1 files changed, 179 insertions, 0 deletions
diff --git a/modules/mahonia/entity.go b/modules/mahonia/entity.go
new file mode 100644
index 00000000..ed31bbaa
--- /dev/null
+++ b/modules/mahonia/entity.go
@@ -0,0 +1,179 @@
+package mahonia
+
+// decoding HTML entities
+
+import (
+	"sort"
+)
+
+// EntityDecoder returns a Decoder that decodes HTML character entities.
+// If there is no valid character entity at the current position, it returns INVALID_CHAR.
+// So it needs to be combined with another Decoder via FallbackDecoder.
+func EntityDecoder() Decoder {
+	var leftover rune // leftover rune from two-rune entity
+	return func(p []byte) (r rune, size int, status Status) {
+		if leftover != 0 {
+			r = leftover
+			leftover = 0
+			return r, 0, SUCCESS
+		}
+
+		if len(p) == 0 {
+			return 0, 0, NO_ROOM
+		}
+
+		if p[0] != '&' {
+			return 0xfffd, 1, INVALID_CHAR
+		}
+
+		if len(p) < 3 {
+			return 0, 1, NO_ROOM
+		}
+
+		r, size, status = 0xfffd, 1, INVALID_CHAR
+		n := 1 // number of bytes read so far
+
+		if p[n] == '#' {
+			n++
+			c := p[n]
+			hex := false
+			if c == 'x' || c == 'X' {
+				hex = true
+				n++
+			}
+
+			var x rune
+			for n < len(p) {
+				c = p[n]
+				n++
+				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 != ';' {
+					n--
+				}
+				break
+			}
+
+			if n == len(p) && p[n-1] != ';' {
+				return 0, 0, NO_ROOM
+			}
+
+			size = n
+			if p[n-1] == ';' {
+				n--
+			}
+			if hex {
+				n--
+			}
+			n--
+			// Now n is the number of actual digits read.
+			if n == 0 {
+				return 0xfffd, 1, INVALID_CHAR
+			}
+
+			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.
+				return 0xfffd, size, INVALID_CHAR
+			}
+
+			r = x
+			status = SUCCESS
+			return
+		}
+
+		// Look for a named entity in EntityList.
+
+		possible := entityList
+		for len(possible) > 0 {
+			if len(p) <= n {
+				leftover = 0
+				return 0, 0, NO_ROOM
+			}
+
+			c := p[n]
+
+			// Narrow down the selection in possible to those items that have c in the
+			// appropriate byte.
+			first := sort.Search(len(possible), func(i int) bool {
+				e := possible[i].name
+				if len(e) < n {
+					return false
+				}
+				return e[n-1] >= c
+			})
+			possible = possible[first:]
+			last := sort.Search(len(possible), func(i int) bool {
+				return possible[i].name[n-1] > c
+			})
+			possible = possible[:last]
+
+			n++
+			if len(possible) > 0 && len(possible[0].name) == n-1 {
+				r, leftover = possible[0].r1, possible[0].r2
+				size = n
+				status = SUCCESS
+				// but don't return yet, since we need the longest match
+			}
+		}
+
+		return
+	}
+}
+
+// This table is copied from /src/pkg/html/escape.go in the Go source
+//
+// These replacements permit compatibility with old numeric entities that
+// assumed Windows-1252 encoding.
+// http://www.whatwg.org/specs/web-apps/current-work/multipage/tokenization.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.
+}