third_party/libwebp/demux/demux.c

   1 // Copyright 2012 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 //  WebP container demux.
  11 //
  12
  13 #ifdef HAVE_CONFIG_H
  14 #include "config.h"
  15 #endif
  16
  17 #include <assert.h>
  18 #include <stdlib.h>
  19 #include <string.h>
  20
  21 #include "../utils/utils.h"
  22 #include "../webp/decode.h"     // WebPGetFeatures
  23 #include "../webp/demux.h"
  24 #include "../webp/format_constants.h"
  25
  26 #define DMUX_MAJ_VERSION 0
  27 #define DMUX_MIN_VERSION 2
  28 #define DMUX_REV_VERSION 0
  29
  30 typedef struct {
  31   size_t start_;        // start location of the data
  32   size_t end_;          // end location
  33   size_t riff_end_;     // riff chunk end location, can be > end_.
  34   size_t buf_size_;     // size of the buffer
  35   const uint8_t* buf_;
  36 } MemBuffer;
  37
  38 typedef struct {
  39   size_t offset_;
  40   size_t size_;
  41 } ChunkData;
  42
  43 typedef struct Frame {
  44   int x_offset_, y_offset_;
  45   int width_, height_;
  46   int has_alpha_;
  47   int duration_;
  48   WebPMuxAnimDispose dispose_method_;
  49   WebPMuxAnimBlend blend_method_;
  50   int is_fragment_;  // this is a frame fragment (and not a full frame).
  51   int frame_num_;  // the referent frame number for use in assembling fragments.
  52   int complete_;   // img_components_ contains a full image.
  53   ChunkData img_components_[2];  // 0=VP8{,L} 1=ALPH
  54   struct Frame* next_;
  55 } Frame;
  56
  57 typedef struct Chunk {
  58   ChunkData data_;
  59   struct Chunk* next_;
  60 } Chunk;
  61
  62 struct WebPDemuxer {
  63   MemBuffer mem_;
  64   WebPDemuxState state_;
  65   int is_ext_format_;
  66   uint32_t feature_flags_;
  67   int canvas_width_, canvas_height_;
  68   int loop_count_;
  69   uint32_t bgcolor_;
  70   int num_frames_;
  71   Frame* frames_;
  72   Frame** frames_tail_;
  73   Chunk* chunks_;  // non-image chunks
  74   Chunk** chunks_tail_;
  75 };
  76
  77 typedef enum {
  78   PARSE_OK,
  79   PARSE_NEED_MORE_DATA,
  80   PARSE_ERROR
  81 } ParseStatus;
  82
  83 typedef struct ChunkParser {
  84   uint8_t id[4];
  85   ParseStatus (*parse)(WebPDemuxer* const dmux);
  86   int (*valid)(const WebPDemuxer* const dmux);
  87 } ChunkParser;
  88
  89 static ParseStatus ParseSingleImage(WebPDemuxer* const dmux);
  90 static ParseStatus ParseVP8X(WebPDemuxer* const dmux);
  91 static int IsValidSimpleFormat(const WebPDemuxer* const dmux);
  92 static int IsValidExtendedFormat(const WebPDemuxer* const dmux);
  93
  94 static const ChunkParser kMasterChunks[] = {
  95   { { 'V', 'P', '8', ' ' }, ParseSingleImage, IsValidSimpleFormat },
  96   { { 'V', 'P', '8', 'L' }, ParseSingleImage, IsValidSimpleFormat },
  97   { { 'V', 'P', '8', 'X' }, ParseVP8X,        IsValidExtendedFormat },
  98   { { '0', '0', '0', '0' }, NULL,             NULL },
  99 };
 100
 101 //------------------------------------------------------------------------------
 102
 103 int WebPGetDemuxVersion(void) {
 104   return (DMUX_MAJ_VERSION << 16) | (DMUX_MIN_VERSION << 8) | DMUX_REV_VERSION;
 105 }
 106
 107 // -----------------------------------------------------------------------------
 108 // MemBuffer
 109
 110 static int RemapMemBuffer(MemBuffer* const mem,
 111                           const uint8_t* data, size_t size) {
 112   if (size < mem->buf_size_) return 0;  // can't remap to a shorter buffer!
 113
 114   mem->buf_ = data;
 115   mem->end_ = mem->buf_size_ = size;
 116   return 1;
 117 }
 118
 119 static int InitMemBuffer(MemBuffer* const mem,
 120                          const uint8_t* data, size_t size) {
 121   memset(mem, 0, sizeof(*mem));
 122   return RemapMemBuffer(mem, data, size);
 123 }
 124
 125 // Return the remaining data size available in 'mem'.
 126 static WEBP_INLINE size_t MemDataSize(const MemBuffer* const mem) {
 127   return (mem->end_ - mem->start_);
 128 }
 129
 130 // Return true if 'size' exceeds the end of the RIFF chunk.
 131 static WEBP_INLINE int SizeIsInvalid(const MemBuffer* const mem, size_t size) {
 132   return (size > mem->riff_end_ - mem->start_);
 133 }
 134
 135 static WEBP_INLINE void Skip(MemBuffer* const mem, size_t size) {
 136   mem->start_ += size;
 137 }
 138
 139 static WEBP_INLINE void Rewind(MemBuffer* const mem, size_t size) {
 140   mem->start_ -= size;
 141 }
 142
 143 static WEBP_INLINE const uint8_t* GetBuffer(MemBuffer* const mem) {
 144   return mem->buf_ + mem->start_;
 145 }
 146
 147 // Read from 'mem' and skip the read bytes.
