src/libFLAC/seekable_stream_decoder.c

   1 /* libFLAC - Free Lossless Audio Codec library
   2  * Copyright (C) 2000,2001,2002,2003,2004  Josh Coalson
   3  *
   4  * Redistribution and use in source and binary forms, with or without
   5  * modification, are permitted provided that the following conditions
   6  * are met:
   7  *
   8  * - Redistributions of source code must retain the above copyright
   9  * notice, this list of conditions and the following disclaimer.
  10  *
  11  * - Redistributions in binary form must reproduce the above copyright
  12  * notice, this list of conditions and the following disclaimer in the
  13  * documentation and/or other materials provided with the distribution.
  14  *
  15  * - Neither the name of the Xiph.org Foundation nor the names of its
  16  * contributors may be used to endorse or promote products derived from
  17  * this software without specific prior written permission.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  20  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  21  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  22  * A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR
  23  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  24  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  25  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  26  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
  27  * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
  28  * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
  29  * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  30  */
  31
  32 #include <stdio.h>
  33 #include <stdlib.h> /* for calloc() */
  34 #include <string.h> /* for memcpy()/memcmp() */
  35 #include "FLAC/assert.h"
  36 #include "protected/seekable_stream_decoder.h"
  37 #include "protected/stream_decoder.h"
  38 #include "private/md5.h"
  39
  40 /***********************************************************************
  41  *
  42  * Private class method prototypes
  43  *
  44  ***********************************************************************/
  45
  46 static void set_defaults_(FLAC__SeekableStreamDecoder *decoder);
  47 static FLAC__StreamDecoderReadStatus read_callback_(const FLAC__StreamDecoder *decoder, FLAC__byte buffer[], unsigned *bytes, void *client_data);
  48 static FLAC__StreamDecoderWriteStatus write_callback_(const FLAC__StreamDecoder *decoder, const FLAC__Frame *frame, const FLAC__int32 * const buffer[], void *client_data);
  49 static void metadata_callback_(const FLAC__StreamDecoder *decoder, const FLAC__StreamMetadata *metadata, void *client_data);
  50 static void error_callback_(const FLAC__StreamDecoder *decoder, FLAC__StreamDecoderErrorStatus status, void *client_data);
  51 static FLAC__bool seek_to_absolute_sample_(FLAC__SeekableStreamDecoder *decoder, FLAC__uint64 stream_length, FLAC__uint64 target_sample);
  52
  53 /***********************************************************************
  54  *
  55  * Private class data
  56  *
  57  ***********************************************************************/
  58
  59 typedef struct FLAC__SeekableStreamDecoderPrivate {
  60         FLAC__SeekableStreamDecoderReadCallback read_callback;
  61         FLAC__SeekableStreamDecoderSeekCallback seek_callback;
  62         FLAC__SeekableStreamDecoderTellCallback tell_callback;
  63         FLAC__SeekableStreamDecoderLengthCallback length_callback;
  64         FLAC__SeekableStreamDecoderEofCallback eof_callback;
  65         FLAC__SeekableStreamDecoderWriteCallback write_callback;
  66         FLAC__SeekableStreamDecoderMetadataCallback metadata_callback;
  67         FLAC__SeekableStreamDecoderErrorCallback error_callback;
  68         void *client_data;
  69         FLAC__StreamDecoder *stream_decoder;
  70         FLAC__bool do_md5_checking; /* initially gets protected_->md5_checking but is turned off after a seek */
  71         struct MD5Context md5context;
  72         FLAC__byte stored_md5sum[16]; /* this is what is stored in the metadata */
  73         FLAC__byte computed_md5sum[16]; /* this is the sum we computed from the decoded data */
  74         /* the rest of these are only used for seeking: */
  75         FLAC__StreamMetadata_StreamInfo stream_info; /* we keep this around so we can figure out how to seek quickly */
  76         const FLAC__StreamMetadata_SeekTable *seek_table; /* we hold a pointer to the stream decoder's seek table for the same reason */
  77         /* Since we always want to see the STREAMINFO and SEEK_TABLE blocks at this level, we need some extra flags to keep track of whether they should be passed on up through the metadata_callback */
  78         FLAC__bool ignore_stream_info_block;
  79         FLAC__bool ignore_seek_table_block;
  80         FLAC__Frame last_frame; /* holds the info of the last frame we seeked to */
  81         FLAC__uint64 target_sample;
  82 } FLAC__SeekableStreamDecoderPrivate;
  83
  84 /***********************************************************************
  85  *
  86  * Public static class data
  87  *
  88  ***********************************************************************/
  89
  90 FLAC_API const char * const FLAC__SeekableStreamDecoderStateString[] = {
  91         "FLAC__SEEKABLE_STREAM_DECODER_OK",
  92         "FLAC__SEEKABLE_STREAM_DECODER_SEEKING",
  93         "FLAC__SEEKABLE_STREAM_DECODER_END_OF_STREAM",
  94         "FLAC__SEEKABLE_STREAM_DECODER_MEMORY_ALLOCATION_ERROR",
  95         "FLAC__SEEKABLE_STREAM_DECODER_STREAM_DECODER_ERROR",
  96         "FLAC__SEEKABLE_STREAM_DECODER_READ_ERROR",
  97         "FLAC__SEEKABLE_STREAM_DECODER_SEEK_ERROR",
  98         "FLAC__SEEKABLE_STREAM_DECODER_ALREADY_INITIALIZED",
  99         "FLAC__SEEKABLE_STREAM_DECODER_INVALID_CALLBACK",
 100         "FLAC__SEEKABLE_STREAM_DECODER_UNINITIALIZED"
 101 };
 102
 103 FLAC_API const char * const FLAC__SeekableStreamDecoderReadStatusString[] = {
 104         "FLAC__SEEKABLE_STREAM_DECODER_READ_STATUS_OK",
 105         "FLAC__SEEKABLE_STREAM_DECODER_READ_STATUS_ERROR"
 106 };
 107
 108 FLAC_API const char * const FLAC__SeekableStreamDecoderSeekStatusString[] = {
 109         "FLAC__SEEKABLE_STREAM_DECODER_SEEK_STATUS_OK",
 110         "FLAC__SEEKABLE_STREAM_DECODER_SEEK_STATUS_ERROR"
 111 };
 112
 113 FLAC_API const char * const FLAC__SeekableStreamDecoderTellStatusString[] = {
 114         "FLAC__SEEKABLE_STREAM_DECODER_TELL_STATUS_OK",
 115         "FLAC__SEEKABLE_STREAM_DECODER_TELL_STATUS_ERROR"
 116 };
 117
 118 FLAC_API const char * const FLAC__SeekableStreamDecoderLengthStatusString[] = {
 119         "FLAC__SEEKABLE_STREAM_DECODER_LENGTH_STATUS_OK",
 120         "FLAC__SEEKABLE_STREAM_DECODER_LENGTH_STATUS_ERROR"
 121 };
 122
 123
