pcre_try_flipped.c

Revision 905, 5.3 kB (checked in by alo, 1 year ago)
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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) 1997-2007 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	#include "local_config.h"
47	#include "pcre_internal.h"
48
49
50	/*************************************************
51	* Flip bytes in an integer *
52	*************************************************/
53
54	/* This function is called when the magic number in a regex doesn't match, in
55	order to flip its bytes to see if we are dealing with a pattern that was
56	compiled on a host of different endianness. If so, this function is used to
57	flip other byte values.
58
59	Arguments:
60	value the number to flip
61	n the number of bytes to flip (assumed to be 2 or 4)
62
63	Returns: the flipped value
64	*/
65
66	static unsigned long int
67	byteflip(unsigned long int value, int n)
68	{
69	if (n == 2) return ((value & 0x00ff) << 8) \| ((value & 0xff00) >> 8);
70	return ((value & 0x000000ff) << 24) \|
71	((value & 0x0000ff00) << 8) \|
72	((value & 0x00ff0000) >> 8) \|
73	((value & 0xff000000) >> 24);
74	}
75
76
77
78	/*************************************************
79	* Test for a byte-flipped compiled regex *
80	*************************************************/
81
82	/* This function is called from pcre_exec(), pcre_dfa_exec(), and also from
83	pcre_fullinfo(). Its job is to test whether the regex is byte-flipped - that
84	is, it was compiled on a system of opposite endianness. The function is called
85	only when the native MAGIC_NUMBER test fails. If the regex is indeed flipped,
86	we flip all the relevant values into a different data block, and return it.
87
88	Arguments:
89	re points to the regex
90	study points to study data, or NULL
91	internal_re points to a new regex block
92	internal_study points to a new study block
93
94	Returns: the new block if is is indeed a byte-flipped regex
95	NULL if it is not
96	*/
97
98	real_pcre *
99	_pcre_try_flipped(const real_pcre re, real_pcre internal_re,
100	const pcre_study_data study, pcre_study_data internal_study)
101	{
102	if (byteflip(re->magic_number, sizeof(re->magic_number)) != MAGIC_NUMBER)
103	return NULL;
104
105	internal_re = re; /* To copy other fields */
106	internal_re->size = byteflip(re->size, sizeof(re->size));
107	internal_re->options = byteflip(re->options, sizeof(re->options));
108	internal_re->top_bracket =
109	(pcre_uint16)byteflip(re->top_bracket, sizeof(re->top_bracket));
110	internal_re->top_backref =
111	(pcre_uint16)byteflip(re->top_backref, sizeof(re->top_backref));
112	internal_re->first_byte =
113	(pcre_uint16)byteflip(re->first_byte, sizeof(re->first_byte));
114	internal_re->req_byte =
115	(pcre_uint16)byteflip(re->req_byte, sizeof(re->req_byte));
116	internal_re->name_table_offset =
117	(pcre_uint16)byteflip(re->name_table_offset, sizeof(re->name_table_offset));
118	internal_re->name_entry_size =
119	(pcre_uint16)byteflip(re->name_entry_size, sizeof(re->name_entry_size));
120	internal_re->name_count =
121	(pcre_uint16)byteflip(re->name_count, sizeof(re->name_count));
122
123	if (study != NULL)
124	{
125	internal_study = study; /* To copy other fields */
126	internal_study->size = byteflip(study->size, sizeof(study->size));
127	internal_study->options = byteflip(study->options, sizeof(study->options));
128	}
129
130	return internal_re;
131	}
132
133	/* End of pcre_tryflipped.c */

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