 148 static WEBP_INLINE uint8_t ReadByte(MemBuffer* const mem) {
 149   const uint8_t byte = mem->buf_[mem->start_];
 150   Skip(mem, 1);
 151   return byte;
 152 }
 153
 154 static WEBP_INLINE int ReadLE16s(MemBuffer* const mem) {
 155   const uint8_t* const data = mem->buf_ + mem->start_;
 156   const int val = GetLE16(data);
 157   Skip(mem, 2);
 158   return val;
 159 }
 160
 161 static WEBP_INLINE int ReadLE24s(MemBuffer* const mem) {
 162   const uint8_t* const data = mem->buf_ + mem->start_;
 163   const int val = GetLE24(data);
 164   Skip(mem, 3);
 165   return val;
 166 }
 167
 168 static WEBP_INLINE uint32_t ReadLE32(MemBuffer* const mem) {
 169   const uint8_t* const data = mem->buf_ + mem->start_;
 170   const uint32_t val = GetLE32(data);
 171   Skip(mem, 4);
 172   return val;
 173 }
 174
 175 // -----------------------------------------------------------------------------
 176 // Secondary chunk parsing
 177
 178 static void AddChunk(WebPDemuxer* const dmux, Chunk* const chunk) {
 179   *dmux->chunks_tail_ = chunk;
 180   chunk->next_ = NULL;
 181   dmux->chunks_tail_ = &chunk->next_;
 182 }
 183
 184 // Add a frame to the end of the list, ensuring the last frame is complete.
 185 // Returns true on success, false otherwise.
 186 static int AddFrame(WebPDemuxer* const dmux, Frame* const frame) {
 187   const Frame* const last_frame = *dmux->frames_tail_;
 188   if (last_frame != NULL && !last_frame->complete_) return 0;
 189
 190   *dmux->frames_tail_ = frame;
 191   frame->next_ = NULL;
 192   dmux->frames_tail_ = &frame->next_;
 193   return 1;
 194 }
 195
 196 // Store image bearing chunks to 'frame'.
 197 static ParseStatus StoreFrame(int frame_num, uint32_t min_size,
 198                               MemBuffer* const mem, Frame* const frame) {
 199   int alpha_chunks = 0;
 200   int image_chunks = 0;
 201   int done = (MemDataSize(mem) < min_size);
 202   ParseStatus status = PARSE_OK;
 203
 204   if (done) return PARSE_NEED_MORE_DATA;
 205
 206   do {
 207     const size_t chunk_start_offset = mem->start_;
 208     const uint32_t fourcc = ReadLE32(mem);
 209     const uint32_t payload_size = ReadLE32(mem);
 210     const uint32_t payload_size_padded = payload_size + (payload_size & 1);
 211     const size_t payload_available = (payload_size_padded > MemDataSize(mem))
 212                                    ? MemDataSize(mem) : payload_size_padded;
 213     const size_t chunk_size = CHUNK_HEADER_SIZE + payload_available;
 214
 215     if (payload_size > MAX_CHUNK_PAYLOAD) return PARSE_ERROR;
 216     if (SizeIsInvalid(mem, payload_size_padded)) return PARSE_ERROR;
 217     if (payload_size_padded > MemDataSize(mem)) status = PARSE_NEED_MORE_DATA;
 218
 219     switch (fourcc) {
 220       case MKFOURCC('A', 'L', 'P', 'H'):
 221         if (alpha_chunks == 0) {
 222           ++alpha_chunks;
 223           frame->img_components_[1].offset_ = chunk_start_offset;
 224           frame->img_components_[1].size_ = chunk_size;
 225           frame->has_alpha_ = 1;
 226           frame->frame_num_ = frame_num;
 227           Skip(mem, payload_available);
 228         } else {
 229           goto Done;
 230         }
 231         break;
 232       case MKFOURCC('V', 'P', '8', 'L'):
 233         if (alpha_chunks > 0) return PARSE_ERROR;  // VP8L has its own alpha
 234         // fall through
 235       case MKFOURCC('V', 'P', '8', ' '):
 236         if (image_chunks == 0) {
 237           // Extract the bitstream features, tolerating failures when the data
 238           // is incomplete.
 239           WebPBitstreamFeatures features;
 240           const VP8StatusCode vp8_status =
 241               WebPGetFeatures(mem->buf_ + chunk_start_offset, chunk_size,
 242                               &features);
 243           if (status == PARSE_NEED_MORE_DATA &&
 244               vp8_status == VP8_STATUS_NOT_ENOUGH_DATA) {
 245             return PARSE_NEED_MORE_DATA;
 246           } else if (vp8_status != VP8_STATUS_OK) {
 247             // We have enough data, and yet WebPGetFeatures() failed.
 248             return PARSE_ERROR;
 249           }
 250           ++image_chunks;
 251           frame->img_components_[0].offset_ = chunk_start_offset;
 252           frame->img_components_[0].size_ = chunk_size;
 253           frame->width_ = features.width;
 254           frame->height_ = features.height;
 255           frame->has_alpha_ |= features.has_alpha;
 256           frame->frame_num_ = frame_num;
 257           frame->complete_ = (status == PARSE_OK);
 258           Skip(mem, payload_available);
 259         } else {
 260           goto Done;
 261         }
 262         break;
 263  Done:
 264       default:
 265         // Restore fourcc/size when moving up one level in parsing.
 266         Rewind(mem, CHUNK_HEADER_SIZE);
 267         done = 1;
 268         break;
 269     }
 270
 271     if (mem->start_ == mem->riff_end_) {
 272       done = 1;
 273     } else if (MemDataSize(mem) < CHUNK_HEADER_SIZE) {
 274       status = PARSE_NEED_MORE_DATA;
 275     }
 276   } while (!done && status == PARSE_OK);
 277
 278   return status;
 279 }
 280
 281 // Creates a new Frame if 'actual_size' is within bounds and 'mem' contains
 282 // enough data ('min_size') to parse the payload.