 124 /***********************************************************************
 125  *
 126  * Class constructor/destructor
 127  *
 128  ***********************************************************************/
 129
 130 FLAC_API FLAC__SeekableStreamDecoder *FLAC__seekable_stream_decoder_new()
 131 {
 132         FLAC__SeekableStreamDecoder *decoder;
 133
 134         FLAC__ASSERT(sizeof(int) >= 4); /* we want to die right away if this is not true */
 135
 136         decoder = (FLAC__SeekableStreamDecoder*)calloc(1, sizeof(FLAC__SeekableStreamDecoder));
 137         if(decoder == 0) {
 138                 return 0;
 139         }
 140
 141         decoder->protected_ = (FLAC__SeekableStreamDecoderProtected*)calloc(1, sizeof(FLAC__SeekableStreamDecoderProtected));
 142         if(decoder->protected_ == 0) {
 143                 free(decoder);
 144                 return 0;
 145         }
 146
 147         decoder->private_ = (FLAC__SeekableStreamDecoderPrivate*)calloc(1, sizeof(FLAC__SeekableStreamDecoderPrivate));
 148         if(decoder->private_ == 0) {
 149                 free(decoder->protected_);
 150                 free(decoder);
 151                 return 0;
 152         }
 153
 154         decoder->private_->stream_decoder = FLAC__stream_decoder_new();
 155         if(0 == decoder->private_->stream_decoder) {
 156                 free(decoder->private_);
 157                 free(decoder->protected_);
 158                 free(decoder);
 159                 return 0;
 160         }
 161
 162         set_defaults_(decoder);
 163
 164         decoder->protected_->state = FLAC__SEEKABLE_STREAM_DECODER_UNINITIALIZED;
 165
 166         return decoder;
 167 }
 168
 169 FLAC_API void FLAC__seekable_stream_decoder_delete(FLAC__SeekableStreamDecoder *decoder)
 170 {
 171         FLAC__ASSERT(0 != decoder);
 172         FLAC__ASSERT(0 != decoder->protected_);
 173         FLAC__ASSERT(0 != decoder->private_);
 174         FLAC__ASSERT(0 != decoder->private_->stream_decoder);
 175
 176         (void)FLAC__seekable_stream_decoder_finish(decoder);
 177
 178         FLAC__stream_decoder_delete(decoder->private_->stream_decoder);
 179
 180         free(decoder->private_);
 181         free(decoder->protected_);
 182         free(decoder);
 183 }
 184
 185 /***********************************************************************
 186  *
 187  * Public class methods
 188  *
 189  ***********************************************************************/
 190
 191 FLAC_API FLAC__SeekableStreamDecoderState FLAC__seekable_stream_decoder_init(FLAC__SeekableStreamDecoder *decoder)
 192 {
 193         FLAC__ASSERT(0 != decoder);
 194
 195         if(decoder->protected_->state != FLAC__SEEKABLE_STREAM_DECODER_UNINITIALIZED)
 196                 return decoder->protected_->state = FLAC__SEEKABLE_STREAM_DECODER_ALREADY_INITIALIZED;
 197
 198         if(0 == decoder->private_->read_callback || 0 == decoder->private_->seek_callback || 0 == decoder->private_->tell_callback || 0 == decoder->private_->length_callback || 0 == decoder->private_->eof_callback)
 199                 return decoder->protected_->state = FLAC__SEEKABLE_STREAM_DECODER_INVALID_CALLBACK;
 200
 201         if(0 == decoder->private_->write_callback || 0 == decoder->private_->metadata_callback || 0 == decoder->private_->error_callback)
 202                 return decoder->protected_->state = FLAC__SEEKABLE_STREAM_DECODER_INVALID_CALLBACK;
 203
 204         decoder->private_->seek_table = 0;
 205
 206         decoder->private_->do_md5_checking = decoder->protected_->md5_checking;
 207
 208         /* We initialize the MD5Context even though we may never use it.  This is
 209          * because md5 checking may be turned on to start and then turned off if a
 210          * seek occurs.  So we always init the context here and finalize it in
 211          * FLAC__seekable_stream_decoder_finish() to make sure things are always
 212          * cleaned up properly.
 213          */
 214         MD5Init(&decoder->private_->md5context);
 215
 216         FLAC__stream_decoder_set_read_callback(decoder->private_->stream_decoder, read_callback_);
 217         FLAC__stream_decoder_set_write_callback(decoder->private_->stream_decoder, write_callback_);
 218         FLAC__stream_decoder_set_metadata_callback(decoder->private_->stream_decoder, metadata_callback_);
 219         FLAC__stream_decoder_set_error_callback(decoder->private_->stream_decoder, error_callback_);
 220         FLAC__stream_decoder_set_client_data(decoder->private_->stream_decoder, decoder);
 221
 222         /* We always want to see these blocks.  Whether or not we pass them up
 223          * through the metadata callback will be determined by flags set in our
 224          * implementation of ..._set_metadata_respond/ignore...()
 225          */
 226         FLAC__stream_decoder_set_metadata_respond(decoder->private_->stream_decoder, FLAC__METADATA_TYPE_STREAMINFO);
 227         FLAC__stream_decoder_set_metadata_respond(decoder->private_->stream_decoder, FLAC__METADATA_TYPE_SEEKTABLE);
 228
 229         if(FLAC__stream_decoder_init(decoder->private_->stream_decoder) != FLAC__STREAM_DECODER_SEARCH_FOR_METADATA)
 230                 return decoder->protected_->state = FLAC__SEEKABLE_STREAM_DECODER_STREAM_DECODER_ERROR;
 231
 232         return decoder->protected_->state = FLAC__SEEKABLE_STREAM_DECODER_OK;
 233 }
 234
 235 FLAC_API FLAC__bool FLAC__seekable_stream_decoder_finish(FLAC__SeekableStreamDecoder *decoder)
 236 {
 237         FLAC__bool md5_failed = false;
 238
 239         FLAC__ASSERT(0 != decoder);
 240         FLAC__ASSERT(0 != decoder->private_);
 241         FLAC__ASSERT(0 != decoder->protected_);
 242
 243         if(decoder->protected_->state == FLAC__SEEKABLE_STREAM_DECODER_UNINITIALIZED)
 244                 return true;
 245
 246         FLAC__ASSERT(0 != decoder->private_->stream_decoder);
 247
 248         /* see the comment in FLAC__seekable_stream_decoder_init() as to why we
 249          * always call MD5Final()
 250          */
 251         MD5Final(decoder->private_->computed_md5sum, &decoder->private_->md5context);
 252
 253         FLAC__stream_decoder_finish(decoder->private_->stream_decoder);
 254
 255         if(decoder->private_->do_md5_checking) {
 256                 if(memcmp(decoder->private_->stored_md5sum, decoder->private_->computed_md5sum, 16))
 257                         md5_failed = true;
 258         }
 259
 260         set_defaults_(decoder);
 261
 262         decoder->protected_->state = FLAC__SEEKABLE_STREAM_DECODER_UNINITIALIZED;
 263
 264         return !md5_failed;
 265 }
 266
 267 FLAC_API FLAC__bool FLAC__seekable_stream_decoder_set_md5_checking(FLAC__SeekableStreamDecoder *decoder, FLAC__bool value)
 268 {
