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
100
101
|
// 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 utf16 implements encoding and decoding of UTF-16 sequences.
package utf16
import "unicode"
const (
// 0xd800-0xdc00 encodes the high 10 bits of a pair.
// 0xdc00-0xe000 encodes the low 10 bits of a pair.
// the value is those 20 bits plus 0x10000.
surr1 = 0xd800
surr2 = 0xdc00
surr3 = 0xe000
surrSelf = 0x10000
)
// IsSurrogate returns true if the specified Unicode code point
// can appear in a surrogate pair.
func IsSurrogate(rune int) bool {
return surr1 <= rune && rune < surr3
}
// DecodeRune returns the UTF-16 decoding of a surrogate pair.
// If the pair is not a valid UTF-16 surrogate pair, DecodeRune returns
// the Unicode replacement code point U+FFFD.
func DecodeRune(r1, r2 int) int {
if surr1 <= r1 && r1 < surr2 && surr2 <= r2 && r2 < surr3 {
return (int(r1)-surr1)<<10 | (int(r2) - surr2) + 0x10000
}
return unicode.ReplacementChar
}
// EncodeRune returns the UTF-16 surrogate pair r1, r2 for the given rune.
// If the rune is not a valid Unicode code point or does not need encoding,
// EncodeRune returns U+FFFD, U+FFFD.
func EncodeRune(rune int) (r1, r2 int) {
if rune < surrSelf || rune > unicode.MaxRune || IsSurrogate(rune) {
return unicode.ReplacementChar, unicode.ReplacementChar
}
rune -= surrSelf
return surr1 + (rune>>10)&0x3ff, surr2 + rune&0x3ff
}
// Encode returns the UTF-16 encoding of the Unicode code point sequence s.
func Encode(s []int) []uint16 {
n := len(s)
for _, v := range s {
if v >= surrSelf {
n++
}
}
a := make([]uint16, n)
n = 0
for _, v := range s {
switch {
case v < 0, surr1 <= v && v < surr3, v > unicode.MaxRune:
v = unicode.ReplacementChar
fallthrough
case v < surrSelf:
a[n] = uint16(v)
n++
default:
r1, r2 := EncodeRune(v)
a[n] = uint16(r1)
a[n+1] = uint16(r2)
n += 2
}
}
return a[0:n]
}
// Decode returns the Unicode code point sequence represented
// by the UTF-16 encoding s.
func Decode(s []uint16) []int {
a := make([]int, len(s))
n := 0
for i := 0; i < len(s); i++ {
switch r := s[i]; {
case surr1 <= r && r < surr2 && i+1 < len(s) &&
surr2 <= s[i+1] && s[i+1] < surr3:
// valid surrogate sequence
a[n] = DecodeRune(int(r), int(s[i+1]))
i++
n++
case surr1 <= r && r < surr3:
// invalid surrogate sequence
a[n] = unicode.ReplacementChar
n++
default:
// normal rune
a[n] = int(r)
n++
}
}
return a[0:n]
}
|
