modules/stream_filter/skiptags.c

   1 /*****************************************************************************
   2  * skiptags.c:
   3  *****************************************************************************
   4  * Copyright © 2005-2008 VLC authors and VideoLAN
   5  * Copyright © 2016-2017 Rémi Denis-Courmont
   6  *
   7  * This program is free software; you can redistribute it and/or modify it
   8  * under the terms of the GNU Lesser General Public License as published by
   9  * the Free Software Foundation; either version 2.1 of the License, or
  10  * (at your option) any later version.
  11  *
  12  * This program 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
  15  * GNU Lesser General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU Lesser General Public License
  18  * along with this program; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
  20  *****************************************************************************/
  21
  22 #ifdef HAVE_CONFIG_H
  23 # include "config.h"
  24 #endif
  25
  26 #include <limits.h>
  27 #include <stdlib.h>
  28 #include <string.h>
  29
  30 #include <vlc_common.h>
  31 #include <vlc_plugin.h>
  32 #include <vlc_stream.h>
  33 #include <vlc_block.h>
  34
  35 #define MAX_TAGS 16
  36 #define MAX_TAG_SIZE (1<<21)
  37
  38 struct skiptags_sys_t
  39 {
  40     uint64_t header_skip;
  41     /* TODO? also discard trailer tags? */
  42     block_t *p_tags;
  43 };
  44
  45 static struct skiptags_sys_t * skiptags_sys_New(void)
  46 {
  47     struct skiptags_sys_t *sys = malloc(sizeof (*sys));
  48     if(sys)
  49     {
  50         sys->header_skip = 0;
  51         sys->p_tags = NULL;
  52     }
  53     return sys;
  54 }
  55
  56 static void skiptags_sys_Delete(struct skiptags_sys_t *sys)
  57 {
  58     block_ChainRelease(sys->p_tags);
  59     free(sys);
  60 }
  61
  62 static uint_fast32_t SkipID3Tag(stream_t *s)
  63 {
  64     const uint8_t *peek;
  65
  66     /* Get 10-bytes ID3 header */
  67     if (vlc_stream_Peek(s, &peek, 10) < 10)
  68         return 0;
  69     if (memcmp(peek, "ID3", 3))
  70         return 0;
  71
  72     uint_fast8_t version = peek[3];
  73     uint_fast8_t revision = peek[4];
  74     bool has_footer = (peek[5] & 0x10) != 0;
  75     uint_fast32_t size = 10u + (peek[6] << 21) + (peek[7] << 14)
  76                          + (peek[8] << 7) + peek[9] + (has_footer ? 10u : 0u);
  77
  78     /* Skip the entire tag */
  79     msg_Dbg(s, "ID3v2.%"PRIuFAST8" revision %"PRIuFAST8" tag found, "
  80             "skipping %"PRIuFAST32" bytes", version, revision, size);
  81
  82     return size;
  83 }
  84
  85 static uint_fast32_t SkipAPETag(stream_t *s)
  86 {
  87     const uint8_t *peek;
  88
  89     /* Get 32-bytes APE header */
  90     if (vlc_stream_Peek(s, &peek, 32) < 32)
  91         return 0;
  92     if (memcmp(peek, "APETAGEX", 8))
  93         return 0;
  94
  95     uint_fast32_t version = GetDWLE(peek + 8);
  96     if (version != 1000 && version != 2000)
  97         return 0;
  98
  99     uint_fast32_t size = GetDWLE(peek + 12);
 100     if (size > SSIZE_MAX - 32u)
 101         return 0; /* impossibly long tag */
 102
 103     uint_fast32_t flags = GetDWLE(peek + 16);
 104     if ((flags & (1u << 29)) == 0)
 105         return 0;
 106
 107     if (flags & (1u << 30))
 108         size += 32;
 109
 110     msg_Dbg(s, "AP2 v%"PRIuFAST32" tag found, "
 111             "skipping %"PRIuFAST32" bytes", version / 1000, size);
 112     return size;
 113 }
 114
 115 static bool SkipTag(stream_t *s, uint_fast32_t (*skipper)(stream_t *),
 116                     block_t **pp_block, unsigned *pi_tags_count)
 117 {
 118     uint_fast64_t offset = vlc_stream_Tell(s);
 119     uint_fast32_t size = skipper(s);
 120     if(size> 0)
 121     {
