58 lines
1.5 KiB
JavaScript
58 lines
1.5 KiB
JavaScript
function Snowflake() {
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this.epoch = 1698796800000 // 自定义起始时间（毫秒）
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this.machineId = 1 // 固定 machineId
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this.sequence = 0
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this.lastTimestamp = -1
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this.sequenceBits = 12
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this.machineBits = 10
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this.maxSequence = 2 ** this.sequenceBits - 1 // 4095
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}
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// 获取当前时间（毫秒）
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Snowflake.prototype.currentTime = function () {
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return Date.now()
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}
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// 等待下一毫秒
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Snowflake.prototype.waitNextMillisecond = function (lastTimestamp) {
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let timestamp = this.currentTime()
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while (timestamp <= lastTimestamp) {
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timestamp = this.currentTime()
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}
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return timestamp
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}
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// 生成 BigInt ID
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Snowflake.prototype.nextId = function () {
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let timestamp = this.currentTime()
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if (timestamp < this.lastTimestamp) {
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throw new Error('Clock moved backwards. Refusing to generate id.')
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}
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if (timestamp === this.lastTimestamp) {
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this.sequence = (this.sequence + 1) & this.maxSequence
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if (this.sequence === 0) {
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timestamp = this.waitNextMillisecond(this.lastTimestamp)
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}
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}
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else {
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this.sequence = 0
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}
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this.lastTimestamp = timestamp
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const id
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= (BigInt(timestamp - this.epoch) << BigInt(this.machineBits + this.sequenceBits))
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| (BigInt(this.machineId) << BigInt(this.sequenceBits))
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| BigInt(this.sequence)
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return id
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}
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// 返回固定长度字符串 ID（适合数据库存储）
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Snowflake.prototype.nextIdStr = function (padLength = 20) {
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return this.nextId().toString().padStart(padLength, '0')
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}
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