MegaProcessor

#!/usr/bin/env lua
require ('./lib');
require ('./symtab');
local Directive = require("./asm_instr");
require( './opcodes' );


LineNr = 1;
AssemblerPass = 1;

function ProcessFile( inFileName )
    local inFile = Check( io.open(inFileName,"r"),
                        "Can't open file " .. inFileName
                        );

-- Pass 1
    for l in inFile:lines() do
        Pass1_line( Chomp(l) );
        LineNr = LineNr + 1;
    end

    inFile:seek("set",0) -- rewind input file

-- [[ Pass 2
    LineNr = 1;
    AssemblerPass = 2;
    PC_reset();
    for l in inFile:lines() do
        Printf("%04d : ", LineNr ); 
        ProcessLine( Chomp(l) );
        LineNr = LineNr + 1;
    end
--]]
    symtab_dump();
end

function Fields( line )
    if( line == "" or line:match("^%s*[;//]") ) then return 0; end;
    local retVal = 0;
    local n, n1, label, instr, dst, src;

    end
    if( dst ) then n=n1; retVal = retVal + 1; end
    src,n1  = line:match("[%s,]+([^%s;]+)()",n);
    if( src ) then n=n1; retVal = retVal + 1; end
    return retVal, label, instr, dst, src;
end

function Pass1_line( l ) -- Processing for pass 1, gathering of all symbols and labels.
    local asm_instr;
    local n,label,Mnemonic,op1,op2 = Fields(l);
    local b1, b2, b3;
    local insLen = 0;

    -- Printf( "%s:%s - %s - %s - %s - %s\n",PC_get(),label,Mnemonic,op1,op2,l);

    if( not Mnemonic ) then return; end;

    Mnemonic = Mnemonic:upper();

    asm_instr = Directive[ Mnemonic ];
    if( asm_instr ) then asm_instr(label,Mnemonic,op1,l); return; end
    
    asm_instr = CPU_instr[ Mnemonic ];
    if( asm_instr ) then
        if( label ) then symtab_addLabel(label) end;
        insLen = asm_instr[1];
        if( type(insLen)== 'function' ) then insLen = insLen(Mnemonic,op1,op2) end;
    end

    PC_add(insLen);
end

function ProcessLine( l ) -- Processing for pass 2
    local asm_instr;
    local n,label,Mnemonic,op1,op2 = Fields(l);
    local b1, b2, b3;
    local insLen = 0;

    if( not Mnemonic ) then Printf("%s : %s\n", PC_get(), l ); return; end

    Mnemonic = Mnemonic:upper();

    asm_instr = Directive[ Mnemonic ];
    if( asm_instr ) then asm_instr(label,Mnemonic,op1,l); return; end

require('./symtab');

local M = {
['DB'] = function( lbl,mnem,op1,srcLine ) 
    Printf("%s\n", srcLine);
    if( lbl ~= nil and AssemblerPass==1 ) then symtab_addLabel( lbl ); end;
    PC_add(1); -- TODO, count and evaluate the number of fields and PC_add that result instead.
    return 'DB';
end,

['DL'] = function( lbl,mnem,op1,srcLine ) 
    Printf("%s\n", srcLine);
    return 'DL';
end,

['DM'] = function( lbl,mnem,op1,srcLine ) 
    Printf("%s\n", srcLine);
    return 'DM';
end,

['DS'] = function( lbl,mnem,op1,srcLine ) 
    if( op1 == nil ) then Error("DS must specify a number of bytes"); end;--if
    if( lbl ~= nil and AssemblerPass==1 ) then symtab_addLabel( lbl ); end;
    PC_add( tonumber(op1) ); -- TODO more advanced evaluation of op1.
    return 'DS';
end,

['DW'] = function( lbl,mnem,op1,srcLine ) 
    Printf("%s\n", srcLine);
    if( lbl ~= nil and AssemblerPass==1 ) then symtab_addLabel( lbl ); end;
    PC_add(2);
    return 'DW';
end,

['EQU'] = function( lbl,mnem,op1,srcLine ) 
    Printf("%s\n", srcLine);

    if( op1 == "$" ) then op1 = PC_get(); end;

    if( lbl ~= nil and AssemblerPass==1 ) then symtab_addLabel( lbl ); end;
    
    return 'EQU';
end,

['ORG'] = function( lbl,mnem,op1,srcLine ) 
    Printf("%s\n", srcLine);
    PC_set( tonumber(op1) ); -- TODO more advanced evaluation of op1.
    if( lbl ~= nil and AssemblerPass==1 ) then symtab_addLabel( lbl ); end;
    return 'ORG';
end

};

-- End module
return M;

--
-- File: lib.lua
-- usage: require('lib');  
--    as early as possible, preferrably before all other requires,
--

function Printf( format, ... )
    io.write( string.format(format, ... ) );
end

function Warn( text )
    Printf("Line %04d : %s\n", LineNr, text );
end

function Error( text )
    Warn( text );
    os.exit(-1);
end

function htob_2( s )
    local hi,lo = s:byte(1,2);
    local hiA,loA;

--
-- Usage: require 'thisfile'
--
--

local symCount = 0;
local symtab = {};

function symtab_add(symbol,value)
    if( symtab[symbol] ) then
        Warn( "Redefining symbol " .. symbol );

    end
    symtab[symbol] = value;
    symCount = symCount + 1;
end

function symtab_addLabel( label )
    -- Printf( "Adding symbol : %s\n", label );
    label = label or ( '_L' .. PC_get() );
    if( label:sub(-1,-1) == ':' ) then label = label:sub(1,-2) end;
    symtab_add( label, ProgramCounter );
end

function symtab_lookup(symbol)
    return( symtab[symbol] )
end

function symtab_dump()
    Printf( "\n-------- SYMBOLS -------\n" );
    if( symCount == 0 ) then Printf("no symbols defined\n"); return; end;

    for k,v in pairs(symtab) do
        Printf("%32.32s : 0x%04x\n", k, v );
    end
end

ProgramCounter = 0;