atomics-sync/es/condition.js

JavaScript multithreading synchronization library

import { Mutex } from "./mutex";
const { wait, notify } = Atomics;
/**
 * A condition variable implementation for thread synchronization.
 * Allows threads to wait for some condition to become true while properly releasing
 * and reacquiring a mutex lock. Uses SharedArrayBuffer for cross-thread communication.
 */
export class Condition {
    /**
     * Initializes a new condition variable in shared memory
     * @returns A new Int32Array backed by SharedArrayBuffer
     */
    static init() {
        return new Int32Array(new SharedArrayBuffer(Int32Array.BYTES_PER_ELEMENT));
    }
    /**
     * Wakes up one thread waiting on the condition variable
     * @param cond The condition variable to signal
     */
    static signal(cond) {
        notify(cond, 0, 1);
    }
    /**
     * Wakes up all threads waiting on the condition variable
     * @param cond The condition variable to broadcast to
     */
    static broadcast(cond) {
        notify(cond, 0);
    }
    /**
     * Blocks the current thread until the condition variable is signaled
     * @param cond The condition variable to wait on
     * @param mutex The associated mutex to release while waiting
     * @param threadId The ID of the current thread
     * @remarks Automatically releases mutex before waiting and reacquires after
     */
    static wait(cond, mutex, threadId) {
        Mutex.unlock(mutex, threadId);
        wait(cond, 0, 0);
        Mutex.lock(mutex, threadId);
    }
    /**
     * Blocks the current thread until either:
     * - The condition variable is signaled, or
     * - The specified timeout expires
     * @param cond The condition variable to wait on
     * @param mutex The associated mutex to release while waiting
     * @param threadId The ID of the current thread
     * @param timestamp The absolute timeout timestamp in milliseconds
     * @returns true if the condition was signaled, false if timed out
     * @remarks Automatically releases mutex before waiting and reacquires after
     */
    static timedWait(cond, mutex, threadId, timestamp) {
        try {
            Mutex.unlock(mutex, threadId);
            return wait(cond, 0, 0, timestamp - Date.now()) !== "timed-out";
        }
        finally {
            Mutex.lock(mutex, threadId);
        }
    }
}
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