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xor_shift128.go
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xor_shift128.go
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// Copyright 2014-2021 Aerospike, 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 rand
import (
"encoding/binary"
"sync"
"sync/atomic"
"time"
)
const (
poolSize = 512
)
// random number generator pool
var (
pool = make([]*Xor128Rand, poolSize)
pos uint64
rndInit = &Xor128Rand{src: [2]uint64{uint64(time.Now().UnixNano()), uint64(time.Now().UnixNano())}}
)
func init() {
for i := range pool {
pool[i] = NewXorRand()
}
}
// Int64 returns a random int64 number. It can be negative.
// This function uses a pool and is lockless.
func Int64() int64 {
apos := int(atomic.AddUint64(&pos, 1) % poolSize)
return pool[apos].Int64()
}
// Uint64 returns a random uint64 number.
// This function uses a pool and is lockless.
func Uint64() uint64 {
apos := int(atomic.AddUint64(&pos, 1) % poolSize)
return pool[apos].Uint64()
}
// Xor128Rand is a random number generator
type Xor128Rand struct {
src [2]uint64
l sync.Mutex
}
// NewXorRand creates a XOR Shift random number generator.
func NewXorRand() *Xor128Rand {
t := time.Now().UnixNano() + rndInit.Int64()
return &Xor128Rand{src: [2]uint64{uint64(t), uint64(t)}}
}
// Int64 returns a random int64 number. It can be negative.
func (r *Xor128Rand) Int64() int64 {
return int64(r.Uint64())
}
// Uint64 returns a random uint64 number.
func (r *Xor128Rand) Uint64() uint64 {
r.l.Lock()
s1 := r.src[0]
s0 := r.src[1]
r.src[0] = s0
s1 ^= s1 << 23
r.src[1] = (s1 ^ s0 ^ (s1 >> 17) ^ (s0 >> 26))
res := r.src[1] + s0
r.l.Unlock()
return res
}
// Read will fill the argument slice with random bytes.
// Implements the Reader interface.
func (r *Xor128Rand) Read(p []byte) (n int, err error) {
l := len(p) / 8
for i := 0; i < l; i += 8 {
binary.PutUvarint(p[i:], r.Uint64())
}
return len(p), nil
}