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assembler.js
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assembler.js
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var fs = require('fs');
var argv = require('minimist')(process.argv.slice(2));
require('string-format');
if (argv.h || argv.help || !argv._[0]) {
console.log('Usage: {} input [-o|--out output] [-h|--help]'.format(__filename));
process.exit();
}
var input = argv._[0];
var output = argv.o || argv.out;
var data = fs.readFileSync(input);
var prog = data.toString().split('\n');
var map = {
'NOP': { opcode: 0x00, args: 0},
'LOAD': { opcode: 0x10, args: 2},
'STORE': { opcode: 0x20, args: 2},
'BRANCH': { opcode: 0x30, args: 1},
'SET': { opcode: 0x40, args: 2},
'ADD': { opcode: 0x50, args: 2},
'SUB': { opcode: 0x60, args: 2},
'BNZ': { opcode: 0x70, args: 2},
'EXIT': { opcode: 0x80, args: 0},
'DEF': { opcode: 0x00, args: 1}
};
var pointer = 0;
var instructions = [];
var labels = {};
prog.forEach(function (line) {
// Remove comments and trailing spaces, ignore blank lines
line = line.replace(/;.*/, '').trim();
if (!line) return;
if (line.slice(-1) == ':') {
// Store address of label
var label = line.slice(0, -1);
labels[label] = pointer;
return
}
var parts = line.split(/ +/);
if (!(parts[0] in map)) {
throw 'ParseError: unknown instruction ' + parts[0];
}
var opcode = map[parts[0]].opcode;
var args = map[parts[0]].args;
if (parts.length - 1 != args) {
throw 'ParseError: {} takes {} arguments'.format(parts[0], args);
}
if (parts.length > 1) {
// Merge opcode and operand
instructions[pointer] = opcode | parts[1].slice(1);
if (parts.length > 2) {
// Put address in next memory location
instructions[++pointer] = parts[0] == 'BNZ' ? parts[2] : parseInt(parts[2]);
}
} else {
instructions[pointer] = opcode;
}
if (parts[0] == 'DEF') {
// Set this location to the value specified
instructions[pointer] = parts[1];
}
if (parts[0] == 'BRANCH') {
// Add label to instructions - it will be replaced next pass
instructions[++pointer] = parts[1];
}
pointer++;
});
// Replace labels with addresses
if (Object.keys(labels).length) {
Object.keys(instructions).forEach(function (key) {
var token = instructions[key];
if (token in labels) {
instructions[key] = labels[token];
}
});
}
if (output) {
var stream = fs.createWriteStream(output);
stream.write(new Buffer(instructions));
stream.end();
} else if (!process.stdout.isTTY) {
process.stdout.write(new Buffer(instructions));
} else {
console.log(labels)
console.log(instructions);
}