third_party/libwebp/dec/idec.c

   1 // Copyright 2011 Google Inc. All Rights Reserved.
   2 //
   3 // Use of this source code is governed by a BSD-style license
   4 // that can be found in the COPYING file in the root of the source
   5 // tree. An additional intellectual property rights grant can be found
   6 // in the file PATENTS. All contributing project authors may
   7 // be found in the AUTHORS file in the root of the source tree.
   8 // -----------------------------------------------------------------------------
   9 //
  10 // Incremental decoding
  11 //
  12 // Author: somnath@google.com (Somnath Banerjee)
  13
  14 #include <assert.h>
  15 #include <string.h>
  16 #include <stdlib.h>
  17
  18 #include "./alphai.h"
  19 #include "./webpi.h"
  20 #include "./vp8i.h"
  21 #include "../utils/utils.h"
  22
  23 // In append mode, buffer allocations increase as multiples of this value.
  24 // Needs to be a power of 2.
  25 #define CHUNK_SIZE 4096
  26 #define MAX_MB_SIZE 4096
  27
  28 //------------------------------------------------------------------------------
  29 // Data structures for memory and states
  30
  31 // Decoding states. State normally flows as:
  32 // WEBP_HEADER->VP8_HEADER->VP8_PARTS0->VP8_DATA->DONE for a lossy image, and
  33 // WEBP_HEADER->VP8L_HEADER->VP8L_DATA->DONE for a lossless image.
  34 // If there is any error the decoder goes into state ERROR.
  35 typedef enum {
  36   STATE_WEBP_HEADER,  // All the data before that of the VP8/VP8L chunk.
  37   STATE_VP8_HEADER,   // The VP8 Frame header (within the VP8 chunk).
  38   STATE_VP8_PARTS0,
  39   STATE_VP8_DATA,
  40   STATE_VP8L_HEADER,
  41   STATE_VP8L_DATA,
  42   STATE_DONE,
  43   STATE_ERROR
  44 } DecState;
  45
  46 // Operating state for the MemBuffer
  47 typedef enum {
  48   MEM_MODE_NONE = 0,
  49   MEM_MODE_APPEND,
  50   MEM_MODE_MAP
  51 } MemBufferMode;
  52
  53 // storage for partition #0 and partial data (in a rolling fashion)
  54 typedef struct {
  55   MemBufferMode mode_;  // Operation mode
  56   size_t start_;        // start location of the data to be decoded
  57   size_t end_;          // end location
  58   size_t buf_size_;     // size of the allocated buffer
  59   uint8_t* buf_;        // We don't own this buffer in case WebPIUpdate()
  60
  61   size_t part0_size_;         // size of partition #0
  62   const uint8_t* part0_buf_;  // buffer to store partition #0
  63 } MemBuffer;
  64
  65 struct WebPIDecoder {
  66   DecState state_;         // current decoding state
  67   WebPDecParams params_;   // Params to store output info
  68   int is_lossless_;        // for down-casting 'dec_'.
  69   void* dec_;              // either a VP8Decoder or a VP8LDecoder instance
  70   VP8Io io_;
  71
  72   MemBuffer mem_;          // input memory buffer.
  73   WebPDecBuffer output_;   // output buffer (when no external one is supplied)
  74   size_t chunk_size_;      // Compressed VP8/VP8L size extracted from Header.
  75
  76   int last_mb_y_;          // last row reached for intra-mode decoding
  77 };
  78
  79 // MB context to restore in case VP8DecodeMB() fails
  80 typedef struct {
  81   VP8MB left_;
  82   VP8MB info_;
  83   VP8BitReader token_br_;
  84 } MBContext;
  85
  86 //------------------------------------------------------------------------------
  87 // MemBuffer: incoming data handling
  88
  89 static WEBP_INLINE size_t MemDataSize(const MemBuffer* mem) {
  90   return (mem->end_ - mem->start_);
  91 }
  92
  93 // Check if we need to preserve the compressed alpha data, as it may not have
  94 // been decoded yet.
  95 static int NeedCompressedAlpha(const WebPIDecoder* const idec) {
  96   if (idec->state_ == STATE_WEBP_HEADER) {
  97     // We haven't parsed the headers yet, so we don't know whether the image is
  98     // lossy or lossless. This also means that we haven't parsed the ALPH chunk.
  99     return 0;
 100   }
 101   if (idec->is_lossless_) {
 102     return 0;  // ALPH chunk is not present for lossless images.
 103   } else {
 104     const VP8Decoder* const dec = (VP8Decoder*)idec->dec_;
 105     assert(dec != NULL);  // Must be true as idec->state_ != STATE_WEBP_HEADER.
 106     return (dec->alpha_data_ != NULL) && !dec->is_alpha_decoded_;
 107   }
 108 }
 109
 110 static void DoRemap(WebPIDecoder* const idec, ptrdiff_t offset) {
 111   MemBuffer* const mem = &idec->mem_;
 112   const uint8_t* const new_base = mem->buf_ + mem->start_;
 113   // note: for VP8, setting up idec->io_ is only really needed at the beginning
 114   // of the decoding, till partition #0 is complete.