 269         FLAC__ASSERT(0 != decoder);
 270         FLAC__ASSERT(0 != decoder->protected_);
 271         if(decoder->protected_->state != FLAC__SEEKABLE_STREAM_DECODER_UNINITIALIZED)
 272                 return false;
 273         decoder->protected_->md5_checking = value;
 274         return true;
 275 }
 276
 277 FLAC_API FLAC__bool FLAC__seekable_stream_decoder_set_read_callback(FLAC__SeekableStreamDecoder *decoder, FLAC__SeekableStreamDecoderReadCallback value)
 278 {
 279         FLAC__ASSERT(0 != decoder);
 280         FLAC__ASSERT(0 != decoder->private_);
 281         FLAC__ASSERT(0 != decoder->protected_);
 282         if(decoder->protected_->state != FLAC__SEEKABLE_STREAM_DECODER_UNINITIALIZED)
 283                 return false;
 284         decoder->private_->read_callback = value;
 285         return true;
 286 }
 287
 288 FLAC_API FLAC__bool FLAC__seekable_stream_decoder_set_seek_callback(FLAC__SeekableStreamDecoder *decoder, FLAC__SeekableStreamDecoderSeekCallback value)
 289 {
 290         FLAC__ASSERT(0 != decoder);
 291         FLAC__ASSERT(0 != decoder->private_);
 292         FLAC__ASSERT(0 != decoder->protected_);
 293         if(decoder->protected_->state != FLAC__SEEKABLE_STREAM_DECODER_UNINITIALIZED)
 294                 return false;
 295         decoder->private_->seek_callback = value;
 296         return true;
 297 }
 298
 299 FLAC_API FLAC__bool FLAC__seekable_stream_decoder_set_tell_callback(FLAC__SeekableStreamDecoder *decoder, FLAC__SeekableStreamDecoderTellCallback value)
 300 {
 301         FLAC__ASSERT(0 != decoder);
 302         FLAC__ASSERT(0 != decoder->private_);
 303         FLAC__ASSERT(0 != decoder->protected_);
 304         if(decoder->protected_->state != FLAC__SEEKABLE_STREAM_DECODER_UNINITIALIZED)
 305                 return false;
 306         decoder->private_->tell_callback = value;
 307         return true;
 308 }
 309
 310 FLAC_API FLAC__bool FLAC__seekable_stream_decoder_set_length_callback(FLAC__SeekableStreamDecoder *decoder, FLAC__SeekableStreamDecoderLengthCallback value)
 311 {
 312         FLAC__ASSERT(0 != decoder);
 313         FLAC__ASSERT(0 != decoder->private_);
 314         FLAC__ASSERT(0 != decoder->protected_);
 315         if(decoder->protected_->state != FLAC__SEEKABLE_STREAM_DECODER_UNINITIALIZED)
 316                 return false;
 317         decoder->private_->length_callback = value;
 318         return true;
 319 }
 320
 321 FLAC_API FLAC__bool FLAC__seekable_stream_decoder_set_eof_callback(FLAC__SeekableStreamDecoder *decoder, FLAC__SeekableStreamDecoderEofCallback value)
 322 {
 323         FLAC__ASSERT(0 != decoder);
 324         FLAC__ASSERT(0 != decoder->private_);
 325         FLAC__ASSERT(0 != decoder->protected_);
 326         if(decoder->protected_->state != FLAC__SEEKABLE_STREAM_DECODER_UNINITIALIZED)
 327                 return false;
 328         decoder->private_->eof_callback = value;
 329         return true;
 330 }
 331
 332 FLAC_API FLAC__bool FLAC__seekable_stream_decoder_set_write_callback(FLAC__SeekableStreamDecoder *decoder, FLAC__SeekableStreamDecoderWriteCallback value)
 333 {
 334         FLAC__ASSERT(0 != decoder);
 335         FLAC__ASSERT(0 != decoder->private_);
 336         FLAC__ASSERT(0 != decoder->protected_);
 337         if(decoder->protected_->state != FLAC__SEEKABLE_STREAM_DECODER_UNINITIALIZED)
 338                 return false;
 339         decoder->private_->write_callback = value;
 340         return true;
 341 }
 342
 343 FLAC_API FLAC__bool FLAC__seekable_stream_decoder_set_metadata_callback(FLAC__SeekableStreamDecoder *decoder, FLAC__SeekableStreamDecoderMetadataCallback value)
 344 {
 345         FLAC__ASSERT(0 != decoder);
 346         FLAC__ASSERT(0 != decoder->private_);
 347         FLAC__ASSERT(0 != decoder->protected_);
 348         if(decoder->protected_->state != FLAC__SEEKABLE_STREAM_DECODER_UNINITIALIZED)
 349                 return false;
 350         decoder->private_->metadata_callback = value;
 351         return true;
 352 }
 353
 354 FLAC_API FLAC__bool FLAC__seekable_stream_decoder_set_error_callback(FLAC__SeekableStreamDecoder *decoder, FLAC__SeekableStreamDecoderErrorCallback value)
 355 {
 356         FLAC__ASSERT(0 != decoder);
 357         FLAC__ASSERT(0 != decoder->private_);
 358         FLAC__ASSERT(0 != decoder->protected_);
 359         if(decoder->protected_->state != FLAC__SEEKABLE_STREAM_DECODER_UNINITIALIZED)
 360                 return false;
 361         decoder->private_->error_callback = value;
 362         return true;
 363 }
 364
 365 FLAC_API FLAC__bool FLAC__seekable_stream_decoder_set_client_data(FLAC__SeekableStreamDecoder *decoder, void *value)
 366 {
 367         FLAC__ASSERT(0 != decoder);
 368         FLAC__ASSERT(0 != decoder->private_);
 369         FLAC__ASSERT(0 != decoder->protected_);
 370         if(decoder->protected_->state != FLAC__SEEKABLE_STREAM_DECODER_UNINITIALIZED)
 371                 return false;
 372         decoder->private_->client_data = value;
 373         return true;
 374 }
 375
 376 FLAC_API FLAC__bool FLAC__seekable_stream_decoder_set_metadata_respond(FLAC__SeekableStreamDecoder *decoder, FLAC__MetadataType type)
 377 {
 378         FLAC__ASSERT(0 != decoder);
 379         FLAC__ASSERT(0 != decoder->private_);
 380         FLAC__ASSERT(0 != decoder->protected_);
 381         FLAC__ASSERT(0 != decoder->private_->stream_decoder);
 382         if(decoder->protected_->state != FLAC__SEEKABLE_STREAM_DECODER_UNINITIALIZED)
 383                 return false;
 384         if(type == FLAC__METADATA_TYPE_STREAMINFO)
 385                 decoder->private_->ignore_stream_info_block = false;
 386         else if(type == FLAC__METADATA_TYPE_SEEKTABLE)
 387                 decoder->private_->ignore_seek_table_block = false;
 388         return FLAC__stream_decoder_set_metadata_respond(decoder->private_->stream_decoder, type);
 389 }
 390
 391 FLAC_API FLAC__bool FLAC__seekable_stream_decoder_set_metadata_respond_application(FLAC__SeekableStreamDecoder *decoder, const FLAC__byte id[4])
 392 {
 393         FLAC__ASSERT(0 != decoder);
 394         FLAC__ASSERT(0 != decoder->private_);
 395         FLAC__ASSERT(0 != decoder->protected_);
 396         FLAC__ASSERT(0 != decoder->private_->stream_decoder);
 397         if(decoder->protected_->state != FLAC__SEEKABLE_STREAM_DECODER_UNINITIALIZED)
 398                 return false;
 399         return FLAC__stream_decoder_set_metadata_respond_application(decoder->private_->stream_decoder, id);
 400 }
 401
 402 FLAC_API FLAC__bool FLAC__seekable_stream_decoder_set_metadata_respond_all(FLAC__SeekableStreamDecoder *decoder)
 403 {
 404         FLAC__ASSERT(0 != decoder);
 405         FLAC__ASSERT(0 != decoder->private_);
 406         FLAC__ASSERT(0 != decoder->protected_);
