-
Notifications
You must be signed in to change notification settings - Fork 16
/
ll1_analyzer.go
219 lines (190 loc) · 7.48 KB
/
ll1_analyzer.go
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
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
// 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
type LL1Analyzer struct {
atn *ATN
}
func NewLL1Analyzer(atn *ATN) *LL1Analyzer {
la := new(LL1Analyzer)
la.atn = atn
return la
}
const (
// LL1AnalyzerHitPred is a special value added to the lookahead sets to indicate that we hit
// a predicate during analysis if
//
// seeThruPreds==false
LL1AnalyzerHitPred = TokenInvalidType
)
// *
// Calculates the SLL(1) expected lookahead set for each outgoing transition
// of an {@link ATNState}. The returned array has one element for each
// outgoing transition in {@code s}. If the closure from transition
// <em>i</em> leads to a semantic predicate before Matching a symbol, the
// element at index <em>i</em> of the result will be {@code nil}.
//
// @param s the ATN state
// @return the expected symbols for each outgoing transition of {@code s}.
func (la *LL1Analyzer) getDecisionLookahead(s ATNState) []*IntervalSet {
if s == nil {
return nil
}
count := len(s.GetTransitions())
look := make([]*IntervalSet, count)
for alt := 0; alt < count; alt++ {
look[alt] = NewIntervalSet()
// TODO: This is one of the reasons that ATNConfigs are allocated and freed all the time - fix this tomorrow jim!
lookBusy := NewJStore[*ATNConfig, Comparator[*ATNConfig]](aConfEqInst, ClosureBusyCollection, "LL1Analyzer.getDecisionLookahead for lookBusy")
la.look1(s.GetTransitions()[alt].getTarget(), nil, BasePredictionContextEMPTY, look[alt], lookBusy, NewBitSet(), false, false)
// Wipe out lookahead for la alternative if we found nothing,
// or we had a predicate when we !seeThruPreds
if look[alt].length() == 0 || look[alt].contains(LL1AnalyzerHitPred) {
look[alt] = nil
}
}
return look
}
// Look computes the set of tokens that can follow s in the [ATN] in the
// specified ctx.
//
// If ctx is nil and the end of the rule containing
// s is reached, [EPSILON] is added to the result set.
//
// If ctx is not nil and the end of the outermost rule is
// reached, [EOF] is added to the result set.
//
// Parameter s the ATN state, and stopState is the ATN state to stop at. This can be a
// [BlockEndState] to detect epsilon paths through a closure.
//
// Parameter ctx is the complete parser context, or nil if the context
// should be ignored
//
// The func returns the set of tokens that can follow s in the [ATN] in the
// specified ctx.
func (la *LL1Analyzer) Look(s, stopState ATNState, ctx RuleContext) *IntervalSet {
r := NewIntervalSet()
var lookContext *PredictionContext
if ctx != nil {
lookContext = predictionContextFromRuleContext(s.GetATN(), ctx)
}
la.look1(s, stopState, lookContext, r, NewJStore[*ATNConfig, Comparator[*ATNConfig]](aConfEqInst, ClosureBusyCollection, "LL1Analyzer.Look for la.look1()"),
NewBitSet(), true, true)
return r
}
//*
// Compute set of tokens that can follow {@code s} in the ATN in the
// specified {@code ctx}.
//
// <p>If {@code ctx} is {@code nil} and {@code stopState} or the end of the
// rule containing {@code s} is reached, {@link Token//EPSILON} is added to
// the result set. If {@code ctx} is not {@code nil} and {@code addEOF} is
// {@code true} and {@code stopState} or the end of the outermost rule is
// reached, {@link Token//EOF} is added to the result set.</p>
//
// @param s the ATN state.
// @param stopState the ATN state to stop at. This can be a
// {@link BlockEndState} to detect epsilon paths through a closure.
// @param ctx The outer context, or {@code nil} if the outer context should
// not be used.
// @param look The result lookahead set.
// @param lookBusy A set used for preventing epsilon closures in the ATN
// from causing a stack overflow. Outside code should pass
// {@code NewSet<ATNConfig>} for la argument.
// @param calledRuleStack A set used for preventing left recursion in the
// ATN from causing a stack overflow. Outside code should pass
// {@code NewBitSet()} for la argument.
