1 files changed, 61 insertions, 0 deletions
diff --git a/src/net/http/internal/ascii/print.go b/src/net/http/internal/ascii/print.go
new file mode 100644
index 0000000..585e5ba
--- /dev/null
+++ b/src/net/http/internal/ascii/print.go
@@ -0,0 +1,61 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ascii
+
+import (
+	"strings"
+	"unicode"
+)
+
+// EqualFold is strings.EqualFold, ASCII only. It reports whether s and t
+// are equal, ASCII-case-insensitively.
+func EqualFold(s, t string) bool {
+	if len(s) != len(t) {
+		return false
+	}
+	for i := 0; i < len(s); i++ {
+		if lower(s[i]) != lower(t[i]) {
+			return false
+		}
+	}
+	return true
+}
+
+// lower returns the ASCII lowercase version of b.
+func lower(b byte) byte {
+	if 'A' <= b && b <= 'Z' {
+		return b + ('a' - 'A')
+	}
+	return b
+}
+
+// IsPrint returns whether s is ASCII and printable according to
+// https://tools.ietf.org/html/rfc20#section-4.2.
+func IsPrint(s string) bool {
+	for i := 0; i < len(s); i++ {
+		if s[i] < ' ' || s[i] > '~' {
+			return false
+		}
+	}
+	return true
+}
+
+// Is returns whether s is ASCII.
+func Is(s string) bool {
+	for i := 0; i < len(s); i++ {
+		if s[i] > unicode.MaxASCII {
+			return false
+		}
+	}
+	return true
+}
+
+// ToLower returns the lowercase version of s if s is ASCII and printable.
+func ToLower(s string) (lower string, ok bool) {
+	if !IsPrint(s) {
+		return "", false
+	}
+	return strings.ToLower(s), true
+}