argo-cd/util/rand/rand.go at stable · dominikbraun/argo-cd

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package rand

import (

"math/rand"

"time"

)

const letterBytes = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"

const (

letterIdxBits = 6 // 6 bits to represent a letter index

letterIdxMask = 1<<letterIdxBits - 1 // All 1-bits, as many as letterIdxBits

letterIdxMax = 63 / letterIdxBits // # of letter indices fitting in 63 bits

)

var src = rand.NewSource(time.Now().UnixNano())

// RandString generates, from a given charset, a cryptographically-secure pseudo-random string of a given length.

func RandString(n int) string {

return RandStringCharset(n, letterBytes)

}

func RandStringCharset(n int, charset string) string {

b := make([]byte, n)

// A src.Int63() generates 63 random bits, enough for letterIdxMax characters!

for i, cache, remain := n-1, src.Int63(), letterIdxMax; i >= 0; {

if remain == 0 {

cache, remain = src.Int63(), letterIdxMax

}

if idx := int(cache & letterIdxMask); idx < len(charset) {

b[i] = charset[idx]

i--

}

cache >>= letterIdxBits

remain--

}

return string(b)

}