 115   idec->io_.data = new_base;
 116   idec->io_.data_size = MemDataSize(mem);
 117
 118   if (idec->dec_ != NULL) {
 119     if (!idec->is_lossless_) {
 120       VP8Decoder* const dec = (VP8Decoder*)idec->dec_;
 121       const int last_part = dec->num_parts_ - 1;
 122       if (offset != 0) {
 123         int p;
 124         for (p = 0; p <= last_part; ++p) {
 125           VP8RemapBitReader(dec->parts_ + p, offset);
 126         }
 127         // Remap partition #0 data pointer to new offset, but only in MAP
 128         // mode (in APPEND mode, partition #0 is copied into a fixed memory).
 129         if (mem->mode_ == MEM_MODE_MAP) {
 130           VP8RemapBitReader(&dec->br_, offset);
 131         }
 132       }
 133       assert(last_part >= 0);
 134       dec->parts_[last_part].buf_end_ = mem->buf_ + mem->end_;
 135       if (NeedCompressedAlpha(idec)) {
 136         ALPHDecoder* const alph_dec = dec->alph_dec_;
 137         dec->alpha_data_ += offset;
 138         if (alph_dec != NULL) {
 139           if (alph_dec->method_ == ALPHA_LOSSLESS_COMPRESSION) {
 140             VP8LDecoder* const alph_vp8l_dec = alph_dec->vp8l_dec_;
 141             assert(alph_vp8l_dec != NULL);
 142             assert(dec->alpha_data_size_ >= ALPHA_HEADER_LEN);
 143             VP8LBitReaderSetBuffer(&alph_vp8l_dec->br_,
 144                                    dec->alpha_data_ + ALPHA_HEADER_LEN,
 145                                    dec->alpha_data_size_ - ALPHA_HEADER_LEN);
 146           } else {  // alph_dec->method_ == ALPHA_NO_COMPRESSION
 147             // Nothing special to do in this case.
 148           }
 149         }
 150       }
 151     } else {    // Resize lossless bitreader
 152       VP8LDecoder* const dec = (VP8LDecoder*)idec->dec_;
 153       VP8LBitReaderSetBuffer(&dec->br_, new_base, MemDataSize(mem));
 154     }
 155   }
 156 }
 157
 158 // Appends data to the end of MemBuffer->buf_. It expands the allocated memory
 159 // size if required and also updates VP8BitReader's if new memory is allocated.
 160 static int AppendToMemBuffer(WebPIDecoder* const idec,
 161                              const uint8_t* const data, size_t data_size) {
 162   VP8Decoder* const dec = (VP8Decoder*)idec->dec_;
 163   MemBuffer* const mem = &idec->mem_;
 164   const int need_compressed_alpha = NeedCompressedAlpha(idec);
 165   const uint8_t* const old_start = mem->buf_ + mem->start_;
 166   const uint8_t* const old_base =
 167       need_compressed_alpha ? dec->alpha_data_ : old_start;
 168   assert(mem->mode_ == MEM_MODE_APPEND);
 169   if (data_size > MAX_CHUNK_PAYLOAD) {
 170     // security safeguard: trying to allocate more than what the format
 171     // allows for a chunk should be considered a smoke smell.
 172     return 0;
 173   }
 174
 175   if (mem->end_ + data_size > mem->buf_size_) {  // Need some free memory
 176     const size_t new_mem_start = old_start - old_base;
 177     const size_t current_size = MemDataSize(mem) + new_mem_start;
 178     const uint64_t new_size = (uint64_t)current_size + data_size;
 179     const uint64_t extra_size = (new_size + CHUNK_SIZE - 1) & ~(CHUNK_SIZE - 1);
 180     uint8_t* const new_buf =
 181         (uint8_t*)WebPSafeMalloc(extra_size, sizeof(*new_buf));
 182     if (new_buf == NULL) return 0;
 183     memcpy(new_buf, old_base, current_size);
 184     WebPSafeFree(mem->buf_);
 185     mem->buf_ = new_buf;
 186     mem->buf_size_ = (size_t)extra_size;
 187     mem->start_ = new_mem_start;
 188     mem->end_ = current_size;
 189   }
 190
 191   memcpy(mem->buf_ + mem->end_, data, data_size);
 192   mem->end_ += data_size;
 193   assert(mem->end_ <= mem->buf_size_);
 194
 195   DoRemap(idec, mem->buf_ + mem->start_ - old_start);
 196   return 1;
 197 }
 198
 199 static int RemapMemBuffer(WebPIDecoder* const idec,
 200                           const uint8_t* const data, size_t data_size) {
 201   MemBuffer* const mem = &idec->mem_;
 202   const uint8_t* const old_buf = mem->buf_;
 203   const uint8_t* const old_start = old_buf + mem->start_;
 204   assert(mem->mode_ == MEM_MODE_MAP);
 205
 206   if (data_size < mem->buf_size_) return 0;  // can't remap to a shorter buffer!