 407         FLAC__ASSERT(0 != decoder->private_->stream_decoder);
 408         if(decoder->protected_->state != FLAC__SEEKABLE_STREAM_DECODER_UNINITIALIZED)
 409                 return false;
 410         decoder->private_->ignore_stream_info_block = false;
 411         decoder->private_->ignore_seek_table_block = false;
 412         return FLAC__stream_decoder_set_metadata_respond_all(decoder->private_->stream_decoder);
 413 }
 414
 415 FLAC_API FLAC__bool FLAC__seekable_stream_decoder_set_metadata_ignore(FLAC__SeekableStreamDecoder *decoder, FLAC__MetadataType type)
 416 {
 417         FLAC__ASSERT(0 != decoder);
 418         FLAC__ASSERT(0 != decoder->private_);
 419         FLAC__ASSERT(0 != decoder->protected_);
 420         FLAC__ASSERT(0 != decoder->private_->stream_decoder);
 421         if(decoder->protected_->state != FLAC__SEEKABLE_STREAM_DECODER_UNINITIALIZED)
 422                 return false;
 423         if(type == FLAC__METADATA_TYPE_STREAMINFO)
 424                 decoder->private_->ignore_stream_info_block = true;
 425         else if(type == FLAC__METADATA_TYPE_SEEKTABLE)
 426                 decoder->private_->ignore_seek_table_block = true;
 427         return FLAC__stream_decoder_set_metadata_ignore(decoder->private_->stream_decoder, type);
 428 }
 429
 430 FLAC_API FLAC__bool FLAC__seekable_stream_decoder_set_metadata_ignore_application(FLAC__SeekableStreamDecoder *decoder, const FLAC__byte id[4])
 431 {
 432         FLAC__ASSERT(0 != decoder);
 433         FLAC__ASSERT(0 != decoder->private_);
 434         FLAC__ASSERT(0 != decoder->protected_);
 435         FLAC__ASSERT(0 != decoder->private_->stream_decoder);
 436         if(decoder->protected_->state != FLAC__SEEKABLE_STREAM_DECODER_UNINITIALIZED)
 437                 return false;
 438         return FLAC__stream_decoder_set_metadata_ignore_application(decoder->private_->stream_decoder, id);
 439 }
 440
 441 FLAC_API FLAC__bool FLAC__seekable_stream_decoder_set_metadata_ignore_all(FLAC__SeekableStreamDecoder *decoder)
 442 {
 443         FLAC__ASSERT(0 != decoder);
 444         FLAC__ASSERT(0 != decoder->private_);
 445         FLAC__ASSERT(0 != decoder->protected_);
 446         FLAC__ASSERT(0 != decoder->private_->stream_decoder);
 447         if(decoder->protected_->state != FLAC__SEEKABLE_STREAM_DECODER_UNINITIALIZED)
 448                 return false;
 449         decoder->private_->ignore_stream_info_block = true;
 450         decoder->private_->ignore_seek_table_block = true;
 451         return FLAC__stream_decoder_set_metadata_ignore_all(decoder->private_->stream_decoder);
 452 }
 453
 454 FLAC_API FLAC__SeekableStreamDecoderState FLAC__seekable_stream_decoder_get_state(const FLAC__SeekableStreamDecoder *decoder)
 455 {
 456         FLAC__ASSERT(0 != decoder);
 457         FLAC__ASSERT(0 != decoder->protected_);
 458         return decoder->protected_->state;
 459 }
 460
 461 FLAC_API FLAC__StreamDecoderState FLAC__seekable_stream_decoder_get_stream_decoder_state(const FLAC__SeekableStreamDecoder *decoder)
 462 {
 463         FLAC__ASSERT(0 != decoder);
 464         FLAC__ASSERT(0 != decoder->private_);
 465         return FLAC__stream_decoder_get_state(decoder->private_->stream_decoder);
 466 }
 467
 468 FLAC_API const char *FLAC__seekable_stream_decoder_get_resolved_state_string(const FLAC__SeekableStreamDecoder *decoder)
 469 {
 470         if(decoder->protected_->state != FLAC__SEEKABLE_STREAM_DECODER_STREAM_DECODER_ERROR)
 471                 return FLAC__SeekableStreamDecoderStateString[decoder->protected_->state];
 472         else
 473                 return FLAC__stream_decoder_get_resolved_state_string(decoder->private_->stream_decoder);
 474 }
 475
 476 FLAC_API FLAC__bool FLAC__seekable_stream_decoder_get_md5_checking(const FLAC__SeekableStreamDecoder *decoder)
 477 {
 478         FLAC__ASSERT(0 != decoder);
 479         FLAC__ASSERT(0 != decoder->protected_);
 480         return decoder->protected_->md5_checking;
 481 }
 482
 483 FLAC_API unsigned FLAC__seekable_stream_decoder_get_channels(const FLAC__SeekableStreamDecoder *decoder)
 484 {
 485         FLAC__ASSERT(0 != decoder);
 486         FLAC__ASSERT(0 != decoder->private_);
 487         return FLAC__stream_decoder_get_channels(decoder->private_->stream_decoder);
 488 }
 489
 490 FLAC_API FLAC__ChannelAssignment FLAC__seekable_stream_decoder_get_channel_assignment(const FLAC__SeekableStreamDecoder *decoder)
 491 {
 492         FLAC__ASSERT(0 != decoder);
 493         FLAC__ASSERT(0 != decoder->private_);
 494         return FLAC__stream_decoder_get_channel_assignment(decoder->private_->stream_decoder);
 495 }
 496
 497 FLAC_API unsigned FLAC__seekable_stream_decoder_get_bits_per_sample(const FLAC__SeekableStreamDecoder *decoder)
 498 {
 499         FLAC__ASSERT(0 != decoder);
 500         FLAC__ASSERT(0 != decoder->private_);
 501         return FLAC__stream_decoder_get_bits_per_sample(decoder->private_->stream_decoder);
 502 }
 503
 504 FLAC_API unsigned FLAC__seekable_stream_decoder_get_sample_rate(const FLAC__SeekableStreamDecoder *decoder)
 505 {
 506         FLAC__ASSERT(0 != decoder);
 507         FLAC__ASSERT(0 != decoder->private_);
 508         return FLAC__stream_decoder_get_sample_rate(decoder->private_->stream_decoder);
 509 }
 510
 511 FLAC_API unsigned FLAC__seekable_stream_decoder_get_blocksize(const FLAC__SeekableStreamDecoder *decoder)
 512 {
 513         FLAC__ASSERT(0 != decoder);
 514         FLAC__ASSERT(0 != decoder->private_);
 515         return FLAC__stream_decoder_get_blocksize(decoder->private_->stream_decoder);
 516 }
 517
 518 FLAC_API FLAC__bool FLAC__seekable_stream_decoder_get_decode_position(const FLAC__SeekableStreamDecoder *decoder, FLAC__uint64 *position)
 519 {
 520         FLAC__ASSERT(0 != decoder);
 521         FLAC__ASSERT(0 != decoder->private_);
 522         FLAC__ASSERT(0 != position);
 523
 524         if(decoder->private_->tell_callback(decoder, position, decoder->private_->client_data) != FLAC__SEEKABLE_STREAM_DECODER_TELL_STATUS_OK)
 525                 return false;
 526         FLAC__ASSERT(*position >= FLAC__stream_decoder_get_input_bytes_unconsumed(decoder->private_->stream_decoder));
 527         *position -= FLAC__stream_decoder_get_input_bytes_unconsumed(decoder->private_->stream_decoder);
 528         return true;
 529 }
 530
 531 FLAC_API FLAC__bool FLAC__seekable_stream_decoder_flush(FLAC__SeekableStreamDecoder *decoder)
 532 {
 533         FLAC__ASSERT(0 != decoder);
 534         FLAC__ASSERT(0 != decoder->private_);
 535         FLAC__ASSERT(0 != decoder->protected_);
 536
 537         decoder->private_->do_md5_checking = false;
 538
 539         if(!FLAC__stream_decoder_flush(decoder->private_->stream_decoder)) {
