ASM: a very small and fast Java bytecode manipulation framework
Copyright (c) 2000-2011 INRIA, France Telecom
All rights reserved.
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modification, are permitted provided that the following conditions
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   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.
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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
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * 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 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. 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/**
 * 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.
 * 
 * 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 {

    public TryCatchBlockSorter(final MethodVisitor mv, final int access,
            final String name, final String desc, final String signature,
            final String[] exceptions) {
        this(Opcodes.ASM4, mv, access, name, desc, signature, exceptions);
    }

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

    @Override
    public void visitEnd() {
        // Compares TryCatchBlockNodes by the length of their "try" block.
        Comparator<TryCatchBlockNode> comp = new Comparator<TryCatchBlockNode>() {

            public int compare(TryCatchBlockNode t1, TryCatchBlockNode t2) {
                int len1 = blockLength(t1);
                int len2 = blockLength(t2);
                return len1 - len2;
            }

            private int blockLength(TryCatchBlockNode block) {
                int startidx = instructions.indexOf(block.start);
                int endidx = instructions.indexOf(block.end);
                return endidx - startidx;
            }
        };
        Collections.sort(tryCatchBlocks, comp);
        if (mv != null) {
            accept(mv);
        }
    }
}