src/riff.c

   1 /*
   2  * Copyright (C) 2003-2010 The Music Player Daemon Project
   3  * http://www.musicpd.org
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License along
  16  * with this program; if not, write to the Free Software Foundation, Inc.,
  17  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  18  */
  19
  20 #include "config.h" /* must be first for large file support */
  21 #include "riff.h"
  22
  23 #include <glib.h>
  24
  25 #include <stdint.h>
  26 #include <sys/types.h>
  27 #include <sys/stat.h>
  28 #include <unistd.h>
  29 #include <errno.h>
  30 #include <string.h>
  31
  32 #undef G_LOG_DOMAIN
  33 #define G_LOG_DOMAIN "riff"
  34
  35 struct riff_header {
  36         char id[4];
  37         uint32_t size;
  38         char format[4];
  39 };
  40
  41 struct riff_chunk_header {
  42         char id[4];
  43         uint32_t size;
  44 };
  45
  46 size_t
  47 riff_seek_id3(FILE *file)
  48 {
  49         int ret;
  50         struct stat st;
  51         struct riff_header header;
  52         struct riff_chunk_header chunk;
  53         size_t size;
  54
  55         /* determine the file size */
  56
  57         ret = fstat(fileno(file), &st);
  58         if (ret < 0) {
  59                 g_warning("Failed to stat file descriptor: %s",
  60                           strerror(errno));
  61                 return 0;
  62         }
  63
  64         /* seek to the beginning and read the RIFF header */
  65
  66         ret = fseek(file, 0, SEEK_SET);
  67         if (ret != 0) {
  68                 g_warning("Failed to seek: %s", g_strerror(errno));
  69                 return 0;
  70         }
  71
  72         size = fread(&header, sizeof(header), 1, file);
  73         if (size != 1 ||
  74             memcmp(header.id, "RIFF", 4) != 0 ||
  75             GUINT32_FROM_LE(header.size) > (uint32_t)st.st_size)
  76                 /* not a RIFF file */
  77                 return 0;
  78
  79         while (true) {
  80                 /* read the chunk header */
  81
  82                 size = fread(&chunk, sizeof(chunk), 1, file);
  83                 if (size != 1)
  84                         return 0;
  85
  86                 size = GUINT32_FROM_LE(chunk.size);
  87                 if (size > G_MAXINT32)
  88                         /* too dangerous, bail out: possible integer
  89                            underflow when casting to off_t */
  90                         return 0;
  91
  92                 if (size % 2 != 0)
  93                         /* pad byte */
  94                         ++size;
  95
  96                 if (memcmp(chunk.id, "id3 ", 4) == 0)
  97                         /* found it! */
  98                         return size;
  99
 100                 ret = fseek(file, size, SEEK_CUR);
 101                 if (ret != 0)
 102                         return 0;
 103         }
 104 }