tidb rand 代码
文件路径：/util/mathutil/rand.go
/ Copyright 2020 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,
/ 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 mathutil
import (
"sync"
"time"
)
const maxRandValue = 0x3FFFFFFF
/ MysqlRng is random number generator and this implementation is ported from MySQL.
/ See https://github.com/tikv/tikv/pull/6117#issuecomment-562489078.
type MysqlRng struct {
mu *sync.Mutex
seed1 uint32
seed2 uint32
}
/ NewWithSeed create a rng with random seed.
func NewWithSeed(seed int64) *MysqlRng {
seed1 := uint32(seed*0x10001+55555555) % maxRandValue
seed2 := uint32(seed*0x10000001) % maxRandValue
return &MysqlRng{
seed1: seed1,
seed2: seed2,
mu: &sync.Mutex{},
}
}
/ NewWithTime create a rng with time stamp.
func NewWithTime() *MysqlRng {
return NewWithSeed(time.Now().UnixNano())
}
/ Gen will generate random number.
func (rng *MysqlRng) Gen() float64 {
rng.mu.Lock()
defer rng.mu.Unlock()
rng.seed1 = (rng.seed1*3 + rng.seed2) % maxRandValue
rng.seed2 = (rng.seed1 + rng.seed2 + 33) % maxRandValue
return float64(rng.seed1) / float64(maxRandValue)
}
/ SetSeed1 is a interface to set seed1
func (rng *MysqlRng) SetSeed1(seed uint32) {
rng.mu.Lock()
defer rng.mu.Unlock()
rng.seed1 = seed
}
/ SetSeed2 is a interface to set seed2
func (rng *MysqlRng) SetSeed2(seed uint32) {
rng.mu.Lock()
defer rng.mu.Unlock()
rng.seed2 = seed
}
/ GetSeed1 is an interface to get seed1. It's only used for getting session states.
func (rng *MysqlRng) GetSeed1() uint32 {
rng.mu.Lock()
defer rng.mu.Unlock()
return rng.seed1
}
/ GetSeed2 is an interface to get seed2. It's only used for getting session states.
func (rng *MysqlRng) GetSeed2() uint32 {
rng.mu.Lock()
defer rng.mu.Unlock()
return rng.seed2
}