 207
 208   mem->buf_ = (uint8_t*)data;
 209   mem->end_ = mem->buf_size_ = data_size;
 210
 211   DoRemap(idec, mem->buf_ + mem->start_ - old_start);
 212   return 1;
 213 }
 214
 215 static void InitMemBuffer(MemBuffer* const mem) {
 216   mem->mode_       = MEM_MODE_NONE;
 217   mem->buf_        = NULL;
 218   mem->buf_size_   = 0;
 219   mem->part0_buf_  = NULL;
 220   mem->part0_size_ = 0;
 221 }
 222
 223 static void ClearMemBuffer(MemBuffer* const mem) {
 224   assert(mem);
 225   if (mem->mode_ == MEM_MODE_APPEND) {
 226     WebPSafeFree(mem->buf_);
 227     WebPSafeFree((void*)mem->part0_buf_);
 228   }
 229 }
 230
 231 static int CheckMemBufferMode(MemBuffer* const mem, MemBufferMode expected) {
 232   if (mem->mode_ == MEM_MODE_NONE) {
 233     mem->mode_ = expected;    // switch to the expected mode
 234   } else if (mem->mode_ != expected) {
 235     return 0;         // we mixed the modes => error
 236   }
 237   assert(mem->mode_ == expected);   // mode is ok
 238   return 1;
 239 }
 240
 241 // To be called last.
 242 static VP8StatusCode FinishDecoding(WebPIDecoder* const idec) {
 243 #if WEBP_DECODER_ABI_VERSION > 0x0203
 244   const WebPDecoderOptions* const options = idec->params_.options;
 245   WebPDecBuffer* const output = idec->params_.output;
 246
 247   idec->state_ = STATE_DONE;
 248   if (options != NULL && options->flip) {
 249     return WebPFlipBuffer(output);
 250   }
 251 #endif
 252   idec->state_ = STATE_DONE;
 253   return VP8_STATUS_OK;
 254 }
 255
 256 //------------------------------------------------------------------------------
 257 // Macroblock-decoding contexts
 258
 259 static void SaveContext(const VP8Decoder* dec, const VP8BitReader* token_br,
 260                         MBContext* const context) {
 261   context->left_ = dec->mb_info_[-1];
 262   context->info_ = dec->mb_info_[dec->mb_x_];
 263   context->token_br_ = *token_br;
 264 }
 265
 266 static void RestoreContext(const MBContext* context, VP8Decoder* const dec,
 267                            VP8BitReader* const token_br) {
 268   dec->mb_info_[-1] = context->left_;
 269   dec->mb_info_[dec->mb_x_] = context->info_;
 270   *token_br = context->token_br_;
 271 }
 272
 273 //------------------------------------------------------------------------------
 274
 275 static VP8StatusCode IDecError(WebPIDecoder* const idec, VP8StatusCode error) {
 276   if (idec->state_ == STATE_VP8_DATA) {
 277     VP8Io* const io = &idec->io_;
 278     if (io->teardown != NULL) {
 279       io->teardown(io);
 280     }
 281   }
 282   idec->state_ = STATE_ERROR;
 283   return error;
 284 }
 285
 286 static void ChangeState(WebPIDecoder* const idec, DecState new_state,
 287                         size_t consumed_bytes) {
 288   MemBuffer* const mem = &idec->mem_;
 289   idec->state_ = new_state;
 290   mem->start_ += consumed_bytes;
 291   assert(mem->start_ <= mem->end_);
 292   idec->io_.data = mem->buf_ + mem->start_;
 293   idec->io_.data_size = MemDataSize(mem);
 294 }
 295
 296 // Headers
 297 static VP8StatusCode DecodeWebPHeaders(WebPIDecoder* const idec) {
 298   MemBuffer* const mem = &idec->mem_;
 299   const uint8_t* data = mem->buf_ + mem->start_;
 300   size_t curr_size = MemDataSize(mem);
 301   VP8StatusCode status;
 302   WebPHeaderStructure headers;
 303
 304   headers.data = data;
 305   headers.data_size = curr_size;
 306   headers.have_all_data = 0;
 307   status = WebPParseHeaders(&headers);
 308   if (status == VP8_STATUS_NOT_ENOUGH_DATA) {
 309     return VP8_STATUS_SUSPENDED;  // We haven't found a VP8 chunk yet.
