// Resets [fiber] back to an initial state where it is ready to invoke [fn].
private void ResetFiber(Obj fn)
{
Stack = new Obj[InitialStackSize];
Capacity = InitialStackSize;
Frames = new List<CallFrame>();
// Push the stack frame for the function.
StackTop = 0;
NumFrames = 1;
OpenUpvalues = null;
Caller = null;
Error = null;
CallerIsTrying = false;
CallFrame frame = new CallFrame { Fn = fn, StackStart = 0, Ip = 0 };
Frames.Add(frame);
}
// The main bytecode interpreter loop. This is where the magic happens. It is
// also, as you can imagine, highly performance critical. Returns `true` if the
// fiber completed without error.
private bool RunInterpreter()
{
Instruction instruction;
int index;
/* Load Frame */
CallFrame frame = Fiber.Frames[Fiber.NumFrames - 1];
int ip = frame.Ip;
int stackStart = frame.StackStart;
Obj[] stack = Fiber.Stack;
ObjFn fn = frame.Fn as ObjFn ?? ((ObjClosure)frame.Fn).Function;
byte[] bytecode = fn.Bytecode;
while (true)
{
switch (instruction = (Instruction)bytecode[ip++])
{
case Instruction.LoadLocal0:
case Instruction.LoadLocal1:
case Instruction.LoadLocal2:
case Instruction.LoadLocal3:
case Instruction.LoadLocal4:
case Instruction.LoadLocal5:
case Instruction.LoadLocal6:
case Instruction.LoadLocal7:
case Instruction.LoadLocal8:
index = stackStart + (int)instruction; // LOAD_LOCAL_0 has code 0
if (Fiber.StackTop >= Fiber.Capacity)
stack = Fiber.IncreaseStack();
stack[Fiber.StackTop++] = stack[index];
break;
case Instruction.LoadLocal:
index = stackStart + bytecode[ip++];
if (Fiber.StackTop >= Fiber.Capacity)
stack = Fiber.IncreaseStack();
stack[Fiber.StackTop++] = stack[index];
break;
case Instruction.LoadFieldThis:
{
byte field = bytecode[ip++];
Obj receiver = stack[stackStart];
ObjInstance instance = receiver as ObjInstance;
if (Fiber.StackTop >= Fiber.Capacity)
Fiber.IncreaseStack();
stack[Fiber.StackTop++] = instance.Fields[field];
break;
}
case Instruction.Pop:
Fiber.StackTop--;
break;
case Instruction.Dup:
if (Fiber.StackTop >= Fiber.Capacity)
stack = Fiber.IncreaseStack();
stack[Fiber.StackTop] = stack[Fiber.StackTop - 1];
Fiber.StackTop++;
break;
case Instruction.Null:
if (Fiber.StackTop >= Fiber.Capacity)
stack = Fiber.IncreaseStack();
stack[Fiber.StackTop++] = Obj.Null;
break;
case Instruction.False:
if (Fiber.StackTop >= Fiber.Capacity)
stack = Fiber.IncreaseStack();
stack[Fiber.StackTop++] = Obj.False;
break;
case Instruction.True:
if (Fiber.StackTop >= Fiber.Capacity)
stack = Fiber.IncreaseStack();
stack[Fiber.StackTop++] = Obj.True;
break;
case Instruction.Zero:
if (Fiber.StackTop >= Fiber.Capacity)
stack = Fiber.IncreaseStack();
stack[Fiber.StackTop++] = Obj.Zero;
break;
case Instruction.One:
if (Fiber.StackTop >= Fiber.Capacity)
stack = Fiber.IncreaseStack();
stack[Fiber.StackTop++] = Obj.One;
break;
case Instruction.Call0:
case Instruction.Call1:
case Instruction.Call2:
case Instruction.Call3:
case Instruction.Call4:
case Instruction.Call5:
case Instruction.Call6:
case Instruction.Call7:
case Instruction.Call8:
case Instruction.Call9:
case Instruction.Call10:
case Instruction.Call11:
case Instruction.Call12:
case Instruction.Call13:
case Instruction.Call14:
case Instruction.Call15:
case Instruction.Call16:
// Handle Super calls
case Instruction.Super0:
case Instruction.Super1:
case Instruction.Super2:
case Instruction.Super3:
case Instruction.Super4:
case Instruction.Super5:
case Instruction.Super6:
case Instruction.Super7:
case Instruction.Super8:
case Instruction.Super9:
case Instruction.Super10:
case Instruction.Super11:
case Instruction.Super12:
case Instruction.Super13:
case Instruction.Super14:
case Instruction.Super15:
case Instruction.Super16:
{
int numArgs = instruction - (instruction >= Instruction.Super0 ? Instruction.Super0 : Instruction.Call0) + 1;
int symbol = (bytecode[ip] << 8) + bytecode[ip + 1];
ip += 2;
// The receiver is the first argument.
