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/*
* Javassist, a Java-bytecode translator toolkit.
* Copyright (C) 1999- Shigeru Chiba. All Rights Reserved.
*
* The contents of this file are subject to the Mozilla Public License Version
* 1.1 (the "License"); you may not use this file except in compliance with
* the License. Alternatively, the contents of this file may be used under
* the terms of the GNU Lesser General Public License Version 2.1 or later,
* or the Apache License Version 2.0.
*
* Software distributed under the License is distributed on an "AS IS" basis,
* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
* for the specific language governing rights and limitations under the
* License.
*/
package scouter.javassist.convert;
import scouter.javassist.CannotCompileException;
import scouter.javassist.CtClass;
import scouter.javassist.NotFoundException;
import scouter.javassist.CodeConverter.ArrayAccessReplacementMethodNames;
import scouter.javassist.bytecode.BadBytecode;
import scouter.javassist.bytecode.CodeIterator;
import scouter.javassist.bytecode.ConstPool;
import scouter.javassist.bytecode.Descriptor;
import scouter.javassist.bytecode.MethodInfo;
import scouter.javassist.bytecode.analysis.Analyzer;
import scouter.javassist.bytecode.analysis.Frame;
import scouter.javassist.convert.Transformer;
/**
* A transformer which replaces array access with static method invocations.
*
* @author Kabir Khan
* @author Jason T. Greene
* @version $Revision: 1.8 $
*/
public final class TransformAccessArrayField extends Transformer {
private final String methodClassname;
private final ArrayAccessReplacementMethodNames names;
private Frame[] frames;
private int offset;
public TransformAccessArrayField(Transformer next, String methodClassname,
ArrayAccessReplacementMethodNames names) throws NotFoundException {
super(next);
this.methodClassname = methodClassname;
this.names = names;
}
public void initialize(ConstPool cp, CtClass clazz, MethodInfo minfo) throws CannotCompileException {
/*
* This transformer must be isolated from other transformers, since some
* of them affect the local variable and stack maximums without updating
* the code attribute to reflect the changes. This screws up the
* data-flow analyzer, since it relies on consistent code state. Even
* if the attribute values were updated correctly, we would have to
* detect it, and redo analysis, which is not cheap. Instead, we are
* better off doing all changes in initialize() before everyone else has
* a chance to muck things up.
*/
CodeIterator iterator = minfo.getCodeAttribute().iterator();
while (iterator.hasNext()) {
try {
int pos = iterator.next();
int c = iterator.byteAt(pos);
if (c == AALOAD)
initFrames(clazz, minfo);
if (c == AALOAD || c == BALOAD || c == CALOAD || c == DALOAD
|| c == FALOAD || c == IALOAD || c == LALOAD
|| c == SALOAD) {
pos = replace(cp, iterator, pos, c, getLoadReplacementSignature(c));
} else if (c == AASTORE || c == BASTORE || c == CASTORE
|| c == DASTORE || c == FASTORE || c == IASTORE
|| c == LASTORE || c == SASTORE) {
pos = replace(cp, iterator, pos, c, getStoreReplacementSignature(c));
}
} catch (Exception e) {
throw new CannotCompileException(e);
}
}
}
public void clean() {
frames = null;
offset = -1;
}
public int transform(CtClass tclazz, int pos, CodeIterator iterator,
ConstPool cp) throws BadBytecode {
// Do nothing, see above comment
return pos;
}
private Frame getFrame(int pos) throws BadBytecode {
return frames[pos - offset]; // Adjust pos
}
private void initFrames(CtClass clazz, MethodInfo minfo) throws BadBytecode {
if (frames == null) {
frames = ((new Analyzer())).analyze(clazz, minfo);
offset = 0; // start tracking changes
}
}
private int updatePos(int pos, int increment) {
if (offset > -1)
offset += increment;
return pos + increment;
}
private String getTopType(int pos) throws BadBytecode {
Frame frame = getFrame(pos);
if (frame == null)
return null;
CtClass clazz = frame.peek().getCtClass();
return clazz != null ? Descriptor.toJvmName(clazz) : null;
}
private int replace(ConstPool cp, CodeIterator iterator, int pos,
int opcode, String signature) throws BadBytecode {
String castType = null;
String methodName = getMethodName(opcode);
if (methodName != null) {
// See if the object must be cast
if (opcode == AALOAD) {
castType = getTopType(iterator.lookAhead());
// Do not replace an AALOAD instruction that we do not have a type for
// This happens when the state is guaranteed to be null (Type.UNINIT)
// So we don't really care about this case.