 310   } else if (status != VP8_STATUS_OK) {
 311     return IDecError(idec, status);
 312   }
 313
 314   idec->chunk_size_ = headers.compressed_size;
 315   idec->is_lossless_ = headers.is_lossless;
 316   if (!idec->is_lossless_) {
 317     VP8Decoder* const dec = VP8New();
 318     if (dec == NULL) {
 319       return VP8_STATUS_OUT_OF_MEMORY;
 320     }
 321     idec->dec_ = dec;
 322     dec->alpha_data_ = headers.alpha_data;
 323     dec->alpha_data_size_ = headers.alpha_data_size;
 324     ChangeState(idec, STATE_VP8_HEADER, headers.offset);
 325   } else {
 326     VP8LDecoder* const dec = VP8LNew();
 327     if (dec == NULL) {
 328       return VP8_STATUS_OUT_OF_MEMORY;
 329     }
 330     idec->dec_ = dec;
 331     ChangeState(idec, STATE_VP8L_HEADER, headers.offset);
 332   }
 333   return VP8_STATUS_OK;
 334 }
 335
 336 static VP8StatusCode DecodeVP8FrameHeader(WebPIDecoder* const idec) {
 337   const uint8_t* data = idec->mem_.buf_ + idec->mem_.start_;
 338   const size_t curr_size = MemDataSize(&idec->mem_);
 339   int width, height;
 340   uint32_t bits;
 341
 342   if (curr_size < VP8_FRAME_HEADER_SIZE) {
 343     // Not enough data bytes to extract VP8 Frame Header.
 344     return VP8_STATUS_SUSPENDED;
 345   }
 346   if (!VP8GetInfo(data, curr_size, idec->chunk_size_, &width, &height)) {
 347     return IDecError(idec, VP8_STATUS_BITSTREAM_ERROR);
 348   }
 349
 350   bits = data[0] | (data[1] << 8) | (data[2] << 16);
 351   idec->mem_.part0_size_ = (bits >> 5) + VP8_FRAME_HEADER_SIZE;
 352
 353   idec->io_.data = data;
 354   idec->io_.data_size = curr_size;
 355   idec->state_ = STATE_VP8_PARTS0;
 356   return VP8_STATUS_OK;
 357 }
 358
 359 // Partition #0
 360 static int CopyParts0Data(WebPIDecoder* const idec) {
 361   VP8Decoder* const dec = (VP8Decoder*)idec->dec_;
 362   VP8BitReader* const br = &dec->br_;
 363   const size_t psize = br->buf_end_ - br->buf_;
 364   MemBuffer* const mem = &idec->mem_;
 365   assert(!idec->is_lossless_);
 366   assert(mem->part0_buf_ == NULL);
 367   assert(psize > 0);
 368   assert(psize <= mem->part0_size_);  // Format limit: no need for runtime check
 369   if (mem->mode_ == MEM_MODE_APPEND) {
 370     // We copy and grab ownership of the partition #0 data.
 371     uint8_t* const part0_buf = (uint8_t*)WebPSafeMalloc(1ULL, psize);
 372     if (part0_buf == NULL) {
 373       return 0;
 374     }
 375     memcpy(part0_buf, br->buf_, psize);
 376     mem->part0_buf_ = part0_buf;
 377     br->buf_ = part0_buf;
 378     br->buf_end_ = part0_buf + psize;
 379   } else {
 380     // Else: just keep pointers to the partition #0's data in dec_->br_.
 381   }
 382   mem->start_ += psize;
 383   return 1;
 384 }
 385
 386 static VP8StatusCode DecodePartition0(WebPIDecoder* const idec) {
 387   VP8Decoder* const dec = (VP8Decoder*)idec->dec_;
 388   VP8Io* const io = &idec->io_;
 389   const WebPDecParams* const params = &idec->params_;
 390   WebPDecBuffer* const output = params->output;
 391
 392   // Wait till we have enough data for the whole partition #0
 393   if (MemDataSize(&idec->mem_) < idec->mem_.part0_size_) {
 394     return VP8_STATUS_SUSPENDED;
 395   }
 396
 397   if (!VP8GetHeaders(dec, io)) {
 398     const VP8StatusCode status = dec->status_;
 399     if (status == VP8_STATUS_SUSPENDED ||
 400         status == VP8_STATUS_NOT_ENOUGH_DATA) {
 401       // treating NOT_ENOUGH_DATA as SUSPENDED state
 402       return VP8_STATUS_SUSPENDED;
 403     }
 404     return IDecError(idec, status);
 405   }
 406
 407   // Allocate/Verify output buffer now
 408   dec->status_ = WebPAllocateDecBuffer(io->width, io->height, params->options,
 409                                        output);
 410   if (dec->status_ != VP8_STATUS_OK) {
 411     return IDecError(idec, dec->status_);
 412   }
 413   // This change must be done before calling VP8InitFrame()
 414   dec->mt_method_ = VP8GetThreadMethod(params->options, NULL,
 415                                        io->width, io->height);
 416   VP8InitDithering(params->options, dec);
 417   if (!CopyParts0Data(idec)) {
 418     return IDecError(idec, VP8_STATUS_OUT_OF_MEMORY);
 419   }
 420
 421   // Finish setting up the decoding parameters. Will call io->setup().