int argStart = Fiber.StackTop - numArgs;
Obj receiver = stack[argStart];
ObjClass classObj;
if (instruction < Instruction.Super0)
{
if (receiver.Type == ObjType.Obj)
classObj = receiver.ClassObj;
else if (receiver.Type == ObjType.Num)
classObj = NumClass;
else if (receiver == Obj.True || receiver == Obj.False)
classObj = BoolClass;
else
classObj = NullClass;
}
else
{
// The superclass is stored in a constant.
classObj = fn.Constants[(bytecode[ip] << 8) + bytecode[ip + 1]] as ObjClass;
ip += 2;
}
// If the class's method table doesn't include the symbol, bail.
Method method = symbol < classObj.Methods.Length ? classObj.Methods[symbol] : null;
if (method == null)
{
/* Method not found */
frame.Ip = ip;
MethodNotFound(this, classObj, symbol);
if (!HandleRuntimeError())
return false;
frame = Fiber.Frames[Fiber.NumFrames - 1];
ip = frame.Ip;
stackStart = frame.StackStart;
stack = Fiber.Stack;
fn = (frame.Fn as ObjFn) ?? (frame.Fn as ObjClosure).Function;
bytecode = fn.Bytecode;
break;
}
if (method.MType == MethodType.Primitive)
{
// After calling this, the result will be in the first arg slot.
if (method.Primitive(this, stack, argStart))
{
Fiber.StackTop = argStart + 1;
}
else
{
frame.Ip = ip;
if (Fiber.Error != null && Fiber.Error != Obj.Null)
{
if (!HandleRuntimeError())
return false;
}
else
{
// If we don't have a fiber to switch to, stop interpreting.
if (stack[argStart] == Obj.Null)
return true;
Fiber = stack[argStart] as ObjFiber;
if (Fiber == null)
return false;
}
/* Load Frame */
frame = Fiber.Frames[Fiber.NumFrames - 1];
ip = frame.Ip;
stackStart = frame.StackStart;
stack = Fiber.Stack;
fn = (frame.Fn as ObjFn) ?? (frame.Fn as ObjClosure).Function;
bytecode = fn.Bytecode;
}
break;
}
frame.Ip = ip;
if (method.MType == MethodType.Block)
{
receiver = method.Obj;
}
else if (!CheckArity(stack, numArgs, argStart))
{
if (!HandleRuntimeError())
return false;
frame = Fiber.Frames[Fiber.NumFrames - 1];
ip = frame.Ip;
stackStart = frame.StackStart;
stack = Fiber.Stack;
fn = (frame.Fn as ObjFn) ?? (frame.Fn as ObjClosure).Function;
bytecode = fn.Bytecode;
break;
}
Fiber.Frames.Add(frame = new CallFrame { Fn = receiver, StackStart = argStart, Ip = 0 });
Fiber.NumFrames++;
/* Load Frame */
ip = 0;
stackStart = argStart;
fn = (receiver as ObjFn) ?? (receiver as ObjClosure).Function;
bytecode = fn.Bytecode;
break;
}
case Instruction.StoreLocal:
index = stackStart + bytecode[ip++];
stack[index] = stack[Fiber.StackTop - 1];
break;
case Instruction.SmallConstant:
if (Fiber.StackTop >= Fiber.Capacity)
stack = Fiber.IncreaseStack();
stack[Fiber.StackTop++] = fn.Constants[bytecode[ip]];
ip += 1;
break;
case Instruction.Constant:
if (Fiber.StackTop >= Fiber.Capacity)
stack = Fiber.IncreaseStack();
stack[Fiber.StackTop++] = fn.Constants[(bytecode[ip] << 8) + bytecode[ip + 1]];
ip += 2;
break;
case Instruction.LoadUpvalue:
{
if (Fiber.StackTop >= Fiber.Capacity)
stack = Fiber.IncreaseStack();
stack[Fiber.StackTop++] = ((ObjClosure)frame.Fn).Upvalues[bytecode[ip++]].Container;
break;
}
case Instruction.StoreUpvalue:
{
ObjUpvalue[] upvalues = ((ObjClosure)frame.Fn).Upvalues;
upvalues[bytecode[ip++]].Container = stack[Fiber.StackTop - 1];
break;
}
case Instruction.LoadModuleVar:
if (Fiber.StackTop >= Fiber.Capacity)
stack = Fiber.IncreaseStack();
