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 ch6.sec1;
030:
031: import static org.objectweb.asm.Opcodes.ALOAD;
032: import static org.objectweb.asm.Opcodes.GETFIELD;
033: import static org.objectweb.asm.Opcodes.PUTFIELD;
034:
035: import java.util.Iterator;
036:
037: import org.objectweb.asm.tree.AbstractInsnNode;
038: import org.objectweb.asm.tree.FieldInsnNode;
039: import org.objectweb.asm.tree.InsnList;
040: import org.objectweb.asm.tree.LineNumberNode;
041: import org.objectweb.asm.tree.MethodNode;
042: import org.objectweb.asm.tree.VarInsnNode;
043:
044: /**
045: * ASM Guide example class.
046: *
047: * @author Eric Bruneton
048: */
049: public class RemoveGetFieldPutFieldTransformer2 extends
050: MethodTransformer {
051:
052: public RemoveGetFieldPutFieldTransformer2(MethodTransformer mt) {
053: super (mt);
054: }
055:
056: public void transform(MethodNode mn) {
057: InsnList insns = mn.instructions;
058: Iterator i = insns.iterator();
059: while (i.hasNext()) {
060: AbstractInsnNode i1 = (AbstractInsnNode) i.next();
061: if (isALOAD0(i1)) {
062: AbstractInsnNode i2 = getNext(i);
063: if (i2 != null && isALOAD0(i2)) {
064: AbstractInsnNode i3 = getNext(i);
065: while (i3 != null && isALOAD0(i3)) {
066: i1 = i2;
067: i2 = i3;
068: i3 = getNext(i);
069: }
070: if (i3 != null && i3.getOpcode() == GETFIELD) {
071: AbstractInsnNode i4 = getNext(i);
072: if (i4 != null && i4.getOpcode() == PUTFIELD) {
073: if (sameField(i3, i4)) {
074: insns.remove(i1);
075: insns.remove(i2);
076: insns.remove(i3);
077: insns.remove(i4);
078: }
079: }
080: }
081: }
082: }
083: }
084: super .transform(mn);
085: }
086:
087: private static AbstractInsnNode getNext(Iterator i) {
088: while (i.hasNext()) {
089: AbstractInsnNode in = (AbstractInsnNode) i.next();
090: if (!(in instanceof LineNumberNode)) {
091: return in;
092: }
093: }
094: return null;
095: }
096:
097: private static boolean isALOAD0(AbstractInsnNode i) {
098: return i.getOpcode() == ALOAD && ((VarInsnNode) i).var == 0;
099: }
100:
101: private static boolean sameField(AbstractInsnNode i,
102: AbstractInsnNode j) {
103: return ((FieldInsnNode) i).name
104: .equals(((FieldInsnNode) j).name);
105: }
106: }
|