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
178
179
180
181
182
|
package parser
import (
"fmt"
"strings"
"unicode/utf8"
)
const eof rune = -1
type lexem struct {
Type lexType // Type of Lexem.
Value string // Value of Lexem.
Start int // Start position at input string.
End int // End position at input string.
}
//go:generate stringer -type=lexType
type lexType int
const (
lEOF lexType = iota
lError
lObjectStart
lObjectEnd
lObjectKey
lObjectValue
lArrayStart
lArrayEnd
lString
lNumber
lBoolean
lNull
)
// lexer holds current scanner state.
type lexer struct {
Input string // Input string.
Start int // Start position of current lexem.
Pos int // Pos at input string.
Output chan lexem // Lexems channel.
width int // Width of last rune.
states stateStack // Stack of states to realize PrevState.
}
// newLexer returns new scanner for input string.
func newLexer(input string) *lexer {
return &lexer{
Input: input,
Start: 0,
Pos: 0,
Output: make(chan lexem, 2),
width: 0,
}
}
// Run lexing.
func (l *lexer) Run(init stateFunc) {
for state := init; state != nil; {
state = state(l)
}
close(l.Output)
}
// PopState returns previous state function.
func (l *lexer) PopState() stateFunc {
return l.states.Pop()
}
// PushState pushes state before going deeper states.
func (l *lexer) PushState(s stateFunc) {
l.states.Push(s)
}
// Emit current lexem to output.
func (l *lexer) Emit(typ lexType) {
l.Output <- lexem{
Type: typ,
Value: l.Input[l.Start:l.Pos],
Start: l.Start,
End: l.Pos,
}
l.Start = l.Pos
}
// Errorf produces error lexem and stops scanning.
func (l *lexer) Errorf(format string, args ...interface{}) stateFunc {
l.Output <- lexem{
Type: lError,
Value: fmt.Sprintf(format, args...),
Start: l.Start,
End: l.Pos,
}
return nil
}
// Next rune from input.
func (l *lexer) Next() (r rune) {
if int(l.Pos) >= len(l.Input) {
l.width = 0
return eof
}
r, l.width = utf8.DecodeRuneInString(l.Input[l.Pos:])
l.Pos += l.width
return r
}
// Back move position to previos rune.
func (l *lexer) Back() {
l.Pos -= l.width
}
// Ignore previosly buffered text.
func (l *lexer) Ignore() {
l.Start = l.Pos
l.width = 0
}
// Peek rune at current position without moving position.
func (l *lexer) Peek() (r rune) {
r = l.Next()
l.Back()
return r
}
// Accept any rune from valid string. Returns true if Next rune was in valid string.
func (l *lexer) Accept(valid string) bool {
if strings.ContainsRune(valid, l.Next()) {
return true
}
l.Back()
return false
}
// AcceptString returns true if given string was at position.
func (l *lexer) AcceptString(s string, caseInsentive bool) bool {
input := l.Input[l.Start:]
if caseInsentive {
input = strings.ToLower(input)
s = strings.ToLower(s)
}
if strings.HasPrefix(input, s) {
l.width = 0
l.Pos += len(s)
return true
}
return false
}
// AcceptAnyOf substrings. Retuns true if any of substrings was found.
func (l *lexer) AcceptAnyOf(s []string, caseInsentive bool) bool {
for _, substring := range s {
if l.AcceptString(substring, caseInsentive) {
return true
}
}
return false
}
// AcceptWhile passing symbols from input while they at `valid` string.
func (l *lexer) AcceptWhile(valid string) bool {
isValid := false
for l.Accept(valid) {
isValid = true
}
return isValid
}
// AcceptWhileNot passing symbols from input while they NOT in `invalid` string.
func (l *lexer) AcceptWhileNot(invalid string) bool {
isValid := false
for !strings.ContainsRune(invalid, l.Next()) {
isValid = true
}
l.Back()
return isValid
}
// AtStart returns true if current lexem not empty
func (l *lexer) AtStart() bool {
return l.Pos == l.Start
}
|
