Function extractGIF

src/core/lib/FileSignatures.mjs:2733–2766

(bytes, offset)

 * @returns {Uint8Array}
 */
export function extractGIF(bytes, offset) {
    const stream = new Stream(bytes.slice(offset));

    // Move to application extension block.
    stream.continueUntil([0x21, 0xff]);

    // Move to Graphic Control Extension for frame #1.
    stream.continueUntil([0x21, 0xf9]);
    stream.moveForwardsBy(2);

    while (stream.hasMore()) {
        // Move to Image descriptor.
        stream.moveForwardsBy(stream.readInt(1) + 1);

        // Move past Image descriptor to the image data.
        stream.moveForwardsBy(11);

        // Loop until next Graphic Control Extension.
        while (!Array.from(stream.getBytes(2)).equals([0x21, 0xf9])) {
            stream.moveBackwardsBy(2);
            stream.moveForwardsBy(stream.readInt(1));
            if (!stream.readInt(1))
                break;
            stream.moveBackwardsBy(1);
        }

        // When the end of the file is [0x00, 0x3b], end.
        if (stream.readInt(1) === 0x3b)
            break;

        stream.moveForwardsBy(1);
    }
    return stream.carve();
}


/**