/*******************************************************************************
* Copyright (c) 2002, 2005 Object Factory Inc.
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* which accompanies this distribution, and is available at
* http://www.eclipse.org/legal/epl-v10.html
*
* Contributors:
* Object Factory Inc. - Initial implementation
*******************************************************************************/
package org.eclipse.ant.internal.ui.dtd.schema;
import org.eclipse.ant.internal.ui.dtd.IAtom;
import org.eclipse.ant.internal.ui.dtd.util.Factory;
import org.eclipse.ant.internal.ui.dtd.util.FactoryObject;
/**
* Non-deterministic finite state machine node.<p>
*
* Following Aho & Ullman, nfm nodes contain two
* transition links. The graph is constructed so
* that no node requires more than two links.
* There are exactly these kinds of nodes:
* <pre>
* Symbol Next1 Next2 Meaning
* "a" fwd null Regexp "a"
* null null null Accepting node
* null fwd1 fwd2 Start node of ? and * regexp
* fwd2 points to stop node
* null fwd bkw Internal node of + and * regexp
* fwd points to stop node
* bkw points, e.g., in "a*" to start node of "a"
* null fwd1 fwd2 Start node of | regexp, e.g., "a|b",
* fwd nodes point to start nodes of "a" and "b".
* null fwd null Internal node of |.
* fwd points to stop node.
* </pre>
* See Nfm for pictures of how nodes are used.
* @author Bob Foster
*/
public class NfmNode implements FactoryObject {
public IAtom symbol;
public NfmNode next1;
public NfmNode next2;
public Dfm dfm;
public int mark;
private NfmNode() {
}
public static NfmNode nfmNode(IAtom symbol, NfmNode next) {
NfmNode nfm = getFree();
nfm.symbol = symbol;
nfm.next1 = next;
return nfm;
}
public static NfmNode nfmNode(NfmNode next) {
NfmNode nfm = getFree();
nfm.next1 = next;
return nfm;
}
public static NfmNode nfmNode() {
return getFree();
}
/**
* Free all NfmNodes in use.
*/
public static void freeAll() {
while (fUsed != null) {
FactoryObject nfm = fUsed;
fUsed = nfm.next();
setFree((NfmNode)nfm);
}
}
// Below here is factory stuff
/* (non-Javadoc)
* @see org.eclipse.ant.internal.ui.dtd.util.FactoryObject#next()
*/
public FactoryObject next() {
return next;
}
/* (non-Javadoc)
* @see org.eclipse.ant.internal.ui.dtd.util.FactoryObject#next(org.eclipse.ant.internal.ui.dtd.util.FactoryObject)
*/
public void next(FactoryObject obj) {
next = (NfmNode) obj;
}
private NfmNode next;
private static Factory fFactory = new Factory();
private static FactoryObject fUsed = null;
private static NfmNode getFree() {
NfmNode nfm = (NfmNode) fFactory.getFree();
if (nfm == null)
nfm = new NfmNode();
nfm.next(fUsed);
fUsed = nfm;
return nfm;
}
private static void setFree(NfmNode nfm) {
nfm.symbol = null;
nfm.next1 = nfm.next2 = null;
nfm.dfm = null;
nfm.mark = 0;
fFactory.setFree(nfm);
}
}
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