1package mox

2

3import (

4 cryptorand "crypto/rand"

5 "encoding/binary"

6 "fmt"

7 mathrand "math/rand"

8 "sync"

9)

10

11type rand struct {

12 rand *mathrand.Rand

13 sync.Mutex

14}

15

16// NewPseudoRand returns a new PRNG seeded with random bytes from crypto/rand. Its

17// functions can be called concurrently.

18func NewPseudoRand() *rand {

19 return &rand{rand: mathrand.New(mathrand.NewSource(CryptoRandInt()))}

20}

21

22func (r *rand) Float64() float64 {

23 r.Lock()

24 defer r.Unlock()

25 return r.rand.Float64()

26}

27

28func (r *rand) Intn(n int) int {

29 r.Lock()

30 defer r.Unlock()

31 return r.rand.Intn(n)

32}

33

34func (r *rand) Read(buf []byte) (int, error) {

35 r.Lock()

36 defer r.Unlock()

37 return r.rand.Read(buf)

38}

39

40// CryptoRandInt returns a cryptographically random number.

41func CryptoRandInt() int64 {

42 buf := make([]byte, 8)

43 _, err := cryptorand.Read(buf)

44 if err != nil {

45 panic(fmt.Errorf("reading random bytes: %v", err))

46 }

47 return int64(binary.LittleEndian.Uint64(buf))

48}

49