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pcre_try_flipped.c
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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
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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 #define HAVE_CONFIG_H
47 #ifdef HAVE_CONFIG_H
48 #include "config.h"
49 #endif
50 
51 #include "pcre_internal.h"
52 
53 
54 /*************************************************
55 * Flip bytes in an integer *
56 *************************************************/
57 
58 /* This function is called when the magic number in a regex doesn't match, in
59 order to flip its bytes to see if we are dealing with a pattern that was
60 compiled on a host of different endianness. If so, this function is used to
61 flip other byte values.
62 
63 Arguments:
64  value the number to flip
65  n the number of bytes to flip (assumed to be 2 or 4)
66 
67 Returns: the flipped value
68 */
69 
70 static unsigned long int
71 byteflip(unsigned long int value, int n)
72 {
73 if (n == 2) return ((value & 0x00ff) << 8) | ((value & 0xff00) >> 8);
74 return ((value & 0x000000ff) << 24) |
75  ((value & 0x0000ff00) << 8) |
76  ((value & 0x00ff0000) >> 8) |
77  ((value & 0xff000000) >> 24);
78 }
79 
80 
81 
82 /*************************************************
83 * Test for a byte-flipped compiled regex *
84 *************************************************/
85 
86 /* This function is called from pcre_exec(), pcre_dfa_exec(), and also from
87 pcre_fullinfo(). Its job is to test whether the regex is byte-flipped - that
88 is, it was compiled on a system of opposite endianness. The function is called
89 only when the native MAGIC_NUMBER test fails. If the regex is indeed flipped,
90 we flip all the relevant values into a different data block, and return it.
91 
92 Arguments:
93  re points to the regex
94  study points to study data, or NULL
95  internal_re points to a new regex block
96  internal_study points to a new study block
97 
98 Returns: the new block if is is indeed a byte-flipped regex
99  NULL if it is not
100 */
101 
102 real_pcre *
103 _pcre_try_flipped(const real_pcre *re, real_pcre *internal_re,
104  const pcre_study_data *study, pcre_study_data *internal_study)
105 {
106 if (byteflip(re->magic_number, sizeof(re->magic_number)) != MAGIC_NUMBER)
107  return NULL;
108 
109 *internal_re = *re; /* To copy other fields */
110 internal_re->size = byteflip(re->size, sizeof(re->size));
111 internal_re->options = byteflip(re->options, sizeof(re->options));
112 internal_re->flags = (pcre_uint16)byteflip(re->flags, sizeof(re->flags));
113 internal_re->top_bracket =
114  (pcre_uint16)byteflip(re->top_bracket, sizeof(re->top_bracket));
115 internal_re->top_backref =
116  (pcre_uint16)byteflip(re->top_backref, sizeof(re->top_backref));
117 internal_re->first_byte =
118  (pcre_uint16)byteflip(re->first_byte, sizeof(re->first_byte));
119 internal_re->req_byte =
120  (pcre_uint16)byteflip(re->req_byte, sizeof(re->req_byte));
121 internal_re->name_table_offset =
122  (pcre_uint16)byteflip(re->name_table_offset, sizeof(re->name_table_offset));
123 internal_re->name_entry_size =
124  (pcre_uint16)byteflip(re->name_entry_size, sizeof(re->name_entry_size));
125 internal_re->name_count =
126  (pcre_uint16)byteflip(re->name_count, sizeof(re->name_count));
127 
128 if (study != NULL)
129  {
130  *internal_study = *study; /* To copy other fields */
131  internal_study->size = byteflip(study->size, sizeof(study->size));
132  internal_study->flags = byteflip(study->flags, sizeof(study->flags));
133  internal_study->minlength = byteflip(study->minlength,
134  sizeof(study->minlength));
135  }
136 
137 return internal_re;
138 }
139 
140 /* End of pcre_tryflipped.c */