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// 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 http2
import "strings"
// The HTTP protocols are defined in terms of ASCII, not Unicode. This file
// contains helper functions which may use Unicode-aware functions which would
// otherwise be unsafe and could introduce vulnerabilities if used improperly.
// asciiEqualFold is strings.EqualFold, ASCII only. It reports whether s and t
// are equal, ASCII-case-insensitively.
func asciiEqualFold(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
}
// isASCIIPrint returns whether s is ASCII and printable according to
// https://tools.ietf.org/html/rfc20#section-4.2.
func isASCIIPrint(s string) bool {
for i := 0; i < len(s); i++ {
if s[i] < ' ' || s[i] > '~' {
return false
}
}
return true
}
// asciiToLower returns the lowercase version of s if s is ASCII and printable,
// and whether or not it was.
func asciiToLower(s string) (lower string, ok bool) {
if !isASCIIPrint(s) {
return "", false
}
return strings.ToLower(s), true
}
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