stack[Fiber.StackTop++] = fn.Module.Variables[(bytecode[ip] << 8) + bytecode[ip + 1]].Container;
ip += 2;
break;
case Instruction.StoreModuleVar:
fn.Module.Variables[(bytecode[ip] << 8) + bytecode[ip + 1]].Container = stack[Fiber.StackTop - 1];
ip += 2;
break;
case Instruction.StoreFieldThis:
{
byte field = bytecode[ip++];
Obj receiver = stack[stackStart];
ObjInstance instance = receiver as ObjInstance;
instance.Fields[field] = stack[Fiber.StackTop - 1];
break;
}
case Instruction.LoadField:
{
byte field = bytecode[ip++];
Obj receiver = stack[--Fiber.StackTop];
ObjInstance instance = receiver as ObjInstance;
if (Fiber.StackTop >= Fiber.Capacity)
stack = Fiber.IncreaseStack();
stack[Fiber.StackTop++] = instance.Fields[field];
break;
}
case Instruction.StoreField:
{
byte field = bytecode[ip++];
Obj receiver = stack[--Fiber.StackTop];
ObjInstance instance = receiver as ObjInstance;
instance.Fields[field] = stack[Fiber.StackTop - 1];
break;
}
case Instruction.Jump:
{
int offset = (bytecode[ip] << 8) + bytecode[ip + 1];
ip += offset + 2;
break;
}
case Instruction.Loop:
{
// Jump back to the top of the loop.
int offset = (bytecode[ip] << 8) + bytecode[ip + 1];
ip += 2;
ip -= offset;
break;
}
case Instruction.JumpIf:
{
int offset = (bytecode[ip] << 8) + bytecode[ip + 1];
ip += 2;
Obj condition = stack[--Fiber.StackTop];
if (condition == Obj.False || condition == Obj.Null) ip += offset;
break;
}
case Instruction.And:
{
int offset = (bytecode[ip] << 8) + bytecode[ip + 1];
ip += 2;
ObjType condition = stack[Fiber.StackTop - 1].Type;
switch (condition)
{
case ObjType.Null:
case ObjType.False:
ip += offset;
break;
default:
Fiber.StackTop--;
break;
}
break;
}
case Instruction.Or:
{
int offset = (bytecode[ip] << 8) + bytecode[ip + 1];
ip += 2;
Obj condition = stack[Fiber.StackTop - 1];
switch (condition.Type)
{
case ObjType.Null:
case ObjType.False:
Fiber.StackTop--;
break;
default:
ip += offset;
break;
}
break;
}
case Instruction.CloseUpvalue:
Fiber.CloseUpvalue();
Fiber.StackTop--;
break;
case Instruction.Return:
{
Fiber.Frames.RemoveAt(--Fiber.NumFrames);
Obj result = stack[--Fiber.StackTop];
// Close any upvalues still in scope.
if (Fiber.StackTop > stackStart)
{
Obj first = stack[stackStart];
while (Fiber.OpenUpvalues != null &&
Fiber.OpenUpvalues.Container != first)
{
Fiber.CloseUpvalue();
}
Fiber.CloseUpvalue();
}
// If the fiber is complete, end it.
if (Fiber.NumFrames == 0)
{
// If this is the main fiber, we're done.
if (Fiber.Caller == null) return true;
// We have a calling fiber to resume.
Fiber = Fiber.Caller;
stack = Fiber.Stack;
// Store the result in the resuming fiber.
stack[Fiber.StackTop - 1] = result;
}
else
{
// Discard the stack slots for the call frame (leaving one slot for the result).
Fiber.StackTop = stackStart + 1;
// Store the result of the block in the first slot, which is where the
// caller expects it.
stack[Fiber.StackTop - 1] = result;
}
/* Load Frame */
frame = Fiber.Frames[Fiber.NumFrames - 1];
ip = frame.Ip;
stackStart = frame.StackStart;
fn = frame.Fn as ObjFn ?? (frame.Fn as ObjClosure).Function;
bytecode = fn.Bytecode;
break;
}
case Instruction.Closure:
{
ObjFn prototype = fn.Constants[(bytecode[ip] << 8) + bytecode[ip + 1]] as ObjFn;
ip += 2;
// Create the closure and push it on the stack before creating upvalues
// so that it doesn't get collected.
ObjClosure closure = new ObjClosure(prototype);
if (Fiber.StackTop >= Fiber.Capacity)
stack = Fiber.IncreaseStack();
stack[Fiber.StackTop++] = closure;
// Capture upvalues.
for (int i = 0; i < prototype.NumUpvalues; i++)
{
byte isLocal = bytecode[ip++];
index = bytecode[ip++];
if (isLocal > 0)
{
// Make an new upvalue to close over the parent's local variable.
closure.Upvalues[i] = Fiber.CaptureUpvalue(stackStart + index);
}
else
{
// Use the same upvalue as the current call frame.
closure.Upvalues[i] = ((ObjClosure)frame.Fn).Upvalues[index];
}
}
break;
}
case Instruction.Class:
{
Obj name = stack[Fiber.StackTop - 2];
ObjClass superclass = ObjectClass;
// Use implicit Object superclass if none given.
if (stack[Fiber.StackTop - 1] != Obj.Null)
{
Fiber.Error = ValidateSuperclass(name, stack[Fiber.StackTop - 1]);
if (Fiber.Error != null)
{
frame.Ip = ip;
if (!HandleRuntimeError())
return false;
/* Load Frame */
frame = Fiber.Frames[Fiber.NumFrames - 1];
ip = frame.Ip;
stackStart = frame.StackStart;
stack = Fiber.Stack;
fn = (frame.Fn as ObjFn) ?? (frame.Fn as ObjClosure).Function;
bytecode = fn.Bytecode;
break;
}
superclass = stack[Fiber.StackTop - 1] as ObjClass;
}
int numFields = bytecode[ip++];
Obj classObj = new ObjClass(superclass, numFields, name as ObjString);
// Don't pop the superclass and name off the stack until the subclass is
// done being created, to make sure it doesn't get collected.
Fiber.StackTop -= 2;
// Now that we know the total number of fields, make sure we don't overflow.
if (superclass.NumFields + numFields > Compiler.MaxFields)
{
frame.Ip = ip;
Fiber.Error = Obj.MakeString(string.Format("Class '{0}' may not have more than 255 fields, including inherited ones.", name));
if (!HandleRuntimeError())
return false;
/* Load Frame */
frame = Fiber.Frames[Fiber.NumFrames - 1];
ip = frame.Ip;
stackStart = frame.StackStart;
stack = Fiber.Stack;
fn = (frame.Fn as ObjFn) ?? (frame.Fn as ObjClosure).Function;
bytecode = fn.Bytecode;
break;
}
if (Fiber.StackTop >= Fiber.Capacity)
stack = Fiber.IncreaseStack();
stack[Fiber.StackTop++] = classObj;
break;
}
case Instruction.MethodInstance:
case Instruction.MethodStatic:
{
int symbol = (bytecode[ip] << 8) + bytecode[ip + 1];
ip += 2;
ObjClass classObj = stack[Fiber.StackTop - 1] as ObjClass;
Obj method = stack[Fiber.StackTop - 2];
bool isStatic = instruction != Instruction.MethodInstance;
Fiber.Error = BindMethod(isStatic, symbol, classObj, method);
if (Fiber.Error != null)
{
frame.Ip = ip;
if (!HandleRuntimeError())
return false;
/* Load Frame */
frame = Fiber.Frames[Fiber.NumFrames - 1];
ip = frame.Ip;
stackStart = frame.StackStart;
stack = Fiber.Stack;
fn = (frame.Fn as ObjFn) ?? (frame.Fn as ObjClosure).Function;
bytecode = fn.Bytecode;
break;
}
Fiber.StackTop -= 2;
break;
}
case Instruction.LoadModule:
{
Obj name = fn.Constants[(bytecode[ip] << 8) + bytecode[ip + 1]];
ip += 2;
Obj result = ImportModule(name);
// If it returned a string, it was an error message.
if ((result is ObjString))
{
frame.Ip = ip;
Fiber.Error = result;
if (!HandleRuntimeError())
return false;
/* Load Frame */
frame = Fiber.Frames[Fiber.NumFrames - 1];
ip = frame.Ip;
stackStart = frame.StackStart;
stack = Fiber.Stack;
fn = (frame.Fn as ObjFn) ?? (frame.Fn as ObjClosure).Function;
bytecode = fn.Bytecode;
break;
}
// Make a slot that the module's fiber can use to store its result in.
