github.com/argoproj/argo-cd@v1.8.7/util/rand/rand.go (about)

     1  package rand
     2  
     3  import (
     4  	"math/rand"
     5  	"time"
     6  )
     7  
     8  const letterBytes = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"
     9  const (
    10  	letterIdxBits = 6                    // 6 bits to represent a letter index
    11  	letterIdxMask = 1<<letterIdxBits - 1 // All 1-bits, as many as letterIdxBits
    12  	letterIdxMax  = 63 / letterIdxBits   // # of letter indices fitting in 63 bits
    13  )
    14  
    15  var src = rand.NewSource(time.Now().UnixNano())
    16  
    17  // RandString generates, from a given charset, a cryptographically-secure pseudo-random string of a given length.
    18  func RandString(n int) string {
    19  	return RandStringCharset(n, letterBytes)
    20  }
    21  
    22  func RandStringCharset(n int, charset string) string {
    23  	b := make([]byte, n)
    24  	// A src.Int63() generates 63 random bits, enough for letterIdxMax characters!
    25  	for i, cache, remain := n-1, src.Int63(), letterIdxMax; i >= 0; {
    26  		if remain == 0 {
    27  			cache, remain = src.Int63(), letterIdxMax
    28  		}
    29  		if idx := int(cache & letterIdxMask); idx < len(charset) {
    30  			b[i] = charset[idx]
    31  			i--
    32  		}
    33  		cache >>= letterIdxBits
    34  		remain--
    35  	}
    36  	return string(b)
    37  }