// @param seeThruPreds {@code true} to true semantic predicates as
// implicitly {@code true} and "see through them", otherwise {@code false}
// to treat semantic predicates as opaque and add {@link //HitPred} to the
// result if one is encountered.
// @param addEOF Add {@link Token//EOF} to the result if the end of the
// outermost context is reached. This parameter has no effect if {@code ctx}
// is {@code nil}.
func (la *LL1Analyzer) look2(_, stopState ATNState, ctx *PredictionContext, look *IntervalSet, lookBusy *JStore[*ATNConfig, Comparator[*ATNConfig]],
calledRuleStack *BitSet, seeThruPreds, addEOF bool, i int) {
returnState := la.atn.states[ctx.getReturnState(i)]
la.look1(returnState, stopState, ctx.GetParent(i), look, lookBusy, calledRuleStack, seeThruPreds, addEOF)
}
func (la *LL1Analyzer) look1(s, stopState ATNState, ctx *PredictionContext, look *IntervalSet, lookBusy *JStore[*ATNConfig, Comparator[*ATNConfig]], calledRuleStack *BitSet, seeThruPreds, addEOF bool) {
c := NewATNConfig6(s, 0, ctx)
if lookBusy.Contains(c) {
return
}
_, present := lookBusy.Put(c)
if present {
return
}
if s == stopState {
if ctx == nil {
look.addOne(TokenEpsilon)
return
} else if ctx.isEmpty() && addEOF {
look.addOne(TokenEOF)
return
}
}
_, ok := s.(*RuleStopState)
if ok {
if ctx == nil {
look.addOne(TokenEpsilon)
return
} else if ctx.isEmpty() && addEOF {
look.addOne(TokenEOF)
return
}
if ctx.pcType != PredictionContextEmpty {
removed := calledRuleStack.contains(s.GetRuleIndex())
defer func() {
if removed {
calledRuleStack.add(s.GetRuleIndex())
}
}()
calledRuleStack.remove(s.GetRuleIndex())
// run thru all possible stack tops in ctx
for i := 0; i < ctx.length(); i++ {
returnState := la.atn.states[ctx.getReturnState(i)]
la.look2(returnState, stopState, ctx, look, lookBusy, calledRuleStack, seeThruPreds, addEOF, i)
}
return
}
}
n := len(s.GetTransitions())
for i := 0; i < n; i++ {
t := s.GetTransitions()[i]
if t1, ok := t.(*RuleTransition); ok {
if calledRuleStack.contains(t1.getTarget().GetRuleIndex()) {
continue
}
newContext := SingletonBasePredictionContextCreate(ctx, t1.followState.GetStateNumber())
la.look3(stopState, newContext, look, lookBusy, calledRuleStack, seeThruPreds, addEOF, t1)
} else if t2, ok := t.(AbstractPredicateTransition); ok {
if seeThruPreds {
la.look1(t2.getTarget(), stopState, ctx, look, lookBusy, calledRuleStack, seeThruPreds, addEOF)
} else {
look.addOne(LL1AnalyzerHitPred)
}
} else if t.getIsEpsilon() {
la.look1(t.getTarget(), stopState, ctx, look, lookBusy, calledRuleStack, seeThruPreds, addEOF)
} else if _, ok := t.(*WildcardTransition); ok {
look.addRange(TokenMinUserTokenType, la.atn.maxTokenType)
} else {
set := t.getLabel()
if set != nil {
if _, ok := t.(*NotSetTransition); ok {
set = set.complement(TokenMinUserTokenType, la.atn.maxTokenType)
}
look.addSet(set)
}
}
}
}
func (la *LL1Analyzer) look3(stopState ATNState, ctx *PredictionContext, look *IntervalSet, lookBusy *JStore[*ATNConfig, Comparator[*ATNConfig]],
calledRuleStack *BitSet, seeThruPreds, addEOF bool, t1 *RuleTransition) {
newContext := SingletonBasePredictionContextCreate(ctx, t1.followState.GetStateNumber())
defer func() {
calledRuleStack.remove(t1.getTarget().GetRuleIndex())
}()
calledRuleStack.add(t1.getTarget().GetRuleIndex())
la.look1(t1.getTarget(), stopState, newContext, look, lookBusy, calledRuleStack, seeThruPreds, addEOF)
}