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package rand
import (
crand "crypto/rand"
mrand "math/rand"
"sync"
"time"
)
const (
strChars = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz" // 62 characters
)
// Rand is a prng, that is seeded with OS randomness.
// The OS randomness is obtained from crypto/rand, however none of the provided
// methods are suitable for cryptographic usage.
// They all utilize math/rand's prng internally.
//
// All of the methods here are suitable for concurrent use.
// This is achieved by using a mutex lock on all of the provided methods.
type Rand struct {
sync.Mutex
rand *mrand.Rand
}
var grand *Rand
func init() {
grand = NewRand()
grand.init()
}
func NewRand() *Rand {
rand := &Rand{}
rand.init()
return rand
}
func (r *Rand) init() {
bz := cRandBytes(8)
var seed uint64
for i := 0; i < 8; i++ {
seed |= uint64(bz[i])
seed <<= 8
}
r.reset(int64(seed))
}
func (r *Rand) reset(seed int64) {
r.rand = mrand.New(mrand.NewSource(seed))
}
//----------------------------------------
// Global functions
func Seed(seed int64) {
grand.Seed(seed)
}
func Str(length int) string {
return grand.Str(length)
}
func Uint16() uint16 {
return grand.Uint16()
}
func Uint32() uint32 {
return grand.Uint32()
}
func Uint64() uint64 {
return grand.Uint64()
}
func Uint() uint {
return grand.Uint()
}
func Int16() int16 {
return grand.Int16()
}
func Int32() int32 {
return grand.Int32()
}
func Int64() int64 {
return grand.Int64()
}
func Int() int {
return grand.Int()
}
func Int31() int32 {
return grand.Int31()
}
func Int31n(n int32) int32 {
return grand.Int31n(n)
}
func Int63() int64 {
return grand.Int63()
}
func Int63n(n int64) int64 {
return grand.Int63n(n)
}
func Bool() bool {
return grand.Bool()
}
func Float32() float32 {
return grand.Float32()
}
func Float64() float64 {
return grand.Float64()
}
func Time() time.Time {
return grand.Time()
}
func Bytes(n int) []byte {
return grand.Bytes(n)
}
func Intn(n int) int {
return grand.Intn(n)
}
func Perm(n int) []int {
return grand.Perm(n)
}
//----------------------------------------
// Rand methods
func (r *Rand) Seed(seed int64) {
r.Lock()
r.reset(seed)
r.Unlock()
}
// Str constructs a random alphanumeric string of given length.
func (r *Rand) Str(length int) string {
chars := []byte{}
MAIN_LOOP:
for {
val := r.Int63()
for i := 0; i < 10; i++ {
v := int(val & 0x3f) // rightmost 6 bits
if v >= 62 { // only 62 characters in strChars
val >>= 6
continue
} else {
chars = append(chars, strChars[v])
if len(chars) == length {
break MAIN_LOOP
}
val >>= 6
}
}
}
return string(chars)
}
func (r *Rand) Uint16() uint16 {
return uint16(r.Uint32() & (1<<16 - 1))
}
func (r *Rand) Uint32() uint32 {
r.Lock()
u32 := r.rand.Uint32()
r.Unlock()
return u32
}
func (r *Rand) Uint64() uint64 {
return uint64(r.Uint32())<<32 + uint64(r.Uint32())
}
func (r *Rand) Uint() uint {
r.Lock()
i := r.rand.Int()
r.Unlock()
return uint(i)
}
func (r *Rand) Int16() int16 {
return int16(r.Uint32() & (1<<16 - 1))
}
func (r *Rand) Int32() int32 {
return int32(r.Uint32())
}
func (r *Rand) Int64() int64 {
return int64(r.Uint64())
}
func (r *Rand) Int() int {
r.Lock()
i := r.rand.Int()
r.Unlock()
return i
}
func (r *Rand) Int31() int32 {
r.Lock()
i31 := r.rand.Int31()
r.Unlock()
return i31
}
func (r *Rand) Int31n(n int32) int32 {
r.Lock()
i31n := r.rand.Int31n(n)
r.Unlock()
return i31n
}
func (r *Rand) Int63() int64 {
r.Lock()
i63 := r.rand.Int63()
r.Unlock()
return i63
}
func (r *Rand) Int63n(n int64) int64 {
r.Lock()
i63n := r.rand.Int63n(n)
r.Unlock()
return i63n
}
func (r *Rand) Float32() float32 {
r.Lock()
f32 := r.rand.Float32()
r.Unlock()
return f32
}
func (r *Rand) Float64() float64 {
r.Lock()
f64 := r.rand.Float64()
r.Unlock()
return f64
}
func (r *Rand) Time() time.Time {
return time.Unix(int64(r.Uint64()), 0)
}
// Bytes returns n random bytes generated from the internal
// prng.
func (r *Rand) Bytes(n int) []byte {
// cRandBytes isn't guaranteed to be fast so instead
// use random bytes generated from the internal PRNG
bs := make([]byte, n)
for i := 0; i < len(bs); i++ {
bs[i] = byte(r.Int() & 0xFF)
}
return bs
}
// Intn returns, as an int, a uniform pseudo-random number in the range [0, n).
// It panics if n <= 0.
func (r *Rand) Intn(n int) int {
r.Lock()
i := r.rand.Intn(n)
r.Unlock()
return i
}
// Bool returns a uniformly random boolean
func (r *Rand) Bool() bool {
// See https://github.com/golang/go/issues/23804#issuecomment-365370418
// for reasoning behind computing like this
return r.Int63()%2 == 0
}
// Perm returns a pseudo-random permutation of n integers in [0, n).
func (r *Rand) Perm(n int) []int {
r.Lock()
perm := r.rand.Perm(n)
r.Unlock()
return perm
}
// NOTE: This relies on the os's random number generator.
// For real security, we should salt that with some seed.
// See github.com/tendermint/tendermint/crypto for a more secure reader.
func cRandBytes(numBytes int) []byte {
b := make([]byte, numBytes)
_, err := crand.Read(b)
if err != nil {
panic(err)
}
return b
}