 283 // Returns PARSE_OK on success with *frame pointing to the new Frame.
 284 // Returns PARSE_NEED_MORE_DATA with insufficient data, PARSE_ERROR otherwise.
 285 static ParseStatus NewFrame(const MemBuffer* const mem,
 286                             uint32_t min_size, uint32_t actual_size,
 287                             Frame** frame) {
 288   if (SizeIsInvalid(mem, min_size)) return PARSE_ERROR;
 289   if (actual_size < min_size) return PARSE_ERROR;
 290   if (MemDataSize(mem) < min_size)  return PARSE_NEED_MORE_DATA;
 291
 292   *frame = (Frame*)calloc(1, sizeof(**frame));
 293   return (*frame == NULL) ? PARSE_ERROR : PARSE_OK;
 294 }
 295
 296 // Parse a 'ANMF' chunk and any image bearing chunks that immediately follow.
 297 // 'frame_chunk_size' is the previously validated, padded chunk size.
 298 static ParseStatus ParseAnimationFrame(
 299     WebPDemuxer* const dmux, uint32_t frame_chunk_size) {
 300   const int is_animation = !!(dmux->feature_flags_ & ANIMATION_FLAG);
 301   const uint32_t anmf_payload_size = frame_chunk_size - ANMF_CHUNK_SIZE;
 302   int added_frame = 0;
 303   int bits;
 304   MemBuffer* const mem = &dmux->mem_;
 305   Frame* frame;
 306   ParseStatus status =
 307       NewFrame(mem, ANMF_CHUNK_SIZE, frame_chunk_size, &frame);
 308   if (status != PARSE_OK) return status;
 309
 310   frame->x_offset_       = 2 * ReadLE24s(mem);
 311   frame->y_offset_       = 2 * ReadLE24s(mem);
 312   frame->width_          = 1 + ReadLE24s(mem);
 313   frame->height_         = 1 + ReadLE24s(mem);
 314   frame->duration_       = ReadLE24s(mem);
 315   bits = ReadByte(mem);
 316   frame->dispose_method_ =
 317       (bits & 1) ? WEBP_MUX_DISPOSE_BACKGROUND : WEBP_MUX_DISPOSE_NONE;
 318   frame->blend_method_ = (bits & 2) ? WEBP_MUX_NO_BLEND : WEBP_MUX_BLEND;
 319   if (frame->width_ * (uint64_t)frame->height_ >= MAX_IMAGE_AREA) {
 320     free(frame);
 321     return PARSE_ERROR;
 322   }
 323
 324   // Store a frame only if the animation flag is set there is some data for
 325   // this frame is available.
 326   status = StoreFrame(dmux->num_frames_ + 1, anmf_payload_size, mem, frame);
 327   if (status != PARSE_ERROR && is_animation && frame->frame_num_ > 0) {
 328     added_frame = AddFrame(dmux, frame);
 329     if (added_frame) {
 330       ++dmux->num_frames_;
 331     } else {
 332       status = PARSE_ERROR;
 333     }
 334   }
 335
 336   if (!added_frame) free(frame);
 337   return status;
 338 }
 339
 340 #ifdef WEBP_EXPERIMENTAL_FEATURES
 341 // Parse a 'FRGM' chunk and any image bearing chunks that immediately follow.
 342 // 'fragment_chunk_size' is the previously validated, padded chunk size.
 343 static ParseStatus ParseFragment(WebPDemuxer* const dmux,
 344                                  uint32_t fragment_chunk_size) {
 345   const int frame_num = 1;  // All fragments belong to the 1st (and only) frame.
 346   const int is_fragmented = !!(dmux->feature_flags_ & FRAGMENTS_FLAG);
 347   const uint32_t frgm_payload_size = fragment_chunk_size - FRGM_CHUNK_SIZE;
 348   int added_fragment = 0;
 349   MemBuffer* const mem = &dmux->mem_;
 350   Frame* frame;
 351   ParseStatus status =
 352       NewFrame(mem, FRGM_CHUNK_SIZE, fragment_chunk_size, &frame);
 353   if (status != PARSE_OK) return status;
 354
 355   frame->is_fragment_ = 1;
 356   frame->x_offset_ = 2 * ReadLE24s(mem);
 357   frame->y_offset_ = 2 * ReadLE24s(mem);
 358
 359   // Store a fragment only if the 'fragments' flag is set and there is some
 360   // data available.
 361   status = StoreFrame(frame_num, frgm_payload_size, mem, frame);
 362   if (status != PARSE_ERROR && is_fragmented && frame->frame_num_ > 0) {
 363     added_fragment = AddFrame(dmux, frame);
 364     if (!added_fragment) {
 365       status = PARSE_ERROR;
 366     } else {
 367       dmux->num_frames_ = 1;
 368     }
 369   }
 370
 371   if (!added_fragment) free(frame);
 372   return status;
 373 }
 374 #endif  // WEBP_EXPERIMENTAL_FEATURES
 375
 376 // General chunk storage, starting with the header at 'start_offset', allowing
 377 // the user to request the payload via a fourcc string. 'size' includes the
 378 // header and the unpadded payload size.
 379 // Returns true on success, false otherwise.
 380 static int StoreChunk(WebPDemuxer* const dmux,
 381                       size_t start_offset, uint32_t size) {
 382   Chunk* const chunk = (Chunk*)calloc(1, sizeof(*chunk));
 383   if (chunk == NULL) return 0;
 384
 385   chunk->data_.offset_ = start_offset;
 386   chunk->data_.size_ = size;
 387   AddChunk(dmux, chunk);
 388   return 1;
 389 }
 390
 391 // -----------------------------------------------------------------------------
 392 // Primary chunk parsing
 393
 394 static ParseStatus ReadHeader(MemBuffer* const mem) {
 395   const size_t min_size = RIFF_HEADER_SIZE + CHUNK_HEADER_SIZE;
 396   uint32_t riff_size;
 397
 398   // Basic file level validation.
