// 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;
}
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;
}
// 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;
}