import type { MessageSink, MessageSource } from "./message-target.js";
export type ChannelCallHandler = (event: MessageEvent, params: unknown, ...transfers: MessagePort[]) => unknown;
/**
 * A channel call's result that carries transferables, a `MessagePort` say:
 * return `withTransfer({ port }, [port])` from a `handleChannelCalls` handler
 * and `callChannel` resolves with `{ port }`.
 */
export declare function withTransfer<T>(value: T, transfer: Transferable[]): T;
/** Splits a handler's result into the value to post and its transfer list. */
export declare function unwrapTransfer(result: unknown): {
    value: unknown;
    transfer: Transferable[];
};
export declare function callChannel<T = unknown>(target: MessageSink, callType: string, params: unknown, ...transfers: Transferable[]): Promise<T>;
export declare function handleChannelCalls(target: MessageSource, callType: string, handler: ChannelCallHandler): () => void;
/**
 * `callChannel`, failing after `ms` instead of waiting for ever: a peer that
 * died (a ServiceWorker stopped mid-call) or that does not know `callType` (an
 * older version) never answers.
 */
export declare function callChannelWithin<T = unknown>(ms: number, target: MessageSink, callType: string, params: unknown, ...transfers: Transferable[]): Promise<T>;
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