vikunja-api/pkg/utils/random_string.go

37 lines
901 B
Go
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2018-10-27 11:33:28 +02:00
package utils
import (
"math/rand"
"time"
)
func init() {
rand.Seed(time.Now().UnixNano())
}
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
)
// MakeRandomString return a random string
func MakeRandomString(n int) string {
b := make([]byte, n)
// A rand.Int63() generates 63 random bits, enough for letterIdxMax letters!
for i, cache, remain := n-1, rand.Int63(), letterIdxMax; i >= 0; {
if remain == 0 {
cache, remain = rand.Int63(), letterIdxMax
}
if idx := int(cache & letterIdxMask); idx < len(letterBytes) {
b[i] = letterBytes[idx]
i--
}
cache >>= letterIdxBits
remain--
}
return string(b)
}