/
id.go
51 lines (45 loc) · 1.35 KB
/
id.go
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// Copyright 2022 The CubeFS Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
// implied. See the License for the specific language governing
// permissions and limitations under the License.
package raftserver
import (
"math"
"sync/atomic"
"time"
)
// | prefix | suffix |
// | 2 bytes | 5 bytes | 1 byte |
// | memberID | timestamp | cnt |
type Generator struct {
// high order 2 bytes
prefix uint64
// low order 6 bytes
suffix uint64
}
func NewGenerator(memberId uint64, now time.Time) *Generator {
prefix := memberId << 48
unixMilli := uint64(now.UnixNano()) / uint64(time.Millisecond/time.Nanosecond)
suffix := lowbit(unixMilli, 40) << 8
return &Generator{
prefix: prefix,
suffix: suffix,
}
}
// Next generates a id that is unique.
func (g *Generator) Next() uint64 {
suffix := atomic.AddUint64(&g.suffix, 1)
return g.prefix | lowbit(suffix, 48)
}
func lowbit(x uint64, n uint) uint64 {
return x & (math.MaxUint64 >> (64 - n))
}