CodeException.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.classfile;

import java.io.DataInput;
import java.io.DataOutputStream;
import java.io.IOException;

import org.apache.bcel.Const;
import org.apache.bcel.Constants;
import org.apache.bcel.util.Args;

/**
 * This class represents an entry in the exception table of the <em>Code</em> attribute and is used only there. It
 * contains a range in which a particular exception handler is active.
 *
 * <pre>
 * Code_attribute {
 *   u2 attribute_name_index;
 *   u4 attribute_length;
 *   u2 max_stack;
 *   u2 max_locals;
 *   u4 code_length;
 *   u1 code[code_length];
 *   u2 exception_table_length;
 *   {
 *     u2 start_pc;
 *     u2 end_pc;
 *     u2 handler_pc;
 *     u2 catch_type;
 *   } exception_table[exception_table_length];
 *   u2 attributes_count;
 *   attribute_info attributes[attributes_count];
 * }
 * </pre>
 *
 * @see Code
 */
public final class CodeException implements Cloneable, Node, Constants {

    /**
     * Empty array.
     */
    static final CodeException[] EMPTY_ARRAY = {};

    /** Range in the code the exception handler. */
    private int startPc;

    /** Active. startPc is inclusive, endPc exclusive. */
    private int endPc;

    /**
     * Starting address of exception handler, i.e., an offset from start of code.
     */
    private int handlerPc;

    /*
     * If this is zero the handler catches any exception, otherwise it points to the exception class which is to be caught.
     */
    private int catchType;

    /**
     * Constructs a new instance from another instance.
     *
     * @param c Source for copying.
     */
    public CodeException(final CodeException c) {
        this(c.getStartPC(), c.getEndPC(), c.getHandlerPC(), c.getCatchType());
    }

    /**
     * Constructs a new instance from a DataInput.
     *
     * @param file Input stream
     * @throws IOException if an I/O error occurs.
     */
    CodeException(final DataInput file) throws IOException {
        this(file.readUnsignedShort(), file.readUnsignedShort(), file.readUnsignedShort(), file.readUnsignedShort());
    }

    /**
     * Constructs a new instance.
     *
     * @param startPc Range in the code the exception handler is active, startPc is inclusive while
     * @param endPc is exclusive
     * @param handlerPc Starting address of exception handler, i.e., an offset from start of code.
     * @param catchType If zero the handler catches any exception, otherwise it points to the exception class which is to be
     *        caught.
     */
    public CodeException(final int startPc, final int endPc, final int handlerPc, final int catchType) {
        this.startPc = Args.requireU2(startPc, "startPc");
        this.endPc = Args.requireU2(endPc, "endPc");
        this.handlerPc = Args.requireU2(handlerPc, "handlerPc");
        this.catchType = Args.requireU2(catchType, "catchType");
    }

    /**
     * Called by objects that are traversing the nodes of the tree implicitly defined by the contents of a Java class.
     * I.e., the hierarchy of methods, fields, attributes, etc. spawns a tree of objects.
     *
     * @param v Visitor object
     */
    @Override
    public void accept(final Visitor v) {
        v.visitCodeException(this);
    }

    /**
     * @return deep copy of this object
     */
    public CodeException copy() {
        try {
            return (CodeException) clone();
        } catch (final CloneNotSupportedException e) {
            // TODO should this throw?
        }
        return null;
    }

    /**
     * Dumps code exception to file stream in binary format.
     *
     * @param file Output file stream
     * @throws IOException if an I/O error occurs.
     */
    public void dump(final DataOutputStream file) throws IOException {
        file.writeShort(startPc);
        file.writeShort(endPc);
        file.writeShort(handlerPc);
        file.writeShort(catchType);
    }

    /**
     * @return 0, if the handler catches any exception, otherwise it points to the exception class which is to be caught.
     */
    public int getCatchType() {
        return catchType;
    }

    /**
     * @return Exclusive end index of the region where the handler is active.
     */
    public int getEndPC() {
        return endPc;
    }

    /**
     * @return Starting address of exception handler, relative to the code.
     */
    public int getHandlerPC() {
        return handlerPc;
    }

    /**
     * @return Inclusive start index of the region where the handler is active.
     */
    public int getStartPC() {
        return startPc;
    }

    /**
     * @param catchType the type of exception that is caught
     */
    public void setCatchType(final int catchType) {
        this.catchType = catchType;
    }

    /**
     * @param endPc end of handled block
     */
    public void setEndPC(final int endPc) {
        this.endPc = endPc;
    }

    /**
     * @param handlerPc where the actual code is
     */
    public void setHandlerPC(final int handlerPc) { // TODO unused
        this.handlerPc = handlerPc;
    }

    /**
     * @param startPc start of handled block
     */
    public void setStartPC(final int startPc) { // TODO unused
        this.startPc = startPc;
    }

    /**
     * @return String representation.
     */
    @Override
    public String toString() {
        return "CodeException(startPc = " + startPc + ", endPc = " + endPc + ", handlerPc = " + handlerPc + ", catchType = " + catchType + ")";
    }

    public String toString(final ConstantPool cp) {
        return toString(cp, true);
    }

    /**
     * @param cp constant pool source.
     * @param verbose Output more if true.
     * @return String representation.
     */
    public String toString(final ConstantPool cp, final boolean verbose) {
        String str;
        if (catchType == 0) {
            str = "<Any exception>(0)";
        } else {
            str = Utility.compactClassName(cp.getConstantString(catchType, Const.CONSTANT_Class), false) + (verbose ? "(" + catchType + ")" : "");
        }
        return startPc + "\t" + endPc + "\t" + handlerPc + "\t" + str;
    }
}