mirror of
https://github.com/woodpecker-ci/woodpecker.git
synced 2024-12-24 10:07:21 +02:00
72 lines
2.0 KiB
Go
72 lines
2.0 KiB
Go
// Package uniuri generates random strings good for use in URIs to identify
|
|
// unique objects.
|
|
//
|
|
// Example usage:
|
|
//
|
|
// s := uniuri.New() // s is now "apHCJBl7L1OmC57n"
|
|
//
|
|
// A standard string created by New() is 16 bytes in length and consists of
|
|
// Latin upper and lowercase letters, and numbers (from the set of 62 allowed
|
|
// characters), which means that it has ~95 bits of entropy. To get more
|
|
// entropy, you can use NewLen(UUIDLen), which returns 20-byte string, giving
|
|
// ~119 bits of entropy, or any other desired length.
|
|
//
|
|
// Functions read from crypto/rand random source, and panic if they fail to
|
|
// read from it.
|
|
package uniuri
|
|
|
|
import (
|
|
"crypto/rand"
|
|
"io"
|
|
)
|
|
|
|
const (
|
|
// Standard length of uniuri string to achive ~95 bits of entropy.
|
|
StdLen = 16
|
|
// Length of uniurl string to achive ~119 bits of entropy, closest
|
|
// to what can be losslessly converted to UUIDv4 (122 bits).
|
|
UUIDLen = 20
|
|
)
|
|
|
|
// Standard characters allowed in uniuri string.
|
|
var StdChars = []byte("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789")
|
|
|
|
// New returns a new random string of the standard length, consisting of
|
|
// standard characters.
|
|
func New() string {
|
|
return NewLenChars(StdLen, StdChars)
|
|
}
|
|
|
|
// 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 {
|
|
b := make([]byte, length)
|
|
r := make([]byte, length+(length/4)) // storage for random bytes.
|
|
clen := byte(len(chars))
|
|
maxrb := byte(256 - (256 % len(chars)))
|
|
i := 0
|
|
for {
|
|
if _, err := io.ReadFull(rand.Reader, r); err != nil {
|
|
panic("error reading from random source: " + err.Error())
|
|
}
|
|
for _, c := range r {
|
|
if c >= maxrb {
|
|
// Skip this number to avoid modulo bias.
|
|
continue
|
|
}
|
|
b[i] = chars[c%clen]
|
|
i++
|
|
if i == length {
|
|
return string(b)
|
|
}
|
|
}
|
|
}
|
|
panic("unreachable")
|
|
}
|