VP8StatusCode WebPGetFeaturesInternal(byte* data, uint data_size,
WebPBitstreamFeatures* features,
int version)
{
VP8StatusCode status;
if (version != WEBP_DECODER_ABI_VERSION) {
return VP8_STATUS_INVALID_PARAM; // version mismatch
}
if (features == null) {
return VP8_STATUS_INVALID_PARAM;
}
status = GetFeatures(data, data_size, features);
if (status == VP8_STATUS_NOT_ENOUGH_DATA) {
return VP8_STATUS_BITSTREAM_ERROR; // Not-enough-data treated as error.
}
return status;
}
static void DefaultFeatures(WebPBitstreamFeatures* features)
{
assert(features);
memset(features, 0, sizeof(*features));
features.bitstream_version = 0;
}
static VP8StatusCode GetFeatures(byte* data, uint data_size,
WebPBitstreamFeatures* features)
{
uint vp8_chunk_size = 0;
uint riff_size = 0;
uint flags = 0;
uint vp8x_skip_size = 0;
uint vp8_skip_size = 0;
int* width = &features.width;
int* height = &features.height;
VP8StatusCode status;
if (features == null || data == null) {
return VP8_STATUS_INVALID_PARAM;
}
DefaultFeatures(features);
// Skip over RIFF header.
status = WebPParseRIFF(&data, &data_size, &riff_size);
if (status != VP8_STATUS_OK) {
return status; // Wrong RIFF header / insufficient data.
}
// Skip over VP8X.
status = WebPParseVP8X(&data, &data_size, &vp8x_skip_size,
width, height, &flags);
if (status != VP8_STATUS_OK) {
return status; // Wrong VP8X / insufficient data.
}
features.has_alpha = !!(flags & ALPHA_FLAG);
if (vp8x_skip_size > 0) {
return VP8_STATUS_OK; // Return features from VP8X header.
}
// Skip over VP8 header.
status = WebPParseVP8Header(&data, &data_size, riff_size, &vp8_skip_size,
&vp8_chunk_size);
if (status != VP8_STATUS_OK) {
return status; // Wrong VP8 chunk-header / insufficient data.
}
if (vp8_skip_size == 0) {
vp8_chunk_size = data_size; // No VP8 chunk wrapper over raw VP8 data.
}
// Validates raw VP8 data.
if (!VP8GetInfo(data, data_size, vp8_chunk_size, width, height)) {
return VP8_STATUS_BITSTREAM_ERROR;
}
return VP8_STATUS_OK; // Return features from VP8 header.
}
// Retrieve features from the bitstream. The *features structure is filled
// with information gathered from the bitstream.
// Returns false in case of error or version mismatch.
// In case of error, features.bitstream_status will reflect the error code.
static VP8StatusCode WebPGetFeatures(byte* data, uint data_size, ref WebPBitstreamFeatures features)
{
return WebPGetFeaturesInternal(data, data_size, features, WEBP_DECODER_ABI_VERSION);
}