 540                 decoder->protected_->state = FLAC__SEEKABLE_STREAM_DECODER_STREAM_DECODER_ERROR;
 541                 return false;
 542         }
 543
 544         decoder->protected_->state = FLAC__SEEKABLE_STREAM_DECODER_OK;
 545
 546         return true;
 547 }
 548
 549 FLAC_API FLAC__bool FLAC__seekable_stream_decoder_reset(FLAC__SeekableStreamDecoder *decoder)
 550 {
 551         FLAC__ASSERT(0 != decoder);
 552         FLAC__ASSERT(0 != decoder->private_);
 553         FLAC__ASSERT(0 != decoder->protected_);
 554
 555         if(!FLAC__seekable_stream_decoder_flush(decoder)) {
 556                 decoder->protected_->state = FLAC__SEEKABLE_STREAM_DECODER_STREAM_DECODER_ERROR;
 557                 return false;
 558         }
 559
 560         if(!FLAC__stream_decoder_reset(decoder->private_->stream_decoder)) {
 561                 decoder->protected_->state = FLAC__SEEKABLE_STREAM_DECODER_STREAM_DECODER_ERROR;
 562                 return false;
 563         }
 564
 565         decoder->private_->seek_table = 0;
 566
 567         decoder->private_->do_md5_checking = decoder->protected_->md5_checking;
 568
 569         /* We initialize the MD5Context even though we may never use it.  This is
 570          * because md5 checking may be turned on to start and then turned off if a
 571          * seek occurs.  So we always init the context here and finalize it in
 572          * FLAC__seekable_stream_decoder_finish() to make sure things are always
 573          * cleaned up properly.
 574          */
 575         MD5Init(&decoder->private_->md5context);
 576
 577         decoder->protected_->state = FLAC__SEEKABLE_STREAM_DECODER_OK;
 578
 579         return true;
 580 }
 581
 582 FLAC_API FLAC__bool FLAC__seekable_stream_decoder_process_single(FLAC__SeekableStreamDecoder *decoder)
 583 {
 584         FLAC__bool ret;
 585         FLAC__ASSERT(0 != decoder);
 586
 587         if(decoder->private_->stream_decoder->protected_->state == FLAC__STREAM_DECODER_END_OF_STREAM)
 588                 decoder->protected_->state = FLAC__SEEKABLE_STREAM_DECODER_END_OF_STREAM;
 589
 590         if(decoder->protected_->state == FLAC__SEEKABLE_STREAM_DECODER_END_OF_STREAM)
 591                 return true;
 592
 593         FLAC__ASSERT(decoder->protected_->state == FLAC__SEEKABLE_STREAM_DECODER_OK);
 594
 595         ret = FLAC__stream_decoder_process_single(decoder->private_->stream_decoder);
 596         if(!ret)
 597                 decoder->protected_->state = FLAC__SEEKABLE_STREAM_DECODER_STREAM_DECODER_ERROR;
 598
 599         return ret;
 600 }
 601
 602 FLAC_API FLAC__bool FLAC__seekable_stream_decoder_process_until_end_of_metadata(FLAC__SeekableStreamDecoder *decoder)
 603 {
 604         FLAC__bool ret;
 605         FLAC__ASSERT(0 != decoder);
 606
 607         if(decoder->private_->stream_decoder->protected_->state == FLAC__STREAM_DECODER_END_OF_STREAM)
 608                 decoder->protected_->state = FLAC__SEEKABLE_STREAM_DECODER_END_OF_STREAM;
 609
 610         if(decoder->protected_->state == FLAC__SEEKABLE_STREAM_DECODER_END_OF_STREAM)
 611                 return true;
 612
 613         FLAC__ASSERT(decoder->protected_->state == FLAC__SEEKABLE_STREAM_DECODER_OK);
 614
 615         ret = FLAC__stream_decoder_process_until_end_of_metadata(decoder->private_->stream_decoder);
 616         if(!ret)
 617                 decoder->protected_->state = FLAC__SEEKABLE_STREAM_DECODER_STREAM_DECODER_ERROR;
 618
 619         return ret;
 620 }
 621
 622 FLAC_API FLAC__bool FLAC__seekable_stream_decoder_process_until_end_of_stream(FLAC__SeekableStreamDecoder *decoder)
 623 {
 624         FLAC__bool ret;
 625         FLAC__ASSERT(0 != decoder);
 626
 627         if(decoder->private_->stream_decoder->protected_->state == FLAC__STREAM_DECODER_END_OF_STREAM)
 628                 decoder->protected_->state = FLAC__SEEKABLE_STREAM_DECODER_END_OF_STREAM;
 629
 630         if(decoder->protected_->state == FLAC__SEEKABLE_STREAM_DECODER_END_OF_STREAM)
 631                 return true;
 632
 633         FLAC__ASSERT(decoder->protected_->state == FLAC__SEEKABLE_STREAM_DECODER_OK);
 634
 635         ret = FLAC__stream_decoder_process_until_end_of_stream(decoder->private_->stream_decoder);
 636         if(!ret)
 637                 decoder->protected_->state = FLAC__SEEKABLE_STREAM_DECODER_STREAM_DECODER_ERROR;
 638
 639         return ret;
 640 }
 641
 642 FLAC_API FLAC__bool FLAC__seekable_stream_decoder_seek_absolute(FLAC__SeekableStreamDecoder *decoder, FLAC__uint64 sample)
 643 {
 644         FLAC__uint64 length;
 645
 646         FLAC__ASSERT(0 != decoder);
 647         FLAC__ASSERT(decoder->protected_->state == FLAC__SEEKABLE_STREAM_DECODER_OK /*@@@@@ why shouldn't you be able to do this? || decoder->protected_->state == FLAC__SEEKABLE_STREAM_DECODER_END_OF_STREAM*/);
 648
 649         decoder->protected_->state = FLAC__SEEKABLE_STREAM_DECODER_SEEKING;
 650
 651         /* turn off md5 checking if a seek is attempted */
 652         decoder->private_->do_md5_checking = false;
 653
 654         if(!FLAC__stream_decoder_reset(decoder->private_->stream_decoder)) {
 655                 decoder->protected_->state = FLAC__SEEKABLE_STREAM_DECODER_STREAM_DECODER_ERROR;
 656                 return false;
 657         }
 658         /* get the file length */
 659         if(decoder->private_->length_callback(decoder, &length, decoder->private_->client_data) != FLAC__SEEKABLE_STREAM_DECODER_LENGTH_STATUS_OK) {
 660                 decoder->protected_->state = FLAC__SEEKABLE_STREAM_DECODER_SEEK_ERROR;
 661                 return false;
 662         }
 663         /* rewind */
 664         if(decoder->private_->seek_callback(decoder, 0, decoder->private_->client_data) != FLAC__SEEKABLE_STREAM_DECODER_SEEK_STATUS_OK) {
 665                 decoder->protected_->state = FLAC__SEEKABLE_STREAM_DECODER_SEEK_ERROR;
 666                 return false;
 667         }
 668         if(!FLAC__stream_decoder_process_until_end_of_metadata(decoder->private_->stream_decoder)) {
 669                 decoder->protected_->state = FLAC__SEEKABLE_STREAM_DECODER_STREAM_DECODER_ERROR;
 670                 return false;
 671         }
 672         if(decoder->private_->stream_info.total_samples > 0 && sample >= decoder->private_->stream_info.total_samples) {
 673                 decoder->protected_->state = FLAC__SEEKABLE_STREAM_DECODER_SEEK_ERROR;
 674                 return false;
 675         }
 676
 677         return seek_to_absolute_sample_(decoder, length, sample);
 678 }
 679
 680 /***********************************************************************
 681  *
 682  * Private class methods
 683  *
 684  ***********************************************************************/
 685
 686 void set_defaults_(FLAC__SeekableStreamDecoder *decoder)
