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package randutil
import (
mrand "math/rand" // used for non-crypto unique ID and random port selection
"sync"
"time"
)
// MathRandomGenerator is a random generator for non-crypto usage.
type MathRandomGenerator interface {
// Intn returns random integer within [0:n).
Intn(n int) int
// Uint32 returns random 32-bit unsigned integer.
Uint32() uint32
// Uint64 returns random 64-bit unsigned integer.
Uint64() uint64
// GenerateString returns ranom string using given set of runes.
// It can be used for generating unique ID to avoid name collision.
//
// Caution: DO NOT use this for cryptographic usage.
GenerateString(n int, runes string) string
}
type mathRandomGenerator struct {
r *mrand.Rand
mu sync.Mutex
}
// NewMathRandomGenerator creates new mathmatical random generator.
// Random generator is seeded by crypto random.
func NewMathRandomGenerator() MathRandomGenerator {
seed, err := CryptoUint64()
if err != nil {
// crypto/rand is unavailable. Fallback to seed by time.
seed = uint64(time.Now().UnixNano())
}
return &mathRandomGenerator{r: mrand.New(mrand.NewSource(int64(seed)))}
}
func (g *mathRandomGenerator) Intn(n int) int {
g.mu.Lock()
v := g.r.Intn(n)
g.mu.Unlock()
return v
}
func (g *mathRandomGenerator) Uint32() uint32 {
g.mu.Lock()
v := g.r.Uint32()
g.mu.Unlock()
return v
}
func (g *mathRandomGenerator) Uint64() uint64 {
g.mu.Lock()
v := g.r.Uint64()
g.mu.Unlock()
return v
}
func (g *mathRandomGenerator) GenerateString(n int, runes string) string {
letters := []rune(runes)
b := make([]rune, n)
for i := range b {
b[i] = letters[g.Intn(len(letters))]
}
return string(b)
}
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