 422   if (VP8EnterCritical(dec, io) != VP8_STATUS_OK) {
 423     return IDecError(idec, dec->status_);
 424   }
 425
 426   // Note: past this point, teardown() must always be called
 427   // in case of error.
 428   idec->state_ = STATE_VP8_DATA;
 429   // Allocate memory and prepare everything.
 430   if (!VP8InitFrame(dec, io)) {
 431     return IDecError(idec, dec->status_);
 432   }
 433   return VP8_STATUS_OK;
 434 }
 435
 436 // Remaining partitions
 437 static VP8StatusCode DecodeRemaining(WebPIDecoder* const idec) {
 438   VP8Decoder* const dec = (VP8Decoder*)idec->dec_;
 439   VP8Io* const io = &idec->io_;
 440
 441   assert(dec->ready_);
 442   for (; dec->mb_y_ < dec->mb_h_; ++dec->mb_y_) {
 443     if (idec->last_mb_y_ != dec->mb_y_) {
 444       if (!VP8ParseIntraModeRow(&dec->br_, dec)) {
 445         // note: normally, error shouldn't occur since we already have the whole
 446         // partition0 available here in DecodeRemaining(). Reaching EOF while
 447         // reading intra modes really means a BITSTREAM_ERROR.
 448         return IDecError(idec, VP8_STATUS_BITSTREAM_ERROR);
 449       }
 450       idec->last_mb_y_ = dec->mb_y_;
 451     }
 452     for (; dec->mb_x_ < dec->mb_w_; ++dec->mb_x_) {
 453       VP8BitReader* const token_br =
 454           &dec->parts_[dec->mb_y_ & (dec->num_parts_ - 1)];
 455       MBContext context;
 456       SaveContext(dec, token_br, &context);
 457       if (!VP8DecodeMB(dec, token_br)) {
 458         // We shouldn't fail when MAX_MB data was available
 459         if (dec->num_parts_ == 1 && MemDataSize(&idec->mem_) > MAX_MB_SIZE) {
 460           return IDecError(idec, VP8_STATUS_BITSTREAM_ERROR);
 461         }
 462         RestoreContext(&context, dec, token_br);
 463         return VP8_STATUS_SUSPENDED;
 464       }
 465       // Release buffer only if there is only one partition
 466       if (dec->num_parts_ == 1) {
 467         idec->mem_.start_ = token_br->buf_ - idec->mem_.buf_;
 468         assert(idec->mem_.start_ <= idec->mem_.end_);
 469       }
 470     }
 471     VP8InitScanline(dec);   // Prepare for next scanline
 472
 473     // Reconstruct, filter and emit the row.
 474     if (!VP8ProcessRow(dec, io)) {
 475       return IDecError(idec, VP8_STATUS_USER_ABORT);
 476     }
 477   }
 478   // Synchronize the thread and check for errors.
 479   if (!VP8ExitCritical(dec, io)) {
 480     return IDecError(idec, VP8_STATUS_USER_ABORT);
 481   }
 482   dec->ready_ = 0;
 483   return FinishDecoding(idec);
 484 }
 485
 486 static VP8StatusCode ErrorStatusLossless(WebPIDecoder* const idec,
 487                                          VP8StatusCode status) {
 488   if (status == VP8_STATUS_SUSPENDED || status == VP8_STATUS_NOT_ENOUGH_DATA) {
 489     return VP8_STATUS_SUSPENDED;
 490   }
 491   return IDecError(idec, status);
 492 }
 493
 494 static VP8StatusCode DecodeVP8LHeader(WebPIDecoder* const idec) {
 495   VP8Io* const io = &idec->io_;
 496   VP8LDecoder* const dec = (VP8LDecoder*)idec->dec_;
 497   const WebPDecParams* const params = &idec->params_;
 498   WebPDecBuffer* const output = params->output;
 499   size_t curr_size = MemDataSize(&idec->mem_);
 500   assert(idec->is_lossless_);
 501
 502   // Wait until there's enough data for decoding header.
 503   if (curr_size < (idec->chunk_size_ >> 3)) {
 504     return VP8_STATUS_SUSPENDED;
 505   }
 506   if (!VP8LDecodeHeader(dec, io)) {
 507     return ErrorStatusLossless(idec, dec->status_);
 508   }
 509   // Allocate/verify output buffer now.
 510   dec->status_ = WebPAllocateDecBuffer(io->width, io->height, params->options,
 511                                        output);
 512   if (dec->status_ != VP8_STATUS_OK) {
 513     return IDecError(idec, dec->status_);
 514   }
 515
 516   idec->state_ = STATE_VP8L_DATA;
 517   return VP8_STATUS_OK;
 518 }
 519
 520 static VP8StatusCode DecodeVP8LData(WebPIDecoder* const idec) {
 521   VP8LDecoder* const dec = (VP8LDecoder*)idec->dec_;
 522   const size_t curr_size = MemDataSize(&idec->mem_);
 523   assert(idec->is_lossless_);
 524
 525   // At present Lossless decoder can't decode image incrementally. So wait till
 526   // all the image data is aggregated before image can be decoded.
