ResourceTracker.java

/*
 * Bytecode Analysis Framework
 * Copyright (C) 2003-2005 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;

import org.apache.bcel.generic.ConstantPoolGen;
import org.apache.bcel.generic.InstructionHandle;

/**
 * A ResourceTracker is used with ResourceValueAnalysis to determine where in a
 * method a certain kind of resource is created, and to model the effect of
 * instructions on the state of that resource.
 * 
 * @author David Hovemeyer
 * @see ResourceValueAnalysis
 */
public interface ResourceTracker<Resource> {
    /**
     * Determine if the given instruction is the site where a resource is
     * created.
     * 
     * @param basicBlock
     *            basic block containing the instruction
     * @param handle
     *            the instruction
     * @param cpg
     *            the ConstantPoolGen for the method
     * @return an opaque Resource object if it is a creation site, or null if it
     *         is not a creation site
     */
    public Resource isResourceCreation(BasicBlock basicBlock, InstructionHandle handle, ConstantPoolGen cpg)
            throws DataflowAnalysisException;

    /**
     * Determine if the given instruction is the site where a resource is
     * closed.
     * 
     * @param basicBlock
     *            basic block containing the instruction
     * @param handle
     *            the instruction
     * @param cpg
     *            the ConstantPoolGen for the method
     * @param resource
     *            the resource, as returned by isResourceCreation()
     * @param frame
     *            the ResourceValueFrame representing the stack prior to
     *            executing the instruction
     * @return true if the resource is closed here, false otherwise
     */
    public boolean isResourceClose(BasicBlock basicBlock, InstructionHandle handle, ConstantPoolGen cpg, Resource resource,
            ResourceValueFrame frame) throws DataflowAnalysisException;

    /**
     * Determine if the given instruction is the site where a resource is
     * closed.
     * 
     * @param basicBlock
     *            basic block containing the instruction
     * @param handle
     *            the instruction
     * @param cpg
     *            the ConstantPoolGen for the method
     * @param resource
     *            the resource, as returned by isResourceCreation()
     * @param frame
     *            the ResourceValueFrame representing the stack prior to
     *            executing the instruction
     * @return true if the resource is closed here, false otherwise
     */
    public boolean mightCloseResource(BasicBlock basicBlock, InstructionHandle handle, ConstantPoolGen cpg)
            throws DataflowAnalysisException;

    /**
     * Create a ResourceValueFrameModelingVisitor to model the effect of
     * instructions on the state of the resource.
     * 
     * @param resource
     *            the resource we are tracking
     * @param cpg
     *            the ConstantPoolGen of the method
     * @return a ResourceValueFrameModelingVisitor
     */
    public ResourceValueFrameModelingVisitor createVisitor(Resource resource, ConstantPoolGen cpg);

    /**
     * Determine whether the analysis should ignore exception edges on which
     * only implicit exceptions are propagated. This allows different resource
     * types to be tracked with varying precision. For example, we might want to
     * ignore implicit exceptions for stream objects, but treat them as
     * significant for database resources.
     * 
     * @param resource
     *            the resource being tracked
     * @return true if implicit exceptions are significant, false if they should
     *         be ignore
     */
    public boolean ignoreImplicitExceptions(Resource resource);

    /**
     * Determine whether the analysis should ignore given exception edge. This
     * allows the analysis to customize which kinds of exceptions are
     * significant.
     * 
     * @param edge
     *            the exception edge
     * @param resource
     *            the resource
     * @param cpg
     *            the ConstantPoolGen
     * @return true if exception edge should be ignored, false if it should be
     *         considered
     */
    public boolean ignoreExceptionEdge(Edge edge, Resource resource, ConstantPoolGen cpg);

    /**
     * Return if the given parameter slot contains the resource instance upon
     * entry to the method. This is for resources passed as parameters.
     * 
     * @param resource
     *            the resource
     * @param slot
     *            the local variable slot
     * @return true if the slot contains the resource instance, false otherwise
     */
    public boolean isParamInstance(Resource resource, int slot);
}

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