if (castType == null)
return pos;
if ("java/lang/Object".equals(castType))
castType = null;
}
// The gap may include extra padding
// Write a nop in case the padding pushes the instruction forward
iterator.writeByte(NOP, pos);
CodeIterator.Gap gap
= iterator.insertGapAt(pos, castType != null ? 5 : 2, false);
pos = gap.position;
int mi = cp.addClassInfo(methodClassname);
int methodref = cp.addMethodrefInfo(mi, methodName, signature);
iterator.writeByte(INVOKESTATIC, pos);
iterator.write16bit(methodref, pos + 1);
if (castType != null) {
int index = cp.addClassInfo(castType);
iterator.writeByte(CHECKCAST, pos + 3);
iterator.write16bit(index, pos + 4);
}
pos = updatePos(pos, gap.length);
}
return pos;
}
private String getMethodName(int opcode) {
String methodName = null;
switch (opcode) {
case AALOAD:
methodName = names.objectRead();
break;
case BALOAD:
methodName = names.byteOrBooleanRead();
break;
case CALOAD:
methodName = names.charRead();
break;
case DALOAD:
methodName = names.doubleRead();
break;
case FALOAD:
methodName = names.floatRead();
break;
case IALOAD:
methodName = names.intRead();
break;
case SALOAD:
methodName = names.shortRead();
break;
case LALOAD:
methodName = names.longRead();
break;
case AASTORE:
methodName = names.objectWrite();
break;
case BASTORE:
methodName = names.byteOrBooleanWrite();
break;
case CASTORE:
methodName = names.charWrite();
break;
case DASTORE:
methodName = names.doubleWrite();
break;
case FASTORE:
methodName = names.floatWrite();
break;
case IASTORE:
methodName = names.intWrite();
break;
case SASTORE:
methodName = names.shortWrite();
break;
case LASTORE:
methodName = names.longWrite();
break;
}
if (methodName.equals(""))
methodName = null;
return methodName;
}
private String getLoadReplacementSignature(int opcode) throws BadBytecode {
switch (opcode) {
case AALOAD:
return "(Ljava/lang/Object;I)Ljava/lang/Object;";
case BALOAD:
return "(Ljava/lang/Object;I)B";
case CALOAD:
return "(Ljava/lang/Object;I)C";
case DALOAD:
return "(Ljava/lang/Object;I)D";
case FALOAD:
return "(Ljava/lang/Object;I)F";
case IALOAD:
return "(Ljava/lang/Object;I)I";
case SALOAD:
return "(Ljava/lang/Object;I)S";
case LALOAD:
return "(Ljava/lang/Object;I)J";
}
throw new BadBytecode(opcode);
}
private String getStoreReplacementSignature(int opcode) throws BadBytecode {
switch (opcode) {
case AASTORE:
return "(Ljava/lang/Object;ILjava/lang/Object;)V";
case BASTORE:
return "(Ljava/lang/Object;IB)V";
case CASTORE:
return "(Ljava/lang/Object;IC)V";
case DASTORE:
return "(Ljava/lang/Object;ID)V";
case FASTORE:
return "(Ljava/lang/Object;IF)V";
case IASTORE:
return "(Ljava/lang/Object;II)V";
case SASTORE:
return "(Ljava/lang/Object;IS)V";
case LASTORE:
return "(Ljava/lang/Object;IJ)V";
}
throw new BadBytecode(opcode);
}
}
