Snowflake(雪花算法)的JavaScript實現

時間 2019-11-11

標籤 snowflake 雪花算法 javascript 實現欄目 JavaScript 简体版

原文原文鏈接

　　如今好多的ID都是服務器端生成的，固然JS也能夠生成GUID或者UUID之類的，可是若是想要有序……這時就想到了雪花算法，可是都知道JS中Number的最大值爲Number.MAX_SAFE_INTEGER：9007199254740991。在雪花算法中，有的操做在JS中會溢出。不過還好，網上有好多BigInt的類庫，例如本例使用的：http://peterolson.github.io/BigInteger.js/ ，還有就是chrome67 原生支持BigInt類型，這是個好消息……html

　　參考文章：理解分佈式id生成算法SnowFlakegit

　　類庫：http://peterolson.github.io/BigInteger.js/github

　　CDN：https://cdnjs.com/ajax

　　記錄一下代碼算法

　　類庫方式實現：chrome

<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
</head>

<body>
    <script src="https://cdnjs.cloudflare.com/ajax/libs/big-integer/1.6.32/BigInteger.min.js"></script>
    <!-- <script src="http://peterolson.github.com/BigInteger.js/BigInteger.min.js"></script> -->
    <script>
        var Snowflake = /** @class */ (function() {
            function Snowflake(_workerId, _dataCenterId, _sequence) {
                // this.twepoch = 1288834974657;
                this.twepoch = 0;
                this.workerIdBits = 5;
                this.dataCenterIdBits = 5;
                this.maxWrokerId = -1 ^ (-1 << this.workerIdBits); // 值爲：31
                this.maxDataCenterId = -1 ^ (-1 << this.dataCenterIdBits); // 值爲：31
                this.sequenceBits = 12;
                this.workerIdShift = this.sequenceBits; // 值爲：12
                this.dataCenterIdShift = this.sequenceBits + this.workerIdBits; // 值爲：17
                this.timestampLeftShift = this.sequenceBits + this.workerIdBits + this.dataCenterIdBits; // 值爲：22
                this.sequenceMask = -1 ^ (-1 << this.sequenceBits); // 值爲：4095
                this.lastTimestamp = -1;
                //設置默認值,從環境變量取
                this.workerId = 1;
                this.dataCenterId = 1;
                this.sequence = 0;
                if (this.workerId > this.maxWrokerId || this.workerId < 0) {
                    throw new Error('config.worker_id must max than 0 and small than maxWrokerId-[' + this.maxWrokerId + ']');
                }
                if (this.dataCenterId > this.maxDataCenterId || this.dataCenterId < 0) {
                    throw new Error('config.data_center_id must max than 0 and small than maxDataCenterId-[' + this.maxDataCenterId + ']');
                }
                this.workerId = _workerId;
                this.dataCenterId = _dataCenterId;
                this.sequence = _sequence;
            }
            Snowflake.prototype.tilNextMillis = function(lastTimestamp) {
                var timestamp = this.timeGen();
                while (timestamp <= lastTimestamp) {
                    timestamp = this.timeGen();
                }
                return timestamp;
            };
            Snowflake.prototype.timeGen = function() {
                //new Date().getTime() === Date.now()
                return Date.now();
            };
            Snowflake.prototype.nextId = function() {
                var timestamp = this.timeGen();
                if (timestamp < this.lastTimestamp) {
                    throw new Error('Clock moved backwards. Refusing to generate id for ' +
                        (this.lastTimestamp - timestamp));
                }
                if (this.lastTimestamp === timestamp) {
                    this.sequence = (this.sequence + 1) & this.sequenceMask;
                    if (this.sequence === 0) {
                        timestamp = this.tilNextMillis(this.lastTimestamp);
                    }
                } else {
                    this.sequence = 0;
                }
                this.lastTimestamp = timestamp;
                var shiftNum = (this.dataCenterId << this.dataCenterIdShift) |
                    (this.workerId << this.workerIdShift) |
                    this.sequence; // dataCenterId:1,workerId:1,sequence:0  shiftNum:135168
                var nfirst = new bigInt(String(timestamp - this.twepoch), 10);
                nfirst = nfirst.shiftLeft(this.timestampLeftShift);
                var nnextId = nfirst.or(new bigInt(String(shiftNum), 10)).toString(10);
                return nnextId;
            };
            return Snowflake;
        }());
        var tempSnowflake = new Snowflake(1, 1, 0);
        var tempIds = [];
        console.time();
        for (var i = 0; i < 10000; i++) {
            var tempId = tempSnowflake.nextId();
            console.log(tempId);
            if (tempIds.indexOf(tempId) < 0) {
                tempIds.push(tempId);
            }
        }
        console.log(tempIds.length);
        console.timeEnd();
    </script>
</body>