// It ends up getting discarded, but CODE_RETURN expects to be able to
// place a value there.
if (Fiber.StackTop >= Fiber.Capacity)
stack = Fiber.IncreaseStack();
stack[Fiber.StackTop++] = Obj.Null;
// If it returned a fiber to execute the module body, switch to it.
if (result is ObjFiber)
{
// Return to this module when that one is done.
(result as ObjFiber).Caller = Fiber;
frame.Ip = ip;
Fiber = (result as ObjFiber);
/* Load Frame */
frame = Fiber.Frames[Fiber.NumFrames - 1];
ip = frame.Ip;
stackStart = frame.StackStart;
stack = Fiber.Stack;
fn = (frame.Fn as ObjFn) ?? (frame.Fn as ObjClosure).Function;
bytecode = fn.Bytecode;
}
break;
}
case Instruction.ImportVariable:
{
Obj module = fn.Constants[(bytecode[ip] << 8) + bytecode[ip + 1]];
ip += 2;
Obj variable = fn.Constants[(bytecode[ip] << 8) + bytecode[ip + 1]];
ip += 2;
Obj result;
if (ImportVariable(module, variable, out result))
{
if (Fiber.StackTop >= Fiber.Capacity)
stack = Fiber.IncreaseStack();
stack[Fiber.StackTop++] = result;
}
else
{
frame.Ip = ip;
Fiber.Error = result;
if (!HandleRuntimeError())
return false;
/* Load Frame */
frame = Fiber.Frames[Fiber.NumFrames - 1];
ip = frame.Ip;
stackStart = frame.StackStart;
stack = Fiber.Stack;
fn = (frame.Fn as ObjFn) ?? (frame.Fn as ObjClosure).Function;
bytecode = fn.Bytecode;
}
break;
}
case Instruction.End:
// A CODE_END should always be preceded by a CODE_RETURN. If we get here,
// the compiler generated wrong code.
return false;
}
}
// We should only exit this function from an explicit return from CODE_RETURN
// or a runtime error.
}
private ObjFiber LoadModule(Obj name, string source)
{
ObjModule module = GetModule(name);
// See if the module has already been loaded.
if (module == null)
{
module = new ObjModule(name as ObjString);
// Store it in the VM's module registry so we don't load the same module
// multiple times.
_modules.Set(name, module);
// Implicitly import the core module.
ObjModule coreModule = GetCoreModule();
foreach (ModuleVariable t in coreModule.Variables)
{
DefineVariable(module, t.Name, t.Container);
}
}
ObjFn fn = Compiler.Compile(this, module, name.ToString(), source, true);
if (fn == null)
{
// TODO: Should we still store the module even if it didn't compile?
return null;
}
ObjFiber moduleFiber = new ObjFiber(fn);
// Return the fiber that executes the module.
return moduleFiber;
}
// Execute [source] in the context of the core module.
private InterpretResult LoadIntoCore(string source)
{
ObjModule coreModule = GetCoreModule();
ObjFn fn = Compiler.Compile(this, coreModule, "", source, true);
if (fn == null) return InterpretResult.CompileError;
Fiber = new ObjFiber(fn);
return RunInterpreter() ? InterpretResult.Success : InterpretResult.RuntimeError;
}
/* Dirty Hack */
private bool HandleRuntimeError()
{
ObjFiber f = Fiber;
if (f.CallerIsTrying)
{
f.Caller.SetReturnValue(f.Error);
Fiber = f.Caller;
return true;
}
Fiber = null;
// TODO: Fix this so that there is no dependancy on the console
if (!(f.Error is ObjString))
{
f.Error = Obj.MakeString("Error message must be a string.");
}
Console.Error.WriteLine(f.Error as ObjString);
return false;
}
public InterpretResult Interpret(string sourcePath, string source)
{
if (sourcePath.Length == 0) return LoadIntoCore(source);
// TODO: Better module name.
Obj name = Obj.MakeString("main");
ObjFiber f = LoadModule(name, source);
if (f == null)
{
return InterpretResult.CompileError;
}
Fiber = f;
bool succeeded = RunInterpreter();
return succeeded ? InterpretResult.Success : InterpretResult.RuntimeError;
}