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Annotation of embedaddon/pcre/pcre_try_flipped.c, revision 1.1

1.1     ! misho       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 */