 399   if (MemDataSize(mem) < min_size) return PARSE_NEED_MORE_DATA;
 400   if (memcmp(GetBuffer(mem), "RIFF", CHUNK_SIZE_BYTES) ||
 401       memcmp(GetBuffer(mem) + CHUNK_HEADER_SIZE, "WEBP", CHUNK_SIZE_BYTES)) {
 402     return PARSE_ERROR;
 403   }
 404
 405   riff_size = GetLE32(GetBuffer(mem) + TAG_SIZE);
 406   if (riff_size < CHUNK_HEADER_SIZE) return PARSE_ERROR;
 407   if (riff_size > MAX_CHUNK_PAYLOAD) return PARSE_ERROR;
 408
 409   // There's no point in reading past the end of the RIFF chunk
 410   mem->riff_end_ = riff_size + CHUNK_HEADER_SIZE;
 411   if (mem->buf_size_ > mem->riff_end_) {
 412     mem->buf_size_ = mem->end_ = mem->riff_end_;
 413   }
 414
 415   Skip(mem, RIFF_HEADER_SIZE);
 416   return PARSE_OK;
 417 }
 418
 419 static ParseStatus ParseSingleImage(WebPDemuxer* const dmux) {
 420   const size_t min_size = CHUNK_HEADER_SIZE;
 421   MemBuffer* const mem = &dmux->mem_;
 422   Frame* frame;
 423   ParseStatus status;
 424   int image_added = 0;
 425
 426   if (dmux->frames_ != NULL) return PARSE_ERROR;
 427   if (SizeIsInvalid(mem, min_size)) return PARSE_ERROR;
 428   if (MemDataSize(mem) < min_size) return PARSE_NEED_MORE_DATA;
 429
 430   frame = (Frame*)calloc(1, sizeof(*frame));
 431   if (frame == NULL) return PARSE_ERROR;
 432
 433   // For the single image case we allow parsing of a partial frame, but we need
 434   // at least CHUNK_HEADER_SIZE for parsing.
 435   status = StoreFrame(1, CHUNK_HEADER_SIZE, &dmux->mem_, frame);
 436   if (status != PARSE_ERROR) {
 437     const int has_alpha = !!(dmux->feature_flags_ & ALPHA_FLAG);
 438     // Clear any alpha when the alpha flag is missing.
 439     if (!has_alpha && frame->img_components_[1].size_ > 0) {
 440       frame->img_components_[1].offset_ = 0;
 441       frame->img_components_[1].size_ = 0;
 442       frame->has_alpha_ = 0;
 443     }
 444
 445     // Use the frame width/height as the canvas values for non-vp8x files.
 446     // Also, set ALPHA_FLAG if this is a lossless image with alpha.
 447     if (!dmux->is_ext_format_ && frame->width_ > 0 && frame->height_ > 0) {
 448       dmux->state_ = WEBP_DEMUX_PARSED_HEADER;
 449       dmux->canvas_width_ = frame->width_;
 450       dmux->canvas_height_ = frame->height_;
 451       dmux->feature_flags_ |= frame->has_alpha_ ? ALPHA_FLAG : 0;
 452     }
 453     if (!AddFrame(dmux, frame)) {
 454       status = PARSE_ERROR;  // last frame was left incomplete
 455     } else {
 456       image_added = 1;
 457       dmux->num_frames_ = 1;
 458     }
 459   }
 460
 461   if (!image_added) free(frame);
 462   return status;
 463 }
 464
 465 static ParseStatus ParseVP8XChunks(WebPDemuxer* const dmux) {
 466   const int is_animation = !!(dmux->feature_flags_ & ANIMATION_FLAG);
 467   MemBuffer* const mem = &dmux->mem_;
 468   int anim_chunks = 0;
 469   ParseStatus status = PARSE_OK;
 470
 471   do {
 472     int store_chunk = 1;
 473     const size_t chunk_start_offset = mem->start_;
 474     const uint32_t fourcc = ReadLE32(mem);
 475     const uint32_t chunk_size = ReadLE32(mem);
 476     const uint32_t chunk_size_padded = chunk_size + (chunk_size & 1);
 477
 478     if (chunk_size > MAX_CHUNK_PAYLOAD) return PARSE_ERROR;
 479     if (SizeIsInvalid(mem, chunk_size_padded)) return PARSE_ERROR;
 480
 481     switch (fourcc) {
 482       case MKFOURCC('V', 'P', '8', 'X'): {
 483         return PARSE_ERROR;
 484       }
 485       case MKFOURCC('A', 'L', 'P', 'H'):
 486       case MKFOURCC('V', 'P', '8', ' '):
 487       case MKFOURCC('V', 'P', '8', 'L'): {
 488         // check that this isn't an animation (all frames should be in an ANMF).
 489         if (anim_chunks > 0 || is_animation) return PARSE_ERROR;
 490
 491         Rewind(mem, CHUNK_HEADER_SIZE);
 492         status = ParseSingleImage(dmux);
 493         break;
 494       }
 495       case MKFOURCC('A', 'N', 'I', 'M'): {
 496         if (chunk_size_padded < ANIM_CHUNK_SIZE) return PARSE_ERROR;
 497
 498         if (MemDataSize(mem) < chunk_size_padded) {
 499           status = PARSE_NEED_MORE_DATA;
 500         } else if (anim_chunks == 0) {
 501           ++anim_chunks;
 502           dmux->bgcolor_ = ReadLE32(mem);
 503           dmux->loop_count_ = ReadLE16s(mem);
 504           Skip(mem, chunk_size_padded - ANIM_CHUNK_SIZE);
 505         } else {
 506           store_chunk = 0;
 507           goto Skip;
 508         }
 509         break;
 510       }
 511       case MKFOURCC('A', 'N', 'M', 'F'): {
 512         if (anim_chunks == 0) return PARSE_ERROR;  // 'ANIM' precedes frames.
