File: replace.go

package info (click to toggle)
golang-github-dlclark-regexp2 1.2.0-1
  • links: PTS, VCS
  • area: main
  • in suites: bullseye, sid
  • size: 560 kB
  • sloc: makefile: 3
file content (177 lines) | stat: -rw-r--r-- 4,062 bytes parent folder | download | duplicates (2)
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
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
package regexp2

import (
	"bytes"
	"errors"

	"github.com/dlclark/regexp2/syntax"
)

const (
	replaceSpecials     = 4
	replaceLeftPortion  = -1
	replaceRightPortion = -2
	replaceLastGroup    = -3
	replaceWholeString  = -4
)

// MatchEvaluator is a function that takes a match and returns a replacement string to be used
type MatchEvaluator func(Match) string

// Three very similar algorithms appear below: replace (pattern),
// replace (evaluator), and split.

// Replace Replaces all occurrences of the regex in the string with the
// replacement pattern.
//
// Note that the special case of no matches is handled on its own:
// with no matches, the input string is returned unchanged.
// The right-to-left case is split out because StringBuilder
// doesn't handle right-to-left string building directly very well.
func replace(regex *Regexp, data *syntax.ReplacerData, evaluator MatchEvaluator, input string, startAt, count int) (string, error) {
	if count < -1 {
		return "", errors.New("Count too small")
	}
	if count == 0 {
		return "", nil
	}

	m, err := regex.FindStringMatchStartingAt(input, startAt)

	if err != nil {
		return "", err
	}
	if m == nil {
		return input, nil
	}

	buf := &bytes.Buffer{}
	text := m.text

	if !regex.RightToLeft() {
		prevat := 0
		for m != nil {
			if m.Index != prevat {
				buf.WriteString(string(text[prevat:m.Index]))
			}
			prevat = m.Index + m.Length
			if evaluator == nil {
				replacementImpl(data, buf, m)
			} else {
				buf.WriteString(evaluator(*m))
			}

			count--
			if count == 0 {
				break
			}
			m, err = regex.FindNextMatch(m)
			if err != nil {
				return "", nil
			}
		}

		if prevat < len(text) {
			buf.WriteString(string(text[prevat:]))
		}
	} else {
		prevat := len(text)
		var al []string

		for m != nil {
			if m.Index+m.Length != prevat {
				al = append(al, string(text[m.Index+m.Length:prevat]))
			}
			prevat = m.Index
			if evaluator == nil {
				replacementImplRTL(data, &al, m)
			} else {
				al = append(al, evaluator(*m))
			}

			count--
			if count == 0 {
				break
			}
			m, err = regex.FindNextMatch(m)
			if err != nil {
				return "", nil
			}
		}

		if prevat > 0 {
			buf.WriteString(string(text[:prevat]))
		}

		for i := len(al) - 1; i >= 0; i-- {
			buf.WriteString(al[i])
		}
	}

	return buf.String(), nil
}

// Given a Match, emits into the StringBuilder the evaluated
// substitution pattern.
func replacementImpl(data *syntax.ReplacerData, buf *bytes.Buffer, m *Match) {
	for _, r := range data.Rules {

		if r >= 0 { // string lookup
			buf.WriteString(data.Strings[r])
		} else if r < -replaceSpecials { // group lookup
			m.groupValueAppendToBuf(-replaceSpecials-1-r, buf)
		} else {
			switch -replaceSpecials - 1 - r { // special insertion patterns
			case replaceLeftPortion:
				for i := 0; i < m.Index; i++ {
					buf.WriteRune(m.text[i])
				}
			case replaceRightPortion:
				for i := m.Index + m.Length; i < len(m.text); i++ {
					buf.WriteRune(m.text[i])
				}
			case replaceLastGroup:
				m.groupValueAppendToBuf(m.GroupCount()-1, buf)
			case replaceWholeString:
				for i := 0; i < len(m.text); i++ {
					buf.WriteRune(m.text[i])
				}
			}
		}
	}
}

func replacementImplRTL(data *syntax.ReplacerData, al *[]string, m *Match) {
	l := *al
	buf := &bytes.Buffer{}

	for _, r := range data.Rules {
		buf.Reset()
		if r >= 0 { // string lookup
			l = append(l, data.Strings[r])
		} else if r < -replaceSpecials { // group lookup
			m.groupValueAppendToBuf(-replaceSpecials-1-r, buf)
			l = append(l, buf.String())
		} else {
			switch -replaceSpecials - 1 - r { // special insertion patterns
			case replaceLeftPortion:
				for i := 0; i < m.Index; i++ {
					buf.WriteRune(m.text[i])
				}
			case replaceRightPortion:
				for i := m.Index + m.Length; i < len(m.text); i++ {
					buf.WriteRune(m.text[i])
				}
			case replaceLastGroup:
				m.groupValueAppendToBuf(m.GroupCount()-1, buf)
			case replaceWholeString:
				for i := 0; i < len(m.text); i++ {
					buf.WriteRune(m.text[i])
				}
			}
			l = append(l, buf.String())
		}
	}

	*al = l
}