1 /** Support functions for traversing cyclic DFA states as laid
2 * out in static initialized structures by the code generator.
3 *
4 * A DFA implemented as a set of transition tables.
5 *
6 * Any state that has a semantic predicate edge is special; those states
7 * are generated with if-then-else structures in a ->specialStateTransition()
8 * which is generated by cyclicDFA template.
9 *
10 * There are at most 32767 states (16-bit signed short).
11 * Could get away with byte sometimes but would have to generate different
12 * types and the simulation code too. For a point of reference, the Java
13 * lexer's Tokens rule DFA has 326 states roughly.
14 */
15
16 // [The "BSD licence"]
17 // Copyright (c) 2005-2009 Jim Idle, Temporal Wave LLC
18 // http://www.temporal-wave.com
19 // http://www.linkedin.com/in/jimidle
20 //
21 // All rights reserved.
22 //
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24 // modification, are permitted provided that the following conditions
25 // are met:
26 // 1. Redistributions of source code must retain the above copyright
27 // notice, this list of conditions and the following disclaimer.
28 // 2. Redistributions in binary form must reproduce the above copyright
29 // notice, this list of conditions and the following disclaimer in the
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31 // 3. The name of the author may not be used to endorse or promote products
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33 //
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44
45 #include <antlr3defs.h>
46 #include <antlr3cyclicdfa.h>
47
48 #ifdef ANTLR3_WINDOWS
49 #pragma warning( disable : 4100 )
50 #endif
51
52 static void
noViableAlt(pANTLR3_BASE_RECOGNIZER rec,pANTLR3_CYCLIC_DFA cdfa,ANTLR3_UINT32 s)53 noViableAlt(pANTLR3_BASE_RECOGNIZER rec, pANTLR3_CYCLIC_DFA cdfa, ANTLR3_UINT32 s)
54 {
55 // In backtracking mode, we just set the failed flag so that the
56 // alt can just exit right now. If we are parsing though, then
57 // we want the exception to be raised.
58 //
59 if (rec->state->backtracking > 0)
60 {
61 rec->state->failed = ANTLR3_TRUE;
62 }
63 else
64 {
65 rec->exConstruct(rec);
66 rec->state->exception->type = ANTLR3_NO_VIABLE_ALT_EXCEPTION;
67 rec->state->exception->message = cdfa->description;
68 rec->state->exception->decisionNum = cdfa->decisionNumber;
69 rec->state->exception->state = s;
70 }
71 }
72
73 /** From the input stream, predict what alternative will succeed
74 * using this DFA (representing the covering regular approximation
75 * to the underlying CFL). Return an alternative number 1..n. Throw
76 * an exception upon error.
77 */
78 ANTLR3_API ANTLR3_INT32
antlr3dfapredict(void * ctx,pANTLR3_BASE_RECOGNIZER rec,pANTLR3_INT_STREAM is,pANTLR3_CYCLIC_DFA cdfa)79 antlr3dfapredict (void * ctx, pANTLR3_BASE_RECOGNIZER rec, pANTLR3_INT_STREAM is, pANTLR3_CYCLIC_DFA cdfa)
80 {
81 ANTLR3_MARKER mark;
82 ANTLR3_INT32 s;
83 ANTLR3_INT32 specialState;
84 ANTLR3_INT32 c;
85
86 mark = is->mark(is); /* Store where we are right now */
87 s = 0; /* Always start with state 0 */
88
89 for (;;)
90 {
91 /* Pick out any special state entry for this state
92 */
93 specialState = cdfa->special[s];
94
95 /* Transition the special state and consume an input token
96 */
97 if (specialState >= 0)
98 {
99 s = cdfa->specialStateTransition(ctx, rec, is, cdfa, specialState);
100
101 // Error?
102 //
103 if (s<0)
104 {
105 // If the predicate/rule raised an exception then we leave it
106 // in tact, else we have an NVA.
107 //
108 if (rec->state->error != ANTLR3_TRUE)
109 {
110 noViableAlt(rec,cdfa, s);
111 }
112 is->rewind(is, mark);
113 return 0;
114 }
115 is->consume(is);
116 continue;
117 }
118
119 /* Accept state?
120 */
121 if (cdfa->accept[s] >= 1)
122 {
123 is->rewind(is, mark);
124 return cdfa->accept[s];
125 }
126
127 /* Look for a normal transition state based upon the input token element
128 */
129 c = is->_LA(is, 1);
130
131 /* Check against min and max for this state
132 */
133 if (c>= cdfa->min[s] && c <= cdfa->max[s])
134 {
135 ANTLR3_INT32 snext;
136
137 /* What is the next state?
138 */
139 snext = cdfa->transition[s][c - cdfa->min[s]];
140
141 if (snext < 0)
142 {
143 /* Was in range but not a normal transition
144 * must check EOT, which is like the else clause.
145 * eot[s]>=0 indicates that an EOT edge goes to another
146 * state.
147 */
148 if (cdfa->eot[s] >= 0)
149 {
150 s = cdfa->eot[s];
151 is->consume(is);
152 continue;
153 }
154 noViableAlt(rec,cdfa, s);
155 is->rewind(is, mark);
156 return 0;
157 }
158
159 /* New current state - move to it
160 */
161 s = snext;
162 is->consume(is);
163 continue;
164 }
165 /* EOT Transition?
166 */
167 if (cdfa->eot[s] >= 0)
168 {
169 s = cdfa->eot[s];
170 is->consume(is);
171 continue;
172 }
173 /* EOF transition to accept state?
174 */
175 if ( c == ANTLR3_TOKEN_EOF && cdfa->eof[s] >= 0)
176 {
177 is->rewind(is, mark);
178 return cdfa->accept[cdfa->eof[s]];
179 }
180
181 /* No alt, so bomb
182 */
183 noViableAlt(rec, cdfa, s);
184 is->rewind(is, mark);
185 return 0;
186 }
187
188 }
189
190 /** Default special state implementation
191 */
192 ANTLR3_API ANTLR3_INT32
antlr3dfaspecialStateTransition(void * ctx,pANTLR3_BASE_RECOGNIZER recognizer,pANTLR3_INT_STREAM is,pANTLR3_CYCLIC_DFA dfa,ANTLR3_INT32 s)193 antlr3dfaspecialStateTransition (void * ctx, pANTLR3_BASE_RECOGNIZER recognizer, pANTLR3_INT_STREAM is, pANTLR3_CYCLIC_DFA dfa, ANTLR3_INT32 s)
194 {
195 return -1;
196 }
197
198 /* Default special transition implementation
199 */
200 ANTLR3_API ANTLR3_INT32
antlr3dfaspecialTransition(void * ctx,pANTLR3_BASE_RECOGNIZER recognizer,pANTLR3_INT_STREAM is,pANTLR3_CYCLIC_DFA dfa,ANTLR3_INT32 s)201 antlr3dfaspecialTransition (void * ctx, pANTLR3_BASE_RECOGNIZER recognizer, pANTLR3_INT_STREAM is, pANTLR3_CYCLIC_DFA dfa, ANTLR3_INT32 s)
202 {
203 return 0;
204 }
205