antlr-3.4/tool/src/main/java/org/antlr/tool/FASerializer.java

/*
 * [The "BSD license"]
 *  Copyright (c) 2010 Terence Parr
 *  All rights reserved.
 *
 *  Redistribution and use in source and binary forms, with or without
 *  modification, are permitted provided that the following conditions
 *  are met:
 *  1. Redistributions of source code must retain the above copyright
 *      notice, this list of conditions and the following disclaimer.
 *  2. Redistributions in binary form must reproduce the above copyright
 *      notice, this list of conditions and the following disclaimer in the
 *      documentation and/or other materials provided with the distribution.
 *  3. The name of the author may not be used to endorse or promote products
 *      derived from this software without specific prior written permission.
 *
 *  THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 *  IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 *  OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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 *  INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 *  NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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 */
package org.antlr.tool;

import org.antlr.analysis.*;
import org.antlr.misc.Utils;

import java.util.*;

/** An aspect of FA (finite automata) that knows how to dump them to serialized
 *  strings.
 */
public class FASerializer {
    /** To prevent infinite recursion when walking state machines, record
     *  which states we've visited.  Make a new set every time you start
     *  walking in case you reuse this object.  Multiple threads will trash
     *  this shared variable.  Use a different FASerializer per thread.
     */
    protected Set markedStates;

    /** Each state we walk will get a new state number for serialization
     *  purposes.  This is the variable that tracks state numbers.
     */
    protected int stateCounter = 0;

    /** Rather than add a new instance variable to NFA and DFA just for
     *  serializing machines, map old state numbers to new state numbers
     *  by a State object -> Integer new state number HashMap.
     */
    protected Map stateNumberTranslator;

    protected Grammar grammar;

    /** This aspect is associated with a grammar; used to get token names */
    public FASerializer(Grammar grammar) {
        this.grammar = grammar;
    }

	public String serialize(State s) {
		if ( s==null ) {
			return "<no automaton>";
		}
		return serialize(s, true);
	}

	/** Return a string representation of a state machine.  Two identical
     *  NFAs or DFAs will have identical serialized representations.  The
     *  state numbers inside the state are not used; instead, a new number
     *  is computed and because the serialization will walk the two
     *  machines using the same specific algorithm, then the state numbers
     *  will be identical.  Accept states are distinguished from regular
     *  states.
     */
    public String serialize(State s, boolean renumber) {
        markedStates = new HashSet();
        stateCounter = 0;
		if ( renumber ) {
			stateNumberTranslator = new HashMap();
        	walkFANormalizingStateNumbers(s);
		}
		List lines = new ArrayList();
        if ( s.getNumberOfTransitions()>0 ) {
			walkSerializingFA(lines, s);
		}
		else {
			// special case: s0 is an accept
			String s0 = getStateString(0, s);
			lines.add(s0+"\n");
		}
        StringBuffer buf = new StringBuffer(0);
        // sort lines to normalize; makes states come out ordered
        // and then ordered by edge labels then by target state number :)
        Collections.sort(lines);
        for (int i = 0; i < lines.size(); i++) {
            String line = (String) lines.get(i);
            buf.append(line);
        }
        return buf.toString();
    }

    /** In stateNumberTranslator, get a map from State to new, normalized
     *  state number.  Used by walkSerializingFA to make sure any two
     *  identical state machines will serialize the same way.
     */
    protected void walkFANormalizingStateNumbers(State s) {
		if ( s==null ) {
			ErrorManager.internalError("null state s");
			return;
		}
        if ( stateNumberTranslator.get(s)!=null ) {
            return; // already did this state
        }
        // assign a new state number for this node if there isn't one
        stateNumberTranslator.put(s, Utils.integer(stateCounter));
        stateCounter++;

        // visit nodes pointed to by each transition;
        for (int i = 0; i < s.getNumberOfTransitions(); i++) {
            Transition edge = (Transition) s.transition(i);
            walkFANormalizingStateNumbers(edge.target); // keep walkin'
            // if this transition is a rule reference, the node "following" this state
            // will not be found and appear to be not in graph.  Must explicitly jump
            // to it, but don't "draw" an edge.
            if ( edge instanceof RuleClosureTransition ) {
				walkFANormalizingStateNumbers(((RuleClosureTransition) edge).followState);
            }
        }
    }

    protected void walkSerializingFA(List lines, State s) {
        if ( markedStates.contains(s) ) {
            return; // already visited this node
        }

        markedStates.add(s); // mark this node as completed.

		int normalizedStateNumber = s.stateNumber;
		if ( stateNumberTranslator!=null ) {
	        Integer normalizedStateNumberI = (Integer)stateNumberTranslator.get(s);
			normalizedStateNumber = normalizedStateNumberI.intValue();
		}

		String stateStr = getStateString(normalizedStateNumber, s);

        // depth first walk each transition, printing its edge first
        for (int i = 0; i < s.getNumberOfTransitions(); i++) {
            Transition edge = (Transition) s.transition(i);
            StringBuffer buf = new StringBuffer();
            buf.append(stateStr);
			if ( edge.isAction() ) {
				buf.append("-{}->");
			}
			else if ( edge.isEpsilon() ) {
				buf.append("->");
			}
			else if ( edge.isSemanticPredicate() ) {
				buf.append("-{"+edge.label.getSemanticContext()+"}?->");
			}
			else {
				String predsStr = "";
				if ( edge.target instanceof DFAState ) {
					// look for gated predicates; don't add gated to simple sempred edges
					SemanticContext preds =
						((DFAState)edge.target).getGatedPredicatesInNFAConfigurations();
					if ( preds!=null ) {
						predsStr = "&&{"+
							preds.genExpr(grammar.generator,
									   	  grammar.generator.getTemplates(), null).render()
							+"}?";
					}
				}
				buf.append("-"+edge.label.toString(grammar)+predsStr+"->");
			}

			int normalizedTargetStateNumber = edge.target.stateNumber;
			if ( stateNumberTranslator!=null ) {
				Integer normalizedTargetStateNumberI =
					(Integer)stateNumberTranslator.get(edge.target);
				normalizedTargetStateNumber = normalizedTargetStateNumberI.intValue();
			}
			buf.append(getStateString(normalizedTargetStateNumber, edge.target));
            buf.append("\n");
            lines.add(buf.toString());

            // walk this transition
            walkSerializingFA(lines, edge.target);

            // if this transition is a rule reference, the node "following" this state
            // will not be found and appear to be not in graph.  Must explicitly jump
            // to it, but don't "draw" an edge.
            if ( edge instanceof RuleClosureTransition ) {
				walkSerializingFA(lines, ((RuleClosureTransition) edge).followState);
            }
        }

    }

    private String getStateString(int n, State s) {
        String stateStr = ".s"+n;
        if ( s.isAcceptState() ) {
            if ( s instanceof DFAState ) {
                stateStr = ":s"+n+"=>"+((DFAState)s).getUniquelyPredictedAlt();
            }
            else {
                stateStr = ":s"+n;
            }
        }
        return stateStr;
    }


}