bcel/generic/CodeExceptionGen.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 *
 */
package org.apache.bcel.generic;

import org.apache.bcel.classfile.CodeException;

/**
 * This class represents an exception handler, i.e., specifies the  region where
 * a handler is active and an instruction where the actual handling is done.
 * pool as parameters. Opposed to the JVM specification the end of the handled
 * region is set to be inclusive, i.e. all instructions between start and end
 * are protected including the start and end instructions (handles) themselves.
 * The end of the region is automatically mapped to be exclusive when calling
 * getCodeException(), i.e., there is no difference semantically.
 *
 * @version $Id$
 * @see     MethodGen
 * @see     CodeException
 * @see     InstructionHandle
 */
public final class CodeExceptionGen implements InstructionTargeter, Cloneable {

    private InstructionHandle start_pc;
    private InstructionHandle end_pc;
    private InstructionHandle handler_pc;
    private ObjectType catch_type;


    /**
     * Add an exception handler, i.e., specify region where a handler is active and an
     * instruction where the actual handling is done.
     *
     * @param start_pc Start of handled region (inclusive)
     * @param end_pc End of handled region (inclusive)
     * @param handler_pc Where handling is done
     * @param catch_type which exception is handled, null for ANY
     */
    public CodeExceptionGen(final InstructionHandle start_pc, final InstructionHandle end_pc,
            final InstructionHandle handler_pc, final ObjectType catch_type) {
        setStartPC(start_pc);
        setEndPC(end_pc);
        setHandlerPC(handler_pc);
        this.catch_type = catch_type;
    }


    /**
     * Get CodeException object.<BR>
     *
     * This relies on that the instruction list has already been dumped
     * to byte code or or that the `setPositions' methods has been
     * called for the instruction list.
     *
     * @param cp constant pool
     */
    public CodeException getCodeException( final ConstantPoolGen cp ) {
        return new CodeException(start_pc.getPosition(), end_pc.getPosition()
                + end_pc.getInstruction().getLength(), handler_pc.getPosition(),
                (catch_type == null) ? 0 : cp.addClass(catch_type));
    }


    /* Set start of handler
     * @param start_pc Start of handled region (inclusive)
     */
    public void setStartPC( final InstructionHandle start_pc ) { // TODO could be package-protected?
        BranchInstruction.notifyTarget(this.start_pc, start_pc, this);
        this.start_pc = start_pc;
    }


    /* Set end of handler
     * @param end_pc End of handled region (inclusive)
     */
    public void setEndPC( final InstructionHandle end_pc ) { // TODO could be package-protected?
        BranchInstruction.notifyTarget(this.end_pc, end_pc, this);
        this.end_pc = end_pc;
    }


    /* Set handler code
     * @param handler_pc Start of handler
     */
    public void setHandlerPC( final InstructionHandle handler_pc ) { // TODO could be package-protected?
        BranchInstruction.notifyTarget(this.handler_pc, handler_pc, this);
        this.handler_pc = handler_pc;
    }


    /**
     * @param old_ih old target, either start or end
     * @param new_ih new target
     */
    @Override
    public void updateTarget( final InstructionHandle old_ih, final InstructionHandle new_ih ) {
        boolean targeted = false;
        if (start_pc == old_ih) {
            targeted = true;
            setStartPC(new_ih);
        }
        if (end_pc == old_ih) {
            targeted = true;
            setEndPC(new_ih);
        }
        if (handler_pc == old_ih) {
            targeted = true;
            setHandlerPC(new_ih);
        }
        if (!targeted) {
            throw new ClassGenException("Not targeting " + old_ih + ", but {" + start_pc + ", "
                    + end_pc + ", " + handler_pc + "}");
        }
    }


    /**
     * @return true, if ih is target of this handler
     */
    @Override
    public boolean containsTarget( final InstructionHandle ih ) {
        return (start_pc == ih) || (end_pc == ih) || (handler_pc == ih);
    }


    /** Sets the type of the Exception to catch. Set 'null' for ANY. */
    public void setCatchType( final ObjectType catch_type ) {
        this.catch_type = catch_type;
    }


    /** Gets the type of the Exception to catch, 'null' for ANY. */
    public ObjectType getCatchType() {
        return catch_type;
    }


    /** @return start of handled region (inclusive)
     */
    public InstructionHandle getStartPC() {
        return start_pc;
    }


    /** @return end of handled region (inclusive)
     */
    public InstructionHandle getEndPC() {
        return end_pc;
    }


    /** @return start of handler
     */
    public InstructionHandle getHandlerPC() {
        return handler_pc;
    }


    @Override
    public String toString() {
        return "CodeExceptionGen(" + start_pc + ", " + end_pc + ", " + handler_pc + ")";
    }


    @Override
    public Object clone() {
        try {
            return super.clone();
        } catch (final CloneNotSupportedException e) {
            throw new Error("Clone Not Supported"); // never happens
        }
    }
}