apple2js/js/intbasic/decompiler.js

export default function IntBasicDump(mem)
{
    var _mem = mem;

    var LETTERS =
	'                                ' +
	' !"#$%&\'()*+,-./0123456789:;<=>?' +
	'@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_' +
	'`abcdefghijklmnopqrstuvwxyz{|}~ ';

    var TOKENS = {
        0x02: '_',
        0x03: ':',
        0x04: 'LOAD',
        0x05: 'SAVE',
        0x06: 'CON',
        0x07: 'RUN',
        0x08: 'RUN',
        0x09: 'DEL',
        0x0A: ',',
        0x0B: 'NEW',
        0x0C: 'CLR',
        0x0D: 'AUTO',
        0x0E: ',',
        0x0F: 'MAN',
        0x10: 'HIMEM:',
        0x11: 'LOMEM:',
        0x12: '+',
        0x13: '-',
        0x14: '*',
        0x15: '/',
        0x16: '=',
        0x17: '#',
        0x18: '>=',
        0x19: '>',
        0x1A: '<=',
        0x1B: '<>',
        0x1C: '<',
        0x1D: 'AND',
        0x1E: 'OR',
        0x1F: 'MOD',
        0x20: '^',
        0x21: '+',
        0x22: '(',
        0x23: ',',
        0x24: 'THEN',
        0x25: 'THEN',
        0x26: ',',
        0x27: ',',
        0x28: '\'',
        0x29: '\'',
        0x2A: '(',
        0x2B: '!',
        0x2C: '!',
        0x2D: '(',
        0x2E: 'PEEK',
        0x2F: 'RND',
        0x30: 'SGN',
        0x31: 'ABS',
        0x32: 'PDL',
        0x33: 'RNDX',
        0x34: '(',
        0x35: '+',
        0x36: '-',
        0x37: 'NOT',
        0x38: '(',
        0x39: '=',
        0x3A: '#',
        0x3B: 'LEN(',
        0x3C: 'ASC(',
        0x3D: 'SCRN(',
        0x3E: ',',
        0x3F: '(',
        0x40: '$',
        0x41: '$',
        0x42: '(',
        0x43: ',',
        0x44: ',',
        0x45: ';',
        0x46: ';',
        0x47: ';',
        0x48: ',',
        0x49: ',',
        0x4A: ',',
        0x4B: 'TEXT',
        0x4C: 'GR',
        0x4D: 'CALL',
        0x4E: 'DIM',
        0x4F: 'DIM',
        0x50: 'TAB',
        0x51: 'END',
        0x52: 'INPUT',
        0x53: 'INPUT',
        0x54: 'INPUT',
        0x55: 'FOR',
        0x56: '=',
        0x57: 'TO',
        0x58: 'STEP',
        0x59: 'NEXT',
        0x5A: ',',
        0x5B: 'RETURN',
        0x5C: 'GOSUB',
        0x5D: 'REM',
        0x5E: 'LET',
        0x5F: 'GOTO',
        0x60: 'IF',
        0x61: 'PRINT',
        0x62: 'PRINT',
        0x63: 'PRINT',
        0x64: 'POKE',
        0x65: ',',
        0x66: 'COLOR=',
        0x67: 'PLOT',
        0x68: ',',
        0x69: 'HLIN',
        0x6A: ',',
        0x6B: 'AT',
        0x6C: 'VLIN',
        0x6E: 'AT',
        0x6F: 'VTAB',
        0x70: '=',
        0x71: '=',
        0x72: ')',
        0x73: ')',
        0x74: 'LIST',
        0x76: 'LIST',
        0x77: 'POP',
        0x78: 'NODSP',
        0x79: 'NODSP',
        0x7A: 'NOTRACE',
        0x7B: 'DSP',
        0x7C: 'DSP',
        0x7D: 'TRACE',
        0x7E: 'PR#',
        0x7F: 'IN#'
    };

    function readByte(addr) {
        var page = addr >> 8,
            off = addr & 0xff;

        return _mem.read(page, off);
    }

    function readWord(addr) {
        var lsb, msb;

        lsb = readByte(addr);
        msb = readByte(addr + 1);

        return (msb << 8) | lsb;
    }

    return {
        toString: function () {
            var str = '';
            var addr = readWord(0xca); // Start
            var himem = readWord(0x4c);
            do {
                /*var len = */readByte(addr++);
                var lineno = readWord(addr);
                addr += 2;

                str += lineno;
                str += ' ';
                var val = 0;
                do {
                    val = readByte(addr++);
                    if (val >= 0xB0 && val <= 0xB9) {
                        str += readWord(addr);
                        addr += 2;
                    }
                    else if (val < 0x80 && val > 0x01) {
                        var t = TOKENS[val];
                        if (t.length > 1)
                            str += ' ';
                        str += t;
                        if (t.length > 1)
                            str += ' ';
                    }
                    else if (val > 0x80)
                        str += LETTERS[val - 0x80];
                } while (val != 0x01);
                str += '\n';
            } while (addr < himem);

            return str;
        }
    };
}