 687 {
 688         decoder->private_->read_callback = 0;
 689         decoder->private_->seek_callback = 0;
 690         decoder->private_->tell_callback = 0;
 691         decoder->private_->length_callback = 0;
 692         decoder->private_->eof_callback = 0;
 693         decoder->private_->write_callback = 0;
 694         decoder->private_->metadata_callback = 0;
 695         decoder->private_->error_callback = 0;
 696         decoder->private_->client_data = 0;
 697         /* WATCHOUT: these should match the default behavior of FLAC__StreamDecoder */
 698         decoder->private_->ignore_stream_info_block = false;
 699         decoder->private_->ignore_seek_table_block = true;
 700
 701         decoder->protected_->md5_checking = false;
 702 }
 703
 704 FLAC__StreamDecoderReadStatus read_callback_(const FLAC__StreamDecoder *decoder, FLAC__byte buffer[], unsigned *bytes, void *client_data)
 705 {
 706         FLAC__SeekableStreamDecoder *seekable_stream_decoder = (FLAC__SeekableStreamDecoder *)client_data;
 707         (void)decoder;
 708         if(seekable_stream_decoder->private_->eof_callback(seekable_stream_decoder, seekable_stream_decoder->private_->client_data)) {
 709                 *bytes = 0;
 710                 seekable_stream_decoder->protected_->state = FLAC__SEEKABLE_STREAM_DECODER_END_OF_STREAM;
 711                 return FLAC__STREAM_DECODER_READ_STATUS_END_OF_STREAM;
 712         }
 713         else if(*bytes > 0) {
 714                 if(seekable_stream_decoder->private_->read_callback(seekable_stream_decoder, buffer, bytes, seekable_stream_decoder->private_->client_data) != FLAC__SEEKABLE_STREAM_DECODER_READ_STATUS_OK) {
 715                         seekable_stream_decoder->protected_->state = FLAC__SEEKABLE_STREAM_DECODER_READ_ERROR;
 716                         return FLAC__STREAM_DECODER_READ_STATUS_ABORT;
 717                 }
 718                 if(*bytes == 0) {
 719                         if(seekable_stream_decoder->private_->eof_callback(seekable_stream_decoder, seekable_stream_decoder->private_->client_data)) {
 720                                 seekable_stream_decoder->protected_->state = FLAC__SEEKABLE_STREAM_DECODER_END_OF_STREAM;
 721                                 return FLAC__STREAM_DECODER_READ_STATUS_END_OF_STREAM;
 722                         }
 723                         else
 724                                 return FLAC__STREAM_DECODER_READ_STATUS_CONTINUE;
 725                 }
 726                 else {
 727                         return FLAC__STREAM_DECODER_READ_STATUS_CONTINUE;
 728                 }
 729         }
 730         else
 731                 return FLAC__STREAM_DECODER_READ_STATUS_ABORT; /* abort to avoid a deadlock */
 732 }
 733
 734 FLAC__StreamDecoderWriteStatus write_callback_(const FLAC__StreamDecoder *decoder, const FLAC__Frame *frame, const FLAC__int32 * const buffer[], void *client_data)
 735 {
 736         FLAC__SeekableStreamDecoder *seekable_stream_decoder = (FLAC__SeekableStreamDecoder *)client_data;
 737         (void)decoder;
 738
 739         if(seekable_stream_decoder->protected_->state == FLAC__SEEKABLE_STREAM_DECODER_SEEKING) {
 740                 FLAC__uint64 this_frame_sample = frame->header.number.sample_number;
 741                 FLAC__uint64 next_frame_sample = this_frame_sample + (FLAC__uint64)frame->header.blocksize;
 742                 FLAC__uint64 target_sample = seekable_stream_decoder->private_->target_sample;
 743
 744                 FLAC__ASSERT(frame->header.number_type == FLAC__FRAME_NUMBER_TYPE_SAMPLE_NUMBER);
 745
 746                 seekable_stream_decoder->private_->last_frame = *frame; /* save the frame */
 747                 if(this_frame_sample <= target_sample && target_sample < next_frame_sample) { /* we hit our target frame */
 748                         unsigned delta = (unsigned)(target_sample - this_frame_sample);
 749                         /* kick out of seek mode */
 750                         seekable_stream_decoder->protected_->state = FLAC__SEEKABLE_STREAM_DECODER_OK;
 751                         /* shift out the samples before target_sample */
 752                         if(delta > 0) {
 753                                 unsigned channel;
 754                                 const FLAC__int32 *newbuffer[FLAC__MAX_CHANNELS];
 755                                 for(channel = 0; channel < frame->header.channels; channel++)
 756                                         newbuffer[channel] = buffer[channel] + delta;
 757                                 seekable_stream_decoder->private_->last_frame.header.blocksize -= delta;
 758                                 seekable_stream_decoder->private_->last_frame.header.number.sample_number += (FLAC__uint64)delta;
 759                                 /* write the relevant samples */
 760                                 return seekable_stream_decoder->private_->write_callback(seekable_stream_decoder, &seekable_stream_decoder->private_->last_frame, newbuffer, seekable_stream_decoder->private_->client_data);
 761                         }
 762                         else {
 763                                 /* write the relevant samples */
 764                                 return seekable_stream_decoder->private_->write_callback(seekable_stream_decoder, frame, buffer, seekable_stream_decoder->private_->client_data);
 765                         }
 766                 }
 767                 else {
 768                         return FLAC__STREAM_DECODER_WRITE_STATUS_CONTINUE;
 769                 }
 770         }
 771         else {
 772                 if(seekable_stream_decoder->private_->do_md5_checking) {
 773                         if(!FLAC__MD5Accumulate(&seekable_stream_decoder->private_->md5context, buffer, frame->header.channels, frame->header.blocksize, (frame->header.bits_per_sample+7) / 8))
 774                                 return FLAC__STREAM_DECODER_WRITE_STATUS_ABORT;
 775                 }
 776                 return seekable_stream_decoder->private_->write_callback(seekable_stream_decoder, frame, buffer, seekable_stream_decoder->private_->client_data);
 777         }
 778 }
 779
 780 void metadata_callback_(const FLAC__StreamDecoder *decoder, const FLAC__StreamMetadata *metadata, void *client_data)
 781 {
 782         FLAC__SeekableStreamDecoder *seekable_stream_decoder = (FLAC__SeekableStreamDecoder *)client_data;
 783         (void)decoder;
 784
 785         if(metadata->type == FLAC__METADATA_TYPE_STREAMINFO) {
 786                 seekable_stream_decoder->private_->stream_info = metadata->data.stream_info;
 787                 /* save the MD5 signature for comparison later */
 788                 memcpy(seekable_stream_decoder->private_->stored_md5sum, metadata->data.stream_info.md5sum, 16);
