caddy/modules/caddyhttp/reverseproxy/ascii.go

// Copyright 2015 Matthew Holt and The Caddy Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

// Most of the code in this file was initially borrowed from the Go
// standard library and modified; It had this copyright notice:
// 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.

// Original source, copied because the package was marked internal:
// https://github.com/golang/go/blob/5c489514bc5e61ad9b5b07bd7d8ec65d66a0512a/src/net/http/internal/ascii/print.go

package reverseproxy

// 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 asciiLower(s[i]) != asciiLower(t[i]) {
			return false
		}
	}
	return true
}

// asciiLower returns the ASCII lowercase version of b.
func asciiLower(b byte) byte {
	if 'A' <= b && b <= 'Z' {
		return b + ('a' - 'A')
	}
	return b
}

// asciiIsPrint returns whether s is ASCII and printable according to
// https://tools.ietf.org/html/rfc20#section-4.2.
func asciiIsPrint(s string) bool {
	for i := 0; i < len(s); i++ {
		if s[i] < ' ' || s[i] > '~' {
			return false
		}
	}
	return true
}