/***
* 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 ch7.sec2;
import static org.objectweb.asm.Opcodes.CHECKCAST;
import org.objectweb.asm.Type;
import org.objectweb.asm.tree.AbstractInsnNode;
import org.objectweb.asm.tree.MethodNode;
import org.objectweb.asm.tree.TypeInsnNode;
import org.objectweb.asm.tree.analysis.Analyzer;
import org.objectweb.asm.tree.analysis.AnalyzerException;
import org.objectweb.asm.tree.analysis.BasicValue;
import org.objectweb.asm.tree.analysis.Frame;
import org.objectweb.asm.tree.analysis.SimpleVerifier;
import ch6.sec1.MethodTransformer;
/**
* ASM Guide example class.
*
* @author Eric Bruneton
*/
public class RemoveUnusedCastTransformer extends MethodTransformer {
String owner;
public RemoveUnusedCastTransformer(String owner, MethodTransformer mt) {
super(mt);
this.owner = owner;
}
public void transform(MethodNode mn) {
Analyzer a = new Analyzer(new SimpleVerifier());
try {
a.analyze(owner, mn);
Frame[] frames = a.getFrames();
AbstractInsnNode[] insns = mn.instructions.toArray();
for (int i = 0; i < insns.length; ++i) {
AbstractInsnNode insn = insns[i];
if (insn.getOpcode() == CHECKCAST) {
Frame f = frames[i];
if (f != null && f.getStackSize() > 0) {
Object operand = f.getStack(f.getStackSize() - 1);
Class to, from;
try {
to = getClass(((TypeInsnNode) insn).desc);
from = getClass(((BasicValue) operand).getType());
} catch (ClassNotFoundException t) {
continue;
}
if (to.isAssignableFrom(from)) {
mn.instructions.remove(insn);
}
}
}
}
} catch (AnalyzerException ignored) {
}
super.transform(mn);
}
private static Class getClass(String desc)
throws ClassNotFoundException {
return Class.forName(desc.replace('/', '.'));
}
private static Class getClass(Type t) throws ClassNotFoundException {
if (t.getSort() == Type.OBJECT) {
return getClass(t.getInternalName());
}
return getClass(t.getDescriptor());
}
}