80 lines
1.6 KiB
JavaScript
80 lines
1.6 KiB
JavaScript
import { Queue } from './queue.mjs';
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/**
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* Represents an asynchronous lock for managing access to a shared resource.
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* @class
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*/
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export class AsyncLock {
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/**
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* Creates an instance of AsyncLock.
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* @constructor
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*/
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constructor() {
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/**
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* A queue to store pending requests for acquiring the lock.
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* @type {Queue}
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* @private
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*/
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this.pending_queue = new Queue();
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/**
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* The current state of the lock.
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* @type {boolean}
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* @private
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*/
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this.state = false;
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/**
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* The ID associated with the current lock holder.
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* @type {number}
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* @private
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*/
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this.lock_id = 0;
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}
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/**
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* Checks the current state of the lock.
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* @returns {boolean} True if the lock is acquired; otherwise, false.
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*/
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query() {
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return this.state;
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}
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/**
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* Acquires the lock asynchronously.
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* @returns {Promise<number>} A promise that resolves with the unique ID associated with the acquired lock.
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*/
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acquire() {
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if (!this.state) {
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this.state = true;
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this.lock_id += 1;
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return Promise.resolve(this.lock_id);
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}
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return new Promise((resolve, _reject) => this.pending_queue.push(resolve));
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}
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/**
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* Releases the lock with the specified ID.
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* @param {number} lock_id The ID of the lock to release.
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*/
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release(lock_id) {
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if (!this.state || lock_id !== this.lock_id) { return; }
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if (this.pending_queue.empty()) {
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this.state = false;
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return;
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}
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let resolve = this.pending_queue.front();
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this.pending_queue.popFront();
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this.lock_id += 1;
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resolve(this.lock_id);
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}
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/**
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* Releases the lock forcefully even you are not the owner.
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* BE CAREFUL WHAT YOU WISH FOR!!
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*/
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forceRelease() {
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this.release(this.lock_id);
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}
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}; |