001/***
002 * ASM: a very small and fast Java bytecode manipulation framework
003 * Copyright (c) 2000-2011 INRIA, France Telecom
004 * All rights reserved.
005 *
006 * Redistribution and use in source and binary forms, with or without
007 * modification, are permitted provided that the following conditions
008 * are met:
009 * 1. Redistributions of source code must retain the above copyright
010 *    notice, this list of conditions and the following disclaimer.
011 * 2. Redistributions in binary form must reproduce the above copyright
012 *    notice, this list of conditions and the following disclaimer in the
013 *    documentation and/or other materials provided with the distribution.
014 * 3. Neither the name of the copyright holders nor the names of its
015 *    contributors may be used to endorse or promote products derived from
016 *    this software without specific prior written permission.
017 *
018 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
019 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
020 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
021 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
022 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
023 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
024 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
025 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
026 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
027 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
028 * THE POSSIBILITY OF SUCH DAMAGE.
029 */
030
031package io.ebean.enhance.asm.commons;
032
033import io.ebean.enhance.asm.MethodVisitor;
034import io.ebean.enhance.asm.Opcodes;
035import io.ebean.enhance.asm.tree.MethodNode;
036import io.ebean.enhance.asm.tree.TryCatchBlockNode;
037
038import java.util.Collections;
039import java.util.Comparator;
040
041/**
042 * A {@link MethodVisitor} adapter to sort the exception handlers. The handlers
043 * are sorted in a method innermost-to-outermost. This allows the programmer to
044 * add handlers without worrying about ordering them correctly with respect to
045 * existing, in-code handlers.
046 * 
047 * Behavior is only defined for properly-nested handlers. If any "try" blocks
048 * overlap (something that isn't possible in Java code) then this may not do
049 * what you want. In fact, this adapter just sorts by the length of the "try"
050 * block, taking advantage of the fact that a given try block must be larger
051 * than any block it contains).
052 * 
053 * @author Adrian Sampson
054 */
055public class TryCatchBlockSorter extends MethodNode {
056
057    public TryCatchBlockSorter(final MethodVisitor mv, final int access,
058                               final String name, final String desc, final String signature,
059                               final String[] exceptions) {
060        this(Opcodes.ASM6, mv, access, name, desc, signature, exceptions);
061    }
062
063    protected TryCatchBlockSorter(final int api, final MethodVisitor mv,
064            final int access, final String name, final String desc,
065            final String signature, final String[] exceptions) {
066        super(api, access, name, desc, signature, exceptions);
067        this.mv = mv;
068    }
069
070    @Override
071    public void visitEnd() {
072        // Compares TryCatchBlockNodes by the length of their "try" block.
073        Comparator<TryCatchBlockNode> comp = new Comparator<TryCatchBlockNode>() {
074
075            public int compare(TryCatchBlockNode t1, TryCatchBlockNode t2) {
076                int len1 = blockLength(t1);
077                int len2 = blockLength(t2);
078                return len1 - len2;
079            }
080
081            private int blockLength(TryCatchBlockNode block) {
082                int startidx = instructions.indexOf(block.start);
083                int endidx = instructions.indexOf(block.end);
084                return endidx - startidx;
085            }
086        };
087        Collections.sort(tryCatchBlocks, comp);
088        // Updates the 'target' of each try catch block annotation.
089        for (int i = 0; i < tryCatchBlocks.size(); ++i) {
090            tryCatchBlocks.get(i).updateIndex(i);
091        }
092        if (mv != null) {
093            accept(mv);
094        }
095    }
096}