--- /dev/null
+// Copyright 2010 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"
+ "strings"
+ "unicode/utf8"
+)
+
+// These replacements permit compatibility with old numeric entities that
+// assumed Windows-1252 encoding.
+// https://html.spec.whatwg.org/multipage/syntax.html#consume-a-character-reference
+var replacementTable = [...]rune{
+ '\u20AC', // First entry is what 0x80 should be replaced with.
+ '\u0081',
+ '\u201A',
+ '\u0192',
+ '\u201E',
+ '\u2026',
+ '\u2020',
+ '\u2021',
+ '\u02C6',
+ '\u2030',
+ '\u0160',
+ '\u2039',
+ '\u0152',
+ '\u008D',
+ '\u017D',
+ '\u008F',
+ '\u0090',
+ '\u2018',
+ '\u2019',
+ '\u201C',
+ '\u201D',
+ '\u2022',
+ '\u2013',
+ '\u2014',
+ '\u02DC',
+ '\u2122',
+ '\u0161',
+ '\u203A',
+ '\u0153',
+ '\u009D',
+ '\u017E',
+ '\u0178', // Last entry is 0x9F.
+ // 0x00->'\uFFFD' is handled programmatically.
+ // 0x0D->'\u000D' is a no-op.
+}
+
+// unescapeEntity reads an entity like "<" from b[src:] and writes the
+// corresponding "<" to b[dst:], returning the incremented dst and src cursors.
+// Precondition: b[src] == '&' && dst <= src.
+// attribute should be true if parsing an attribute value.
+func unescapeEntity(b []byte, dst, src int, attribute bool) (dst1, src1 int) {
+ // https://html.spec.whatwg.org/multipage/syntax.html#consume-a-character-reference
+
+ // i starts at 1 because we already know that s[0] == '&'.
+ i, s := 1, b[src:]
+
+ if len(s) <= 1 {
+ b[dst] = b[src]
+ return dst + 1, src + 1
+ }
+
+ if s[i] == '#' {
+ if len(s) <= 3 { // We need to have at least "&#.".
+ b[dst] = b[src]
+ return dst + 1, src + 1
+ }
+ i++
+ c := s[i]
+ hex := false
+ if c == 'x' || c == 'X' {
+ hex = true
+ i++
+ }
+
+ x := '\x00'
+ for i < len(s) {
+ c = s[i]
+ i++
+ if hex {
+ if '0' <= c && c <= '9' {
+ x = 16*x + rune(c) - '0'
+ continue
+ } else if 'a' <= c && c <= 'f' {
+ x = 16*x + rune(c) - 'a' + 10
+ continue
+ } else if 'A' <= c && c <= 'F' {
+ x = 16*x + rune(c) - 'A' + 10
+ continue
+ }
+ } else if '0' <= c && c <= '9' {
+ x = 10*x + rune(c) - '0'
+ continue
+ }
+ if c != ';' {
+ i--
+ }
+ break
+ }
+
+ if i <= 3 { // No characters matched.
+ b[dst] = b[src]
+ return dst + 1, src + 1
+ }
+
+ if 0x80 <= x && x <= 0x9F {
+ // Replace characters from Windows-1252 with UTF-8 equivalents.
+ x = replacementTable[x-0x80]
+ } else if x == 0 || (0xD800 <= x && x <= 0xDFFF) || x > 0x10FFFF {
+ // Replace invalid characters with the replacement character.
+ x = '\uFFFD'
+ }
+
+ return dst + utf8.EncodeRune(b[dst:], x), src + i
+ }
+
+ // Consume the maximum number of characters possible, with the
+ // consumed characters matching one of the named references.
+
+ for i < len(s) {
+ c := s[i]
+ i++
+ // Lower-cased characters are more common in entities, so we check for them first.
+ if 'a' <= c && c <= 'z' || 'A' <= c && c <= 'Z' || '0' <= c && c <= '9' {
+ continue
+ }
+ if c != ';' {
+ i--
+ }
+ break
+ }
+
+ entityName := string(s[1:i])
+ if entityName == "" {
+ // No-op.
