84 lines
2.2 KiB
Go
84 lines
2.2 KiB
Go
// Copyright 2020 PingCAP, Inc.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package mathutil
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import (
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"sync"
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"time"
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)
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const maxRandValue = 0x3FFFFFFF
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// MysqlRng is random number generator and this implementation is ported from MySQL.
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// See https://github.com/tikv/tikv/pull/6117#issuecomment-562489078.
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type MysqlRng struct {
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mu *sync.Mutex
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seed1 uint32
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seed2 uint32
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}
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// NewWithSeed create a rng with random seed.
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func NewWithSeed(seed int64) *MysqlRng {
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seed1 := uint32(seed*0x10001+55555555) % maxRandValue
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seed2 := uint32(seed*0x10000001) % maxRandValue
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return &MysqlRng{
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seed1: seed1,
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seed2: seed2,
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mu: &sync.Mutex{},
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}
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}
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// NewWithTime create a rng with time stamp.
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func NewWithTime() *MysqlRng {
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return NewWithSeed(time.Now().UnixNano())
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}
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// Gen will generate random number.
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func (rng *MysqlRng) Gen() float64 {
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rng.mu.Lock()
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defer rng.mu.Unlock()
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rng.seed1 = (rng.seed1*3 + rng.seed2) % maxRandValue
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rng.seed2 = (rng.seed1 + rng.seed2 + 33) % maxRandValue
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return float64(rng.seed1) / float64(maxRandValue)
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}
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// SetSeed1 is a interface to set seed1
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func (rng *MysqlRng) SetSeed1(seed uint32) {
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rng.mu.Lock()
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defer rng.mu.Unlock()
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rng.seed1 = seed
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}
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// SetSeed2 is a interface to set seed2
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func (rng *MysqlRng) SetSeed2(seed uint32) {
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rng.mu.Lock()
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defer rng.mu.Unlock()
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rng.seed2 = seed
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}
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// GetSeed1 is an interface to get seed1. It's only used for getting session states.
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func (rng *MysqlRng) GetSeed1() uint32 {
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rng.mu.Lock()
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defer rng.mu.Unlock()
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return rng.seed1
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}
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// GetSeed2 is an interface to get seed2. It's only used for getting session states.
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func (rng *MysqlRng) GetSeed2() uint32 {
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rng.mu.Lock()
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defer rng.mu.Unlock()
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return rng.seed2
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}
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