//在构造函数中创建了一个DataView对象和一个position变量追踪当前指针指向哪个字节。
class ByteArray extends ArrayBuffer 
{  
    constructor(...args) {
        super(...args);
        this.dataView = new DataView(this); 
        this.position = 0;
    }

    get length(){
        return this.byteLength;
    }

    get bytesAvailable(){
        let diff = this.byteLength - this.position;
        if(diff < 0){
            diff = 0;
        }
        return diff;
    }

    writeInt8(value){
        this.dataView.setInt8(this.position, value);
        this.position += 1;
    }

    writeUint8(value){
        this.dataView.setUint8(this.position, value);
        this.position += 1;
    }

    writeInt16(value){
        this.dataView.setInt16(this.position, value);
        this.position += 2;
    }

    writeUint16(value){
        this.dataView.setUint16(this.position, value);
        this.position += 2;
    }

    writeInt32(value){
        this.dataView.setInt32(this.position, value);
        this.position += 4;
    }

    writeUint32(value){
        this.dataView.setUint32(this.position, value);
        this.position += 4;
    }

    writeFloat32(value){
        this.dataView.setFloat32(this.position, value);
        this.position += 4;
    }

    writeFloat64(value){
        this.dataView.setFloat64(this.position, value);
        this.position += 8;
    }

    readInt8(){
        let result = this.dataView.getInt8(this.position);
        this.position += 1;
        return result;
    }

    readUint8(){
        let result = this.dataView.getUint8(this.position);
        this.position += 1;
        return result;
    }

    readInt16(){
        let result = this.dataView.getInt16(this.position);
        this.position += 2;
        return result;
    }

    readUint16(){
        let result = this.dataView.getUint16(this.position);
        this.position += 2;
        return result;
    }   

    readInt32(){
        let result = this.dataView.getInt32(this.position);
        this.position += 4;
        return result;
    }

    readUint32(){
        let result = this.dataView.getUint32(this.position);
        this.position += 4;
        return result;
    }

    readFloat32(){
        let result = this.dataView.getFloat32(this.position);
        this.position += 4;
        return result;
    }

    readFloat64(){
        let result = this.dataView.getFloat64(this.position);
        this.position += 8;
        return result;
    }
}

//example
var ds = new ByteArray(32);
console.log("length is:", ds.length, "position is:", ds.position, "bytesAvaliable is:", ds.bytesAvailable); //32, 0, 32

ds.writeInt32(10); //作为32位的整数写入（4个字节）
ds.writeInt16(12); //作为16位的整数写入（2个字节）

console.log("length is:", ds.length, "position is:", ds.position, "bytesAvaliable is:", ds.bytesAvailable); //32, 6, 26

ds.position = 0;
console.log(ds.readInt32()); //10
console.log(ds.readInt16()); //12