added vendor

vendor/golang.org/x/net/html/escape.go

@@ -0,0 +1,379 @@
+// 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"
+	"slices"
+	"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 attempts to consume a character reference from s[src:],
+// returning the rune, potential second rune, and number of bytes consumed
+// (which indicates the length of the character reference). It is assumed that
+// the first byte of s is '&'. attribute should be true if parsing an attribute
+// value.
+func unescapeEntity(s []byte, attribute bool) (rune, rune, 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 := 1
+
+	if len(s) <= 1 {
+		return '&', 0, 1
+	}
+
+	if s[i] == '#' {
+		if len(s) <= 2 { // We need to have at least "&#".
+			return '&', 0, 1
+		}
+		i++
+		c := s[i]
+		hex := false
+		if c == 'x' || c == 'X' {
+			hex = true
+			i++
+		}
+
+		i0 := i
+		x := '\x00'
+		for i < len(s) {
+			c = s[i]
+			var d rune
+			var mult rune
+			if hex {
+				mult = 16
+				if '0' <= c && c <= '9' {
+					d = rune(c) - '0'
+				} else if 'a' <= c && c <= 'f' {
+					d = rune(c) - 'a' + 10
+				} else if 'A' <= c && c <= 'F' {
+					d = rune(c) - 'A' + 10
+				} else {
+					break
+				}
+			} else {
+				mult = 10
+				if '0' <= c && c <= '9' {
+					d = rune(c) - '0'
+				} else {
+					break
+				}
+			}
+			if x <= 0x10FFFF {
+				x = mult*x + d
+			}
+			i++
+		}
+
+		if i == i0 { // No characters matched.
+			return '&', 0, 1
+		}
+
+		if i < len(s) && s[i] == ';' {
+			i++
+		}
+
+		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 x, 0, 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 x, 0, i
+	} else if x := entity2[entityName]; x[0] != 0 {
+		return x[0], x[1], 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 x, 0, j + 1
+			}
+		}
+	}
+
+	return '&', 0, 1
+}
+
+// unescape unescapes b's entites, so that "a&lt;b" becomes "a<b". It attempts
+// to do so in place, but if the unescaped value is longer than the input it
+// allocates a new slice. attribute should be true if parsing an attribute
+// value.
+func unescape(b []byte, attribute bool) []byte {
+	firstAmp := slices.Index(b, '&')
+	if firstAmp == -1 {
+		return b
+	}
+
+	out := b[:firstAmp]
+	src := firstAmp
+	reusingB := true
+	for src < len(b) {
+		if b[src] != '&' {
+			out = append(out, b[src])
+			src++
+			continue
+		}
+
+		r1, r2, entityNameLen := unescapeEntity(b[src:], attribute)
+		if entityNameLen == 1 && r1 == '&' {
+			// Not an entity
+			out = append(out, '&')
+			src++
+			continue
+		}
+
+		// Compute replacement length
+		replLen := utf8.RuneLen(r1)
+		if r2 != 0 {
+			replLen += utf8.RuneLen(r2)
+		}
+
+		// If the name of the entity is shorter than the width of the
+		// replacement runes then we need to expand the output slice to
+		// fit the replacement.
+		if replLen > entityNameLen {
+			if reusingB {
+				out = slices.Clone(out)
+				reusingB = false
+			}
+			out = slices.Grow(out, replLen)
+		}
+		out = utf8.AppendRune(out, r1)
+		if r2 != 0 {
+			out = utf8.AppendRune(out, r2)
+		}
+
+		src += entityNameLen
+	}
+
+	return out
+}
+
+// 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
+}
+
+// escapeComment is like func escape but escapes its input bytes less often.
+// Per https://github.com/golang/go/issues/58246 some HTML comments are (1)
+// meaningful and (2) contain angle brackets that we'd like to avoid escaping
+// unless we have to.
+//
+// "We have to" includes the '&' byte, since that introduces other escapes.
+//
+// It also includes those bytes (not including EOF) that would otherwise end
+// the comment. Per the summary table at the bottom of comment_test.go, this is
+// the '>' byte that, per above, we'd like to avoid escaping unless we have to.
+//
+// Studying the summary table (and T actions in its '>' column) closely, we
+// only need to escape in states 43, 44, 49, 51 and 52. State 43 is at the
+// start of the comment data. State 52 is after a '!'. The other three states
+// are after a '-'.
+//
+// Our algorithm is thus to escape every '&' and to escape '>' if and only if:
+//   - The '>' is after a '!' or '-' (in the unescaped data) or
+//   - The '>' is at the start of the comment data (after the opening "<!--").
+func escapeComment(w writer, s string) error {
+	// When modifying this function, consider manually increasing the
+	// maxSuffixLen constant in func TestComments, from 6 to e.g. 9 or more.
+	// That increase should only be temporary, not committed, as it
+	// exponentially affects the test running time.
+
+	if len(s) == 0 {
+		return nil
+	}
+
+	// Loop:
+	//   - Grow j such that s[i:j] does not need escaping.
+	//   - If s[j] does need escaping, output s[i:j] and an escaped s[j],
+	//     resetting i and j to point past that s[j] byte.
+	i := 0
+	for j := 0; j < len(s); j++ {
+		escaped := ""
+		switch s[j] {
+		case '&':
+			escaped = "&amp;"
+
+		case '>':
+			if j > 0 {
+				if prev := s[j-1]; (prev != '!') && (prev != '-') {
+					continue
+				}
+			}
+			escaped = "&gt;"
+
+		default:
+			continue
+		}
+
+		if i < j {
+			if _, err := w.WriteString(s[i:j]); err != nil {
+				return err
+			}
+		}
+		if _, err := w.WriteString(escaped); err != nil {
+			return err
+		}
+		i = j + 1
+	}
+
+	if i < len(s) {
+		if _, err := w.WriteString(s[i:]); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+// escapeCommentString is to EscapeString as escapeComment is to escape.
+func escapeCommentString(s string) string {
+	if strings.IndexAny(s, "&>") == -1 {
+		return s
+	}
+	var buf bytes.Buffer
+	escapeComment(&buf, s)
+	return buf.String()
+}
+
+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 = "&amp;"
+		case '\'':
+			// "&#39;" is shorter than "&apos;" and apos was not in HTML until HTML5.
+			esc = "&#39;"
+		case '<':
+			esc = "&lt;"
+		case '>':
+			esc = "&gt;"
+		case '"':
+			// "&#34;" is shorter than "&quot;".
+			esc = "&#34;"
+		case '\r':
+			esc = "&#13;"
+		default:
+			panic("html: 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 "&lt;". 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 "&lt;" to become "<". It unescapes a
+// larger range of entities than EscapeString escapes. For example, "&aacute;"
+// unescapes to "á", as does "&#225;" 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
+}