static void SkipLabel()
{
do
{
ch = src.ReadChar();
if (ch == ';')
{
src.ReadLn(); // ignore comments
}
} while (!(src.EOF() || char.IsLetter(ch)));
}
public static bool Assemble(string sourceName)
{
// Assembles source code from an input file sourceName and loads codeLen
// words of code directly into memory PVM.mem[0 .. codeLen-1],
// storing strings in the string pool at the top of memory in
// PVM.mem[stkBase .. memSize-1].
//
// Returns true if assembly succeeded
//
// Instruction format :
// Instruction = [ Label ] Opcode [ AddressField ] [ Comment ]
// Label = [ "{" ] Integer [ "}" ]
// Opcode = Mnemonic
// AddressField = Integer | "String"
// Comment = String
//
// A string AddressField may only be used with a PRNS opcode
// Instructions are supplied one to a line; terminated at end of input file
string mnemonic; // mnemonic for matching
char quote; // string delimiter
src = new InFile(sourceName);
if (src.OpenError())
{
Console.WriteLine("Could not open input file\n");
System.Environment.Exit(1);
}
Console.WriteLine("Assembling code ... \n");
codeLen = 0;
stkBase = PVM.memSize - 1;
okay = true;
do
{
SkipLabel(); // ignore labels at start of line
if (!src.EOF()) // we must have a line
{
mnemonic = ReadMnemonic(); // unpack mnemonic
if (mnemonic == null)
{
continue; // ignore directives
}
int op = PVM.OpCode(mnemonic); // look it up
PVM.mem[codeLen] = op; // store in memory
switch (op)
{
case PVM.prns: // requires a string address field
do
{
quote = src.ReadChar(); // search for opening quote character
}while (quote != '"' && quote != '\'' && quote != '\n');
codeLen = (codeLen + 1) % PVM.memSize;
PVM.mem[codeLen] = stkBase - 1; // pointer to start of string
if (quote == '\n')
{
Error("Missing string address", codeLen);
}
else // stack string in literal pool
{
ch = src.ReadChar();
while (ch != quote && ch != '\n')
{
if (ch == '\\')
{
ch = src.ReadChar();
if (ch == '\n') // closing quote missing
{
Error("Malformed string", codeLen);
}
switch (ch)
{
case 't': ch = '\t'; break;
case 'n': ch = '\n'; break;
case '\"': ch = '\"'; break;
case '\'': ch = '\''; break;
default: break;
}
}
stkBase--;
PVM.mem[stkBase] = ch;
ch = src.ReadChar();
}
if (ch == '\n') // closing quote missing
{
Error("Malformed string", codeLen);
}
}
stkBase--;
PVM.mem[stkBase] = 0; // terminate string with nul
break;
case PVM.brn: // all require numeric address field
case PVM.bze:
case PVM.dsp:
case PVM.lda:
case PVM.ldc:
codeLen = (codeLen + 1) % PVM.memSize;
if (ch == '\n') // no field could be found
{
Error("Missing address", codeLen);
}
else // unpack it and store
{
PVM.mem[codeLen] = src.ReadInt();
if (src.Error())
{
Error("Bad address", codeLen);
}
}
break;
case PVM.nul: // unrecognized mnemonic
Console.Write(mnemonic);
Error(" - Invalid opcode", codeLen);
break;
default: // no address needed
break;
}
if (!src.EOL())
{
src.ReadLn(); // skip comments
}
codeLen = (codeLen + 1) % PVM.memSize;
}
} while (!src.EOF());
for (int i = codeLen; i < stkBase; i++) // fill with invalid OpCodes
{
PVM.mem[i] = PVM.nul;
}
return(okay);
}
public static bool Assemble(string sourceName)
{
string mnemonic; // mnemonic for matching
char quote; // string delimiter
src = new InFile(sourceName);
if (src.OpenError())
{
Console.WriteLine("Could not open input file\n");
System.Environment.Exit(1);
}
Console.WriteLine("Assembling code ... \n");
codeLen = 0;
stkBase = PVM.memSize - 1;
okay = true;
do
{
SkipLabel(); // ignore labels at start of line
if (!src.EOF()) // we must have a line
{
mnemonic = ReadMnemonic(); // unpack mnemonic
if (mnemonic == null)
{
continue; // ignore directives
}
int op = PVM.OpCode(mnemonic); // look it up
PVM.mem[codeLen] = op; // store in memory
switch (op)
{
case PVM.prns: // requires a string address field
do
{
quote = src.ReadChar(); // search for opening quote character
}while (quote != '"' && quote != '\'' && quote != '\n');
codeLen = (codeLen + 1) % PVM.memSize;
PVM.mem[codeLen] = stkBase - 1; // pointer to start of string
if (quote == '\n')
{
Error("Missing string address", codeLen);
}
else // stack string in literal pool
{
ch = src.ReadChar();
while (ch != quote && ch != '\n')
{
if (ch == '\\')
{
ch = src.ReadChar();
if (ch == '\n') // closing quote missing
{
Error("Malformed string", codeLen);
}
switch (ch)
{
case 't': ch = '\t'; break;
case 'n': ch = '\n'; break;
case '\"': ch = '\"'; break;
case '\'': ch = '\''; break;
default: break;
}
}
stkBase--;
PVM.mem[stkBase] = ch;
ch = src.ReadChar();
}
if (ch == '\n') // closing quote missing
{
Error("Malformed string", codeLen);
}
}
stkBase--;
PVM.mem[stkBase] = 0; // terminate string with nul
break;
case PVM.brn: // all require numeric address field
case PVM.bze:
case PVM.dsp:
case PVM.lda:
case PVM.ldc:
case PVM.ldl:
case PVM.stl:
codeLen = (codeLen + 1) % PVM.memSize;
if (ch == '\n') // no field could be found
{
Error("Missing address", codeLen);
}
else // unpack it and store
{
PVM.mem[codeLen] = src.ReadInt();
if (src.Error())
{
Error("Bad address", codeLen);
}
}
break;
case PVM.nul: // unrecognized mnemonic
Console.Write(mnemonic);
Error(" - Invalid opcode", codeLen);
break;
default: // no address needed
break;
}
if (!src.EOL())
{
src.ReadLn(); // skip comments
}
codeLen = (codeLen + 1) % PVM.memSize;
}
} while (!src.EOF());
for (int i = codeLen; i < stkBase; i++) // fill with invalid OpCodes
{
PVM.mem[i] = PVM.nul;
}
return(okay);
}