Method _readSegment

systemvm/agent/noVNC/core/decoders/jpeg.js:89–145

(sock)

    }

    _readSegment(sock) {
        if (sock.rQwait("JPEG", 2)) {
            return null;
        }

        let marker = sock.rQshift8();
        if (marker != 0xFF) {
            throw new Error("Illegal JPEG marker received (byte: " +
                               marker + ")");
        }
        let type = sock.rQshift8();
        if (type >= 0xD0 && type <= 0xD9 || type == 0x01) {
            // No length after marker
            return new Uint8Array([marker, type]);
        }

        if (sock.rQwait("JPEG", 2, 2)) {
            return null;
        }

        let length = sock.rQshift16();
        if (length < 2) {
            throw new Error("Illegal JPEG length received (length: " +
                               length + ")");
        }

        if (sock.rQwait("JPEG", length-2, 4)) {
            return null;
        }

        let extra = 0;
        if (type === 0xDA) {
            // start of scan
            extra += 2;
            while (true) {
                if (sock.rQwait("JPEG", length-2+extra, 4)) {
                    return null;
                }
                let data = sock.rQpeekBytes(length-2+extra, false);
                if (data.at(-2) === 0xFF && data.at(-1) !== 0x00 &&
                    !(data.at(-1) >= 0xD0 && data.at(-1) <= 0xD7)) {
                    extra -= 2;
                    break;
                }
                extra++;
            }
        }

        let segment = new Uint8Array(2 + length + extra);
        segment[0] = marker;
        segment[1] = type;
        segment[2] = length >> 8;
        segment[3] = length;
        segment.set(sock.rQshiftBytes(length-2+extra, false), 4);

        return segment;
    }
}