 527   if (curr_size < idec->chunk_size_) {
 528     return VP8_STATUS_SUSPENDED;
 529   }
 530
 531   if (!VP8LDecodeImage(dec)) {
 532     // The decoding is called after all the data-bytes are aggregated. Change
 533     // the error to VP8_BITSTREAM_ERROR in case lossless decoder fails to decode
 534     // all the pixels (VP8_STATUS_SUSPENDED).
 535     if (dec->status_ == VP8_STATUS_SUSPENDED) {
 536       dec->status_ = VP8_STATUS_BITSTREAM_ERROR;
 537     }
 538     return ErrorStatusLossless(idec, dec->status_);
 539   }
 540
 541   return FinishDecoding(idec);
 542 }
 543
 544   // Main decoding loop
 545 static VP8StatusCode IDecode(WebPIDecoder* idec) {
 546   VP8StatusCode status = VP8_STATUS_SUSPENDED;
 547
 548   if (idec->state_ == STATE_WEBP_HEADER) {
 549     status = DecodeWebPHeaders(idec);
 550   } else {
 551     if (idec->dec_ == NULL) {
 552       return VP8_STATUS_SUSPENDED;    // can't continue if we have no decoder.
 553     }
 554   }
 555   if (idec->state_ == STATE_VP8_HEADER) {
 556     status = DecodeVP8FrameHeader(idec);
 557   }
 558   if (idec->state_ == STATE_VP8_PARTS0) {
 559     status = DecodePartition0(idec);
 560   }
 561   if (idec->state_ == STATE_VP8_DATA) {
 562     status = DecodeRemaining(idec);
 563   }
 564   if (idec->state_ == STATE_VP8L_HEADER) {
 565     status = DecodeVP8LHeader(idec);
 566   }
 567   if (idec->state_ == STATE_VP8L_DATA) {
 568     status = DecodeVP8LData(idec);
 569   }
 570   return status;
 571 }
 572
 573 //------------------------------------------------------------------------------
 574 // Public functions
 575
 576 WebPIDecoder* WebPINewDecoder(WebPDecBuffer* output_buffer) {
 577   WebPIDecoder* idec = (WebPIDecoder*)WebPSafeCalloc(1ULL, sizeof(*idec));
 578   if (idec == NULL) {
 579     return NULL;
 580   }
 581
 582   idec->state_ = STATE_WEBP_HEADER;
 583   idec->chunk_size_ = 0;
 584
 585   idec->last_mb_y_ = -1;
 586
 587   InitMemBuffer(&idec->mem_);
 588   WebPInitDecBuffer(&idec->output_);
 589   VP8InitIo(&idec->io_);
 590
 591   WebPResetDecParams(&idec->params_);
 592   idec->params_.output = (output_buffer != NULL) ? output_buffer
 593                                                  : &idec->output_;
 594   WebPInitCustomIo(&idec->params_, &idec->io_);  // Plug the I/O functions.
 595
 596   return idec;
 597 }
 598
 599 WebPIDecoder* WebPIDecode(const uint8_t* data, size_t data_size,
 600                           WebPDecoderConfig* config) {
 601   WebPIDecoder* idec;
 602
 603   // Parse the bitstream's features, if requested:
 604   if (data != NULL && data_size > 0 && config != NULL) {
 605     if (WebPGetFeatures(data, data_size, &config->input) != VP8_STATUS_OK) {
 606       return NULL;
 607     }
 608   }
 609   // Create an instance of the incremental decoder
 610   idec = WebPINewDecoder(config ? &config->output : NULL);
 611   if (idec == NULL) {
 612     return NULL;
 613   }
 614   // Finish initialization
 615   if (config != NULL) {
 616     idec->params_.options = &config->options;
 617   }
 618   return idec;
 619 }
 620
 621 void WebPIDelete(WebPIDecoder* idec) {
 622   if (idec == NULL) return;
 623   if (idec->dec_ != NULL) {
 624     if (!idec->is_lossless_) {
 625       if (idec->state_ == STATE_VP8_DATA) {
 626         // Synchronize the thread, clean-up and check for errors.
 627         VP8ExitCritical((VP8Decoder*)idec->dec_, &idec->io_);
 628       }
 629       VP8Delete((VP8Decoder*)idec->dec_);
 630     } else {
 631       VP8LDelete((VP8LDecoder*)idec->dec_);
 632     }
 633   }
 634   ClearMemBuffer(&idec->mem_);
 635   WebPFreeDecBuffer(&idec->output_);
 636   WebPSafeFree(idec);
 637 }
 638
 639 //------------------------------------------------------------------------------
 640 // Wrapper toward WebPINewDecoder
 641
 642 WebPIDecoder* WebPINewRGB(WEBP_CSP_MODE mode, uint8_t* output_buffer,
 643                           size_t output_buffer_size, int output_stride) {
 644   const int is_external_memory = (output_buffer != NULL);
 645   WebPIDecoder* idec;
 646
 647   if (mode >= MODE_YUV) return NULL;
 648   if (!is_external_memory) {    // Overwrite parameters to sane values.