</html>

View Code

　　原生BigInt實現：segmentfault

<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
</head>

<body>
    <script>
        var Snowflake = /** @class */ (function() {
            function Snowflake(_workerId, _dataCenterId, _sequence) {
                this.twepoch = 1288834974657n;
                //this.twepoch = 0n;
                this.workerIdBits = 5n;
                this.dataCenterIdBits = 5n;
                this.maxWrokerId = -1n ^ (-1n << this.workerIdBits); // 值爲：31
                this.maxDataCenterId = -1n ^ (-1n << this.dataCenterIdBits); // 值爲：31
                this.sequenceBits = 12n;
                this.workerIdShift = this.sequenceBits; // 值爲：12
                this.dataCenterIdShift = this.sequenceBits + this.workerIdBits; // 值爲：17
                this.timestampLeftShift = this.sequenceBits + this.workerIdBits + this.dataCenterIdBits; // 值爲：22
                this.sequenceMask = -1n ^ (-1n << this.sequenceBits); // 值爲：4095
                this.lastTimestamp = -1n;
                //設置默認值,從環境變量取
                this.workerId = 1n;
                this.dataCenterId = 1n;
                this.sequence = 0n;
                if (this.workerId > this.maxWrokerId || this.workerId < 0) {
                    throw new Error('_workerId must max than 0 and small than maxWrokerId-[' + this.maxWrokerId + ']');
                }
                if (this.dataCenterId > this.maxDataCenterId || this.dataCenterId < 0) {
                    throw new Error('_dataCenterId must max than 0 and small than maxDataCenterId-[' + this.maxDataCenterId + ']');
                }

                this.workerId = BigInt(_workerId);
                this.dataCenterId = BigInt(_dataCenterId);
                this.sequence = BigInt(_sequence);
            }
            Snowflake.prototype.tilNextMillis = function(lastTimestamp) {
                var timestamp = this.timeGen();
                while (timestamp <= lastTimestamp) {
                    timestamp = this.timeGen();
                }
                return BigInt(timestamp);
            };
            Snowflake.prototype.timeGen = function() {
                return BigInt(Date.now());
            };
            Snowflake.prototype.nextId = function() {
                var timestamp = this.timeGen();
                if (timestamp < this.lastTimestamp) {
                    throw new Error('Clock moved backwards. Refusing to generate id for ' +
                        (this.lastTimestamp - timestamp));
                }
                if (this.lastTimestamp === timestamp) {
                    this.sequence = (this.sequence + 1n) & this.sequenceMask;
                    if (this.sequence === 0n) {
                        timestamp = this.tilNextMillis(this.lastTimestamp);
                    }
                } else {
                    this.sequence = 0n;
                }
                this.lastTimestamp = timestamp;
                return ((timestamp - this.twepoch) << this.timestampLeftShift) |
                    (this.dataCenterId << this.dataCenterIdShift) |
                    (this.workerId << this.workerIdShift) |
                    this.sequence;
            };
            return Snowflake;
        }());
        console.time();
        var tempSnowflake = new Snowflake(1n, 1n, 0n);
        var tempIds = [];
        for (var i = 0; i < 10000; i++) {
            var tempId = tempSnowflake.nextId();
            console.log(tempId);
            if (tempIds.indexOf(tempId) < 0) {
                tempIds.push(tempId);
            }
        }
        console.log(tempIds.length);
        console.timeEnd();
    </script>
</body>

</html>