sourcegraph/internal/randstring/string.go at main · flyinprogrammer/sourcegraph · GitHub

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// Package randstring generates random strings.

// Example usage:

// s := randstring.NewLen(4) // s is now "apHC"

// A standard string created by NewLen consists of Latin upper and

// lowercase letters, and numbers (from the set of 62 allowed

// characters).

// Functions read from crypto/rand random source, and panic if they fail to

// read from it.

// This package is adapted (simplified) from Dmitry Chestnykh's uniuri

// package.

package randstring

import "crypto/rand"

// stdChars is a set of standard characters allowed in the string.

var stdChars = []byte("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789")

// NewLen returns a new random string of the provided length,

// consisting of standard characters.

func NewLen(length int) string {

return NewLenChars(length, stdChars)

}

// NewLenChars returns a new random string of the provided length,

// consisting of the provided byte slice of allowed characters

// (maximum 256).

func NewLenChars(length int, chars []byte) string {

if length == 0 {

return ""

}

clen := len(chars)

if clen < 2 || clen > 256 {

panic("randstring: wrong charset length for NewLenChars")

}

maxrb := 255 - (256 % clen)

b := make([]byte, length)

r := make([]byte, length+(length/4)) // storage for random bytes.

i := 0

for {

if _, err := rand.Read(r); err != nil {

panic("randstring: error reading random bytes: " + err.Error())

}

for _, rb := range r {

c := int(rb)

if c > maxrb {

// Skip this number to avoid modulo bias.

continue

}

b[i] = chars[c%clen]

i++

if i == length {

return string(b)

}

sourcegraph/internal/randstring/string.go at main · flyinprogrammer/sourcegraph · GitHub

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