121   (pcre_uint16)byteflip(re->name_table_offset, sizeof(re->name_table_offset));
 122 internal_re->name_entry_size =
 123   (pcre_uint16)byteflip(re->name_entry_size, sizeof(re->name_entry_size));
 124 internal_re->name_count =
 125   (pcre_uint16)byteflip(re->name_count, sizeof(re->name_count));
 126
 127 if (study != NULL)
 128   {
 129   *internal_study = *study;   /* To copy other fields */
 130   internal_study->size = byteflip(study->size, sizeof(study->size));
 131   internal_study->flags = byteflip(study->flags, sizeof(study->flags));
 132   internal_study->minlength = byteflip(study->minlength,
 133     sizeof(study->minlength));
 134   }
 135
 136 return internal_re;
 137 }
 138
 139 /* End of pcre_tryflipped.c */