static ParseStatus StoreFrame()

in Extended/libwebp/src/demux/demux.c [210:288]
68 lines of code
20 McCabe index (conditional complexity)

static ParseStatus StoreFrame(int frame_num, uint32_t min_size,
                              MemBuffer* const mem, Frame* const frame) {
  int alpha_chunks = 0;
  int image_chunks = 0;
  int done = (MemDataSize(mem) < CHUNK_HEADER_SIZE ||
              MemDataSize(mem) < min_size);
  ParseStatus status = PARSE_OK;

  if (done) return PARSE_NEED_MORE_DATA;

  do {
    const size_t chunk_start_offset = mem->start_;
    const uint32_t fourcc = ReadLE32(mem);
    const uint32_t payload_size = ReadLE32(mem);
    const uint32_t payload_size_padded = payload_size + (payload_size & 1);
    const size_t payload_available = (payload_size_padded > MemDataSize(mem))
                                   ? MemDataSize(mem) : payload_size_padded;
    const size_t chunk_size = CHUNK_HEADER_SIZE + payload_available;

    if (payload_size > MAX_CHUNK_PAYLOAD) return PARSE_ERROR;
    if (SizeIsInvalid(mem, payload_size_padded)) return PARSE_ERROR;
    if (payload_size_padded > MemDataSize(mem)) status = PARSE_NEED_MORE_DATA;

    switch (fourcc) {
      case MKFOURCC('A', 'L', 'P', 'H'):
        if (alpha_chunks == 0) {
          ++alpha_chunks;
          frame->img_components_[1].offset_ = chunk_start_offset;
          frame->img_components_[1].size_ = chunk_size;
          frame->has_alpha_ = 1;
          frame->frame_num_ = frame_num;
          Skip(mem, payload_available);
        } else {
          goto Done;
        }
        break;
      case MKFOURCC('V', 'P', '8', 'L'):
        if (alpha_chunks > 0) return PARSE_ERROR;  // VP8L has its own alpha
        // fall through
      case MKFOURCC('V', 'P', '8', ' '):
        if (image_chunks == 0) {
          // Extract the bitstream features, tolerating failures when the data
          // is incomplete.
          WebPBitstreamFeatures features;
          const VP8StatusCode vp8_status =
              WebPGetFeatures(mem->buf_ + chunk_start_offset, chunk_size,
                              &features);
          if (status == PARSE_NEED_MORE_DATA &&
              vp8_status == VP8_STATUS_NOT_ENOUGH_DATA) {
            return PARSE_NEED_MORE_DATA;
          } else if (vp8_status != VP8_STATUS_OK) {
            // We have enough data, and yet WebPGetFeatures() failed.
            return PARSE_ERROR;
          }
          ++image_chunks;
          SetFrameInfo(chunk_start_offset, chunk_size, frame_num,
                       status == PARSE_OK, &features, frame);
          Skip(mem, payload_available);
        } else {
          goto Done;
        }
        break;
 Done:
      default:
        // Restore fourcc/size when moving up one level in parsing.
        Rewind(mem, CHUNK_HEADER_SIZE);
        done = 1;
        break;
    }

    if (mem->start_ == mem->riff_end_) {
      done = 1;
    } else if (MemDataSize(mem) < CHUNK_HEADER_SIZE) {
      status = PARSE_NEED_MORE_DATA;
    }
  } while (!done && status == PARSE_OK);

  return status;
}