snow flake

snow_flake/snow_flake.go

@@ -0,0 +1,57 @@
+package snowflake
+
+import (
+	"sync"
+	"time"
+)
+
+// 雪花算法默认起始时间 2020-01-01
+const defaultStarTimestamp = 1579536000
+
+const (
+	MachineIdBits = uint(8)  //机器id所占的位数
+	SequenceBits  = uint(12) //序列所占的位数
+	//MachineIdMax   = int64(-1 ^ (-1 << MachineIdBits)) //支持的最大机器id数量
+	SequenceMask   = int64(-1 ^ (-1 << SequenceBits)) //
+	MachineIdShift = SequenceBits                     //机器id左移位数
+	TimestampShift = SequenceBits + MachineIdBits     //时间戳左移位数
+)
+
+type SnowFlake interface {
+	GetId() int64
+}
+
+type snowflake struct {
+	sync.Mutex
+	startTimeStamp int64
+	timestamp      int64
+	machineId      int64
+	sequence       int64
+}
+
+func CreateSnowflake(machineId int64) SnowFlake {
+	return &snowflake{
+		startTimeStamp: defaultStarTimestamp,
+		machineId:      machineId,
+	}
+}
+
+func (s *snowflake) GetId() int64 {
+	s.Lock()
+	defer s.Unlock()
+
+	now := time.Now().UnixNano() / 1e6
+	if s.timestamp == now {
+		s.sequence = (s.sequence + 1) & SequenceMask
+		if s.sequence == 0 {
+			for now <= s.timestamp {
+				now = time.Now().UnixNano() / 1e6
+			}
+		}
+	} else {
+		s.sequence = 0
+	}
+	s.timestamp = now
+	r := (now-s.startTimeStamp)<<TimestampShift | (s.machineId << MachineIdShift) | (s.sequence)
+	return r
+}

snow_flake/snow_flake_test.go

@@ -0,0 +1,10 @@
+package snowflake
+
+import "testing"
+
+func TestGetId(t *testing.T) {
+	s := CreateSnowflake(22)
+	for i := 0; i < 100; i++ {
+		t.Log(s.GetId())
+	}
+}