public class LoopQueue {
    private byte[] _buf;
    private int _head;
    private int _tail;
    private int _size;
    private int _capacity;

    public LoopQueue(int capacity){
        _capacity = capacity;
        _buf = new byte[_capacity];
        _head = 0;
        _tail = 0;
        _size = 0;
    }
//将len长的buf加入到lp中
    public boolean push(byte[] buf, int len){
        if(this._size+len>this._capacity){
            Public.mylog.d(LOG_TAG,"_buf is over flow");
            return false;
        }

    for (int i = 0; i < len; i++) {
        _buf[(_tail + i) % _capacity] = buf[i];
    }
        _tail = (_tail+len)%_capacity;
        _size +=len;

        return true;
    }
//消费掉len长的数据
    public boolean pop(int len){
        if(_size<len){
            Public.mylog.d(LOG_TAG,"loopQueue demanding more than exists");
            return false;
        }
        _head = (_head+len)%_capacity;
        _size -=len;

        return true;
    }
//查看从head开始的len长度的内容，把这些内容放到buf里面
    public boolean peek(byte[] buf, int len){
        if(_size<len){
            Public.mylog.d(LOG_TAG,"loopQueue demanding more than exists");
            return false;
        }

        for(int i=0;i<len;i++){
            buf[i]=_buf[(_head+i)%_capacity];
        }

        return true;
    }
//判断是不是满了
    public boolean isfull(){
        return (_capacity == _size);
    }
//判断是不是空的
    public boolean isempty(){
        return (_size==0);
    }
//总的大小
    public int capacity(){
        return _capacity;
    }
//当前数据量
    public int size(){
        return _size;
    }
//clear all data
    public void clear(){
        _tail = _head;
        _size = 0;
    }

    public int read(byte[] buf){
        int size = size();
        size = Math.min(size,buf.length);
        if(size>0) {
            peek(buf, size);
            pop(size);
            return size;
        }else
            return 0;
    }
}