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Root/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
6and semantics are as close as possible to those of the Perl 5 language.
7
8 Written by Philip Hazel
9 Copyright (c) 1997-2008 University of Cambridge
10
11-----------------------------------------------------------------------------
12Redistribution and use in source and binary forms, with or without
13modification, 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
26THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
27AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
28IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
29ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
30LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
31CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
32SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
33INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
34CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
35ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
36POSSIBILITY OF SUCH DAMAGE.
37-----------------------------------------------------------------------------
38*/
39
40
41/* This module contains an internal function that tests a compiled pattern to
42see if it was compiled with the opposite endianness. If so, it uses an
43auxiliary local function to flip the appropriate bytes. */
44
45
46#include "pcre_config.h"
47
48#include "pcre_internal.h"
49
50
51/*************************************************
52* Flip bytes in an integer *
53*************************************************/
54
55/* This function is called when the magic number in a regex doesn't match, in
56order to flip its bytes to see if we are dealing with a pattern that was
57compiled on a host of different endianness. If so, this function is used to
58flip other byte values.
59
60Arguments:
61 value the number to flip
62 n the number of bytes to flip (assumed to be 2 or 4)
63
64Returns: the flipped value
65*/
66
67static unsigned long int
68byteflip(unsigned long int value, int n)
69{
70if (n == 2) return ((value & 0x00ff) << 8) | ((value & 0xff00) >> 8);
71return ((value & 0x000000ff) << 24) |
72 ((value & 0x0000ff00) << 8) |
73 ((value & 0x00ff0000) >> 8) |
74 ((value & 0xff000000) >> 24);
75}
76
77
78
79/*************************************************
80* Test for a byte-flipped compiled regex *
81*************************************************/
82
83/* This function is called from pcre_exec(), pcre_dfa_exec(), and also from
84pcre_fullinfo(). Its job is to test whether the regex is byte-flipped - that
85is, it was compiled on a system of opposite endianness. The function is called
86only when the native MAGIC_NUMBER test fails. If the regex is indeed flipped,
87we flip all the relevant values into a different data block, and return it.
88
89Arguments:
90 re points to the regex
91 study points to study data, or NULL
92 internal_re points to a new regex block
93 internal_study points to a new study block
94
95Returns: the new block if is is indeed a byte-flipped regex
96 NULL if it is not
97*/
98
99real_pcre *
100_pcre_try_flipped(const real_pcre *re, real_pcre *internal_re,
101 const pcre_study_data *study, pcre_study_data *internal_study)
102{
103if (byteflip(re->magic_number, sizeof(re->magic_number)) != MAGIC_NUMBER)
104 return NULL;
105
106*internal_re = *re; /* To copy other fields */
107internal_re->size = byteflip(re->size, sizeof(re->size));
108internal_re->options = byteflip(re->options, sizeof(re->options));
109internal_re->flags = (pcre_uint16)byteflip(re->flags, sizeof(re->flags));
110internal_re->top_bracket =
111 (pcre_uint16)byteflip(re->top_bracket, sizeof(re->top_bracket));
112internal_re->top_backref =
113 (pcre_uint16)byteflip(re->top_backref, sizeof(re->top_backref));
114internal_re->first_byte =
115 (pcre_uint16)byteflip(re->first_byte, sizeof(re->first_byte));
116internal_re->req_byte =
117 (pcre_uint16)byteflip(re->req_byte, sizeof(re->req_byte));
118internal_re->name_table_offset =
119 (pcre_uint16)byteflip(re->name_table_offset, sizeof(re->name_table_offset));
120internal_re->name_entry_size =
121 (pcre_uint16)byteflip(re->name_entry_size, sizeof(re->name_entry_size));
122internal_re->name_count =
123 (pcre_uint16)byteflip(re->name_count, sizeof(re->name_count));
124
125if (study != NULL)
126 {
127 *internal_study = *study; /* To copy other fields */
128 internal_study->size = byteflip(study->size, sizeof(study->size));
129 internal_study->options = byteflip(study->options, sizeof(study->options));
130 }
131
132return internal_re;
133}
134
135/* End of pcre_tryflipped.c */

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