 789                 if(0 == memcmp(seekable_stream_decoder->private_->stored_md5sum, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0", 16))
 790                         seekable_stream_decoder->private_->do_md5_checking = false;
 791         }
 792         else if(metadata->type == FLAC__METADATA_TYPE_SEEKTABLE) {
 793                 seekable_stream_decoder->private_->seek_table = &metadata->data.seek_table;
 794         }
 795
 796         if(seekable_stream_decoder->protected_->state != FLAC__SEEKABLE_STREAM_DECODER_SEEKING) {
 797                 FLAC__bool ignore_block = false;
 798                 if(metadata->type == FLAC__METADATA_TYPE_STREAMINFO && seekable_stream_decoder->private_->ignore_stream_info_block)
 799                         ignore_block = true;
 800                 else if(metadata->type == FLAC__METADATA_TYPE_SEEKTABLE && seekable_stream_decoder->private_->ignore_seek_table_block)
 801                         ignore_block = true;
 802                 if(!ignore_block)
 803                         seekable_stream_decoder->private_->metadata_callback(seekable_stream_decoder, metadata, seekable_stream_decoder->private_->client_data);
 804         }
 805 }
 806
 807 void error_callback_(const FLAC__StreamDecoder *decoder, FLAC__StreamDecoderErrorStatus status, void *client_data)
 808 {
 809         FLAC__SeekableStreamDecoder *seekable_stream_decoder = (FLAC__SeekableStreamDecoder *)client_data;
 810         (void)decoder;
 811
 812         if(seekable_stream_decoder->protected_->state != FLAC__SEEKABLE_STREAM_DECODER_SEEKING)
 813                 seekable_stream_decoder->private_->error_callback(seekable_stream_decoder, status, seekable_stream_decoder->private_->client_data);
 814 }
 815
 816 FLAC__bool seek_to_absolute_sample_(FLAC__SeekableStreamDecoder *decoder, FLAC__uint64 stream_length, FLAC__uint64 target_sample)
 817 {
 818         FLAC__uint64 first_frame_offset, lower_bound, upper_bound;
 819         FLAC__int64 pos = -1, last_pos = -1;
 820         int i, lower_seek_point = -1, upper_seek_point = -1;
 821         unsigned approx_bytes_per_frame;
 822         FLAC__uint64 last_frame_sample = 0xffffffffffffffff;
 823         FLAC__bool needs_seek;
 824         const FLAC__uint64 total_samples = decoder->private_->stream_info.total_samples;
 825         const unsigned min_blocksize = decoder->private_->stream_info.min_blocksize;
 826         const unsigned max_blocksize = decoder->private_->stream_info.max_blocksize;
 827         const unsigned max_framesize = decoder->private_->stream_info.max_framesize;
 828         const unsigned channels = FLAC__seekable_stream_decoder_get_channels(decoder);
 829         const unsigned bps = FLAC__seekable_stream_decoder_get_bits_per_sample(decoder);
 830
 831         /* we are just guessing here, but we want to guess high, not low */
 832         if(max_framesize > 0) {
 833                 approx_bytes_per_frame = max_framesize;
 834         }
 835         /*
 836          * Check if it's a known fixed-blocksize stream.  Note that though
 837          * the spec doesn't allow zeroes in the STREAMINFO block, we may
 838          * never get a STREAMINFO block when decoding so the value of
 839          * min_blocksize might be zero.
 840          */
 841         else if(min_blocksize == max_blocksize && min_blocksize > 0) {
 842                 /* note there are no () around 'bps/8' to keep precision up since it's an integer calulation */
 843                 approx_bytes_per_frame = min_blocksize * channels * bps/8 + 64;
 844         }
 845         else
 846                 approx_bytes_per_frame = 4608 * channels * bps/8 + 64;
 847
 848         /*
 849          * The decode position is currently at the first frame since we
 850          * rewound and processed metadata.
 851          */
 852         if(!FLAC__seekable_stream_decoder_get_decode_position(decoder, &first_frame_offset)) {
 853                 decoder->protected_->state = FLAC__SEEKABLE_STREAM_DECODER_SEEK_ERROR;
 854                 return false;
 855         }
 856
 857         /*
 858          * First, we set an upper and lower bound on where in the
 859          * stream we will search.  For now we assume the worst case
 860          * scenario, which is our best guess at the beginning of
 861          * the first and last frames.
 862          */
 863         lower_bound = first_frame_offset;
 864
 865         /* calc the upper_bound, beyond which we never want to seek */
 866         if(max_framesize > 0)
 867                 upper_bound = stream_length - (max_framesize + 128 + 2); /* 128 for a possible ID3V1 tag, 2 for indexing differences */
 868         else
 869                 upper_bound = stream_length - ((channels * bps * FLAC__MAX_BLOCK_SIZE) / 8 + 128 + 2);
 870
 871         /*
 872          * Now we refine the bounds if we have a seektable with
 873          * suitable points.  Note that according to the spec they
 874          * must be ordered by ascending sample number.
 875          */
 876         if(0 != decoder->private_->seek_table) {
 877                 /* find the closest seek point <= target_sample, if it exists */
 878                 for(i = (int)decoder->private_->seek_table->num_points - 1; i >= 0; i--) {
 879                         if(decoder->private_->seek_table->points[i].sample_number != FLAC__STREAM_METADATA_SEEKPOINT_PLACEHOLDER && decoder->private_->seek_table->points[i].sample_number <= target_sample)
 880                                 break;
 881                 }
 882                 if(i >= 0) { /* i.e. we found a suitable seek point... */
 883                         lower_bound = first_frame_offset + decoder->private_->seek_table->points[i].stream_offset;
 884                         lower_seek_point = i;
 885                 }
 886
 887                 /* find the closest seek point > target_sample, if it exists */
 888                 for(i = 0; i < (int)decoder->private_->seek_table->num_points; i++) {
 889                         if(decoder->private_->seek_table->points[i].sample_number != FLAC__STREAM_METADATA_SEEKPOINT_PLACEHOLDER && decoder->private_->seek_table->points[i].sample_number > target_sample)
 890                                 break;
 891                 }
 892                 if(i < (int)decoder->private_->seek_table->num_points) { /* i.e. we found a suitable seek point... */
 893                         upper_bound = first_frame_offset + decoder->private_->seek_table->points[i].stream_offset;
 894                         upper_seek_point = i;
 895                 }
 896         }
 897
 898         /*
 899          * Now guess at where within those bounds our target
 900          * sample will be.
