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
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
|
// Copyright 2015 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 runes
import (
"unicode/utf8"
"golang.org/x/text/transform"
)
// Note: below we pass invalid UTF-8 to the tIn and tNotIn transformers as is.
// This is done for various reasons:
// - To retain the semantics of the Nop transformer: if input is passed to a Nop
// one would expect it to be unchanged.
// - It would be very expensive to pass a converted RuneError to a transformer:
// a transformer might need more source bytes after RuneError, meaning that
// the only way to pass it safely is to create a new buffer and manage the
// intermingling of RuneErrors and normal input.
// - Many transformers leave ill-formed UTF-8 as is, so this is not
// inconsistent. Generally ill-formed UTF-8 is only replaced if it is a
// logical consequence of the operation (as for Map) or if it otherwise would
// pose security concerns (as for Remove).
// - An alternative would be to return an error on ill-formed UTF-8, but this
// would be inconsistent with other operations.
// If returns a transformer that applies tIn to consecutive runes for which
// s.Contains(r) and tNotIn to consecutive runes for which !s.Contains(r). Reset
// is called on tIn and tNotIn at the start of each run. A Nop transformer will
// substitute a nil value passed to tIn or tNotIn. Invalid UTF-8 is translated
// to RuneError to determine which transformer to apply, but is passed as is to
// the respective transformer.
func If(s Set, tIn, tNotIn transform.Transformer) Transformer {
if tIn == nil && tNotIn == nil {
return Transformer{transform.Nop}
}
if tIn == nil {
tIn = transform.Nop
}
if tNotIn == nil {
tNotIn = transform.Nop
}
a := &cond{
tIn: tIn,
tNotIn: tNotIn,
f: s.Contains,
}
a.Reset()
return Transformer{a}
}
type cond struct {
tIn, tNotIn transform.Transformer
f func(rune) bool
check func(rune) bool // current check to perform
t transform.Transformer // current transformer to use
}
// Reset implements transform.Transformer.
func (t *cond) Reset() {
t.check = t.is
t.t = t.tIn
t.t.Reset() // notIn will be reset on first usage.
}
func (t *cond) is(r rune) bool {
if t.f(r) {
return true
}
t.check = t.isNot
t.t = t.tNotIn
t.tNotIn.Reset()
return false
}
func (t *cond) isNot(r rune) bool {
if !t.f(r) {
return true
}
t.check = t.is
t.t = t.tIn
t.tIn.Reset()
return false
}
func (t *cond) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
p := 0
for nSrc < len(src) && err == nil {
// Don't process too much at a time, as the work might be wasted if the
// destination buffer isn't large enough to hold the result or a
// transform returns an error early.
const maxChunk = 4096
max := len(src)
if n := nSrc + maxChunk; n < len(src) {
max = n
}
atEnd := false
size := 0
current := t.t
for ; p < max; p += size {
var r rune
r, size = utf8.DecodeRune(src[p:])
if r == utf8.RuneError && size == 1 {
if !atEOF && !utf8.FullRune(src[p:]) {
err = transform.ErrShortSrc
break
}
}
if !t.check(r) {
// The next rune will be the start of a new run.
atEnd = true
break
}
}
nDst2, nSrc2, err2 := current.Transform(dst[nDst:], src[nSrc:p], atEnd || (atEOF && p == len(src)))
nDst += nDst2
nSrc += nSrc2
if err2 != nil {
return nDst, nSrc, err2
}
// At this point either err != nil or t.check will pass for the rune at p.
p = nSrc + size
}
return nDst, nSrc, err
}
|
