static int IsValidExtendedFormat()

in Extended/libwebp/src/demux/demux.c [593:646]

• 39 lines of code
• 26 McCabe index (conditional complexity)

static int IsValidExtendedFormat(const WebPDemuxer* const dmux) {
  const int is_animation = !!(dmux->feature_flags_ & ANIMATION_FLAG);
  const Frame* f = dmux->frames_;

  if (dmux->state_ == WEBP_DEMUX_PARSING_HEADER) return 1;

  if (dmux->canvas_width_ <= 0 || dmux->canvas_height_ <= 0) return 0;
  if (dmux->loop_count_ < 0) return 0;
  if (dmux->state_ == WEBP_DEMUX_DONE && dmux->frames_ == NULL) return 0;
  if (dmux->feature_flags_ & ~ALL_VALID_FLAGS) return 0;  // invalid bitstream

  while (f != NULL) {
    const int cur_frame_set = f->frame_num_;
    int frame_count = 0;

    // Check frame properties.
    for (; f != NULL && f->frame_num_ == cur_frame_set; f = f->next_) {
      const ChunkData* const image = f->img_components_;
      const ChunkData* const alpha = f->img_components_ + 1;

      if (!is_animation && f->frame_num_ > 1) return 0;

      if (f->complete_) {
        if (alpha->size_ == 0 && image->size_ == 0) return 0;
        // Ensure alpha precedes image bitstream.
        if (alpha->size_ > 0 && alpha->offset_ > image->offset_) {
          return 0;
        }

        if (f->width_ <= 0 || f->height_ <= 0) return 0;
      } else {
        // There shouldn't be a partial frame in a complete file.
        if (dmux->state_ == WEBP_DEMUX_DONE) return 0;

        // Ensure alpha precedes image bitstream.
        if (alpha->size_ > 0 && image->size_ > 0 &&
            alpha->offset_ > image->offset_) {
          return 0;
        }
        // There shouldn't be any frames after an incomplete one.
        if (f->next_ != NULL) return 0;
      }

      if (f->width_ > 0 && f->height_ > 0 &&
          !CheckFrameBounds(f, !is_animation,
                            dmux->canvas_width_, dmux->canvas_height_)) {
        return 0;
      }

      ++frame_count;
    }
  }
  return 1;
}