Source Code Cross Referenced for NFAState.java in  » Parser » antlr-3.0.1 » org » antlr » analysis » Java Source Code / Java DocumentationJava Source Code and Java Documentation

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Java Source Code / Java Documentation » Parser » antlr 3.0.1 » org.antlr.analysis 
Source Cross Referenced  Class Diagram Java Document (Java Doc) 


001:        /*
002:         [The "BSD licence"]
003:         Copyright (c) 2005-2006 Terence Parr
004:         All rights reserved.
005:
006:         Redistribution and use in source and binary forms, with or without
007:         modification, are permitted provided that the following conditions
008:         are met:
009:         1. Redistributions of source code must retain the above copyright
010:            notice, this list of conditions and the following disclaimer.
011:         2. Redistributions in binary form must reproduce the above copyright
012:            notice, this list of conditions and the following disclaimer in the
013:            documentation and/or other materials provided with the distribution.
014:         3. The name of the author may not be used to endorse or promote products
015:            derived from this software without specific prior written permission.
016:
017:         THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
018:         IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
019:         OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
020:         IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
021:         INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
022:         NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
023:         DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
024:         THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
025:         (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
026:         THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
027:         */
028:        package org.antlr.analysis;
029:
030:        import org.antlr.tool.GrammarAST;
031:
032:        /** A state within an NFA. At most 2 transitions emanate from any NFA state. */
033:        public class NFAState extends State {
034:            // I need to distinguish between NFA decision states for (...)* and (...)+
035:            // during NFA interpretation.
036:            public static final int LOOPBACK = 1;
037:            public static final int BLOCK_START = 2;
038:            public static final int OPTIONAL_BLOCK_START = 3;
039:            public static final int BYPASS = 4;
040:            public static final int RIGHT_EDGE_OF_BLOCK = 5;
041:
042:            public static final int MAX_TRANSITIONS = 2;
043:
044:            /** How many transitions; 0, 1, or 2 transitions */
045:            int numTransitions = 0;
046:            Transition[] transition = new Transition[MAX_TRANSITIONS];
047:
048:            /** Which NFA are we in? */
049:            public NFA nfa = null;
050:
051:            /** What's its decision number from 1..n? */
052:            protected int decisionNumber = 0;
053:
054:            /** Subrules (...)* and (...)+ have more than one decision point in
055:             *  the NFA created for them.  They both have a loop-exit-or-stay-in
056:             *  decision node (the loop back node).  They both have a normal
057:             *  alternative block decision node at the left edge.  The (...)* is
058:             *  worse as it even has a bypass decision (2 alts: stay in or bypass)
059:             *  node at the extreme left edge.  This is not how they get generated
060:             *  in code as a while-loop or whatever deals nicely with either.  For
061:             *  error messages (where I need to print the nondeterministic alts)
062:             *  and for interpretation, I need to use the single DFA that is created
063:             *  (for efficiency) but interpret the results differently depending
064:             *  on which of the 2 or 3 decision states uses the DFA.  For example,
065:             *  the DFA will always report alt n+1 as the exit branch for n real
066:             *  alts, so I need to translate that depending on the decision state.
067:             *
068:             *  If decisionNumber>0 then this var tells you what kind of decision
069:             *  state it is.
070:             */
071:            public int decisionStateType;
072:
073:            /** What rule do we live in? */
074:            protected String enclosingRule;
075:
076:            /** During debugging and for nondeterminism warnings, it's useful
077:             *  to know what relationship this node has to the original grammar.
078:             *  For example, "start of alt 1 of rule a".
079:             */
080:            protected String description;
081:
082:            /** Associate this NFAState with the corresponding GrammarAST node
083:             *  from which this node was created.  This is useful not only for
084:             *  associating the eventual lookahead DFA with the associated
085:             *  Grammar position, but also for providing users with
086:             *  nondeterminism warnings.  Mainly used by decision states to
087:             *  report line:col info.  Could also be used to track line:col
088:             *  for elements such as token refs.
089:             */
090:            protected GrammarAST associatedASTNode;
091:
092:            /** Is this state the sole target of an EOT transition? */
093:            protected boolean EOTTargetState = false;
094:
095:            /** Jean Bovet needs in the GUI to know which state pairs correspond
096:             *  to the start/stop of a block.
097:             */
098:            public int endOfBlockStateNumber = State.INVALID_STATE_NUMBER;
099:
100:            public NFAState(NFA nfa) {
101:                this .nfa = nfa;
102:            }
103:
104:            public int getNumberOfTransitions() {
105:                return numTransitions;
106:            }
107:
108:            public void addTransition(Transition e) {
109:                if (numTransitions > transition.length) {
110:                    throw new IllegalArgumentException("You can only have "
111:                            + transition.length + " transitions");
112:                }
113:                if (e != null) {
114:                    transition[numTransitions] = e;
115:                    numTransitions++;
116:                }
117:            }
118:
119:            /** Used during optimization to reset a state to have the (single)
120:             *  transition another state has.
