nodejs实现bitmap/bitset

代码在github上面有最新版
https://github.com/zhoujiaping/doc/blob/master/nodenode/algol/bitset.js

/**
 * Bitmap算法（java中叫BitSet，作为javascript，还是跟着java老大哥叫bitset吧）
 * http://www.cnblogs.com/huangxincheng/archive/2012/12/06/2804756.html
 */
function newBitset(){
    let buf = Buffer.alloc(10);
    function resizeBuf(buf,size){
        let newSize = buf.length;
        if(newSize>=size){
            return buf;
        }
        while(newSize<size){
            newSize = newSize<<1+1;
        }
        let newBuf = Buffer.alloc(newSize);
        buf.copy(newBuf,0,buf.length);
        return newBuf;
    }
    return {
        set(n){
            if(n<1){
                throw new Error('n必须大于等于1');
            }
            let i = n>>3;//n除以8取整
            buf = resizeBuf(buf,i);
            let r = n&0x07;//n除以8取余
            r = 1<<r;//余数 设置 字节对应的位为1
            console.info(i);
            buf[i] = buf[i]|r;
        },
        clear(n){
            if(n==undefined){
                buf.fill(0);
                return;
            }
            if(n<1){
                throw new Error('n必须大于等于1');
            }
            let i = n>>3;
            buf = resizeBuf(buf,i);
            let r = n&0x07;
            r = ~(1<<r);
            buf[i] = buf[i]&r;
        },
        get(n){
            if(n<1){
                throw new Error('n必须大于等于1');
            }
            let i = n>>3;
            let r = n&0x07;
            r = 1<<r;//00001000
            return !!(buf[i]&r);
        },
        buf(){
            return buf;
        }
    };
}
function test(){
    let bitset = newBitset();
    bitset.set(100);
    bitset.set(90);
    //bitset.clear();
    bitset.clear(99);
    console.info(bitset.buf());
    console.info(bitset.get(100));
    console.info(bitset.get(90));
    console.info(bitset.get(99));
    //console.info(bitset.get(0));
    //console.info(bitset.get(-1));
}
test();
module.exports = newBitset;