private Instruction[] GetStringLiteralRetreivalInstructions(string value)
{
var stringValue = StringDatabase.Register(value);
return(new[]
{
Instruction.LoadString(stringValue)
});
}
public Value Evaluate(ExecutionContext context)
{
if (IsEmpty)
{
return(default(Value));
}
var originalSize = context.Size;
for (int i = 0; i < _instructions.Length; i++)
{
var instruction = _instructions[i];
switch (instruction.Opcode)
{
case Opcode.LoadInteger:
case Opcode.LoadFloat:
case Opcode.LoadBoolean:
context.Push(instruction.Operand);
break;
case Opcode.LoadType:
{
var type = (Types)(uint)instruction.Operand.Raw;
context.Push(new Value(type));
break;
}
case Opcode.LoadOpcode:
{
var opcode = (Opcode)(ushort)instruction.Operand.Raw;
context.Push(new Value(opcode));
break;
}
case Opcode.LoadString:
{
Debug.Assert(instruction.Operand.Type == Types.@string);
var rawValue = StringDatabase.GetRawValue(instruction.Operand.Raw);
var value = Heap.AllocatePersistentString(rawValue);
context.Push(value);
value.AddRef();
break;
}
case Opcode.GetType:
{
var value = context.Pop();
var type = value.Type;
context.Push(new Value(type));
value.RemoveRef();
break;
}
case Opcode.TypeIs:
{
var rhsValue = context.Pop();
Debug.Assert(rhsValue.Type == Types.type);
var rhsType = (Types)(uint)rhsValue.Raw;
var lhsValue = context.Pop();
Debug.Assert(lhsValue.Type == Types.type);
var lhsType = (Types)(uint)lhsValue.Raw;
var lhsTypeIsRhsType = (lhsType & rhsType) != 0 && lhsType >= rhsType;
context.Push(new Value(lhsTypeIsRhsType));
break;
}
case Opcode.TypeEquals:
{
var rhsValue = context.Pop();
Debug.Assert(rhsValue.Type == Types.type);
var rhsType = (Types)(uint)rhsValue.Raw;
var lhsValue = context.Pop();
Debug.Assert(lhsValue.Type == Types.type);
var lhsType = (Types)(uint)lhsValue.Raw;
var lhsTypeEqualsRhsType = lhsType == rhsType;
context.Push(new Value(lhsTypeEqualsRhsType));
break;
}
case Opcode.TupleArity:
{
var tupleValue = context.Pop();
Debug.Assert(tupleValue.Type == Types.tuple);
var tuple = Heap.GetTuple((int)tupleValue.Raw);
var arity = tuple.Items.Count;
context.Push(new Value(arity));
tupleValue.RemoveRef();
break;
}
case Opcode.TupleItem:
{
var tupleValue = context.Pop();
var tuple = Heap.GetTuple((int)tupleValue.Raw);
var index = (int)instruction.Operand.Raw;
var item = tuple.Items[index];
context.Push(item);
item.AddRef();
tupleValue.RemoveRef();
break;
}
case Opcode.NewTuple:
{
var arity = (int)instruction.Operand.Raw;
var tuple = Heap.AllocateTuple(arity, context);
context.Push(tuple);
tuple.AddRef();
break;
}
case Opcode.NewExpression:
{
var instructionCount = (int)instruction.Operand.Raw;
var typeValue = context.Pop();
Debug.Assert(typeValue.Type == Types.type);
var type = (Types)(uint)typeValue.Raw;
var instructions = new Instruction[instructionCount];
for (int j = 0; j < instructionCount; j++)
{
var instructionTupleValue = context.Pop();
var instructionTuple = Heap.GetTuple((int)instructionTupleValue.Raw);
Debug.Assert(instructionTuple.Items.Count == 2);
Debug.Assert(instructionTuple.Items[0].Type == Types.opcode);
instructions[j] = Instruction.FromTuple(instructionTuple);
instructionTupleValue.RemoveRef();
}
var expressionValue = Heap.AllocateExpression(type, instructions.ToArray());
context.Push(expressionValue);
expressionValue.AddRef();
break;
}
case Opcode.ListEmpty:
{
context.Push(Empty.List);
break;
}
case Opcode.ListAdd:
{
var head = context.Pop();
var tail = context.Pop();
// No need to remove ref for head and tail - their refs are "taken" by the new list.
var list = Heap.AllocateList(head, tail);
context.Push(list);
list.AddRef();
break;
}
case Opcode.ListHead:
{
var listValue = context.Pop();
var list = Heap.GetList((int)listValue.Raw);
var head = list.Head;
context.Push(head);
listValue.RemoveRef();
break;
}
case Opcode.ListTail:
{
var listValue = context.Pop();
var list = Heap.GetList((int)listValue.Raw);
var tail = new Value(Types.list, list.TailIndex);
context.Push(tail);
tail.AddRef();
listValue.RemoveRef();
break;
}
case Opcode.AssignVariable:
{
var value = context.Pop();
var variableIndex = (int)instruction.Operand.Raw;
var result = context.Scope.SetValue(context, variableIndex, value, false);
if (result.Type == Types.error)
{
return(default(Value));
}
context.Push(result);
break;
}
case Opcode.AssignMutableVariable:
{
var value = context.Pop();
var variableIndex = (int)instruction.Operand.Raw;
var result = context.Scope.SetValue(context, variableIndex, value, true);
if (result.Type == Types.error)
{
return(default(Value));
}
context.Push(result);
break;
}
case Opcode.ReadVariable:
{
Debug.Assert(instruction.Operand.Type == Types.@int);
var value = context.Scope.GetValue((int)instruction.Operand.Raw);
if (value.Type == Types.error)
{
return(default(Value));
}
context.Push(value);
value.AddRef();
break;
}
case Opcode.EvaluateExpression:
{
var value = context.Pop();
if (value.Type != Types.expression)
{
context.AddError(new Error("Invalid eval target - must be an expression."));
return(default(Value));
}
var expression = Heap.GetExpression((int)value.Raw);
var evaluatedValue = expression.Evaluate(context);
context.Push(evaluatedValue);
evaluatedValue.AddRef();
value.RemoveRef();
break;
}
default:
throw new ArgumentOutOfRangeException("opcode");
}
}
if (context.Size == 0)
{
context.AddError(new Error($"Invalid expression - evaluation stack was empty upon exit."));
return(default(Value));
}
var returnValue = context.Pop();
if (context.Size != originalSize)
{
context.AddError(new Error($"Invalid expression - evaluation stack size was modified. Original size: {originalSize}, size upon exist: {context.Size}."));
return(default(Value));
}
return(returnValue);
}