 513         status = ParseAnimationFrame(dmux, chunk_size_padded);
 514         break;
 515       }
 516 #ifdef WEBP_EXPERIMENTAL_FEATURES
 517       case MKFOURCC('F', 'R', 'G', 'M'): {
 518         status = ParseFragment(dmux, chunk_size_padded);
 519         break;
 520       }
 521 #endif
 522       case MKFOURCC('I', 'C', 'C', 'P'): {
 523         store_chunk = !!(dmux->feature_flags_ & ICCP_FLAG);
 524         goto Skip;
 525       }
 526       case MKFOURCC('E', 'X', 'I', 'F'): {
 527         store_chunk = !!(dmux->feature_flags_ & EXIF_FLAG);
 528         goto Skip;
 529       }
 530       case MKFOURCC('X', 'M', 'P', ' '): {
 531         store_chunk = !!(dmux->feature_flags_ & XMP_FLAG);
 532         goto Skip;
 533       }
 534  Skip:
 535       default: {
 536         if (chunk_size_padded <= MemDataSize(mem)) {
 537           if (store_chunk) {
 538             // Store only the chunk header and unpadded size as only the payload
 539             // will be returned to the user.
 540             if (!StoreChunk(dmux, chunk_start_offset,
 541                             CHUNK_HEADER_SIZE + chunk_size)) {
 542               return PARSE_ERROR;
 543             }
 544           }
 545           Skip(mem, chunk_size_padded);
 546         } else {
 547           status = PARSE_NEED_MORE_DATA;
 548         }
 549       }
 550     }
 551
 552     if (mem->start_ == mem->riff_end_) {
 553       break;
 554     } else if (MemDataSize(mem) < CHUNK_HEADER_SIZE) {
 555       status = PARSE_NEED_MORE_DATA;
 556     }
 557   } while (status == PARSE_OK);
 558
 559   return status;
 560 }
 561
 562 static ParseStatus ParseVP8X(WebPDemuxer* const dmux) {
 563   MemBuffer* const mem = &dmux->mem_;
 564   uint32_t vp8x_size;
 565
 566   if (MemDataSize(mem) < CHUNK_HEADER_SIZE) return PARSE_NEED_MORE_DATA;
 567
 568   dmux->is_ext_format_ = 1;
 569   Skip(mem, TAG_SIZE);  // VP8X
 570   vp8x_size = ReadLE32(mem);
 571   if (vp8x_size > MAX_CHUNK_PAYLOAD) return PARSE_ERROR;
 572   if (vp8x_size < VP8X_CHUNK_SIZE) return PARSE_ERROR;
 573   vp8x_size += vp8x_size & 1;
 574   if (SizeIsInvalid(mem, vp8x_size)) return PARSE_ERROR;
 575   if (MemDataSize(mem) < vp8x_size) return PARSE_NEED_MORE_DATA;
 576
 577   dmux->feature_flags_ = ReadByte(mem);
 578   Skip(mem, 3);  // Reserved.
 579   dmux->canvas_width_  = 1 + ReadLE24s(mem);
 580   dmux->canvas_height_ = 1 + ReadLE24s(mem);
 581   if (dmux->canvas_width_ * (uint64_t)dmux->canvas_height_ >= MAX_IMAGE_AREA) {
 582     return PARSE_ERROR;  // image final dimension is too large
 583   }
 584   Skip(mem, vp8x_size - VP8X_CHUNK_SIZE);  // skip any trailing data.
 585   dmux->state_ = WEBP_DEMUX_PARSED_HEADER;
 586
 587   if (SizeIsInvalid(mem, CHUNK_HEADER_SIZE)) return PARSE_ERROR;
 588   if (MemDataSize(mem) < CHUNK_HEADER_SIZE) return PARSE_NEED_MORE_DATA;
 589
 590   return ParseVP8XChunks(dmux);
 591 }
 592
 593 // -----------------------------------------------------------------------------
 594 // Format validation
 595
 596 static int IsValidSimpleFormat(const WebPDemuxer* const dmux) {
 597   const Frame* const frame = dmux->frames_;
 598   if (dmux->state_ == WEBP_DEMUX_PARSING_HEADER) return 1;
 599
 600   if (dmux->canvas_width_ <= 0 || dmux->canvas_height_ <= 0) return 0;
 601   if (dmux->state_ == WEBP_DEMUX_DONE && frame == NULL) return 0;
 602
 603   if (frame->width_ <= 0 || frame->height_ <= 0) return 0;
 604   return 1;
 605 }
 606
 607 // If 'exact' is true, check that the image resolution matches the canvas.
 608 // If 'exact' is false, check that the x/y offsets do not exceed the canvas.
 609 // TODO(jzern): this is insufficient in the fragmented image case if the
 610 // expectation is that the fragments completely cover the canvas.
