queue-cb/dist/esm/index.js

A scalable queue for parallel callbacks

import LinkedArray from './LinkedArray.js';
let Queue = class Queue {
    _callAwait() {
        if (this._state.awaitCalled || !this._state.awaitCallback) return;
        this._state.awaitCalled = true;
        return this._state.awaitCallback(this._state.error);
    }
    _flush() {
        this._state.flushing = true;
        while(!this._state.error && this._state.tasks.length && this._state.runningCount < this._state.parallelism){
            this._state.runningCount++;
            this._state.tasks.shift()(this._callDefer);
        }
        this._state.flushing = false;
        if (this._state.error || !(this._state.tasks.length + this._state.runningCount)) {
            this._callAwait();
        }
    }
    _callDefer(err) {
        this._state.runningCount--;
        if (err && !this._state.error) this._state.error = err;
        if (this._state.flushing) return;
        this._flush();
    }
    defer(defer) {
        if (this._state.error) return;
        if (this._state.runningCount < this._state.parallelism) {
            this._state.runningCount++;
            defer(this._callDefer);
        } else this._state.tasks.push(defer);
    }
    await(callback) {
        if (this._state.awaitCallback) throw new Error(`Awaiting callback was added twice: ${callback}`);
        this._state.awaitCallback = callback;
        if (this._state.error || !(this._state.tasks.length + this._state.runningCount)) return this._callAwait();
    }
    constructor(parallelism = Infinity){
        this._state = {
            parallelism,
            tasks: new LinkedArray(),
            runningCount: 0,
            error: null,
            awaitCallback: null,
            awaitCalled: false,
            flushing: false
        };
        this._callAwait = this._callAwait.bind(this);
        this._callDefer = this._callDefer.bind(this);
    }
};
export { Queue as default };