static int AllocateMemory()

in Extended/libwebp/src/dec/frame_dec.c [682:782]

• 80 lines of code
• 13 McCabe index (conditional complexity)

static int AllocateMemory(VP8Decoder* const dec) {
  const int num_caches = dec->num_caches_;
  const int mb_w = dec->mb_w_;
  // Note: we use 'size_t' when there's no overflow risk, uint64_t otherwise.
  const size_t intra_pred_mode_size = 4 * mb_w * sizeof(uint8_t);
  const size_t top_size = sizeof(VP8TopSamples) * mb_w;
  const size_t mb_info_size = (mb_w + 1) * sizeof(VP8MB);
  const size_t f_info_size =
      (dec->filter_type_ > 0) ?
          mb_w * (dec->mt_method_ > 0 ? 2 : 1) * sizeof(VP8FInfo)
        : 0;
  const size_t yuv_size = YUV_SIZE * sizeof(*dec->yuv_b_);
  const size_t mb_data_size =
      (dec->mt_method_ == 2 ? 2 : 1) * mb_w * sizeof(*dec->mb_data_);
  const size_t cache_height = (16 * num_caches
                            + kFilterExtraRows[dec->filter_type_]) * 3 / 2;
  const size_t cache_size = top_size * cache_height;
  // alpha_size is the only one that scales as width x height.
  const uint64_t alpha_size = (dec->alpha_data_ != NULL) ?
      (uint64_t)dec->pic_hdr_.width_ * dec->pic_hdr_.height_ : 0ULL;
  const uint64_t needed = (uint64_t)intra_pred_mode_size
                        + top_size + mb_info_size + f_info_size
                        + yuv_size + mb_data_size
                        + cache_size + alpha_size + WEBP_ALIGN_CST;
  uint8_t* mem;

  if (needed != (size_t)needed) return 0;  // check for overflow
  if (needed > dec->mem_size_) {
    WebPSafeFree(dec->mem_);
    dec->mem_size_ = 0;
    dec->mem_ = WebPSafeMalloc(needed, sizeof(uint8_t));
    if (dec->mem_ == NULL) {
      return VP8SetError(dec, VP8_STATUS_OUT_OF_MEMORY,
                         "no memory during frame initialization.");
    }
    // down-cast is ok, thanks to WebPSafeMalloc() above.
    dec->mem_size_ = (size_t)needed;
  }

  mem = (uint8_t*)dec->mem_;
  dec->intra_t_ = mem;
  mem += intra_pred_mode_size;

  dec->yuv_t_ = (VP8TopSamples*)mem;
  mem += top_size;

  dec->mb_info_ = ((VP8MB*)mem) + 1;
  mem += mb_info_size;

  dec->f_info_ = f_info_size ? (VP8FInfo*)mem : NULL;
  mem += f_info_size;
  dec->thread_ctx_.id_ = 0;
  dec->thread_ctx_.f_info_ = dec->f_info_;
  if (dec->filter_type_ > 0 && dec->mt_method_ > 0) {
    // secondary cache line. The deblocking process need to make use of the
    // filtering strength from previous macroblock row, while the new ones
    // are being decoded in parallel. We'll just swap the pointers.
    dec->thread_ctx_.f_info_ += mb_w;
  }

  mem = (uint8_t*)WEBP_ALIGN(mem);
  assert((yuv_size & WEBP_ALIGN_CST) == 0);
  dec->yuv_b_ = mem;
  mem += yuv_size;

  dec->mb_data_ = (VP8MBData*)mem;
  dec->thread_ctx_.mb_data_ = (VP8MBData*)mem;
  if (dec->mt_method_ == 2) {
    dec->thread_ctx_.mb_data_ += mb_w;
  }
  mem += mb_data_size;

  dec->cache_y_stride_ = 16 * mb_w;
  dec->cache_uv_stride_ = 8 * mb_w;
  {
    const int extra_rows = kFilterExtraRows[dec->filter_type_];
    const int extra_y = extra_rows * dec->cache_y_stride_;
    const int extra_uv = (extra_rows / 2) * dec->cache_uv_stride_;
    dec->cache_y_ = mem + extra_y;
    dec->cache_u_ = dec->cache_y_
                  + 16 * num_caches * dec->cache_y_stride_ + extra_uv;
    dec->cache_v_ = dec->cache_u_
                  + 8 * num_caches * dec->cache_uv_stride_ + extra_uv;
    dec->cache_id_ = 0;
  }
  mem += cache_size;

  // alpha plane
  dec->alpha_plane_ = alpha_size ? mem : NULL;
  mem += alpha_size;
  assert(mem <= (uint8_t*)dec->mem_ + dec->mem_size_);

  // note: left/top-info is initialized once for all.
  memset(dec->mb_info_ - 1, 0, mb_info_size);
  VP8InitScanline(dec);   // initialize left too.

  // initialize top
  memset(dec->intra_t_, B_DC_PRED, intra_pred_mode_size);

  return 1;
}