 611 static int CheckFrameBounds(const Frame* const frame, int exact,
 612                             int canvas_width, int canvas_height) {
 613   if (exact) {
 614     if (frame->x_offset_ != 0 || frame->y_offset_ != 0) {
 615       return 0;
 616     }
 617     if (frame->width_ != canvas_width || frame->height_ != canvas_height) {
 618       return 0;
 619     }
 620   } else {
 621     if (frame->x_offset_ < 0 || frame->y_offset_ < 0) return 0;
 622     if (frame->width_ + frame->x_offset_ > canvas_width) return 0;
 623     if (frame->height_ + frame->y_offset_ > canvas_height) return 0;
 624   }
 625   return 1;
 626 }
 627
 628 static int IsValidExtendedFormat(const WebPDemuxer* const dmux) {
 629   const int is_animation = !!(dmux->feature_flags_ & ANIMATION_FLAG);
 630   const int is_fragmented = !!(dmux->feature_flags_ & FRAGMENTS_FLAG);
 631   const Frame* f = dmux->frames_;
 632
 633   if (dmux->state_ == WEBP_DEMUX_PARSING_HEADER) return 1;
 634
 635   if (dmux->canvas_width_ <= 0 || dmux->canvas_height_ <= 0) return 0;
 636   if (dmux->loop_count_ < 0) return 0;
 637   if (dmux->state_ == WEBP_DEMUX_DONE && dmux->frames_ == NULL) return 0;
 638 #ifndef WEBP_EXPERIMENTAL_FEATURES
 639   if (is_fragmented) return 0;
 640 #endif
 641
 642   while (f != NULL) {
 643     const int cur_frame_set = f->frame_num_;
 644     int frame_count = 0, fragment_count = 0;
 645
 646     // Check frame properties and if the image is composed of fragments that
 647     // each fragment came from a fragment.
 648     for (; f != NULL && f->frame_num_ == cur_frame_set; f = f->next_) {
 649       const ChunkData* const image = f->img_components_;
 650       const ChunkData* const alpha = f->img_components_ + 1;
 651
 652       if (is_fragmented && !f->is_fragment_) return 0;
 653       if (!is_fragmented && f->is_fragment_) return 0;
 654       if (!is_animation && f->frame_num_ > 1) return 0;
 655
 656       if (f->complete_) {
 657         if (alpha->size_ == 0 && image->size_ == 0) return 0;
 658         // Ensure alpha precedes image bitstream.
 659         if (alpha->size_ > 0 && alpha->offset_ > image->offset_) {
 660           return 0;
 661         }
 662
 663         if (f->width_ <= 0 || f->height_ <= 0) return 0;
 664       } else {
 665         // There shouldn't be a partial frame in a complete file.
 666         if (dmux->state_ == WEBP_DEMUX_DONE) return 0;
 667
 668         // Ensure alpha precedes image bitstream.
 669         if (alpha->size_ > 0 && image->size_ > 0 &&
 670             alpha->offset_ > image->offset_) {
 671           return 0;
 672         }
 673         // There shouldn't be any frames after an incomplete one.
 674         if (f->next_ != NULL) return 0;
 675       }
 676
 677       if (f->width_ > 0 && f->height_ > 0 &&
 678           !CheckFrameBounds(f, !(is_animation || is_fragmented),
 679                             dmux->canvas_width_, dmux->canvas_height_)) {
 680         return 0;
 681       }
 682
 683       fragment_count += f->is_fragment_;
 684       ++frame_count;
 685     }
 686     if (!is_fragmented && frame_count > 1) return 0;
 687     if (fragment_count > 0 && frame_count != fragment_count) return 0;
 688   }
 689   return 1;
 690 }
 691
 692 // -----------------------------------------------------------------------------
 693 // WebPDemuxer object
 694
 695 static void InitDemux(WebPDemuxer* const dmux, const MemBuffer* const mem) {
 696   dmux->state_ = WEBP_DEMUX_PARSING_HEADER;
 697   dmux->loop_count_ = 1;
 698   dmux->bgcolor_ = 0xFFFFFFFF;  // White background by default.
 699   dmux->canvas_width_ = -1;
 700   dmux->canvas_height_ = -1;
 701   dmux->frames_tail_ = &dmux->frames_;
 702   dmux->chunks_tail_ = &dmux->chunks_;
 703   dmux->mem_ = *mem;
 704 }
 705
 706 WebPDemuxer* WebPDemuxInternal(const WebPData* data, int allow_partial,
 707                                WebPDemuxState* state, int version) {
 708   const ChunkParser* parser;
 709   int partial;
 710   ParseStatus status = PARSE_ERROR;
 711   MemBuffer mem;
 712   WebPDemuxer* dmux;
 713
 714   if (state != NULL) *state = WEBP_DEMUX_PARSE_ERROR;
 715
 716   if (WEBP_ABI_IS_INCOMPATIBLE(version, WEBP_DEMUX_ABI_VERSION)) return NULL;
 717   if (data == NULL || data->bytes == NULL || data->size == 0) return NULL;
 718
 719   if (!InitMemBuffer(&mem, data->bytes, data->size)) return NULL;
 720   status = ReadHeader(&mem);
