Function avifCodecDecodeInputFillFromDecoderItem

src/read.c:613–732

}

static avifResult avifCodecDecodeInputFillFromDecoderItem(avifCodecDecodeInput * decodeInput,
                                                          avifDecoderItem * item,
                                                          avifBool allowProgressive,
                                                          const uint32_t imageCountLimit,
                                                          const uint64_t sizeHint,
                                                          avifDiagnostics * diag)
{
    if (sizeHint && (item->size > sizeHint)) {
        avifDiagnosticsPrintf(diag, "Exceeded avifIO's sizeHint, possibly truncated data");
        return AVIF_RESULT_BMFF_PARSE_FAILED;
    }

    uint8_t layerCount = 0;
    size_t layerSizes[4] = { 0 };
    const avifProperty * a1lxProp = avifPropertyArrayFind(&item->properties, "a1lx");
    if (a1lxProp) {
        // Calculate layer count and all layer sizes from the a1lx box, and then validate

        size_t remainingSize = item->size;
        for (int i = 0; i < 3; ++i) {
            ++layerCount;

            const size_t layerSize = (size_t)a1lxProp->u.a1lx.layerSize[i];
            if (layerSize) {
                if (layerSize >= remainingSize) { // >= instead of > because there must be room for the last layer
                    avifDiagnosticsPrintf(diag, "a1lx layer index [%d] does not fit in item size", i);
                    return AVIF_RESULT_BMFF_PARSE_FAILED;
                }
                layerSizes[i] = layerSize;
                remainingSize -= layerSize;
            } else {
                layerSizes[i] = remainingSize;
                remainingSize = 0;
                break;
            }
        }
        if (remainingSize > 0) {
            AVIF_ASSERT_OR_RETURN(layerCount == 3);
            ++layerCount;
            layerSizes[3] = remainingSize;
        }
    }

    const avifProperty * lselProp = avifPropertyArrayFind(&item->properties, "lsel");
    // Progressive images offer layers via the a1lxProp, but don't specify a layer selection with lsel.
    //
    // For backward compatibility with earlier drafts of AVIF spec v1.1.0, treat an absent lsel as
    // equivalent to layer_id == 0xFFFF during the transitional period. Remove !lselProp when the test
    // images have been updated to the v1.1.0 spec.
    item->progressive = (a1lxProp && (!lselProp || (lselProp->u.lsel.layerID == 0xFFFF)));
    if (lselProp && (lselProp->u.lsel.layerID != 0xFFFF)) {
        // Layer selection. This requires that the underlying AV1 codec decodes all layers,
        // and then only returns the requested layer as a single frame. To the user of libavif,
        // this appears to be a single frame.

        decodeInput->allLayers = AVIF_TRUE;

        size_t sampleSize = 0;