streamframemodelingvisitor.java

一个查找java程序里bug的程序的源代码,该程序本身也是java写的,对提高java编程水平很有用

/*
 * FindBugs - Find bugs in Java programs
 * Copyright (C) 2003,2004 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.detect;

import edu.umd.cs.findbugs.ba.*;
import org.apache.bcel.Constants;
import org.apache.bcel.generic.ConstantPoolGen;
import org.apache.bcel.generic.Instruction;
import org.apache.bcel.generic.InstructionHandle;
import org.apache.bcel.generic.InvokeInstruction;

/**
 * A visitor to model the effect of instructions on the status
 * of the resource (in this case, Streams).
 */
public class StreamFrameModelingVisitor extends ResourceValueFrameModelingVisitor {
	private StreamResourceTracker resourceTracker;
	private Stream stream;
	private Location location;

	public StreamFrameModelingVisitor(ConstantPoolGen cpg, StreamResourceTracker resourceTracker,
	                                  Stream stream) {
		super(cpg);
		this.resourceTracker = resourceTracker;
		this.stream = stream;
	}

	public void transferInstruction(InstructionHandle handle, BasicBlock basicBlock) {
		// Record what Location we are analyzing
		this.location = new Location(handle, basicBlock);

		final Instruction ins = handle.getInstruction();
		final ConstantPoolGen cpg = getCPG();
		final ResourceValueFrame frame = getFrame();

		int status = -1;
		boolean created = false;

		// Is a resource created, opened, or closed by this instruction?
		Location creationPoint = stream.getLocation();
		if (handle == creationPoint.getHandle() && basicBlock == creationPoint.getBasicBlock()) {
			// Resource creation
			if (stream.isOpenOnCreation()) {
				status = ResourceValueFrame.OPEN;
				stream.setOpenLocation(location);
				resourceTracker.addStreamOpenLocation(location, stream);
			} else {
				status = ResourceValueFrame.CREATED;
			}
			created = true;
		} else if (resourceTracker.isResourceOpen(basicBlock, handle, cpg, stream, frame)) {
			// Resource opened
			status = ResourceValueFrame.OPEN;
			stream.setOpenLocation(location);
			resourceTracker.addStreamOpenLocation(location, stream);
		} else if (resourceTracker.isResourceClose(basicBlock, handle, cpg, stream, frame)) {
			// Resource closed
			status = ResourceValueFrame.CLOSED;
		}

		// Model use of instance values in frame slots
		ins.accept(this);

		// If needed, update frame status
		if (status != -1) {
			frame.setStatus(status);
			if (created)
				frame.setValue(frame.getNumSlots() - 1, ResourceValue.instance());
		}

	}

	protected boolean instanceEscapes(InvokeInstruction inv, int instanceArgNum) {
		//ConstantPoolGen cpg = getCPG();
		// String className = inv.getClassName(cpg);

		//System.out.print("[Passed as arg="+instanceArgNum+" at " + inv + "]");

		boolean escapes = (inv.getOpcode() == Constants.INVOKESTATIC || instanceArgNum != 0);
		//if (escapes) System.out.print("[Escape at " + inv + " argNum=" + instanceArgNum + "]");

		if (FindOpenStream.DEBUG && escapes) System.out.println("ESCAPE at " + location);

		// Record the fact that this might be a stream escape
		if (stream.getOpenLocation() != null)
			resourceTracker.addStreamEscape(stream, location);

		return escapes;
	}
}

// vim:ts=3