1 // Copyright 2021 The Go Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style
3 // license that can be found in the LICENSE file.
4 5 package ascii
6 7 import (
8 "bytes"
9 "unicode"
10 )
11 12 // EqualFold is [bytes.EqualFold], ASCII only. It reports whether s and t
13 // are equal, ASCII-case-insensitively.
14 func EqualFold(s, t []byte) bool {
15 if len(s) != len(t) {
16 return false
17 }
18 for i := 0; i < len(s); i++ {
19 if lower(s[i]) != lower(t[i]) {
20 return false
21 }
22 }
23 return true
24 }
25 26 // lower returns the ASCII lowercase version of b.
27 func lower(b byte) byte {
28 if 'A' <= b && b <= 'Z' {
29 return b + ('a' - 'A')
30 }
31 return b
32 }
33 34 // IsPrint returns whether s is ASCII and printable according to
35 // https://tools.ietf.org/html/rfc20#section-4.2.
36 func IsPrint(s []byte) bool {
37 for i := 0; i < len(s); i++ {
38 if s[i] < ' ' || s[i] > '~' {
39 return false
40 }
41 }
42 return true
43 }
44 45 // Is returns whether s is ASCII.
46 func Is(s []byte) bool {
47 for i := 0; i < len(s); i++ {
48 if s[i] > unicode.MaxASCII {
49 return false
50 }
51 }
52 return true
53 }
54 55 // ToLower returns the lowercase version of s if s is ASCII and printable.
56 func ToLower(s []byte) (lower []byte, ok bool) {
57 if !IsPrint(s) {
58 return "", false
59 }
60 return bytes.ToLower(s), true
61 }
62