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
183
184
185
186
|
// Copyright (c) 2012-2022 The ANTLR Project. All rights reserved.
// Use of this file is governed by the BSD 3-clause license that
// can be found in the LICENSE.txt file in the project root.
package antlr
import "golang.org/x/exp/slices"
// Represents an executor for a sequence of lexer actions which traversed during
// the Matching operation of a lexer rule (token).
//
// <p>The executor tracks position information for position-dependent lexer actions
// efficiently, ensuring that actions appearing only at the end of the rule do
// not cause bloating of the {@link DFA} created for the lexer.</p>
type LexerActionExecutor struct {
lexerActions []LexerAction
cachedHash int
}
func NewLexerActionExecutor(lexerActions []LexerAction) *LexerActionExecutor {
if lexerActions == nil {
lexerActions = make([]LexerAction, 0)
}
l := new(LexerActionExecutor)
l.lexerActions = lexerActions
// Caches the result of {@link //hashCode} since the hash code is an element
// of the performance-critical {@link LexerATNConfig//hashCode} operation.
l.cachedHash = murmurInit(57)
for _, a := range lexerActions {
l.cachedHash = murmurUpdate(l.cachedHash, a.Hash())
}
return l
}
// Creates a {@link LexerActionExecutor} which executes the actions for
// the input {@code lexerActionExecutor} followed by a specified
// {@code lexerAction}.
//
// @param lexerActionExecutor The executor for actions already traversed by
// the lexer while Matching a token within a particular
// {@link LexerATNConfig}. If this is {@code nil}, the method behaves as
// though it were an empty executor.
// @param lexerAction The lexer action to execute after the actions
// specified in {@code lexerActionExecutor}.
//
// @return A {@link LexerActionExecutor} for executing the combine actions
// of {@code lexerActionExecutor} and {@code lexerAction}.
func LexerActionExecutorappend(lexerActionExecutor *LexerActionExecutor, lexerAction LexerAction) *LexerActionExecutor {
if lexerActionExecutor == nil {
return NewLexerActionExecutor([]LexerAction{lexerAction})
}
return NewLexerActionExecutor(append(lexerActionExecutor.lexerActions, lexerAction))
}
// Creates a {@link LexerActionExecutor} which encodes the current offset
// for position-dependent lexer actions.
//
// <p>Normally, when the executor encounters lexer actions where
// {@link LexerAction//isPositionDependent} returns {@code true}, it calls
// {@link IntStream//seek} on the input {@link CharStream} to set the input
// position to the <em>end</em> of the current token. This behavior provides
// for efficient DFA representation of lexer actions which appear at the end
// of a lexer rule, even when the lexer rule Matches a variable number of
// characters.</p>
//
// <p>Prior to traversing a Match transition in the ATN, the current offset
// from the token start index is assigned to all position-dependent lexer
// actions which have not already been assigned a fixed offset. By storing
// the offsets relative to the token start index, the DFA representation of
// lexer actions which appear in the middle of tokens remains efficient due
// to sharing among tokens of the same length, regardless of their absolute
// position in the input stream.</p>
//
// <p>If the current executor already has offsets assigned to all
// position-dependent lexer actions, the method returns {@code this}.</p>
//
// @param offset The current offset to assign to all position-dependent
// lexer actions which do not already have offsets assigned.
//
// @return A {@link LexerActionExecutor} which stores input stream offsets
// for all position-dependent lexer actions.
// /
func (l *LexerActionExecutor) fixOffsetBeforeMatch(offset int) *LexerActionExecutor {
var updatedLexerActions []LexerAction
for i := 0; i < len(l.lexerActions); i++ {
_, ok := l.lexerActions[i].(*LexerIndexedCustomAction)
if l.lexerActions[i].getIsPositionDependent() && !ok {
if updatedLexerActions == nil {
updatedLexerActions = make([]LexerAction, 0)
for _, a := range l.lexerActions {
updatedLexerActions = append(updatedLexerActions, a)
}
}
updatedLexerActions[i] = NewLexerIndexedCustomAction(offset, l.lexerActions[i])
}
}
if updatedLexerActions == nil {
return l
}
return NewLexerActionExecutor(updatedLexerActions)
}
// Execute the actions encapsulated by l executor within the context of a
// particular {@link Lexer}.
//
// <p>This method calls {@link IntStream//seek} to set the position of the
// {@code input} {@link CharStream} prior to calling
// {@link LexerAction//execute} on a position-dependent action. Before the
// method returns, the input position will be restored to the same position
// it was in when the method was invoked.</p>
//
// @param lexer The lexer instance.
// @param input The input stream which is the source for the current token.
// When l method is called, the current {@link IntStream//index} for
// {@code input} should be the start of the following token, i.e. 1
// character past the end of the current token.
// @param startIndex The token start index. This value may be passed to
// {@link IntStream//seek} to set the {@code input} position to the beginning
// of the token.
// /
func (l *LexerActionExecutor) execute(lexer Lexer, input CharStream, startIndex int) {
requiresSeek := false
stopIndex := input.Index()
defer func() {
if requiresSeek {
input.Seek(stopIndex)
}
}()
for i := 0; i < len(l.lexerActions); i++ {
lexerAction := l.lexerActions[i]
if la, ok := lexerAction.(*LexerIndexedCustomAction); ok {
offset := la.offset
input.Seek(startIndex + offset)
lexerAction = la.lexerAction
requiresSeek = (startIndex + offset) != stopIndex
} else if lexerAction.getIsPositionDependent() {
input.Seek(stopIndex)
requiresSeek = false
}
lexerAction.execute(lexer)
}
}
func (l *LexerActionExecutor) Hash() int {
if l == nil {
// TODO: Why is this here? l should not be nil
return 61
}
// TODO: This is created from the action itself when the struct is created - will this be an issue at some point? Java uses the runtime assign hashcode
return l.cachedHash
}
func (l *LexerActionExecutor) Equals(other interface{}) bool {
if l == other {
return true
}
othert, ok := other.(*LexerActionExecutor)
if !ok {
return false
}
if othert == nil {
return false
}
if l.cachedHash != othert.cachedHash {
return false
}
if len(l.lexerActions) != len(othert.lexerActions) {
return false
}
return slices.EqualFunc(l.lexerActions, othert.lexerActions, func(i, j LexerAction) bool {
return i.Equals(j)
})
}
|
