feat(Go-StudyExample):2020/12/16: 包重命名

example/snowflake/Snowflake.go

@@ -0,0 +1,96 @@
+/*
+ *  @Author : huangzj
+ *  @Time : 2020/12/16 9:32
+ *  @Description：
+ */
+
+package snowflake
+
+import (
+	"errors"
+	"sync"
+	"time"
+)
+
+const (
+	workerBits  uint8 = 10
+	numberBits  uint8 = 12
+	workerMax   int64 = -1 ^ (-1 << workerBits)
+	numberMax   int64 = -1 ^ (-1 << numberBits)
+	timeShift   uint8 = workerBits + numberBits
+	workerShift uint8 = numberBits
+	startTime   int64 = 1525705533000 // 如果在程序跑了一段时间修改了epoch这个值 可能会导致生成相同的ID
+)
+
+const (
+	workerIDBits     = uint64(5) // 10bit 工作机器ID中的 5bit workerID
+	dataCenterIDBits = uint64(5) // 10 bit 工作机器ID中的 5bit dataCenterID
+	sequenceBits     = uint64(12)
+
+	maxWorkerID     = int64(-1) ^ (int64(-1) << workerIDBits) //节点ID的最大值 用于防止溢出
+	maxDataCenterID = int64(-1) ^ (int64(-1) << dataCenterIDBits)
+	maxSequence     = int64(-1) ^ (int64(-1) << sequenceBits)
+
+	timeLeft = uint8(22) // timeLeft = workerIDBits + sequenceBits // 时间戳向左偏移量
+	dataLeft = uint8(17) // dataLeft = dataCenterIDBits + sequenceBits
+	workLeft = uint8(12) // workLeft = sequenceBits // 节点IDx向左偏移量
+	// 2020-05-20 08:00:00 +0800 CST
+	twepoch = int64(1589923200000) // 常量时间戳(毫秒)
+)
+
+type Worker struct {
+	mu           sync.Mutex
+	LastStamp    int64 // 记录上一次ID的时间戳
+	WorkerID     int64 // 该节点的ID
+	DataCenterID int64 // 该节点的 数据中心ID
+	Sequence     int64 // 当前毫秒已经生成的ID序列号(从0 开始累加) 1毫秒内最多生成4096个ID
+}
+
+//分布式情况下,我们应通过外部配置文件或其他方式为每台机器分配独立的id
+func NewWorker(workerID, dataCenterID int64) *Worker {
+	return &Worker{
+		WorkerID:     workerID,
+		LastStamp:    0,
+		Sequence:     0,
+		DataCenterID: dataCenterID,
+	}
+}
+
+func (w *Worker) getMilliSeconds() int64 {
+	return time.Now().UnixNano() / 1e6
+}
+
+func (w *Worker) NextID() (uint64, error) {
+	w.mu.Lock()
+	defer w.mu.Unlock()
+
+	return w.nextID()
+}
+
+func (w *Worker) nextID() (uint64, error) {
+	timeStamp := w.getMilliSeconds()
+	if timeStamp < w.LastStamp {
+		return 0, errors.New("time is moving backwards,waiting until")
+	}
+
+	if w.LastStamp == timeStamp {
+
+		w.Sequence = (w.Sequence + 1) & maxSequence
+
+		if w.Sequence == 0 {
+			for timeStamp <= w.LastStamp {
+				timeStamp = w.getMilliSeconds()
+			}
+		}
+	} else {
+		w.Sequence = 0
+	}
+
+	w.LastStamp = timeStamp
+	id := ((timeStamp - twepoch) << timeLeft) |
+		(w.DataCenterID << dataLeft) |
+		(w.WorkerID << workLeft) |
+		w.Sequence
+
+	return uint64(id), nil
+}