export declare class UtpHeaderExtension {
    type: number;
    len: number;
    bitmask: Uint8Array;
    constructor(type: number, bitmask: Uint8Array);
}
/**
 * Constructor for Selective Ack Packet Header Extensions
 * The 0 passed to `super()` indicates the extension type of Selective Ack (the only currently defined extension type for uTP packet headers)
 * @param bitmask - A `Uint8Array` corresponding to the packet numbers missing in the uTP stream
 * @returns `SelectiveAckHeaderExtension`
 */
export declare class SelectiveAckHeaderExtension extends UtpHeaderExtension {
    constructor(bitmask: Uint8Array);
    static create: (bitmask: Uint8Array) => SelectiveAckHeaderExtension;
}
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