Created
March 7, 2019 10:25
-
-
Save nanmu42/ca12803fa230a53f255c0e7bb623e539 to your computer and use it in GitHub Desktop.
Superfast Golang Random String
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
// credits: https://stackoverflow.com/questions/22892120/how-to-generate-a-random-string-of-a-fixed-length-in-go | |
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 | |
) | |
func init() { | |
rand.Seed(time.Now().UnixNano()) | |
} | |
func randString(n int) string { | |
b := make([]byte, n) | |
// A src.Int63() generates 63 random bits, enough for letterIdxMax characters! | |
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) | |
} |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment