/***
* ASM Guide
* Copyright (c) 2007 Eric Bruneton
* 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 ch6.sec1;
import static org.objectweb.asm.Opcodes.ALOAD;
import static org.objectweb.asm.Opcodes.GETFIELD;
import static org.objectweb.asm.Opcodes.PUTFIELD;
import java.util.Iterator;
import org.objectweb.asm.tree.AbstractInsnNode;
import org.objectweb.asm.tree.FieldInsnNode;
import org.objectweb.asm.tree.InsnList;
import org.objectweb.asm.tree.LineNumberNode;
import org.objectweb.asm.tree.MethodNode;
import org.objectweb.asm.tree.VarInsnNode;
/**
* ASM Guide example class.
*
* @author Eric Bruneton
*/
public class RemoveGetFieldPutFieldTransformer2 extends
MethodTransformer {
public RemoveGetFieldPutFieldTransformer2(MethodTransformer mt) {
super(mt);
}
public void transform(MethodNode mn) {
InsnList insns = mn.instructions;
Iterator i = insns.iterator();
while (i.hasNext()) {
AbstractInsnNode i1 = (AbstractInsnNode) i.next();
if (isALOAD0(i1)) {
AbstractInsnNode i2 = getNext(i);
if (i2 != null && isALOAD0(i2)) {
AbstractInsnNode i3 = getNext(i);
while (i3 != null && isALOAD0(i3)) {
i1 = i2;
i2 = i3;
i3 = getNext(i);
}
if (i3 != null && i3.getOpcode() == GETFIELD) {
AbstractInsnNode i4 = getNext(i);
if (i4 != null && i4.getOpcode() == PUTFIELD) {
if (sameField(i3, i4)) {
insns.remove(i1);
insns.remove(i2);
insns.remove(i3);
insns.remove(i4);
}
}
}
}
}
}
super.transform(mn);
}
private static AbstractInsnNode getNext(Iterator i) {
while (i.hasNext()) {
AbstractInsnNode in = (AbstractInsnNode) i.next();
if (!(in instanceof LineNumberNode)) {
return in;
}
}
return null;
}
private static boolean isALOAD0(AbstractInsnNode i) {
return i.getOpcode() == ALOAD && ((VarInsnNode) i).var == 0;
}
private static boolean sameField(AbstractInsnNode i,
AbstractInsnNode j) {
return ((FieldInsnNode) i).name.equals(((FieldInsnNode) j).name);
}
}