libmpcdec: src/idtag.c Source File

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# idtag.c

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    00001 /*
    00002   Copyright (c) 2005, The Musepack Development Team
    00003   All rights reserved.
    00004
    00005   Redistribution and use in source and binary forms, with or without
    00006   modification, are permitted provided that the following conditions are
    00007   met:
    00008
    00009   * Redistributions of source code must retain the above copyright
    00010   notice, this list of conditions and the following disclaimer.
    00011
    00012   * Redistributions in binary form must reproduce the above
    00013   copyright notice, this list of conditions and the following
    00014   disclaimer in the documentation and/or other materials provided
    00015   with the distribution.
    00016
    00017   * Neither the name of the The Musepack Development Team nor the
    00018   names of its contributors may be used to endorse or promote
    00019   products derived from this software without specific prior
    00020   written permission.
    00021
    00022   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
    00023   "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
    00024   LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
    00025   A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
    00026   OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
    00027   SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
    00028   LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
    00029   DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
    00030   THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
    00031   (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
    00032   OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
    00033 */
    00034
    00038
    00039 #include <mpcdec/mpcdec.h>
    00040 #include <mpcdec/internal.h>
    00041
    00042 mpc_int32_t
    00043 JumpID3v2 (mpc_reader* r) {
    00044     unsigned char  tmp [10];
    00045     mpc_uint32_t   Unsynchronisation;   // ID3v2.4-flag
    00046     mpc_uint32_t   ExtHeaderPresent;    // ID3v2.4-flag
    00047     mpc_uint32_t   ExperimentalFlag;    // ID3v2.4-flag
    00048     mpc_uint32_t   FooterPresent;       // ID3v2.4-flag
    00049     mpc_int32_t    ret;
    00050
    00051     // seek to first byte of mpc data
    00052     if (!r->seek (r->data, 0)) {
    00053         return 0;
    00054     }
    00055
    00056     r->read(r->data, tmp, sizeof(tmp));
    00057
    00058     // check id3-tag
    00059     if ( 0 != memcmp ( tmp, "ID3", 3) )
    00060         return 0;
    00061
    00062     // read flags
    00063     Unsynchronisation = tmp[5] & 0x80;
    00064     ExtHeaderPresent  = tmp[5] & 0x40;
    00065     ExperimentalFlag  = tmp[5] & 0x20;
    00066     FooterPresent     = tmp[5] & 0x10;
    00067
    00068     if ( tmp[5] & 0x0F )
    00069         return -1;              // not (yet???) allowed
    00070     if ( (tmp[6] | tmp[7] | tmp[8] | tmp[9]) & 0x80 )
    00071         return -1;              // not allowed
    00072
    00073     // read HeaderSize (syncsave: 4 * $0xxxxxxx = 28 significant bits)
    00074     ret  = tmp[6] << 21;
    00075     ret += tmp[7] << 14;
    00076     ret += tmp[8] <<  7;
    00077     ret += tmp[9]      ;
    00078     ret += 10;
    00079     if ( FooterPresent )
    00080         ret += 10;
    00081
    00082     return ret;
    00083 }