/**
* Emulates the storing of a value to a local variable.
*
* @param index the index of the local variable being stored to
* @param type the type of the value
* @param local the variable to which the value is stored
*/
public void store(int index, Klass type, Local local) {
Klass localType = local.getType();
Assert.that(localType.isAssignableFrom(type) || localType == getLocalTypeFor(type));
verifyLocalVariableIndex(localType, index);
localTypes[index] = type;
if (localType.isDoubleWord()) {
localTypes[index + 1] = Klass.getSecondWordType(localType);
} else {
verifyUseOfSquawkPrimitive(localType, type);
}
}
/**
* Verify that a local variable index for a given type is not out of bounds.
*
* @param type the type of the local variable at <code>index</code> in the local variables array
* @param index the index of a local variable
*/
public void verifyLocalVariableIndex(Klass type, int index) {
if (index < 0) {
throw codeParser.verifyError("invalid local variable index");
}
if (type.isDoubleWord()) {
index++;
}
if (index >= localTypes.length) {
throw codeParser.verifyError("invalid local variable index");
}
}
/**
* Pops a value off the operand stack.
*
* @param type the type that the value popped off the operand stack must be assignable to
* @return the instruction that produced the popped value
*/
public StackProducer pop(Klass type) {
StackProducer producer;
if (type.isDoubleWord()) {
if (sp < 2) {
throw codeParser.verifyError("operand stack underflow");
}
if (!isTopDoubleWord()) {
throw codeParser.verifyError("incompatible type on operand stack " + tosKlassName());
}
sp -= 2;
producer = stack[sp];
} else {
if (sp < 1) {
throw codeParser.verifyError("operand stack underflow");
}
if (isTopDoubleWord()) {
throw codeParser.verifyError("incompatible type on operand stack " + tosKlassName());
}
producer = stack[--sp];
/*
* The primitive one-word, non-float types are all assignment compatible with each other
*/
if (type.isPrimitive() && type != Klass.FLOAT) {
type = Klass.INT;
}
}
Assert.that(producer != null);
/*
* Interfaces are treated as java.lang.Object in the verifier.
*/
if (type.isInterface()) {
type = Klass.OBJECT;
}
/*
* Verify that the instruction is producing the correct type.
*/
if (!type.isAssignableFrom(producer.getType())) {
throw codeParser.verifyError(
"incompatible type: '" + type + "' is not assignable from '" + producer.getType() + "'");
}
return producer;
}
/**
* Emulates loading a value of a given type from a local variable.
*
* @param index the index of the local variable being loaded from
* @param localType the expected type of the variable from which the value is loaded
* @return the variable from which the value is loaded
*/
public Local load(int index, Klass localType) {
verifyLocalVariableIndex(localType, index);
Klass derivedType = localTypes[index];
if (!localType.isAssignableFrom(derivedType)) {
throw codeParser.verifyError("incompatible type in local variable");
}
if (localType.isDoubleWord()) {
Klass secondWordType = Klass.getSecondWordType(localType);
if (!secondWordType.isAssignableFrom(localTypes[index + 1])) {
throw codeParser.verifyError("incompatible type in local variable");
}
}
if (derivedType.isSquawkPrimitive()) {
localType = derivedType;
}
return allocateLocal(localType, index);
}
/**
* Pushes a value to the operand stack.
*
* @param producer the instruction producing the value being pushed
*/
public void push(StackProducer producer) {
Klass type = producer.getType();
Assert.that(type != Klass.VOID);
/*
* Check for overflow and push the producer.
*/
if (sp == maxStack) {
throw codeParser.verifyError("operand stack overflow");
}
stack[sp++] = producer;
/*
* For long and double check for overflow and then add a null word to the stack.
*/
if (type.isDoubleWord()) {
if (sp == maxStack) {
throw codeParser.verifyError("operand stack overflow");
}
stack[sp++] = null;
}
}
/**
* Creates a Frame instance to emulate and verify the execution of a single class file method.
*
* @param codeParser the parser used to parse the "Code" attribute of the method being emulated
* @param extraLocals the number of extra local variables needed
*/
public Frame(CodeParser codeParser, int extraLocals) {
this.maxStack = codeParser.getMaxStack();
this.codeParser = codeParser;
/*
* Initialize the operand stack
*/
stack = new StackProducer[maxStack];
/*
* Initialize the types in the local variables
*/
localTypes = new Klass[codeParser.getMaxLocals() + extraLocals];
Method method = codeParser.getMethod();
Klass[] parameterTypes = method.getParameterTypes();
Local[] parameterLocals = null;
if (Translator.REVERSE_PARAMETERS && method.isInterpreterInvoked()) {
parameterLocals = new Local[parameterTypes.length];
}
int javacIndex = 0;
/*
* Initialize 'this' in non-static methods. The type of 'this' is
* UNINITIALIZED_THIS if this method is a constructor in any class
* except java.lang.Object otherwise it is the class in which the
* method was defined.
*/
if (!method.isStatic() || method.isConstructor()) {
Assert.that(parameterLocals == null);
Klass thisType = method.getDefiningClass();
if (method.isConstructor() && thisType != Klass.OBJECT) {
thisType = Klass.UNINITIALIZED_THIS;
}
Local thisLocal = allocateParameter(thisType, javacIndex);
store(javacIndex, thisType, thisLocal);
javacIndex++;
}
/*
* Initialize locals for the parameters.
*/
int parameterIndex = javacIndex;
for (int i = 0; i < parameterTypes.length; i++) {
Klass parameterType = parameterTypes[i];
Local parameterLocal = allocateParameter(parameterType, javacIndex);
if (parameterLocals != null) {
parameterLocals[i] = parameterLocal;
}
if (Klass.SQUAWK_64) {
if (javacIndex != parameterIndex) {
Assert.that(parameterIndex < javacIndex);
parameterLocal.setParameterIndex(parameterIndex);
}
parameterIndex++;
}
store(javacIndex, parameterType, parameterLocal);
javacIndex += (parameterType.isDoubleWord() ? 2 : 1);
}
parameterLocalsCount = javacIndex;
/*
* Adjust the parameter offsets for parameter order reversal.
*/
if (parameterLocals != null) {
parameterIndex = 0;
for (int i = parameterTypes.length - 1; i >= 0; i--) {
Klass parameterType = parameterTypes[i];
parameterLocals[i].setParameterIndex(parameterIndex++);
if (!Klass.SQUAWK_64 && parameterType.isDoubleWord()) {
parameterIndex++;
}
}
}
/*
* Initialize the remaining local variables to the TOP type
*/
while (javacIndex < localTypes.length) {
localTypes[javacIndex++] = Klass.TOP;
}
}
