78 lines
1.9 KiB
Go
78 lines
1.9 KiB
Go
// Copyright 2017 PingCAP, Inc.
|
|
//
|
|
// 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,
|
|
// See the License for the specific language governing permissions and
|
|
// limitations under the License.
|
|
|
|
package kvenc
|
|
|
|
import (
|
|
"sync/atomic"
|
|
|
|
"github.com/pingcap/tidb/meta/autoid"
|
|
)
|
|
|
|
var _ autoid.Allocator = &Allocator{}
|
|
|
|
var (
|
|
step = int64(5000)
|
|
)
|
|
|
|
// NewAllocator creates an Allocator.
|
|
func NewAllocator() *Allocator {
|
|
return &Allocator{}
|
|
}
|
|
|
|
// Allocator is an id allocator, it is only used in lightning.
|
|
type Allocator struct {
|
|
base int64
|
|
}
|
|
|
|
// Alloc allocs a next autoID for table with tableID.
|
|
func (alloc *Allocator) Alloc(tableID int64) (int64, error) {
|
|
return atomic.AddInt64(&alloc.base, 1), nil
|
|
}
|
|
|
|
// Reset allow newBase smaller than alloc.base, and will set the alloc.base to newBase.
|
|
func (alloc *Allocator) Reset(newBase int64) {
|
|
atomic.StoreInt64(&alloc.base, newBase)
|
|
}
|
|
|
|
// Rebase not allow newBase smaller than alloc.base, and will skip the smaller newBase.
|
|
func (alloc *Allocator) Rebase(tableID, newBase int64, allocIDs bool) error {
|
|
// CAS
|
|
for {
|
|
oldBase := atomic.LoadInt64(&alloc.base)
|
|
if newBase <= oldBase {
|
|
break
|
|
}
|
|
if atomic.CompareAndSwapInt64(&alloc.base, oldBase, newBase) {
|
|
break
|
|
}
|
|
}
|
|
|
|
return nil
|
|
}
|
|
|
|
// Base returns the current base of Allocator.
|
|
func (alloc *Allocator) Base() int64 {
|
|
return atomic.LoadInt64(&alloc.base)
|
|
}
|
|
|
|
// End is only used for test.
|
|
func (alloc *Allocator) End() int64 {
|
|
return alloc.Base() + step
|
|
}
|
|
|
|
// NextGlobalAutoID returns the next global autoID.
|
|
func (alloc *Allocator) NextGlobalAutoID(tableID int64) (int64, error) {
|
|
return alloc.End() + 1, nil
|
|
}
|