 901          */
 902         if(lower_seek_point >= 0) {
 903                 /* first see if our sample is within a few frames of the lower seekpoint */
 904                 if(decoder->private_->seek_table->points[lower_seek_point].sample_number <= target_sample && target_sample < decoder->private_->seek_table->points[lower_seek_point].sample_number + (decoder->private_->seek_table->points[lower_seek_point].frame_samples * 4)) {
 905                         pos = (FLAC__int64)lower_bound;
 906                 }
 907                 else if(upper_seek_point >= 0) {
 908                         const FLAC__uint64 target_offset = target_sample - decoder->private_->seek_table->points[lower_seek_point].sample_number;
 909                         const FLAC__uint64 range_samples = decoder->private_->seek_table->points[upper_seek_point].sample_number - decoder->private_->seek_table->points[lower_seek_point].sample_number;
 910                         const FLAC__uint64 range_bytes = upper_bound - lower_bound;
 911 #if defined _MSC_VER || defined __MINGW32__
 912                         /* with VC++ you have to spoon feed it the casting */
 913                         pos = (FLAC__int64)lower_bound + (FLAC__int64)((double)(FLAC__int64)target_offset / (double)(FLAC__int64)range_samples * (double)(FLAC__int64)(range_bytes-1)) - approx_bytes_per_frame;
 914 #else
 915                         pos = (FLAC__int64)lower_bound + (FLAC__int64)((double)target_offset / (double)range_samples * (double)(range_bytes-1)) - approx_bytes_per_frame;
 916 #endif
 917                 }
 918         }
 919
 920         /*
 921          * If there's no seek table, we need to use the metadata (if we
 922          * have it) and the filelength to estimate the position of the
 923          * frame with the correct sample.
 924          */
 925         if(pos < 0 && total_samples > 0) {
 926 #if defined _MSC_VER || defined __MINGW32__
 927                 /* with VC++ you have to spoon feed it the casting */
 928                 pos = (FLAC__int64)first_frame_offset + (FLAC__int64)((double)(FLAC__int64)target_sample / (double)(FLAC__int64)total_samples * (double)(FLAC__int64)(stream_length-first_frame_offset-1)) - approx_bytes_per_frame;
 929 #else
 930                 pos = (FLAC__int64)first_frame_offset + (FLAC__int64)((double)target_sample / (double)total_samples * (double)(stream_length-first_frame_offset-1)) - approx_bytes_per_frame;
 931 #endif
 932         }
 933
 934         /*
 935          * If there's no seek table and total_samples is unknown, we
 936          * don't even bother trying to figure out a target, we just use
 937          * our current position.
 938          */
 939         if(pos < 0) {
 940                 FLAC__uint64 upos;
 941                 if(decoder->private_->tell_callback(decoder, &upos, decoder->private_->client_data) != FLAC__SEEKABLE_STREAM_DECODER_TELL_STATUS_OK) {
 942                         decoder->protected_->state = FLAC__SEEKABLE_STREAM_DECODER_SEEK_ERROR;
 943                         return false;
 944                 }
 945                 pos = (FLAC__int32)upos;
 946                 needs_seek = false;
 947         }
 948         else
 949                 needs_seek = true;
 950
 951         /* clip the position to the bounds, lower bound takes precedence */
 952         if(pos >= (FLAC__int64)upper_bound) {
 953                 pos = (FLAC__int64)upper_bound-1;
 954                 needs_seek = true;
 955         }
 956         if(pos < (FLAC__int64)lower_bound) {
 957                 pos = (FLAC__int64)lower_bound;
 958                 needs_seek = true;
 959         }
 960
 961         decoder->private_->target_sample = target_sample;
 962         while(1) {
 963                 if(needs_seek) {
 964                         if(decoder->private_->seek_callback(decoder, (FLAC__uint64)pos, decoder->private_->client_data) != FLAC__SEEKABLE_STREAM_DECODER_SEEK_STATUS_OK) {
 965                                 decoder->protected_->state = FLAC__SEEKABLE_STREAM_DECODER_SEEK_ERROR;
 966                                 return false;
 967                         }
 968                         if(!FLAC__stream_decoder_flush(decoder->private_->stream_decoder)) {
 969                                 decoder->protected_->state = FLAC__SEEKABLE_STREAM_DECODER_STREAM_DECODER_ERROR;
 970                                 return false;
 971                         }
 972                 }
 973                 if(!FLAC__stream_decoder_process_single(decoder->private_->stream_decoder)) {
 974                         decoder->protected_->state = FLAC__SEEKABLE_STREAM_DECODER_SEEK_ERROR;
 975                         return false;
 976                 }
 977                 /* our write callback will change the state when it gets to the target frame */
 978                 if(decoder->protected_->state != FLAC__SEEKABLE_STREAM_DECODER_SEEKING) {
 979                         break;
 980                 }
 981                 else { /* we need to narrow the search */
 982                         FLAC__uint64 this_frame_sample = decoder->private_->last_frame.header.number.sample_number;
 983                         FLAC__ASSERT(decoder->private_->last_frame.header.number_type == FLAC__FRAME_NUMBER_TYPE_SAMPLE_NUMBER);
 984                         if(this_frame_sample == last_frame_sample && pos < last_pos) {
 985                                 /* our last move backwards wasn't big enough, double it */
 986                                 pos -= (last_pos - pos);
 987                                 needs_seek = true;
 988                         }
 989                         else {
 990                                 if(target_sample < this_frame_sample) {
 991                                         last_pos = pos;
 992                                         approx_bytes_per_frame = decoder->private_->last_frame.header.blocksize * channels * bps/8 + 64;
 993                                         pos -= approx_bytes_per_frame;
 994                                         needs_seek = true;
 995                                 }
 996                                 else { /* target_sample >= this_frame_sample + this frame's blocksize */
 997                                         FLAC__uint64 upos;
 998                                         if(decoder->private_->tell_callback(decoder, &upos, decoder->private_->client_data) != FLAC__SEEKABLE_STREAM_DECODER_TELL_STATUS_OK) {
 999                                                 decoder->protected_->state = FLAC__SEEKABLE_STREAM_DECODER_SEEK_ERROR;
1000                                                 return false;
1001                                         }
1002                                         last_pos = pos;
1003                                         pos = (FLAC__int32)upos;
1004                                         pos -= FLAC__stream_decoder_get_input_bytes_unconsumed(decoder->private_->stream_decoder);
1005                                         needs_seek = false;
1006                                         /*
1007                                          * if we haven't hit the target frame yet and our position hasn't changed,
1008                                          * it means we're at the end of the stream and the seek target does not exist.
1009                                          */
1010                                         if(last_pos == pos) {
1011                                                 decoder->protected_->state = FLAC__SEEKABLE_STREAM_DECODER_SEEK_ERROR;
1012                                                 return false;
1013                                         }
1014                                 }
1015                         }
1016                         if(pos < (FLAC__int64)lower_bound)
1017                                 pos = (FLAC__int64)lower_bound;
1018                         last_frame_sample = this_frame_sample;
1019                 }
1020         }
1021
1022         return true;
1023 }