+ } else if attribute && entityName[len(entityName)-1] != ';' && len(s) > i && s[i] == '=' {
+ // No-op.
+ } else if x := entity[entityName]; x != 0 {
+ return dst + utf8.EncodeRune(b[dst:], x), src + i
+ } else if x := entity2[entityName]; x[0] != 0 {
+ dst1 := dst + utf8.EncodeRune(b[dst:], x[0])
+ return dst1 + utf8.EncodeRune(b[dst1:], x[1]), src + i
+ } else if !attribute {
+ maxLen := len(entityName) - 1
+ if maxLen > longestEntityWithoutSemicolon {
+ maxLen = longestEntityWithoutSemicolon
+ }
+ for j := maxLen; j > 1; j-- {
+ if x := entity[entityName[:j]]; x != 0 {
+ return dst + utf8.EncodeRune(b[dst:], x), src + j + 1
+ }
+ }
+ }
+
+ dst1, src1 = dst+i, src+i
+ copy(b[dst:dst1], b[src:src1])
+ return dst1, src1
+}
+
+// unescape unescapes b's entities in-place, so that "a<b" becomes "a<b".
+// attribute should be true if parsing an attribute value.
+func unescape(b []byte, attribute bool) []byte {
+ for i, c := range b {
+ if c == '&' {
+ dst, src := unescapeEntity(b, i, i, attribute)
+ for src < len(b) {
+ c := b[src]
+ if c == '&' {
+ dst, src = unescapeEntity(b, dst, src, attribute)
+ } else {
+ b[dst] = c
+ dst, src = dst+1, src+1
+ }
+ }
+ return b[0:dst]
+ }
+ }
+ return b
+}
+
+// lower lower-cases the A-Z bytes in b in-place, so that "aBc" becomes "abc".
+func lower(b []byte) []byte {
+ for i, c := range b {
+ if 'A' <= c && c <= 'Z' {
+ b[i] = c + 'a' - 'A'
+ }
+ }
+ return b
+}
+
+const escapedChars = "&'<>\"\r"
+
+func escape(w writer, s string) error {
+ i := strings.IndexAny(s, escapedChars)
+ for i != -1 {
+ if _, err := w.WriteString(s[:i]); err != nil {
+ return err
+ }
+ var esc string
+ switch s[i] {
+ case '&':
+ esc = "&"
+ case '\'':
+ // "'" is shorter than "'" and apos was not in HTML until HTML5.
+ esc = "'"
+ case '<':
+ esc = "<"
+ case '>':
+ esc = ">"
+ case '"':
+ // """ is shorter than """.
+ esc = """
+ case '\r':
+ esc = " "
+ default:
+ panic("unrecognized escape character")
+ }
+ s = s[i+1:]
+ if _, err := w.WriteString(esc); err != nil {
+ return err
+ }
+ i = strings.IndexAny(s, escapedChars)
+ }
+ _, err := w.WriteString(s)
+ return err
+}
+
+// EscapeString escapes special characters like "<" to become "<". It
+// escapes only five such characters: <, >, &, ' and ".
+// UnescapeString(EscapeString(s)) == s always holds, but the converse isn't
+// always true.
+func EscapeString(s string) string {
+ if strings.IndexAny(s, escapedChars) == -1 {
+ return s
+ }
+ var buf bytes.Buffer
+ escape(&buf, s)
+ return buf.String()
+}
+
+// UnescapeString unescapes entities like "<" to become "<". It unescapes a
+// larger range of entities than EscapeString escapes. For example, "á"
+// unescapes to "รก", as does "á" and "&xE1;".
+// UnescapeString(EscapeString(s)) == s always holds, but the converse isn't
+// always true.
+func UnescapeString(s string) string {
+ for _, c := range s {
+ if c == '&' {
+ return string(unescape([]byte(s), false))
+ }
+ }
+ return s
+}
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