121:             */
122:            public void setTransition0(Transition e) {
123:                transition[0] = e;
124:                transition[1] = null;
125:                numTransitions = 1;
126:            }
127:
128:            public Transition transition(int i) {
129:                return transition[i];
130:            }
131:
132:            /** The DFA decision for this NFA decision state always has
133:             *  an exit path for loops as n+1 for n alts in the loop.
134:             *  That is really useful for displaying nondeterministic alts
135:             *  and so on, but for walking the NFA to get a sequence of edge
136:             *  labels or for actually parsing, we need to get the real alt
137:             *  number.  The real alt number for exiting a loop is always 1
138:             *  as transition 0 points at the exit branch (we compute DFAs
139:             *  always for loops at the loopback state).
140:             *
141:             *  For walking/parsing the loopback state:
142:             * 		1 2 3 display alt (for human consumption)
143:             * 		2 3 1 walk alt
144:             *
145:             *  For walking the block start:
146:             * 		1 2 3 display alt
147:             * 		1 2 3
148:             *
149:             *  For walking the bypass state of a (...)* loop:
150:             * 		1 2 3 display alt
151:             * 		1 1 2 all block alts map to entering loop exit means take bypass
152:             *
153:             *  Non loop EBNF do not need to be translated; they are ignored by
154:             *  this method as decisionStateType==0.
155:             *
156:             *  Return same alt if we can't translate.
157:             */
158:            public int translateDisplayAltToWalkAlt(DFA dfa, int displayAlt) {
159:                if (decisionNumber == 0 || decisionStateType == 0) {
160:                    return displayAlt;
161:                }
162:                int walkAlt = 0;
163:                // find the NFA loopback state associated with this DFA
164:                // and count number of alts (all alt numbers are computed
165:                // based upon the loopback's NFA state.
166:                /*
167:                DFA dfa = nfa.grammar.getLookaheadDFA(decisionNumber);
168:                if ( dfa==null ) {
169:                	ErrorManager.internalError("can't get DFA for decision "+decisionNumber);
170:                }
171:                 */
172:                NFAState nfaStart = dfa.getNFADecisionStartState();
173:                int nAlts = nfa.grammar.getNumberOfAltsForDecisionNFA(nfaStart);
174:                switch (decisionStateType) {
175:                case LOOPBACK:
176:                    walkAlt = displayAlt % nAlts + 1; // rotate right mod 1..3
177:                    break;
178:                case BLOCK_START:
179:                case OPTIONAL_BLOCK_START:
180:                    walkAlt = displayAlt; // identity transformation
181:                    break;
182:                case BYPASS:
183:                    if (displayAlt == nAlts) {
184:                        walkAlt = 2; // bypass
185:                    } else {
186:                        walkAlt = 1; // any non exit branch alt predicts entering
187:                    }
188:                    break;
189:                }
190:                return walkAlt;
191:            }
192:
193:            // Setter/Getters
194:
195:            /** What AST node is associated with this NFAState?  When you
196:             *  set the AST node, I set the node to point back to this NFA state.
197:             */
198:            public void setDecisionASTNode(GrammarAST decisionASTNode) {
199:                decisionASTNode.setNFAStartState(this );
200:                this .associatedASTNode = decisionASTNode;
201:            }
202:
203:            public GrammarAST getAssociatedASTNode() {
204:                return associatedASTNode;
205:            }
206:
207:            public void setAssociatedASTNode(GrammarAST ASTNode) {
208:                this .associatedASTNode = ASTNode;
209:            }
210:
211:            public String getDescription() {
212:                return description;
213:            }
214:
215:            public void setDescription(String description) {
216:                this .description = description;
217:            }
218:
219:            public int getDecisionNumber() {
220:                return decisionNumber;
221:            }
222:
223:            public void setDecisionNumber(int decisionNumber) {
224:                this .decisionNumber = decisionNumber;
225:            }
226:
227:            public void setEnclosingRuleName(String rule) {
228:                this .enclosingRule = rule;
229:            }
230:
231:            public String getEnclosingRule() {
232:                return enclosingRule;
233:            }
234:
235:            public boolean isEOTTargetState() {
236:                return EOTTargetState;
237:            }
238:
239:            public void setEOTTargetState(boolean eot) {
240:                EOTTargetState = eot;
241:            }
242:
243:            public boolean isDecisionState() {
244:                return decisionStateType > 0;
245:            }
246:
247:            public String toString() {
248:                return String.valueOf(stateNumber);
249:            }
250:
251:        }
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