 649     output_buffer_size = 0;
 650     output_stride = 0;
 651   } else {  // A buffer was passed. Validate the other params.
 652     if (output_stride == 0 || output_buffer_size == 0) {
 653       return NULL;   // invalid parameter.
 654     }
 655   }
 656   idec = WebPINewDecoder(NULL);
 657   if (idec == NULL) return NULL;
 658   idec->output_.colorspace = mode;
 659   idec->output_.is_external_memory = is_external_memory;
 660   idec->output_.u.RGBA.rgba = output_buffer;
 661   idec->output_.u.RGBA.stride = output_stride;
 662   idec->output_.u.RGBA.size = output_buffer_size;
 663   return idec;
 664 }
 665
 666 WebPIDecoder* WebPINewYUVA(uint8_t* luma, size_t luma_size, int luma_stride,
 667                            uint8_t* u, size_t u_size, int u_stride,
 668                            uint8_t* v, size_t v_size, int v_stride,
 669                            uint8_t* a, size_t a_size, int a_stride) {
 670   const int is_external_memory = (luma != NULL);
 671   WebPIDecoder* idec;
 672   WEBP_CSP_MODE colorspace;
 673
 674   if (!is_external_memory) {    // Overwrite parameters to sane values.
 675     luma_size = u_size = v_size = a_size = 0;
 676     luma_stride = u_stride = v_stride = a_stride = 0;
 677     u = v = a = NULL;
 678     colorspace = MODE_YUVA;
 679   } else {  // A luma buffer was passed. Validate the other parameters.
 680     if (u == NULL || v == NULL) return NULL;
 681     if (luma_size == 0 || u_size == 0 || v_size == 0) return NULL;
 682     if (luma_stride == 0 || u_stride == 0 || v_stride == 0) return NULL;
 683     if (a != NULL) {
 684       if (a_size == 0 || a_stride == 0) return NULL;
 685     }
 686     colorspace = (a == NULL) ? MODE_YUV : MODE_YUVA;
 687   }
 688
 689   idec = WebPINewDecoder(NULL);
 690   if (idec == NULL) return NULL;
 691
 692   idec->output_.colorspace = colorspace;
 693   idec->output_.is_external_memory = is_external_memory;
 694   idec->output_.u.YUVA.y = luma;
 695   idec->output_.u.YUVA.y_stride = luma_stride;
 696   idec->output_.u.YUVA.y_size = luma_size;
 697   idec->output_.u.YUVA.u = u;
 698   idec->output_.u.YUVA.u_stride = u_stride;
 699   idec->output_.u.YUVA.u_size = u_size;
 700   idec->output_.u.YUVA.v = v;
 701   idec->output_.u.YUVA.v_stride = v_stride;
 702   idec->output_.u.YUVA.v_size = v_size;
 703   idec->output_.u.YUVA.a = a;
 704   idec->output_.u.YUVA.a_stride = a_stride;
 705   idec->output_.u.YUVA.a_size = a_size;
 706   return idec;
 707 }
 708
 709 WebPIDecoder* WebPINewYUV(uint8_t* luma, size_t luma_size, int luma_stride,
 710                           uint8_t* u, size_t u_size, int u_stride,
 711                           uint8_t* v, size_t v_size, int v_stride) {
 712   return WebPINewYUVA(luma, luma_size, luma_stride,
 713                       u, u_size, u_stride,
 714                       v, v_size, v_stride,
 715                       NULL, 0, 0);
 716 }
 717
 718 //------------------------------------------------------------------------------
 719
 720 static VP8StatusCode IDecCheckStatus(const WebPIDecoder* const idec) {
 721   assert(idec);
 722   if (idec->state_ == STATE_ERROR) {
 723     return VP8_STATUS_BITSTREAM_ERROR;
 724   }
 725   if (idec->state_ == STATE_DONE) {
 726     return VP8_STATUS_OK;
 727   }
 728   return VP8_STATUS_SUSPENDED;
 729 }
 730
 731 VP8StatusCode WebPIAppend(WebPIDecoder* idec,
 732                           const uint8_t* data, size_t data_size) {
 733   VP8StatusCode status;
 734   if (idec == NULL || data == NULL) {
 735     return VP8_STATUS_INVALID_PARAM;
 736   }
 737   status = IDecCheckStatus(idec);
 738   if (status != VP8_STATUS_SUSPENDED) {
 739     return status;
 740   }
 741   // Check mixed calls between RemapMemBuffer and AppendToMemBuffer.
