static public ushort ToByteCode(string instruction)
{
instruction = instruction.ToUpper();
string[] parts = instruction.Split(new char[] { ' ' }, StringSplitOptions.RemoveEmptyEntries);
if (parts.Length == 0)
{
throw new Exception("An empty string is not valid syntax");
}
//check for numbers
ushort potentialNumber;
if (ushort.TryParse(parts[0], out potentialNumber))
{
return(potentialNumber);
}
else if (parts[0] == "DAT")
{
return(Mnemonic.ToByteCode(parts[1]));//DAT is followed either by an instruction or a number
}
else if (parts[0] == "IN")
{
if (parts.Length > 1)
{
throw new Exception("Unexpected arguments for IN instruction");
}
else
{
return(901);
}
}
else if (parts[0] == "OUT")
{
if (parts.Length > 1)
{
throw new Exception("Unexpected arguments for OUT instruction");
}
else
{
return(902);
}
}
else if (parts[0] == "HLT")
{
if (parts.Length > 1)
{
throw new Exception("Unexpected arguments for HLT instruction");
}
else
{
return(0);
}
}
else
{
if (parts.Length < 2)
{
throw new Exception("Argument expected for " + parts[0] + " instruction");
}
if (parts.Length > 2)
{
throw new Exception("Unexpected second argument for " + parts[0] + " instruction");
}
ushort address;
try { address = ushort.Parse(parts[1]); }
catch (Exception) { throw new Exception("Argument is invalid"); }
if (address > 99)
{
throw new Exception("Argument is out of bounds!");
}
//otherwise we should be ready to parse an instruction with a parameter
switch (parts[0])
{
case "ADD": return((ushort)(100 + address));
case "SUB": return((ushort)(200 + address));
case "STO": return((ushort)(300 + address));
case "LDA": return((ushort)(500 + address));
case "BR": return((ushort)(600 + address));
case "BRZ": return((ushort)(700 + address));
case "BRP": return((ushort)(800 + address));
default: throw new Exception("Invalid opcode " + parts[0]);
}
}
}