协议解析字节流读取与解析逻辑分离

const Readable = require('stream').Readable;

class BufferReader extends Readable {
    constructor(options) {
        super(options);
    }

    init(gFun) {
        this.readBytes = 0;
        this.poolBytes = 0;
        this.needBytes = 0;
        this.gFun = gFun;
        this.need(this.gFun.next(false).value);
    }

    stop() {
        this.gFun.return(true);
    }

    push(buf) {
        super.push(buf);
        this.poolBytes += buf.length;
        this.readBytes += buf.length;
        let enough = this.needBytes > 0 && this.needBytes <= this.poolBytes
        while (enough) {
            enough = this.need(this.gFun.next(this.read(this.needBytes)).value);
        }
    }
    read(size) {
        this.poolBytes -= size;
        return super.read(size);
    }
    need(size) {
        this.needBytes = size;
        return this.poolBytes >= size;
    }
}

module.exports = BufferReader

let br = new BufferReader()
br.init(decode())
function * decode(){
    let buf = yield 4;//读取4个字节（缓存里如果不够4个字节，则等待直到有4个字节就会继续执行）
    buf = yield 8;//读取8个字节
    ……
}

socket.on('data',data=>{
    br.push(data)
}).on('close',()=>{
    br.stop()//停止协议解析
})