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Move TailEpsilonRemover to top-level class

This commit is contained in:
Sam Harwell 2012-07-31 13:25:21 -05:00
parent 170a8347bb
commit eff9e0c47f
2 changed files with 82 additions and 36 deletions
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37
tool/src/org/antlr/v4/automata/ParserATNFactory.java
View File

@ -58,41 +58,6 @@ import java.util.List;
* No side-effects. It builds an ATN object and returns it.
*/
public class ParserATNFactory implements ATNFactory {
class TailEpsilonRemover extends ATNVisitor {
@Override
public void visitState(ATNState p) {
if ( p.getClass() == ATNState.class && p.getNumberOfTransitions()==1 ) {
ATNState q = p.transition(0).target;
if ( p.transition(0) instanceof RuleTransition ) {
q = ((RuleTransition)p.transition(0)).followState;
}
if ( q.getClass() == ATNState.class ) {
// we have p-x->q for x in {rule, action, pred, token, ...}
// if edge out of q is single epsilon to block end
// we can strip epsilon p-x->q-eps->r
Transition trans = q.transition(0);
if ( q.getNumberOfTransitions()==1 && trans.isEpsilon() &&
!(trans instanceof ActionTransition) ) {
ATNState r = trans.target;
if ( r instanceof BlockEndState ||
r instanceof PlusLoopbackState ||
r instanceof StarLoopbackState )
{
// skip over q
if ( p.transition(0) instanceof RuleTransition ) {
((RuleTransition)p.transition(0)).followState = r;
}
else {
p.transition(0).target = r;
}
atn.removeState(q);
}
}
}
}
}
}
@NotNull
public final Grammar g;
@ -373,7 +338,7 @@ public class ParserATNFactory implements ATNFactory {
epsilon(alt.right, end);
// no back link in ATN so must walk entire alt to see if we can
// strip out the epsilon to 'end' state
TailEpsilonRemover opt = new TailEpsilonRemover();
TailEpsilonRemover opt = new TailEpsilonRemover(atn);
opt.visit(alt.left);
}
Handle h = new Handle(start, end);

81
tool/src/org/antlr/v4/automata/TailEpsilonRemover.java Normal file
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@ -0,0 +1,81 @@
/*
[The "BSD license"]
Copyright (c) 2012 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.
IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
package org.antlr.v4.automata;
import org.antlr.v4.runtime.atn.ATN;
import org.antlr.v4.runtime.atn.ATNState;
import org.antlr.v4.runtime.atn.ActionTransition;
import org.antlr.v4.runtime.atn.BlockEndState;
import org.antlr.v4.runtime.atn.PlusLoopbackState;
import org.antlr.v4.runtime.atn.RuleTransition;
import org.antlr.v4.runtime.atn.StarLoopbackState;
import org.antlr.v4.runtime.atn.Transition;
import org.antlr.v4.runtime.misc.NotNull;
/**
*
* @author Terence Parr
*/
public class TailEpsilonRemover extends ATNVisitor {
@NotNull
private final ATN _atn;
public TailEpsilonRemover(@NotNull ATN atn) {
this._atn = atn;
}
@Override
public void visitState(@NotNull ATNState p) {
if (p.getClass() == ATNState.class && p.getNumberOfTransitions() == 1) {
ATNState q = p.transition(0).target;
if (p.transition(0) instanceof RuleTransition) {
q = ((RuleTransition) p.transition(0)).followState;
}
if (q.getClass() == ATNState.class) {
// we have p-x->q for x in {rule, action, pred, token, ...}
// if edge out of q is single epsilon to block end
// we can strip epsilon p-x->q-eps->r
Transition trans = q.transition(0);
if (q.getNumberOfTransitions() == 1 && trans.isEpsilon() && !(trans instanceof ActionTransition)) {
ATNState r = trans.target;
if (r instanceof BlockEndState || r instanceof PlusLoopbackState || r instanceof StarLoopbackState) {
// skip over q
if (p.transition(0) instanceof RuleTransition) {
((RuleTransition) p.transition(0)).followState = r;
} else {
p.transition(0).target = r;
}
_atn.removeState(q);
}
}
}
}
}
}