@Override
protected void onApply(CtBehavior behavior, Bytecode bytecode) throws BadBytecode {
bytecode = BytecodeTools.prepareMethodForBytecode(behavior, bytecode);
// loop through the opcodes and change any GT/GE opcodes to ICMPGT/ICMPGE
CodeIterator iterator = behavior.getMethodInfo().getCodeAttribute().iterator();
while (iterator.hasNext()) {
int index = iterator.next();
int opcode = iterator.byteAt(index);
switch (opcode) {
case Opcode.IFGT:
// overwrite the opcode
iterator.writeByte(Opcode.IF_ICMPGT, index);
// insert the method call
iterator.insertAt(index, bytecode.get());
behavior.getMethodInfo().getCodeAttribute().computeMaxStack();
break;
case Opcode.IFGE:
// overwrite the opcode
iterator.writeByte(Opcode.IF_ICMPGE, index);
// insert the method call
iterator.insertAt(index, bytecode.get());
behavior.getMethodInfo().getCodeAttribute().computeMaxStack();
break;
}
}
}
public static void rewriteFakeMethod(CodeIterator methodBody, String methodDescriptor) {
String ret = DescriptorUtils.getReturnType(methodDescriptor);
// if the return type is larger than one then it is not a primitive
// so it does not need to be boxed
if (ret.length() != 1) {
return;
}
byte ar = (byte) Opcode.ARETURN;
byte[] areturn = {ar};
// void methods are special
if (ret.equals("V")) {
while (methodBody.hasNext()) {
try {
int index = methodBody.next();
int opcode = methodBody.byteAt(index);
// replace a RETURN opcode with
// ACONST_NULL
// ARETURN
// to return a null value
if (opcode == Opcode.RETURN) {
Bytecode code = new Bytecode(methodBody.get().getConstPool());
code.add(Opcode.ACONST_NULL);
code.add(Opcode.ARETURN);
methodBody.insertAt(index, code.get());
}
} catch (BadBytecode e) {
throw new RuntimeException(e);
}
}
} else {
while (methodBody.hasNext()) {
try {
int index = methodBody.next();
int opcode = methodBody.byteAt(index);
switch (opcode) {
case Opcode.IRETURN:
case Opcode.LRETURN:
case Opcode.DRETURN:
case Opcode.FRETURN:
// write a NOP over the old return instruction
// insert the boxing code to get an object on the stack
Bytecode b = new Bytecode(methodBody.get().getConstPool());
Boxing.box(b, ret.charAt(0));
b.addOpcode(Opcode.ARETURN);
methodBody.insertAt(index, b.get());
}
} catch (BadBytecode e) {
throw new RuntimeException(e);
}
}
}
}
private void initExtraHarvest() {
try {
CtClass terraForming =
HookManager.getInstance()
.getClassPool()
.get("com.wurmonline.server.behaviours.Terraforming");
CtClass[] paramTypes = {
HookManager.getInstance().getClassPool().get("com.wurmonline.server.creatures.Creature"),
CtPrimitiveType.intType,
CtPrimitiveType.intType,
CtPrimitiveType.booleanType,
CtPrimitiveType.intType,
CtPrimitiveType.floatType,
HookManager.getInstance().getClassPool().get("com.wurmonline.server.items.Item")
};
CtMethod method =
terraForming.getMethod(
"harvest", Descriptor.ofMethod(CtPrimitiveType.booleanType, paramTypes));
MethodInfo methodInfo = method.getMethodInfo();
CodeAttribute codeAttribute = methodInfo.getCodeAttribute();
CodeIterator codeIterator = codeAttribute.iterator();
LocalVariableAttribute attr =
(LocalVariableAttribute) codeAttribute.getAttribute(LocalVariableAttribute.tag);
int quantityIndex = -1;
for (int i = 0; i < attr.tableLength(); i++) {
if ("quantity".equals(attr.variableName(i))) {
quantityIndex = attr.index(i);
}
}
if (quantityIndex == -1) {
throw new HookException("Quantity variable can not be resolved");
}
while (codeIterator.hasNext()) {
int pos = codeIterator.next();
int op = codeIterator.byteAt(pos);
if (op == CodeIterator.ISTORE) {
int fieldRefIdx = codeIterator.byteAt(pos + 1);
if (quantityIndex == fieldRefIdx) {
Bytecode bytecode = new Bytecode(codeIterator.get().getConstPool());
bytecode.addIconst(extraHarvest);
bytecode.add(Bytecode.IADD);
codeIterator.insertAt(pos, bytecode.get());
break;
}
}
}
} catch (NotFoundException | BadBytecode e) {
throw new HookException(e);
}
}