/*
* FindBugs - Find Bugs in Java programs
* Copyright (C) 2006-2007 University of Maryland
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
package edu.umd.cs.findbugs.ba.npe;
import edu.umd.cs.findbugs.ba.DataflowAnalysisException;
/**
* A dataflow value that indicates what kind of return path is possible at the
* current program location. Either:
* <ul>
* <li>It is possible to return normally</li>
* <li>It is not possible to return normally (i.e., an exception is guaranteed
* to be thrown)</li>
* </ul>
*
* @author David Hovemeyer
*/
public class ReturnPathType {
private static final int CAN_RETURN_NORMALLY = 0;
private static final int CANNOT_RETURN_NORMALLY = 1;
private static final int TOP = 2;
private int type;
/**
* Constructor. Creates a top dataflow fact.
*/
public ReturnPathType() {
type = TOP;
}
/**
* @return true if the method can return normally at this location, false
* otherwise
*/
public boolean canReturnNormally() throws DataflowAnalysisException {
if (!isValid()) {
throw new DataflowAnalysisException("Checking invalid ReturnPathType");
}
return type == CAN_RETURN_NORMALLY;
}
/**
* Make this dataflow fact an exact copy of the other one.
*
* @param other
* another dataflow fact
*/
public void copyFrom(ReturnPathType other) {
this.type = other.type;
}
/**
* Set the dataflow fact to top.
*/
public void setTop() {
type = TOP;
}
/**
* @return true if the dataflow fact is top, false otherwise
*/
public boolean isTop() {
return type == TOP;
}
/**
* Set whether or not it is possible to return normally.
*
* @param canReturnNormally
* true if the method can return normally at this location, false
* otherwise
*/
public void setCanReturnNormally(boolean canReturnNormally) {
type = canReturnNormally ? CAN_RETURN_NORMALLY : CANNOT_RETURN_NORMALLY;
}
/**
* Merge this fact with given fact.
*
* @param fact
* another dataflow fact
*/
public void mergeWith(ReturnPathType fact) {
if (fact.isTop()) {
// other fact is top: no change to this one
return;
} else if (this.isTop()) {
// this fact is top: copy other fact
this.copyFrom(fact);
} else {
// neither fact is top: as long as one of the two
// facts represents a (possible) normal return, then the result
// is a possible normal return
if (fact.type == CAN_RETURN_NORMALLY) {
this.type = CAN_RETURN_NORMALLY;
}
}
}
/**
* Determine whether this dataflow fact is identical to another one.
*
* @param other
* another dataflow fact
* @return true if the two dataflow facts are identical, false if they are
* different
*/
boolean sameAs(ReturnPathType other) {
return this.type == other.type;
}
/**
* @return true if this is a valid dataflow fact (not top or bottom), false
* if not a valid dataflow fact
*/
public boolean isValid() {
return type != TOP;
}
/*
* (non-Javadoc)
*
* @see java.lang.Object#toString()
*/
@Override
public String toString() {
switch (type) {
case TOP:
return "[TOP]";
case CAN_RETURN_NORMALLY:
return "-";
case CANNOT_RETURN_NORMALLY:
return "X";
default:
throw new IllegalStateException();
}
}
}