protected void Write16(ushort address, ushort value)
{
//convert native ushort to big endian format in ram
var bytes = EndianUtils.FromNative(value);
_cpu.Ram[address] = bytes[0]; //msb
_cpu.Ram[(ushort)(address + 1)] = bytes[1]; //lsb;
}
public static ROF Assemble(FileAstNode file)
{
/*
* Rules:
*
* .ORG and .END required
* file must start with EQUs or ORG
* EQUs must be before ORG
* EQUs must have labels
* file must end with END
* reserve statements must come between ORG and END (ORG doesn't mean the start of code, only the image)
*
* address labels are ushort
* constant labels (EQU) may be bytes or ushorts
*
*
*/
//cache instructions
Dictionary <string, Instruction> instructions = new Dictionary <string, Instruction>();
foreach (var instruction in Instruction.GetInstructions())
{
instructions.Add(instruction.Encode(), instruction);
}
byte[] image = new byte[0xFFFF + 1];
Dictionary <string, Label> labels = new Dictionary <string, Label>();
ushort?start = null;
ushort?code = null;
ushort?end = null;
ushort here = 0;
foreach (var statement in file.ChildNodes)
{
if (end != null)
{
throw new AssembleException("END must be last statement in file", statement.SourceSpan);
}
LabelAstNode label = statement[typeof(LabelAstNode)] as LabelAstNode;
if (statement is DirectiveAstNode)
{
IDirective directive = statement[typeof(IDirective)] as IDirective;
if (directive is DeclarationAstNode)
{
if (start != null)
{
throw new AssembleException("EQU must be before ORG", statement.SourceSpan);
}
if (label == null)
{
throw new AssembleException("EQU must have a label", statement.SourceSpan);
}
IntegerAstNode integer = directive[typeof(IntegerAstNode)] as IntegerAstNode;
labels.Add(label.Value, new Label(LabelType.Constant, integer.Value));
}
else
{
if (directive is OriginAstNode)
{
start = GetIntegerRef16(statement, (OriginAstNode)directive, labels);
}
else
{
if (start == null)
{
throw new AssembleException("ORG must be defined first", statement.SourceSpan);
}
if (directive is ReservationAstNodeBase)
{
if (label != null)
{
labels.Add(label.Value, new Label(LabelType.Address, here + start.Value));
}
int byteSize = ((ReservationAstNodeBase)directive).Value;
if (directive is ReservationInitAstNode)
{
var integers = ((AstNodeBase)directive).Find(typeof(IntegerAstNode));
if (integers.Length == 0)
{
here += (ushort)byteSize;
}
else
{
foreach (var integer in integers)
{
var i = (IntegerAstNode)integer;
if (byteSize == 1)
{
if (i.Value is ushort)
{
throw new AssembleException("can't use 16 bit constants in .byte reservation", statement.SourceSpan);
}
image[here] = (byte)i.Value;
}
else if (byteSize == 2)
{
if (i.Value is uint)
{
throw new AssembleException("can't use 32 bit constants in .2byte reservation", statement.SourceSpan);
}
var bytes = EndianUtils.FromNative(Convert.ToUInt16(i.Value));
image[here] = bytes[0]; //msb;
image[here + 1] = bytes[1]; //lsb;
}
else if (byteSize == 4)
{
var bytes = EndianUtils.FromNative(Convert.ToUInt32(i.Value));
image[here] = bytes[0]; //msb;
image[here + 1] = bytes[1];
image[here + 2] = bytes[2];
image[here + 3] = bytes[3]; //lsb;
}
else
{
throw new NotImplementedException("bad byte size");
}
here += (ushort)byteSize;
}
}
}
else if (directive is ReservationStarAstNode)
{
uint bytes = GetIntegerRef32(statement, (AstNode)directive, labels);
//TODO what if this overflows?
here += (ushort)(bytes * byteSize);
}
else
{
throw new InvalidOperationException("bad reservation directive");
}
}
else if (directive is EndAstNode)
{
end = (ushort?)(start + here - 1);
}
}
}
}
else if (statement is InstructionAstNode)
{
if (label != null)
{
labels.Add(label.Value, new Label(LabelType.Address, here + start));
}
if (code == null)
{
code = (ushort)(here + start);
}
MnemonicAstNode mnemonic = statement[typeof(MnemonicAstNode)] as MnemonicAstNode;
IOperand operand = statement[typeof(IOperand)] as IOperand;
string encodedInstruction = EncodeInstruction(mnemonic.Value, operand);
Instruction instruction = instructions[encodedInstruction];
image[here] = instruction.OpCode;
if (instruction.Width == 2)
{
image[here + 1] = GetIntegerRef8(statement, (AstNodeBase)operand, labels);
}
else if (instruction.Width == 3)
{
ushort value = GetIntegerRef16(statement, (AstNodeBase)operand, labels);
var bytes = EndianUtils.FromNative(value);
image[here + 1] = bytes[0]; //msb;
image[here + 2] = bytes[1]; //lsb;
}
here += instruction.Width;
}
else
{
throw new AssembleException("Line must be a statement.", statement.SourceSpan);
}
}
if (end == null)
{
throw new InvalidOperationException("file must have END");
}
return(new ROF {
Start = start.Value, Code = code, End = end.Value, Image = image.ToArray()
});
}