fastrand.go

package utils

import (
	"math/rand"
	"sync"
	"time"
)

// Implement Source and Source64 interfaces
type rngSource struct {
	p sync.Pool
}

func (r *rngSource) Int63() (n int64) {
	src := r.p.Get()
	n = src.(rand.Source).Int63()
	r.p.Put(src)
	return
}

// Seed specify seed when using NewRand()
func (r *rngSource) Seed(_ int64) {}

func (r *rngSource) Uint64() (n uint64) {
	src := r.p.Get()
	n = src.(rand.Source64).Uint64()
	r.p.Put(src)
	return
}

// NewRand goroutine-safe rand.Rand, optional seed value
func NewRand(seed ...int64) *rand.Rand {
	n := time.Now().UnixNano()
	if len(seed) > 0 {
		n = seed[0]
	}
	src := &rngSource{
		p: sync.Pool{
			New: func() interface{} {
				return rand.NewSource(n)
			},
		}}
	return rand.New(src)
}