1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
|
// Copyright 2012 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.
// The trie in this file is used to associate the first full character
// in an UTF-8 string to a collation element.
// All but the last byte in a UTF-8 byte sequence are
// used to lookup offsets in the index table to be used for the next byte.
// The last byte is used to index into a table of collation elements.
// For a full description, see exp/locale/collate/build/trie.go.
package collate
const blockSize = 64
type trie struct {
index0 []uint16 // index for first byte (0xC0-0xFF)
values0 []uint32 // index for first byte (0x00-0x7F)
index []uint16
values []uint32
}
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
)
func (t *trie) lookupValue(n uint16, b byte) colElem {
return colElem(t.values[int(n)<<6+int(b)])
}
// 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 colElem, sz int) {
c0 := s[0]
switch {
case c0 < tx:
return colElem(t.values0[c0]), 1
case c0 < t2:
return 0, 1
case c0 < t3:
if len(s) < 2 {
return 0, 0
}
i := t.index0[c0]
c1 := s[1]
if c1 < tx || t2 <= c1 {
return 0, 1
}
return t.lookupValue(i, c1), 2
case c0 < t4:
if len(s) < 3 {
return 0, 0
}
i := t.index0[c0]
c1 := s[1]
if c1 < tx || t2 <= c1 {
return 0, 1
}
o := int(i)<<6 + int(c1)
i = t.index[o]
c2 := s[2]
if c2 < tx || t2 <= c2 {
return 0, 2
}
return t.lookupValue(i, c2), 3
case c0 < t5:
if len(s) < 4 {
return 0, 0
}
i := t.index0[c0]
c1 := s[1]
if c1 < tx || t2 <= c1 {
return 0, 1
}
o := int(i)<<6 + int(c1)
i = t.index[o]
c2 := s[2]
if c2 < tx || t2 <= c2 {
return 0, 2
}
o = int(i)<<6 + int(c2)
i = t.index[o]
c3 := s[3]
if c3 < tx || t2 <= c3 {
return 0, 3
}
return t.lookupValue(i, c3), 4
}
// Illegal rune
return 0, 1
}
|
