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rand.go
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rand.go
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package rand
import (
"fmt"
"math/rand"
"sync"
"time"
)
func init() {
// initialize global pseudo random generator
rand.Seed(time.Now().Unix())
}
/*
* Top-level convenience functions
*/
var (
globalSource = lockedSource{src: rand.NewSource(time.Now().UnixNano()).(rand.Source64)}
randMu sync.Mutex // rand.Read should not be called concurrently
globalRand = rand.New(&globalSource)
letterRunes = []rune("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ")
)
// Seed uses the provided seed value to initialize the default Source to a
// deterministic state. If Seed is not called, the generator behaves as
// if seeded by Seed(1). Seed values that have the same remainder when
// divided by 2^31-1 generate the same pseudo-random sequence.
// Seed, unlike the Rand.Seed method, is safe for concurrent use.
func Seed(seed int64) {
randMu.Lock()
defer randMu.Unlock()
globalRand.Seed(seed)
}
// Int63 returns a non-negative pseudo-random 63-bit integer as an int64
// from the default Source.
func Int63() int64 {
randMu.Lock()
defer randMu.Unlock()
return globalRand.Int63()
}
// Uint32 returns a pseudo-random 32-bit value as a uint32
// from the default Source.
func Uint32() uint32 {
randMu.Lock()
defer randMu.Unlock()
return globalRand.Uint32()
}
// Uint64 returns a pseudo-random 64-bit value as a uint64
// from the default Source.
func Uint64() uint64 {
randMu.Lock()
defer randMu.Unlock()
return globalRand.Uint64()
}
// Int31 returns a non-negative pseudo-random 31-bit integer as an int32
// from the default Source.
func Int31() int32 {
randMu.Lock()
defer randMu.Unlock()
return globalRand.Int31()
}
// Int returns a non-negative pseudo-random int from the default Source.
func Int() int {
randMu.Lock()
defer randMu.Unlock()
return globalRand.Int()
}
// Int63n returns, as an int64, a non-negative pseudo-random number in [0,n)
// from the default Source.
// It panics if n <= 0.
func Int63n(n int64) int64 {
randMu.Lock()
defer randMu.Unlock()
return globalRand.Int63n(n)
}
// Int31n returns, as an int32, a non-negative pseudo-random number in [0,n)
// from the default Source.
// It panics if n <= 0.
func Int31n(n int32) int32 {
randMu.Lock()
defer randMu.Unlock()
return globalRand.Int31n(n)
}
// Intn returns, as an int, a non-negative pseudo-random number in [0,n)
// from the default Source.
// It panics if n <= 0.
func Intn(n int) int {
randMu.Lock()
defer randMu.Unlock()
return globalRand.Intn(n)
}
// Float64 returns, as a float64, a pseudo-random number in [0.0,1.0)
// from the default Source.
func Float64() float64 {
randMu.Lock()
defer randMu.Unlock()
return globalRand.Float64()
}
// Float32 returns, as a float32, a pseudo-random number in [0.0,1.0)
// from the default Source.
func Float32() float32 {
randMu.Lock()
defer randMu.Unlock()
return globalRand.Float32()
}
// Perm returns, as a slice of n ints, a pseudo-random permutation of the integers [0,n)
// from the default Source.
func Perm(n int) []int {
randMu.Lock()
defer randMu.Unlock()
return globalRand.Perm(n)
}
// Shuffle pseudo-randomizes the order of elements using the default Source.
// n is the number of elements. Shuffle panics if n < 0.
// swap swaps the elements with indexes i and j.
func Shuffle(n int, swap func(i, j int)) {
randMu.Lock()
defer randMu.Unlock()
globalRand.Shuffle(n, swap)
}
// Read generates len(p) random bytes from the default Source and
// writes them into p. It always returns len(p) and a nil error.
// Read, unlike the Rand.Read method, is safe for concurrent use.
func Read(p []byte) (n int, err error) {
randMu.Lock()
defer randMu.Unlock()
n, err = globalRand.Read(p)
if err != nil {
return n, fmt.Errorf("read: %w", err)
}
return n, nil
}
// NormFloat64 returns a normally distributed float64 in the range
// [-math.MaxFloat64, +math.MaxFloat64] with
// standard normal distribution (mean = 0, stddev = 1)
// from the default Source.
// To produce a different normal distribution, callers can
// adjust the output using:
//
// sample = NormFloat64() * desiredStdDev + desiredMean
//
func NormFloat64() float64 {
randMu.Lock()
defer randMu.Unlock()
return globalRand.NormFloat64()
}
// ExpFloat64 returns an exponentially distributed float64 in the range
// (0, +math.MaxFloat64] with an exponential distribution whose rate parameter
// (lambda) is 1 and whose mean is 1/lambda (1) from the default Source.
// To produce a distribution with a different rate parameter,
// callers can adjust the output using:
//
// sample = ExpFloat64() / desiredRateParameter
//
func ExpFloat64() float64 {
randMu.Lock()
defer randMu.Unlock()
return globalRand.ExpFloat64()
}
// String returns an n sized random string.
func String(n int) string {
b := make([]rune, n)
for i := range b {
b[i] = letterRunes[rand.Intn(len(letterRunes))]
}
return string(b)
}
type lockedSource struct {
lock sync.Mutex
src rand.Source64
}
func (ls *lockedSource) Int63() int64 {
ls.lock.Lock()
defer ls.lock.Unlock()
return ls.src.Int63()
}
func (ls *lockedSource) Uint64() uint64 {
ls.lock.Lock()
defer ls.lock.Unlock()
return ls.src.Uint64()
}
func (ls *lockedSource) Seed(seed int64) {
ls.lock.Lock()
defer ls.lock.Unlock()
ls.src.Seed(seed)
}