/**
 * The wire protocol of a WebSocket carried over a `MessagePort`.
 *
 * A `MessagePort` is a natural carrier for a WebSocket: messages arrive in
 * order, and strings and transferable `ArrayBuffer`s cross it as they are. The
 * protocol on top is these frames, the same in both directions:
 *
 * - `m` — one message. An `ArrayBuffer` is transferred, never copied.
 * - `c` — close. The side that closes first sends it; the other answers with
 *   its own `c` (the echo), and both are then closed cleanly.
 * - `p` — ping, client to server, carrying the client's heartbeat period.
 * - `q` — pong, server to client.
 * - `a` — ack: the receiver consumed `n` more bytes of messages. This is the
 *   flow control: what a side has sent and not yet seen acknowledged is its
 *   `bufferedAmount`, and the server end can wait for it to fall
 *   (`whenDrained`). Added in version 2; version 1 had no backpressure.
 *
 * HEARTBEAT. A `MessagePort` never reports that the other side died, so the
 * client pings every `hb` ms and closes with 1006 when pongs stop for `2·hb`;
 * the server closes with 1006 when pings stop for `3·hb`. That is how a socket
 * notices a closed tab or a terminated worker.
 *
 * Unknown frames are ignored, so a later version can add frames a peer of
 * this version skips.
 */
/** The version of this frame protocol. Sent in the upgrade hand-shake. */
export declare const WS_PORT_PROTOCOL_VERSION = 2;
/** Default heartbeat period of the client, in ms. */
export declare const DEFAULT_HEARTBEAT_MS = 10000;
/** How long a side waits for the echo of its close frame, in ms. */
export declare const DEFAULT_CLOSE_TIMEOUT_MS = 5000;
export type WsFrame = {
    t: "m";
    d: string | ArrayBuffer;
} | {
    t: "c";
    code: number;
    reason: string;
} | {
    t: "p";
    hb: number;
} | {
    t: "q";
} | {
    t: "a";
    n: number;
};
/**
 * The timer functions a socket uses. On a page's main thread, background
 * throttling delays timers by up to a minute, which would close healthy
 * sockets; pass unthrottled ones (worker-timers, say) there.
 */
export interface WsTimers {
    setTimeout(fn: () => void, ms: number): unknown;
    clearTimeout(id: unknown): void;
    setInterval(fn: () => void, ms: number): unknown;
    clearInterval(id: unknown): void;
}
export declare const defaultTimers: WsTimers;
/** Recovers a frame from a message's data, or `undefined` for anything else. */
export declare function readFrame(data: unknown): WsFrame | undefined;
/** Posts `frame`, transferring a message's `ArrayBuffer`. */
export declare function postFrame(port: MessagePort, frame: WsFrame): void;
/** The size a message counts for in `bufferedAmount`: UTF-8 bytes, or the buffer's length. */
export declare function messageSize(data: string | ArrayBuffer): number;
/** The UTF-8 length of `text`, without encoding it. */
export declare function utf8Length(text: string): number;
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