 721   if (status != PARSE_OK) {
 722     if (state != NULL) {
 723       *state = (status == PARSE_NEED_MORE_DATA) ? WEBP_DEMUX_PARSING_HEADER
 724                                                 : WEBP_DEMUX_PARSE_ERROR;
 725     }
 726     return NULL;
 727   }
 728
 729   partial = (mem.buf_size_ < mem.riff_end_);
 730   if (!allow_partial && partial) return NULL;
 731
 732   dmux = (WebPDemuxer*)calloc(1, sizeof(*dmux));
 733   if (dmux == NULL) return NULL;
 734   InitDemux(dmux, &mem);
 735
 736   status = PARSE_ERROR;
 737   for (parser = kMasterChunks; parser->parse != NULL; ++parser) {
 738     if (!memcmp(parser->id, GetBuffer(&dmux->mem_), TAG_SIZE)) {
 739       status = parser->parse(dmux);
 740       if (status == PARSE_OK) dmux->state_ = WEBP_DEMUX_DONE;
 741       if (status == PARSE_NEED_MORE_DATA && !partial) status = PARSE_ERROR;
 742       if (status != PARSE_ERROR && !parser->valid(dmux)) status = PARSE_ERROR;
 743       if (status == PARSE_ERROR) dmux->state_ = WEBP_DEMUX_PARSE_ERROR;
 744       break;
 745     }
 746   }
 747   if (state != NULL) *state = dmux->state_;
 748
 749   if (status == PARSE_ERROR) {
 750     WebPDemuxDelete(dmux);
 751     return NULL;
 752   }
 753   return dmux;
 754 }
 755
 756 void WebPDemuxDelete(WebPDemuxer* dmux) {
 757   Chunk* c;
 758   Frame* f;
 759   if (dmux == NULL) return;
 760
 761   for (f = dmux->frames_; f != NULL;) {
 762     Frame* const cur_frame = f;
 763     f = f->next_;
 764     free(cur_frame);
 765   }
 766   for (c = dmux->chunks_; c != NULL;) {
 767     Chunk* const cur_chunk = c;
 768     c = c->next_;
 769     free(cur_chunk);
 770   }
 771   free(dmux);
 772 }
 773
 774 // -----------------------------------------------------------------------------
 775
 776 uint32_t WebPDemuxGetI(const WebPDemuxer* dmux, WebPFormatFeature feature) {
 777   if (dmux == NULL) return 0;
 778
 779   switch (feature) {
 780     case WEBP_FF_FORMAT_FLAGS:     return dmux->feature_flags_;
 781     case WEBP_FF_CANVAS_WIDTH:     return (uint32_t)dmux->canvas_width_;
 782     case WEBP_FF_CANVAS_HEIGHT:    return (uint32_t)dmux->canvas_height_;
 783     case WEBP_FF_LOOP_COUNT:       return (uint32_t)dmux->loop_count_;
 784     case WEBP_FF_BACKGROUND_COLOR: return dmux->bgcolor_;
 785     case WEBP_FF_FRAME_COUNT:      return (uint32_t)dmux->num_frames_;
 786   }
 787   return 0;
 788 }
 789
 790 // -----------------------------------------------------------------------------
 791 // Frame iteration
 792
 793 // Find the first 'frame_num' frame. There may be multiple such frames in a
 794 // fragmented frame.
 795 static const Frame* GetFrame(const WebPDemuxer* const dmux, int frame_num) {
 796   const Frame* f;
 797   for (f = dmux->frames_; f != NULL; f = f->next_) {
 798     if (frame_num == f->frame_num_) break;
 799   }
 800   return f;
 801 }
 802
 803 // Returns fragment 'fragment_num' and the total count.
 804 static const Frame* GetFragment(
 805     const Frame* const frame_set, int fragment_num, int* const count) {
 806   const int this_frame = frame_set->frame_num_;
 807   const Frame* f = frame_set;
 808   const Frame* fragment = NULL;
 809   int total;
 810
 811   for (total = 0; f != NULL && f->frame_num_ == this_frame; f = f->next_) {
 812     if (++total == fragment_num) fragment = f;
 813   }
 814   *count = total;
 815   return fragment;
 816 }
 817
 818 static const uint8_t* GetFramePayload(const uint8_t* const mem_buf,
 819                                       const Frame* const frame,
 820                                       size_t* const data_size) {
 821   *data_size = 0;
 822   if (frame != NULL) {
 823     const ChunkData* const image = frame->img_components_;
 824     const ChunkData* const alpha = frame->img_components_ + 1;
 825     size_t start_offset = image->offset_;
 826     *data_size = image->size_;
 827
 828     // if alpha exists it precedes image, update the size allowing for
 829     // intervening chunks.
 830     if (alpha->size_ > 0) {
 831       const size_t inter_size = (image->offset_ > 0)
 832                               ? image->offset_ - (alpha->offset_ + alpha->size_)
 833                               : 0;
 834       start_offset = alpha->offset_;
 835       *data_size  += alpha->size_ + inter_size;
 836     }
 837     return mem_buf + start_offset;
 838   }
 839   return NULL;
 840 }
 841
 842 // Create a whole 'frame' from VP8 (+ alpha) or lossless.