 122         /* Skip the entire tag */
 123         ssize_t read;
 124         if(*pi_tags_count < MAX_TAGS && size <= MAX_TAG_SIZE)
 125         {
 126             *pp_block = vlc_stream_Block(s, size);
 127             read = *pp_block ? (ssize_t)(*pp_block)->i_buffer : -1;
 128         }
 129         else
 130         {
 131             read = vlc_stream_Read(s, NULL, size);
 132         }
 133
 134         if(read < (ssize_t)size)
 135         {
 136             block_ChainRelease(*pp_block);
 137             *pp_block = NULL;
 138             if (unlikely(read < 0))
 139             {   /* I/O error, try to restore offset. If it fails, screwed. */
 140                 if (vlc_stream_Seek(s, offset))
 141                     msg_Err(s, "seek failure");
 142                 return false;
 143             }
 144         }
 145         else (*pi_tags_count)++;
 146     }
 147     return size != 0;
 148 }
 149
 150 static ssize_t Read(stream_t *stream, void *buf, size_t buflen)
 151 {
 152     return vlc_stream_Read(stream->s, buf, buflen);
 153 }
 154
 155 static int Seek(stream_t *stream, uint64_t offset)
 156 {
 157     const struct skiptags_sys_t *sys = stream->p_sys;
 158
 159     if (unlikely(offset + sys->header_skip < offset))
 160         return -1;
 161     return vlc_stream_Seek(stream->s, sys->header_skip + offset);
 162 }
 163
 164 static int Control(stream_t *stream, int query, va_list args)
 165 {
 166     const struct skiptags_sys_t *sys = stream->p_sys;
 167
 168     /* In principles, we should return the meta-data embedded in the skipped
 169      * tags in STREAM_GET_META. But the meta engine is devoted to that already.
 170      */
 171     switch (query)
 172     {
 173         case STREAM_GET_TAGS:
 174             if (sys->p_tags == NULL)
 175                 break;
 176             *va_arg(args, const block_t **) = sys->p_tags;
 177             return VLC_SUCCESS;
 178
 179         case STREAM_GET_SIZE:
 180         {
 181             uint64_t size;
 182             int ret = vlc_stream_GetSize(stream->s, &size);
 183             if (ret == VLC_SUCCESS)
 184                 *va_arg(args, uint64_t *) = size - sys->header_skip;
 185             return ret;
 186         }
 187     }
 188
 189     return vlc_stream_vaControl(stream->s, query, args);
 190 }
 191
 192 static int Open(vlc_object_t *obj)
 193 {
 194     stream_t *stream = (stream_t *)obj;
 195     stream_t *s = stream->s;
 196     struct skiptags_sys_t *sys;
 197
 198     block_t *p_tags = NULL, *p_tag = NULL;
 199     unsigned i_tagscount = 0;
 200
 201     while (SkipTag(s, SkipID3Tag, &p_tag, &i_tagscount)||
 202            SkipTag(s, SkipAPETag, &p_tag, &i_tagscount))
 203     {
 204         if(p_tag)
 205         {
 206             p_tag->p_next = p_tags;
 207             p_tags = p_tag;
 208             p_tag = NULL;
 209         }
 210     }
 211
 212     uint_fast64_t offset = vlc_stream_Tell(s);
 213     if (offset == 0 || !(sys = skiptags_sys_New()))
 214     {
 215         block_ChainRelease( p_tags );
 216         return VLC_EGENERIC; /* nothing to do */
 217     }
 218
 219     sys->header_skip = offset;
 220     sys->p_tags = p_tags;
 221     stream->p_sys = sys;
 222     stream->pf_read = Read;
 223     stream->pf_seek = Seek;
 224     stream->pf_control = Control;
 225     return VLC_SUCCESS;
 226 }
 227
 228 static void Close(vlc_object_t *obj)
 229 {
 230     stream_t *stream = (stream_t *)obj;
 231     struct skiptags_sys_t *sys = (struct skiptags_sys_t *) stream->p_sys;
 232
 233     skiptags_sys_Delete(sys);
 234 }
 235
 236 vlc_module_begin()
 237     set_category(CAT_INPUT)
 238     set_subcategory(SUBCAT_INPUT_STREAM_FILTER)
 239     set_capability("stream_filter", 330)
 240
 241     set_description(N_("APE/ID3 tags-skipping filter"))
 242     set_callbacks(Open, Close)
 243 vlc_module_end()