libavformat/id3v2.c

   1 /*
   2  * ID3v2 header parser
   3  * Copyright (c) 2003 Fabrice Bellard
   4  *
   5  * This file is part of FFmpeg.
   6  *
   7  * FFmpeg is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU Lesser General Public
   9  * License as published by the Free Software Foundation; either
  10  * version 2.1 of the License, or (at your option) any later version.
  11  *
  12  * FFmpeg is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15  * Lesser General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU Lesser General Public
  18  * License along with FFmpeg; if not, write to the Free Software
  19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  20  */
  21
  22 #include "id3v2.h"
  23
  24 int ff_id3v2_match(const uint8_t *buf)
  25 {
  26     return  buf[0] == 'I' &&
  27             buf[1] == 'D' &&
  28             buf[2] == '3' &&
  29             buf[3] != 0xff &&
  30             buf[4] != 0xff &&
  31             (buf[6] & 0x80) == 0 &&
  32             (buf[7] & 0x80) == 0 &&
  33             (buf[8] & 0x80) == 0 &&
  34             (buf[9] & 0x80) == 0;
  35 }
  36
  37 int ff_id3v2_tag_len(const uint8_t * buf)
  38 {
  39     int len = ((buf[6] & 0x7f) << 21) +
  40         ((buf[7] & 0x7f) << 14) +
  41         ((buf[8] & 0x7f) << 7) +
  42         (buf[9] & 0x7f) +
  43         ID3v2_HEADER_SIZE;
  44     if (buf[5] & 0x10)
  45         len += ID3v2_HEADER_SIZE;
  46     return len;
  47 }