 742   if (!CheckMemBufferMode(&idec->mem_, MEM_MODE_APPEND)) {
 743     return VP8_STATUS_INVALID_PARAM;
 744   }
 745   // Append data to memory buffer
 746   if (!AppendToMemBuffer(idec, data, data_size)) {
 747     return VP8_STATUS_OUT_OF_MEMORY;
 748   }
 749   return IDecode(idec);
 750 }
 751
 752 VP8StatusCode WebPIUpdate(WebPIDecoder* idec,
 753                           const uint8_t* data, size_t data_size) {
 754   VP8StatusCode status;
 755   if (idec == NULL || data == NULL) {
 756     return VP8_STATUS_INVALID_PARAM;
 757   }
 758   status = IDecCheckStatus(idec);
 759   if (status != VP8_STATUS_SUSPENDED) {
 760     return status;
 761   }
 762   // Check mixed calls between RemapMemBuffer and AppendToMemBuffer.
 763   if (!CheckMemBufferMode(&idec->mem_, MEM_MODE_MAP)) {
 764     return VP8_STATUS_INVALID_PARAM;
 765   }
 766   // Make the memory buffer point to the new buffer
 767   if (!RemapMemBuffer(idec, data, data_size)) {
 768     return VP8_STATUS_INVALID_PARAM;
 769   }
 770   return IDecode(idec);
 771 }
 772
 773 //------------------------------------------------------------------------------
 774
 775 static const WebPDecBuffer* GetOutputBuffer(const WebPIDecoder* const idec) {
 776   if (idec == NULL || idec->dec_ == NULL) {
 777     return NULL;
 778   }
 779   if (idec->state_ <= STATE_VP8_PARTS0) {
 780     return NULL;
 781   }
 782   return idec->params_.output;
 783 }
 784
 785 const WebPDecBuffer* WebPIDecodedArea(const WebPIDecoder* idec,
 786                                       int* left, int* top,
 787                                       int* width, int* height) {
 788   const WebPDecBuffer* const src = GetOutputBuffer(idec);
 789   if (left != NULL) *left = 0;
 790   if (top != NULL) *top = 0;
 791   // TODO(skal): later include handling of rotations.
 792   if (src) {
 793     if (width != NULL) *width = src->width;
 794     if (height != NULL) *height = idec->params_.last_y;
 795   } else {
 796     if (width != NULL) *width = 0;
 797     if (height != NULL) *height = 0;
 798   }
 799   return src;
 800 }
 801
 802 uint8_t* WebPIDecGetRGB(const WebPIDecoder* idec, int* last_y,
 803                         int* width, int* height, int* stride) {
 804   const WebPDecBuffer* const src = GetOutputBuffer(idec);
 805   if (src == NULL) return NULL;
 806   if (src->colorspace >= MODE_YUV) {
 807     return NULL;
 808   }
 809
 810   if (last_y != NULL) *last_y = idec->params_.last_y;
 811   if (width != NULL) *width = src->width;
 812   if (height != NULL) *height = src->height;
 813   if (stride != NULL) *stride = src->u.RGBA.stride;
 814
 815   return src->u.RGBA.rgba;
 816 }
 817
 818 uint8_t* WebPIDecGetYUVA(const WebPIDecoder* idec, int* last_y,
 819                          uint8_t** u, uint8_t** v, uint8_t** a,
 820                          int* width, int* height,
 821                          int* stride, int* uv_stride, int* a_stride) {
 822   const WebPDecBuffer* const src = GetOutputBuffer(idec);
 823   if (src == NULL) return NULL;
 824   if (src->colorspace < MODE_YUV) {
 825     return NULL;
 826   }
 827
 828   if (last_y != NULL) *last_y = idec->params_.last_y;
 829   if (u != NULL) *u = src->u.YUVA.u;
 830   if (v != NULL) *v = src->u.YUVA.v;
 831   if (a != NULL) *a = src->u.YUVA.a;
 832   if (width != NULL) *width = src->width;
 833   if (height != NULL) *height = src->height;
 834   if (stride != NULL) *stride = src->u.YUVA.y_stride;
 835   if (uv_stride != NULL) *uv_stride = src->u.YUVA.u_stride;
 836   if (a_stride != NULL) *a_stride = src->u.YUVA.a_stride;
 837
 838   return src->u.YUVA.y;
 839 }
 840
 841 int WebPISetIOHooks(WebPIDecoder* const idec,
 842                     VP8IoPutHook put,
 843                     VP8IoSetupHook setup,
 844                     VP8IoTeardownHook teardown,
 845                     void* user_data) {
 846   if (idec == NULL || idec->state_ > STATE_WEBP_HEADER) {
 847     return 0;
 848   }
 849
 850   idec->io_.put = put;
 851   idec->io_.setup = setup;
 852   idec->io_.teardown = teardown;
 853   idec->io_.opaque = user_data;
 854
 855   return 1;
 856 }
 857