m

code/base-project/base-go/pkg/utils/uid/snowflake.go

@@ -0,0 +1,90 @@
+package uid
+
+import (
+	"base-framework/pkg/config"
+	"sync"
+	"sync/atomic"
+	"time"
+)
+
+const (
+	datacenterBits = uint64(5)
+	workerBits     = uint64(5)
+	sequenceBits   = uint64(12)
+
+	maxSequence     = -1 ^ (-1 << sequenceBits)
+	workerShift     = sequenceBits
+	datacenterShift = sequenceBits + workerBits
+	timestampShift  = sequenceBits + workerBits + datacenterBits
+
+	epoch = int64(1672531200000) // 2023-01-01
+)
+
+type Snowflake struct {
+	lastStamp uint64 // 上一次时间戳 (毫秒)
+	sequence  uint64 // 序列号
+	dcID      uint64
+	workerID  uint64
+}
+
+var (
+	sfInstance *Snowflake
+	once       sync.Once
+)
+
+// lazy 初始化实例
+func initInstance() {
+	var dcID, wID uint64
+	if config.Snowflake != nil {
+		dcID = config.Snowflake.DatacenterID
+		wID = config.Snowflake.WorkerID
+	}
+	sfInstance = &Snowflake{
+		dcID:     dcID,
+		workerID: wID,
+	}
+}
+
+// NextID 生成全局唯一 ID，无锁版本
+func NextID() uint64 {
+	once.Do(initInstance)
+
+	for {
+		now := uint64(time.Now().UnixNano() / 1e6)
+
+		last := atomic.LoadUint64(&sfInstance.lastStamp)
+		seq := atomic.LoadUint64(&sfInstance.sequence)
+
+		if now < last {
+			// 系统时钟回拨，等待
+			now = waitNextMillis(last)
+		}
+
+		if now == last {
+			seq = (seq + 1) & uint64(maxSequence)
+			if seq == 0 {
+				now = waitNextMillis(last)
+			}
+		} else {
+			seq = 0
+		}
+
+		if atomic.CompareAndSwapUint64(&sfInstance.lastStamp, last, now) {
+			atomic.StoreUint64(&sfInstance.sequence, seq)
+			id := ((now - uint64(epoch)) << timestampShift) |
+				(sfInstance.dcID << datacenterShift) |
+				(sfInstance.workerID << workerShift) |
+				seq
+			return id
+		}
+	}
+}
+
+// 等待下一个毫秒
+func waitNextMillis(last uint64) uint64 {
+	now := uint64(time.Now().UnixNano() / 1e6)
+	for now <= last {
+		now = uint64(time.Now().UnixNano() / 1e6)
+	}
+	return now
+}