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alphabet.go
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/
alphabet.go
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package shortuuid
import (
"fmt"
"sort"
"strings"
)
// DefaultAlphabet is the default alphabet used.
const DefaultAlphabet = "23456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz"
type alphabet struct {
chars [57]rune
len int64
}
// Remove duplicates and sort it to ensure reproducability.
func newAlphabet(s string) alphabet {
abc := dedupe(strings.Split(s, ""))
if len(abc) != 57 {
panic("encoding alphabet is not 57-bytes long")
}
sort.Strings(abc)
a := alphabet{
len: int64(len(abc)),
}
for i, char := range strings.Join(abc, "") {
a.chars[i] = char
}
return a
}
func (a *alphabet) Length() int64 {
return a.len
}
// Index returns the index of the first instance of t in the alphabet, or an
// error if t is not present.
func (a *alphabet) Index(t rune) (int64, error) {
for i, char := range a.chars {
if char == t {
return int64(i), nil
}
}
return 0, fmt.Errorf("element '%v' is not part of the alphabet", t)
}
// dudupe removes duplicate characters from s.
func dedupe(s []string) []string {
var out []string
m := make(map[string]bool)
for _, char := range s {
if _, ok := m[char]; !ok {
m[char] = true
out = append(out, char)
}
}
return out
}