001: /***
002: * ASM Guide
003: * Copyright (c) 2007 Eric Bruneton
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: */package ch7.sec2;
030:
031: import static org.objectweb.asm.Opcodes.CHECKCAST;
032:
033: import org.objectweb.asm.Type;
034: import org.objectweb.asm.tree.AbstractInsnNode;
035: import org.objectweb.asm.tree.MethodNode;
036: import org.objectweb.asm.tree.TypeInsnNode;
037: import org.objectweb.asm.tree.analysis.Analyzer;
038: import org.objectweb.asm.tree.analysis.AnalyzerException;
039: import org.objectweb.asm.tree.analysis.BasicValue;
040: import org.objectweb.asm.tree.analysis.Frame;
041: import org.objectweb.asm.tree.analysis.SimpleVerifier;
042:
043: import ch6.sec1.MethodTransformer;
044:
045: /**
046: * ASM Guide example class.
047: *
048: * @author Eric Bruneton
049: */
050: public class RemoveUnusedCastTransformer extends MethodTransformer {
051:
052: String owner;
053:
054: public RemoveUnusedCastTransformer(String owner,
055: MethodTransformer mt) {
056: super (mt);
057: this .owner = owner;
058: }
059:
060: public void transform(MethodNode mn) {
061: Analyzer a = new Analyzer(new SimpleVerifier());
062: try {
063: a.analyze(owner, mn);
064: Frame[] frames = a.getFrames();
065: AbstractInsnNode[] insns = mn.instructions.toArray();
066: for (int i = 0; i < insns.length; ++i) {
067: AbstractInsnNode insn = insns[i];
068: if (insn.getOpcode() == CHECKCAST) {
069: Frame f = frames[i];
070: if (f != null && f.getStackSize() > 0) {
071: Object operand = f
072: .getStack(f.getStackSize() - 1);
073: Class to, from;
074: try {
075: to = getClass(((TypeInsnNode) insn).desc);
076: from = getClass(((BasicValue) operand)
077: .getType());
078: } catch (ClassNotFoundException t) {
079: continue;
080: }
081: if (to.isAssignableFrom(from)) {
082: mn.instructions.remove(insn);
083: }
084: }
085: }
086: }
087: } catch (AnalyzerException ignored) {
088: }
089: super .transform(mn);
090: }
091:
092: private static Class getClass(String desc)
093: throws ClassNotFoundException {
094: return Class.forName(desc.replace('/', '.'));
095: }
096:
097: private static Class getClass(Type t) throws ClassNotFoundException {
098: if (t.getSort() == Type.OBJECT) {
099: return getClass(t.getInternalName());
100: }
101: return getClass(t.getDescriptor());
102: }
103: }
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