AsyncQueue/ParallelQueue.ts at master · haroel/AsyncQueue · GitHub

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/*
 * @Author: ihowe
 * @Date: 2022-07-12 16:23:54
 * @Email: ihowe@outlook.com
 * @Description:
 * 按指定的并行数同时执行多个任务
 */

export class ParallelQueue<T> {
    /**
     * 并行任务状态，0表示正常，1表示暂停
     */
    private _state = 0;
    private _taskIndex = 0;
    private _finishCount = 0;
    private _tasks: Array<T> = null;
    private _workers: Array<number> = [];
    private _handler: (taskIndex: number, taskItem: T, workerIndex: number, next: () => void) => void = null;

    /**
     * 所有任务执行完成回调
     */
    public complete: Function = null;

    constructor(workerNum: number) {
        for (let i = 0; i < workerNum; i++) {
            this._workers.push(i);
        }
    }
    /**
     * 执行任务
     * @param tasks
     * @param handler
     * @returns
     */
    public play(tasks: Array<any>, handler: (taskIndex: number, taskItem: T, workerIndex: number, next: () => void) => void, complete:Function = null) {
        if (tasks.length === 0) {
            return complete();
        }
        if (!handler) {
            throw new Error("handler cannot be null！")
        }
        if (this._taskIndex > 0) {
            return;
        }
        this._state = 0;
        this._taskIndex = 0;
        this._finishCount = 0;
        this._tasks = tasks;
        this._handler = handler;
        this.complete = complete;
        this._doWork();
    }
    /**
     * stop task
     * 停止任务队列，如果任务正在执行，则执行完成后，后续任务将清空且不再处理
     */
    public stop() {
        this._tasks && (this._tasks.length = 0);
    }

    /**
     * pause task
     * 暂停执行停止任务队列，如果任务正在执行，则执行完成后，后续任务将暂停，等待调用resume才会继续执行
     */
    public pause() {
        if (this._state === 0) {
            this._state = 1;
        }
    }
    /**
     * resume task
     * 恢复停止的队列
     */
    public resume() {
        if (this._state === 1) {
            this._state = 0;
        }
    }
    /**
     * 任务执行完成回调
     */
    private _finishWork() {
        this._taskIndex = 0;
        this._finishCount = 0;
        this._state = 0;
        this._handler = null;
        this._tasks = null;
        this.complete && this.complete();
    }
    /**
     * 执行具体任务
     * @returns
     */
    private _doWork() {
        if ( this._tasks.length === 0 || this._taskIndex === this._tasks.length) {
            return;
        }
        if (this._state === 1) {
            return; // 任务暂停状态
        }
        if (this._workers.length > 0) {
            let i = this._taskIndex++;
            if (i < this._tasks.length) {
                let worker = this._workers.pop(); // 从Workers队列尾部取一个
                let next = () => {
                    ++this._finishCount;
                    this._workers.push(worker); // 回收worker
                    if (this._finishCount === this._tasks.length) {
                        return this._finishWork()
                    }
                    this._doWork();
                }
                this._handler(i, this._tasks[i], worker, next);
            }
            this._doWork()
        }
    }
}