feat(stdlibs): add package html

docs/reference/go-gno-compatibility.md

@@ -184,7 +184,7 @@ Legend:
 | hash/crc64                                  | `todo`   |
 | hash/fnv                                    | `todo`   |
 | hash/maphash                                | `todo`   |
-| html                                        | `todo`   |
+| html                                        | `full`   |
 | html/template                               | `todo`   |
 | image                                       | `tbd`    |
 | image/color                                 | `tbd`    |

gnovm/stdlibs/html/entity_test.gno

@@ -0,0 +1,37 @@
+// 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 (
+	"testing"
+	"unicode/utf8"
+)
+
+func init() {
+	UnescapeString("") // force load of entity maps
+}
+
+func TestEntityLength(t *testing.T) {
+	if len(entity) == 0 || len(entity2) == 0 {
+		t.Fatal("maps not loaded")
+	}
+
+	// We verify that the length of UTF-8 encoding of each value is <= 1 + len(key).
+	// The +1 comes from the leading "&". This property implies that the length of
+	// unescaped text is <= the length of escaped text.
+	for k, v := range entity {
+		if 1+len(k) < utf8.RuneLen(v) {
+			t.Error("escaped entity &" + k + " is shorter than its UTF-8 encoding " + string(v))
+		}
+		if len(k) > longestEntityWithoutSemicolon && k[len(k)-1] != ';' {
+			t.Errorf("entity name %s is %d characters, but longestEntityWithoutSemicolon=%d", k, len(k), longestEntityWithoutSemicolon)
+		}
+	}
+	for k, v := range entity2 {
+		if 1+len(k) < utf8.RuneLen(v[0])+utf8.RuneLen(v[1]) {
+			t.Error("escaped entity &" + k + " is shorter than its UTF-8 encoding " + string(v[0]) + string(v[1]))
+		}
+	}
+}

gnovm/stdlibs/html/escape.gno

@@ -0,0 +1,213 @@
+// 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 provides functions for escaping and unescaping HTML text.
+package html
+
+import (
+	"strings"
+	"unicode/utf8"
+)
+
+// These replacements permit compatibility with old numeric entities that
+// assumed Windows-1252 encoding.
+// https://html.spec.whatwg.org/multipage/parsing.html#numeric-character-reference-end-state
+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.
+func unescapeEntity(b []byte, dst, src int) (dst1, src1 int) {
+	const attribute = false
+
+	// http://www.whatwg.org/specs/web-apps/current-work/multipage/tokenization.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 := s[1:i]
+	if len(entityName) == 0 {
+		// No-op.
+	} else if attribute && entityName[len(entityName)-1] != ';' && len(s) > i && s[i] == '=' {
+		// No-op.
+	} else if x := entity[string(entityName)]; x != 0 {
+		return dst + utf8.EncodeRune(b[dst:], x), src + i
+	} else if x := entity2[string(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[string(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
+}
+
+var htmlEscaper = strings.NewReplacer(
+	`&`, "&amp;",
+	`'`, "&#39;", // "&#39;" is shorter than "&apos;" and apos was not in HTML until HTML5.
+	`<`, "&lt;",
+	`>`, "&gt;",
+	`"`, "&#34;", // "&#34;" is shorter than "&quot;".
+)
+
+// 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 {
+	return htmlEscaper.Replace(s)
+}
+
+// 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 {
+	i := strings.IndexByte(s, '&')
+
+	if i < 0 {
+		return s
+	}
+
+	b := []byte(s)
+	dst, src := unescapeEntity(b, i, i)
+	for len(s[src:]) > 0 {
+		if s[src] == '&' {
+			i = 0
+		} else {
+			i = strings.IndexByte(s[src:], '&')
+		}
+		if i < 0 {
+			dst += copy(b[dst:], s[src:])
+			break
+		}
+
+		if i > 0 {
+			copy(b[dst:], s[src:src+i])
+		}
+		dst, src = unescapeEntity(b, dst+i, src+i)
+	}
+	return string(b[:dst])
+}