channels.js

'use strict'

class Channel {

    constructor(buffer) {
        if (!buffer) this.buffer = 1
        else this.buffer = buffer
        this.data = []
        this.putPromiseResolve = null
        this.getPromiseResolve = null
        this.putData = null
        this.closed = false
    }

    put(item) {
        return new Promise((resolve, reject) => {
            if (this.closed) reject(new Error('Channel is closed'))
            else if (this.data.length < this.buffer) {
                this.data.push(item)
                resolve()
                if (this.getPromiseResolve) {
                    const r = this.getPromiseResolve
                    this.getPromiseResolve = null
                    r(this.data.shift())
                }
            }
            else {
                this.putPromiseResolve = resolve
                this.putData = item
            }
        })
    }

    get() {
        return new Promise((resolve, reject) => {
            if (this.data.length) {
                resolve(this.data.shift())
                if (this.putPromiseResolve) {
                    this.data.push(this.putData)
                    const r = this.putPromiseResolve
                    this.putPromiseResolve = null
                    r()
                }
            }
            else if (this.closed) {
                resolve()
            }
            else {
                this.getPromiseResolve = resolve
            }
        })
    }

    close() {
        this.closed = true
        if (!this.data.length && this.getPromiseResolve) {
            const r = this.getPromiseResolve
            this.getPromiseResolve = null
            r()
        }
    }
}

const c = new Channel()

async function getter() {
    while(true) {
        const r = await c.get()
        if (!r) {
            console.log('Channel is closed')
            break
        }
        console.log(r)
    }
}
async function putter() {
    await c.put('hello world 1')
    await c.put('hello world 2')
    await c.put('hello world 3')
    c.close()
}