org.objectweb.asm.commons.TryCatchBlockSorter.java Source code

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Here is the source code for org.objectweb.asm.commons.TryCatchBlockSorter.java

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// ASM: a very small and fast Java bytecode manipulation framework
// Copyright (c) 2000-2011 INRIA, France Telecom
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions
// are met:
// 1. Redistributions of source code must retain the above copyright
//    notice, this list of conditions and the following disclaimer.
// 2. Redistributions in binary form must reproduce the above copyright
//    notice, this list of conditions and the following disclaimer in the
//    documentation and/or other materials provided with the distribution.
// 3. Neither the name of the copyright holders nor the names of its
//    contributors may be used to endorse or promote products derived from
//    this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
// THE POSSIBILITY OF SUCH DAMAGE.

package org.objectweb.asm.commons;

import java.util.Collections;
import java.util.Comparator;
import org.objectweb.asm.MethodVisitor;
import org.objectweb.asm.Opcodes;
import org.objectweb.asm.tree.MethodNode;
import org.objectweb.asm.tree.TryCatchBlockNode;

/**
 * A {@link MethodVisitor} adapter to sort the exception handlers. The handlers are sorted in a
 * method innermost-to-outermost. This allows the programmer to add handlers without worrying about
 * ordering them correctly with respect to existing, in-code handlers.
 *
 * <p>Behavior is only defined for properly-nested handlers. If any "try" blocks overlap (something
 * that isn't possible in Java code) then this may not do what you want. In fact, this adapter just
 * sorts by the length of the "try" block, taking advantage of the fact that a given try block must
 * be larger than any block it contains).
 *
 * @author Adrian Sampson
 */
public class TryCatchBlockSorter extends MethodNode {

    /**
     * Constructs a new {@link TryCatchBlockSorter}.
     *
     * @param methodVisitor the method visitor to which this visitor must delegate method calls. May
     *     be {@literal null}.
     * @param access the method's access flags (see {@link Opcodes}). This parameter also indicates if
     *     the method is synthetic and/or deprecated.
     * @param name the method's name.
     * @param descriptor the method's descriptor (see {@link org.objectweb.asm.Type}).
     * @param signature the method's signature. May be {@literal null} if the method parameters,
     *     return type and exceptions do not use generic types.
     * @param exceptions the internal names of the method's exception classes (see {@link
     *     org.objectweb.asm.Type#getInternalName()}). May be {@literal null}.
     */
    public TryCatchBlockSorter(final MethodVisitor methodVisitor, final int access, final String name,
            final String descriptor, final String signature, final String[] exceptions) {
        this(/* latest api = */ Opcodes.ASM7, methodVisitor, access, name, descriptor, signature, exceptions);
        if (getClass() != TryCatchBlockSorter.class) {
            throw new IllegalStateException();
        }
    }

    protected TryCatchBlockSorter(final int api, final MethodVisitor methodVisitor, final int access,
            final String name, final String descriptor, final String signature, final String[] exceptions) {
        super(api, access, name, descriptor, signature, exceptions);
        this.mv = methodVisitor;
    }

    @Override
    public void visitEnd() {
        // Sort the TryCatchBlockNode elements by the length of their "try" block.
        Collections.sort(tryCatchBlocks, new Comparator<TryCatchBlockNode>() {

            @Override
            public int compare(final TryCatchBlockNode tryCatchBlockNode1,
                    final TryCatchBlockNode tryCatchBlockNode2) {
                return blockLength(tryCatchBlockNode1) - blockLength(tryCatchBlockNode2);
            }

            private int blockLength(final TryCatchBlockNode tryCatchBlockNode) {
                int startIndex = instructions.indexOf(tryCatchBlockNode.start);
                int endIndex = instructions.indexOf(tryCatchBlockNode.end);
                return endIndex - startIndex;
            }
        });
        // Update the 'target' of each try catch block annotation.
        for (int i = 0; i < tryCatchBlocks.size(); ++i) {
            tryCatchBlocks.get(i).updateIndex(i);
        }
        if (mv != null) {
            accept(mv);
        }
    }
}