예제 #1
0
파일: webp.c 프로젝트: ZW19911104/libwebp
// Validates the VP8/VP8L Header ("VP8 nnnn" or "VP8L nnnn") and skips over it.
// Returns VP8_STATUS_BITSTREAM_ERROR for invalid (chunk larger than
//         riff_size) VP8/VP8L header,
//         VP8_STATUS_NOT_ENOUGH_DATA in case of insufficient data, and
//         VP8_STATUS_OK otherwise.
// If a VP8/VP8L chunk is found, *chunk_size is set to the total number of bytes
// extracted from the VP8/VP8L chunk header.
// The flag '*is_lossless' is set to 1 in case of VP8L chunk / raw VP8L data.
static VP8StatusCode ParseVP8Header(const uint8_t** const data_ptr,
                                    size_t* const data_size, int have_all_data,
                                    size_t riff_size, size_t* const chunk_size,
                                    int* const is_lossless) {
  const uint8_t* const data = *data_ptr;
  const int is_vp8 = !memcmp(data, "VP8 ", TAG_SIZE);
  const int is_vp8l = !memcmp(data, "VP8L", TAG_SIZE);
  const uint32_t minimal_size =
      TAG_SIZE + CHUNK_HEADER_SIZE;  // "WEBP" + "VP8 nnnn" OR
                                     // "WEBP" + "VP8Lnnnn"
  assert(data != NULL);
  assert(data_size != NULL);
  assert(chunk_size != NULL);
  assert(is_lossless != NULL);

  if (*data_size < CHUNK_HEADER_SIZE) {
    return VP8_STATUS_NOT_ENOUGH_DATA;  // Insufficient data.
  }

  if (is_vp8 || is_vp8l) {
    // Bitstream contains VP8/VP8L header.
    const uint32_t size = GetLE32(data + TAG_SIZE);
    if ((riff_size >= minimal_size) && (size > riff_size - minimal_size)) {
      return VP8_STATUS_BITSTREAM_ERROR;  // Inconsistent size information.
    }
    if (have_all_data && (size > *data_size - CHUNK_HEADER_SIZE)) {
      return VP8_STATUS_NOT_ENOUGH_DATA;  // Truncated bitstream.
    }
    // Skip over CHUNK_HEADER_SIZE bytes from VP8/VP8L Header.
    *chunk_size = size;
    *data_ptr += CHUNK_HEADER_SIZE;
    *data_size -= CHUNK_HEADER_SIZE;
    *is_lossless = is_vp8l;
  } else {
    // Raw VP8/VP8L bitstream (no header).
    *is_lossless = VP8LCheckSignature(data, *data_size);
    *chunk_size = *data_size;
  }

  return VP8_STATUS_OK;
}
예제 #2
0
static VP8StatusCode ParseVP8Header(const uint8_t** const data_ptr,
                                    size_t* const data_size,
                                    size_t riff_size,
                                    size_t* const chunk_size,
                                    int* const is_lossless) {
  const uint8_t* const data = *data_ptr;
  const int is_vp8 = !memcmp(data, "VP8 ", TAG_SIZE);
  const int is_vp8l = !memcmp(data, "VP8L", TAG_SIZE);
  const uint32_t minimal_size =
      TAG_SIZE + CHUNK_HEADER_SIZE;  
                                     
  assert(data != NULL);
  assert(data_size != NULL);
  assert(chunk_size != NULL);
  assert(is_lossless != NULL);

  if (*data_size < CHUNK_HEADER_SIZE) {
    return VP8_STATUS_NOT_ENOUGH_DATA;  
  }

  if (is_vp8 || is_vp8l) {
    
    const uint32_t size = get_le32(data + TAG_SIZE);
    if ((riff_size >= minimal_size) && (size > riff_size - minimal_size)) {
      return VP8_STATUS_BITSTREAM_ERROR;  
    }
    
    *chunk_size = size;
    *data_ptr += CHUNK_HEADER_SIZE;
    *data_size -= CHUNK_HEADER_SIZE;
    *is_lossless = is_vp8l;
  } else {
    
    *is_lossless = VP8LCheckSignature(data, *data_size);
    *chunk_size = *data_size;
  }

  return VP8_STATUS_OK;
}
예제 #3
0
// Outputs image data given a bitstream. The bitstream can either be a
// single-image WebP file or raw VP8/VP8L data.
// Also outputs 'is_lossless' to be true if the given bitstream is lossless.
static WebPMuxError GetImageData(const WebPData* const bitstream,
                                 WebPData* const image, WebPData* const alpha,
                                 int* const is_lossless) {
  WebPDataInit(alpha);  // Default: no alpha.
  if (bitstream->size < TAG_SIZE ||
      memcmp(bitstream->bytes, "RIFF", TAG_SIZE)) {
    // It is NOT webp file data. Return input data as is.
    *image = *bitstream;
  } else {
    // It is webp file data. Extract image data from it.
    const WebPMuxImage* wpi;
    WebPMux* const mux = WebPMuxCreate(bitstream, 0);
    if (mux == NULL) return WEBP_MUX_BAD_DATA;
    wpi = mux->images_;
    assert(wpi != NULL && wpi->img_ != NULL);
    *image = wpi->img_->data_;
    if (wpi->alpha_ != NULL) {
      *alpha = wpi->alpha_->data_;
    }
    WebPMuxDelete(mux);
  }
  *is_lossless = VP8LCheckSignature(image->bytes, image->size);
  return WEBP_MUX_OK;
}