1 files changed, 234 insertions, 0 deletions
diff --git a/src/pkg/exp/norm/trie.go b/src/pkg/exp/norm/trie.go
new file mode 100644
index 000000000..6b6540187
--- /dev/null
+++ b/src/pkg/exp/norm/trie.go
@@ -0,0 +1,234 @@
+// 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 norm
+
+type trie struct {
+	index  []uint8
+	values []uint16
+}
+
+const (
+	t1 = 0x00 // 0000 0000
+	tx = 0x80 // 1000 0000
+	t2 = 0xC0 // 1100 0000
+	t3 = 0xE0 // 1110 0000
+	t4 = 0xF0 // 1111 0000
+	t5 = 0xF8 // 1111 1000
+	t6 = 0xFC // 1111 1100
+	te = 0xFE // 1111 1110
+
+	maskx = 0x3F // 0011 1111
+	mask2 = 0x1F // 0001 1111
+	mask3 = 0x0F // 0000 1111
+	mask4 = 0x07 // 0000 0111
+)
+
+// lookup returns the trie value for the first UTF-8 encoding in s and
+// the width in bytes of this encoding. The size will be 0 if s does not
+// hold enough bytes to complete the encoding. len(s) must be greater than 0.
+func (t *trie) lookup(s []byte) (v uint16, sz int) {
+	c0 := s[0]
+	switch {
+	case c0 < tx:
+		return t.values[c0], 1
+	case c0 < t2:
+		return 0, 1
+	case c0 < t3:
+		if len(s) < 2 {
+			return 0, 0
+		}
+		i := t.index[c0]
+		c1 := s[1]
+		if c1 < tx || t2 <= c1 {
+			return 0, 1
+		}
+		o := uint16(i)<<6 + uint16(c1)&maskx
+		return t.values[o], 2
+	case c0 < t4:
+		if len(s) < 3 {
+			return 0, 0
+		}
+		i := t.index[c0]
+		c1 := s[1]
+		if c1 < tx || t2 <= c1 {
+			return 0, 1
+		}
+		o := uint16(i)<<6 + uint16(c1)&maskx
+		i = t.index[o]
+		c2 := s[2]
+		if c2 < tx || t2 <= c2 {
+			return 0, 2
+		}
+		o = uint16(i)<<6 + uint16(c2)&maskx
+		return t.values[o], 3
+	case c0 < t5:
+		if len(s) < 4 {
+			return 0, 0
+		}
+		i := t.index[c0]
+		c1 := s[1]
+		if c1 < tx || t2 <= c1 {
+			return 0, 1
+		}
+		o := uint16(i)<<6 + uint16(c1)&maskx
+		i = t.index[o]
+		c2 := s[2]
+		if c2 < tx || t2 <= c2 {
+			return 0, 2
+		}
+		o = uint16(i)<<6 + uint16(c2)&maskx
+		i = t.index[o]
+		c3 := s[3]
+		if c3 < tx || t2 <= c3 {
+			return 0, 3
+		}
+		o = uint16(i)<<6 + uint16(c3)&maskx
+		return t.values[o], 4
+	case c0 < t6:
+		if len(s) < 5 {
+			return 0, 0
+		}
+		return 0, 5
+	case c0 < te:
+		if len(s) < 6 {
+			return 0, 0
+		}
+		return 0, 6
+	}
+	// Illegal rune
+	return 0, 1
+}
+
+// lookupString returns the trie value for the first UTF-8 encoding in s and
+// the width in bytes of this encoding. The size will be 0 if s does not
+// hold enough bytes to complete the encoding. len(s) must be greater than 0.
+func (t *trie) lookupString(s string) (v uint16, sz int) {
+	c0 := s[0]
+	switch {
+	case c0 < tx:
+		return t.values[c0], 1
+	case c0 < t2:
+		return 0, 1
+	case c0 < t3:
+		if len(s) < 2 {
+			return 0, 0
+		}
+		i := t.index[c0]
+		c1 := s[1]
+		if c1 < tx || t2 <= c1 {
+			return 0, 1
+		}
+		o := uint16(i)<<6 + uint16(c1)&maskx
+		return t.values[o], 2
+	case c0 < t4:
+		if len(s) < 3 {
+			return 0, 0
+		}
+		i := t.index[c0]
+		c1 := s[1]
+		if c1 < tx || t2 <= c1 {
+			return 0, 1
+		}
+		o := uint16(i)<<6 + uint16(c1)&maskx
+		i = t.index[o]
+		c2 := s[2]
+		if c2 < tx || t2 <= c2 {
+			return 0, 2
+		}
+		o = uint16(i)<<6 + uint16(c2)&maskx
+		return t.values[o], 3
+	case c0 < t5:
+		if len(s) < 4 {
+			return 0, 0
+		}
+		i := t.index[c0]
+		c1 := s[1]
+		if c1 < tx || t2 <= c1 {
+			return 0, 1
+		}
+		o := uint16(i)<<6 + uint16(c1)&maskx
+		i = t.index[o]
+		c2 := s[2]
+		if c2 < tx || t2 <= c2 {
+			return 0, 2
+		}
+		o = uint16(i)<<6 + uint16(c2)&maskx
+		i = t.index[o]
+		c3 := s[3]
+		if c3 < tx || t2 <= c3 {
+			return 0, 3
+		}
+		o = uint16(i)<<6 + uint16(c3)&maskx
+		return t.values[o], 4
+	case c0 < t6:
+		if len(s) < 5 {
+			return 0, 0
+		}
+		return 0, 5
+	case c0 < te:
+		if len(s) < 6 {
+			return 0, 0
+		}
+		return 0, 6
+	}
+	// Illegal rune
+	return 0, 1
+}
+
+// lookupUnsafe returns the trie value for the first UTF-8 encoding in s.
+// s must hold a full encoding.
+func (t *trie) lookupUnsafe(s []byte) uint16 {
+	c0 := s[0]
+	if c0 < tx {
+		return t.values[c0]
+	}
+	if c0 < t2 {
+		return 0
+	}
+	i := t.index[c0]
+	o := uint16(i)<<6 + uint16(s[1])&maskx
+	if c0 < t3 {
+		return t.values[o]
+	}
+	i = t.index[o]
+	o = uint16(i)<<6 + uint16(s[2])&maskx
+	if c0 < t4 {
+		return t.values[o]
+	}
+	i = t.index[o]
+	o = uint16(i)<<6 + uint16(s[3])&maskx
+	if c0 < t5 {
+		return t.values[o]
+	}
+	return 0
+}
+
+// lookupStringUnsafe returns the trie value for the first UTF-8 encoding in s.
+// s must hold a full encoding.
+func (t *trie) lookupStringUnsafe(s string) uint16 {
+	c0 := s[0]
+	if c0 < tx {
+		return t.values[c0]
+	}
+	if c0 < t2 {
+		return 0
+	}
+	i := t.index[c0]
+	o := uint16(i)<<6 + uint16(s[1])&maskx
+	if c0 < t3 {
+		return t.values[o]
+	}
+	i = t.index[o]
+	o = uint16(i)<<6 + uint16(s[2])&maskx
+	if c0 < t4 {
+		return t.values[o]
+	}
+	i = t.index[o]
+	o = uint16(i)<<6 + uint16(s[3])&maskx
+	if c0 < t5 {
+		return t.values[o]
+	}
+	return 0
+}