 843 static int SynthesizeFrame(const WebPDemuxer* const dmux,
 844                            const Frame* const first_frame,
 845                            int fragment_num, WebPIterator* const iter) {
 846   const uint8_t* const mem_buf = dmux->mem_.buf_;
 847   int num_fragments;
 848   size_t payload_size = 0;
 849   const Frame* const fragment =
 850       GetFragment(first_frame, fragment_num, &num_fragments);
 851   const uint8_t* const payload =
 852       GetFramePayload(mem_buf, fragment, &payload_size);
 853   if (payload == NULL) return 0;
 854   assert(first_frame != NULL);
 855
 856   iter->frame_num      = first_frame->frame_num_;
 857   iter->num_frames     = dmux->num_frames_;
 858   iter->fragment_num   = fragment_num;
 859   iter->num_fragments  = num_fragments;
 860   iter->x_offset       = fragment->x_offset_;
 861   iter->y_offset       = fragment->y_offset_;
 862   iter->width          = fragment->width_;
 863   iter->height         = fragment->height_;
 864   iter->has_alpha      = fragment->has_alpha_;
 865   iter->duration       = fragment->duration_;
 866   iter->dispose_method = fragment->dispose_method_;
 867   iter->blend_method   = fragment->blend_method_;
 868   iter->complete       = fragment->complete_;
 869   iter->fragment.bytes = payload;
 870   iter->fragment.size  = payload_size;
 871   // TODO(jzern): adjust offsets for 'FRGM's embedded in 'ANMF's
 872   return 1;
 873 }
 874
 875 static int SetFrame(int frame_num, WebPIterator* const iter) {
 876   const Frame* frame;
 877   const WebPDemuxer* const dmux = (WebPDemuxer*)iter->private_;
 878   if (dmux == NULL || frame_num < 0) return 0;
 879   if (frame_num > dmux->num_frames_) return 0;
 880   if (frame_num == 0) frame_num = dmux->num_frames_;
 881
 882   frame = GetFrame(dmux, frame_num);
 883   if (frame == NULL) return 0;
 884
 885   return SynthesizeFrame(dmux, frame, 1, iter);
 886 }
 887
 888 int WebPDemuxGetFrame(const WebPDemuxer* dmux, int frame, WebPIterator* iter) {
 889   if (iter == NULL) return 0;
 890
 891   memset(iter, 0, sizeof(*iter));
 892   iter->private_ = (void*)dmux;
 893   return SetFrame(frame, iter);
 894 }
 895
 896 int WebPDemuxNextFrame(WebPIterator* iter) {
 897   if (iter == NULL) return 0;
 898   return SetFrame(iter->frame_num + 1, iter);
 899 }
 900
 901 int WebPDemuxPrevFrame(WebPIterator* iter) {
 902   if (iter == NULL) return 0;
 903   if (iter->frame_num <= 1) return 0;
 904   return SetFrame(iter->frame_num - 1, iter);
 905 }
 906
 907 int WebPDemuxSelectFragment(WebPIterator* iter, int fragment_num) {
 908   if (iter != NULL && iter->private_ != NULL && fragment_num > 0) {
 909     const WebPDemuxer* const dmux = (WebPDemuxer*)iter->private_;
 910     const Frame* const frame = GetFrame(dmux, iter->frame_num);
 911     if (frame == NULL) return 0;
 912
 913     return SynthesizeFrame(dmux, frame, fragment_num, iter);
 914   }
 915   return 0;
 916 }
 917
 918 void WebPDemuxReleaseIterator(WebPIterator* iter) {
 919   (void)iter;
 920 }
 921
 922 // -----------------------------------------------------------------------------
 923 // Chunk iteration
 924
 925 static int ChunkCount(const WebPDemuxer* const dmux, const char fourcc[4]) {
 926   const uint8_t* const mem_buf = dmux->mem_.buf_;
 927   const Chunk* c;
 928   int count = 0;
 929   for (c = dmux->chunks_; c != NULL; c = c->next_) {
 930     const uint8_t* const header = mem_buf + c->data_.offset_;
 931     if (!memcmp(header, fourcc, TAG_SIZE)) ++count;
 932   }
 933   return count;
 934 }
 935
 936 static const Chunk* GetChunk(const WebPDemuxer* const dmux,
 937                              const char fourcc[4], int chunk_num) {
 938   const uint8_t* const mem_buf = dmux->mem_.buf_;
 939   const Chunk* c;
 940   int count = 0;
 941   for (c = dmux->chunks_; c != NULL; c = c->next_) {
 942     const uint8_t* const header = mem_buf + c->data_.offset_;
 943     if (!memcmp(header, fourcc, TAG_SIZE)) ++count;
 944     if (count == chunk_num) break;
 945   }
 946   return c;
 947 }
 948
 949 static int SetChunk(const char fourcc[4], int chunk_num,
 950                     WebPChunkIterator* const iter) {
 951   const WebPDemuxer* const dmux = (WebPDemuxer*)iter->private_;
 952   int count;
 953
 954   if (dmux == NULL || fourcc == NULL || chunk_num < 0) return 0;
 955   count = ChunkCount(dmux, fourcc);
 956   if (count == 0) return 0;
 957   if (chunk_num == 0) chunk_num = count;
 958
 959   if (chunk_num <= count) {
 960     const uint8_t* const mem_buf = dmux->mem_.buf_;
 961     const Chunk* const chunk = GetChunk(dmux, fourcc, chunk_num);
 962     iter->chunk.bytes = mem_buf + chunk->data_.offset_ + CHUNK_HEADER_SIZE;
 963     iter->chunk.size  = chunk->data_.size_ - CHUNK_HEADER_SIZE;
 964     iter->num_chunks  = count;
 965     iter->chunk_num   = chunk_num;
 966     return 1;
 967   }
 968   return 0;
 969 }
 970
 971 int WebPDemuxGetChunk(const WebPDemuxer* dmux,
 972                       const char fourcc[4], int chunk_num,
 973                       WebPChunkIterator* iter) {
 974   if (iter == NULL) return 0;
 975
 976   memset(iter, 0, sizeof(*iter));
 977   iter->private_ = (void*)dmux;
 978   return SetChunk(fourcc, chunk_num, iter);
 979 }
 980
 981 int WebPDemuxNextChunk(WebPChunkIterator* iter) {
 982   if (iter != NULL) {
 983     const char* const fourcc =
 984         (const char*)iter->chunk.bytes - CHUNK_HEADER_SIZE;
 985     return SetChunk(fourcc, iter->chunk_num + 1, iter);
 986   }
 987   return 0;
 988 }
 989
 990 int WebPDemuxPrevChunk(WebPChunkIterator* iter) {
 991   if (iter != NULL && iter->chunk_num > 1) {
 992     const char* const fourcc =
 993         (const char*)iter->chunk.bytes - CHUNK_HEADER_SIZE;
 994     return SetChunk(fourcc, iter->chunk_num - 1, iter);
 995   }
 996   return 0;
 997 }
 998
 999 void WebPDemuxReleaseChunkIterator(WebPChunkIterator* iter) {
1000   (void)iter;
1001 }
1002