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socket = require "socket"
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math = require "math"
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bit = require "bit"
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-- 开始时间截 (2015-01-01)
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twepoch = 1420041600000
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-- 机器id所占的位数
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workerIdBits = 5
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-- 数据标识id所占的位数
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datacenterIdBits = 5
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-- 序列在id中占的位数
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sequenceBits = 12
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-- 支持的最大机器id，结果是31 (这个移位算法可以很快的计算出几位二进制数所能表示的最大十进制数)
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maxWorkerId = bit.lshift(1 , workerIdBits)-1
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-- 支持的最大数据标识id，结果是31
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maxDatacenterId = bit.lshift(1 , datacenterIdBits)-1
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-- 机器ID向左移12位
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workerIdShift = sequenceBits
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-- 数据标识id向左移17位(12+5)
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datacenterIdShift = sequenceBits + workerIdBits
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-- 时间截向左移22位(5+5+12)
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timestampLeftShift = sequenceBits + workerIdBits + datacenterIdBits
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-- 生成序列的掩码，这里为4095 (0b111111111111=0xfff=4095)
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sequenceMask = bit.lshift(1 , sequenceBits) -1
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-- 工作机器ID(0~31)
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workerId=1
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-- 数据中心ID(0~31)
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datacenterId=1
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-- 毫秒内序列(0~4095)
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sequence = 0
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-- 上次生成ID的时间截
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lastTimestamp = -1
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local _M = {}
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function _M.SnowflakeIdWorker (workerIds, datacenterIds)
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if (workerIds > maxWorkerId or workerIds < 0)
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then
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return -1
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end
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if (datacenterIds > maxDatacenterId or datacenterIds < 0)
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then
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return -1
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end
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workerId=workerIds
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datacenterId=datacenterIds
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end
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local function tilNextMillis(lastTimestamp)
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local timestamp = math.floor(socket.gettime() * 1000 )
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while (timestamp <= lastTimestamp)
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do
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timestamp = math.floor(socket.gettime() * 1000 )
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end
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return timestamp
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end
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function _M.nextId ()
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local timestamp = math.floor(socket.gettime() * 1000 )
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-- 如果当前时间小于上一次ID生成的时间戳，说明系统时钟回退过这个时候应当抛出异常
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if (timestamp < lastTimestamp)
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then
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return -1
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end
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-- 如果是同一时间生成的，则进行毫秒内序列
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if (lastTimestamp == timestamp)
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then
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sequence = bit.band((sequence + 1), sequenceMask)
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-- 毫秒内序列溢出
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if (sequence == 0)
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then
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--阻塞到下一个毫秒,获得新的时间戳
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timestamp = tilNextMillis(lastTimestamp)
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end
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else
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sequence = 0
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end
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lastTimestamp = timestamp
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cmd =("sh ./id.sh " .. timestamp .. '\t' ..twepoch .. '\t'.. timestampLeftShift .. '\t'.. datacenterId .. '\t'.. datacenterIdShift .. '\t'.. workerId .. '\t'.. workerIdShift .. '\t'.. sequence)
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id = os.execute(cmd)
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return id
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end
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return _M |
