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// Copyright 2011 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 html
import (
"bytes"
"fmt"
"strings"
)
// urlFilter returns its input unless it contains an unsafe protocol in which
// case it defangs the entire URL.
func urlFilter(args ...interface{}) string {
s, t := stringify(args...)
if t == contentTypeURL {
return s
}
if i := strings.IndexRune(s, ':'); i >= 0 && strings.IndexRune(s[:i], '/') < 0 {
protocol := strings.ToLower(s[:i])
if protocol != "http" && protocol != "https" && protocol != "mailto" {
return "#" + filterFailsafe
}
}
return s
}
// urlEscaper produces an output that can be embedded in a URL query.
// The output can be embedded in an HTML attribute without further escaping.
func urlEscaper(args ...interface{}) string {
return urlProcessor(false, args...)
}
// urlEscaper normalizes URL content so it can be embedded in a quote-delimited
// string or parenthesis delimited url(...).
// The normalizer does not encode all HTML specials. Specifically, it does not
// encode '&' so correct embedding in an HTML attribute requires escaping of
// '&' to '&'.
func urlNormalizer(args ...interface{}) string {
return urlProcessor(true, args...)
}
// urlProcessor normalizes (when norm is true) or escapes its input to produce
// a valid hierarchical or opaque URL part.
func urlProcessor(norm bool, args ...interface{}) string {
s, t := stringify(args...)
if t == contentTypeURL {
norm = true
}
var b bytes.Buffer
written := 0
// The byte loop below assumes that all URLs use UTF-8 as the
// content-encoding. This is similar to the URI to IRI encoding scheme
// defined in section 3.1 of RFC 3987, and behaves the same as the
// EcmaScript builtin encodeURIComponent.
// It should not cause any misencoding of URLs in pages with
// Content-type: text/html;charset=UTF-8.
for i, n := 0, len(s); i < n; i++ {
c := s[i]
switch c {
// Single quote and parens are sub-delims in RFC 3986, but we
// escape them so the output can be embedded in in single
// quoted attributes and unquoted CSS url(...) constructs.
// Single quotes are reserved in URLs, but are only used in
// the obsolete "mark" rule in an appendix in RFC 3986
// so can be safely encoded.
case '!', '#', '$', '&', '*', '+', ',', '/', ':', ';', '=', '?', '@', '[', ']':
if norm {
continue
}
// Unreserved according to RFC 3986 sec 2.3
// "For consistency, percent-encoded octets in the ranges of
// ALPHA (%41-%5A and %61-%7A), DIGIT (%30-%39), hyphen (%2D),
// period (%2E), underscore (%5F), or tilde (%7E) should not be
// created by URI producers
case '-', '.', '_', '~':
continue
case '%':
// When normalizing do not re-encode valid escapes.
if norm && i+2 < len(s) && isHex(s[i+1]) && isHex(s[i+2]) {
continue
}
default:
// Unreserved according to RFC 3986 sec 2.3
if 'a' <= c && c <= 'z' {
continue
}
if 'A' <= c && c <= 'Z' {
continue
}
if '0' <= c && c <= '9' {
continue
}
}
b.WriteString(s[written:i])
fmt.Fprintf(&b, "%%%02x", c)
written = i + 1
}
if written == 0 {
return s
}
b.WriteString(s[written:])
return b.String()
}
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