228 lines
7.1 KiB
JavaScript
228 lines
7.1 KiB
JavaScript
const { logMemory, num2hex } = require('./logging.js');
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const {
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INITIAL_IP_ADDRESS,
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DISPLAY_ADDR,
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KEYPAD_ADDR,
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POINTER_TO_DISPLAY,
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POINTER_TO_KEYPAD
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} = require('./machine.config.js');
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// 1 = verbose
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// 2 = what i'm currently focusing on
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// 3 = always print
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// 4 = silent
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const DEBUG_LEVEL = 2;
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let DEBUG = false; // Turn debugging on/off -- set by assemble()
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exports.assemble = (str, debug = false) => {
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DEBUG = debug;
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return decodeInstructions(str);
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}
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// Configure pseudo-ops:
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const POINTER_TO_CURRENT_ADDR_PSEUDO_OPERAND = '*addr';
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const CONSTANT_PREFIX = '#';
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const LABEL_PREFIX = '@';
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const mnemonicsWithOptionalArgs = ['end', 'nop'];
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const mnemonics2opcodes = {
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end: { direct: 0, indirect: 0 },
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sto: { direct: 1, indirect: 2 },
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lda: { direct: 3, indirect: 4 },
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add: { direct: 5, indirect: 6 },
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sub: { direct: 7, indirect: 8 },
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hop: { direct: 9, indirect: 10 },
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jmp: { direct: 11, indirect: 12 },
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ftg: { direct: 13, indirect: 13 },
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fhp: { direct: 14, indirect: 14 },
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nop: { direct: 15, indirect: 15 },
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};
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/**
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* @param {String} line - One line of assembly to decode
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**/
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function decodeInstructions(line) {
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let lines = line.split(/\n/); // returns an array of lines
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let machineCode = new Array(INITIAL_IP_ADDRESS).fill(0);
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machineCode[POINTER_TO_DISPLAY] = DISPLAY_ADDR;
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machineCode[POINTER_TO_KEYPAD] = KEYPAD_ADDR;
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let labels = {};
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let constants = {};
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let IP = INITIAL_IP_ADDRESS;
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for (let i = 0; i < lines.length; i++) {
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dbg(2, '');
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dbgGroup(1, `Input line ${i}, IP ${num2hex(IP)}`);
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dbg(3, `> ${lines[i]}`);
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let line = stripWhitespaceFromEnds(stripComments(lines[i]));
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// Handle blank lines
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if (line.length === 0) {
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dbg(3, `IP: $${num2hex(IP)}, new code: none`);
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dbg(1, 'blank');
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dbgGroupEnd(1, 'Input line');
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continue;
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}
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// HANDLE OPS
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// Handle label definitions
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if (line.startsWith(LABEL_PREFIX)) {
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let label = line.substring(1); // strip label prefix
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if (label in labels) {
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labels[label].pointsToByte = IP;
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} else {
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labels[label] = {
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pointsToByte: IP,
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bytesToReplace: [],
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};
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}
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dbg(2, `pointsToByte: ${labels[label].pointsToByte}`);
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dbg(2, `bytesToReplace: ${labels[label].bytesToReplace}`);
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dbg(3, `IP: $${num2hex(IP)}, new code: none`);
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dbgGroupEnd(1, 'Input line');
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continue;
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}
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let op_arg_array = line.split(/\s+/); // split line into an array of [op, arg]
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let opName = op_arg_array[0].toLowerCase();
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let arg_str = op_arg_array[1];
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let arg_num = null;
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let addressingMode = 'direct'; // Must be "direct" or "indirect"
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// Handle constant definitions
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if (opName.startsWith(CONSTANT_PREFIX)) {
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// FIXME - a quick hack to get around problems caused by another use of lower-casing to sanitize input:
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let constantName = opName.substring(1).toLowerCase(); // strip '>'
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let constantValue = arg_str;
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if (constantValue.toLowerCase() === POINTER_TO_CURRENT_ADDR_PSEUDO_OPERAND) {
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constantValue = IP.toString();
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}
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constants[constantName] = constantValue;
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dbg(2, `constants:`);
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dbg(2, constants);
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continue;
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}
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// Handle mnemonics without operands (eg END) ...
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if (typeof arg_str === 'undefined') {
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if (mnemonicsWithOptionalArgs.indexOf(opName) < 0) {
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console.error(`Missing opcode: ${line}`);
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throw new Error("Missing opcode");
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}
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arg_num = 0;
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// HANDLE OPERANDS
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// Handle references to labels
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} else if (arg_str.startsWith(LABEL_PREFIX)) {
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let label = arg_str.substring(1); // strip label prefix
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arg_num = 0;
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if (label in labels) {
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dbg(1, `'${label}' already in labels object`);
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labels[label].bytesToReplace.push(IP + 1);
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} else {
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dbg(1, `'${label}' NOT in labels object`);
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labels[label] = {
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bytesToReplace: [IP + 1],
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};
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}
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dbg(2, `pointsToByte: ${labels[label].pointsToByte}`);
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dbg(2, `bytesToReplace: ${labels[label].bytesToReplace}`);
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// Handle references to the Instruction Pointer
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} else if (arg_str.toLowerCase() === POINTER_TO_CURRENT_ADDR_PSEUDO_OPERAND) {
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dbg(2, `operand references current address`);
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arg_num = IP;
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dbg(2, `arg_num: ${num2hex(arg_num)}`);
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// Handle references to constants
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} else if (arg_str.startsWith(CONSTANT_PREFIX)) {
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// FIXME - a quick hack to get around problems caused by another use of lower-casing to sanitize input:
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arg_str = arg_str.substring(1).toLowerCase(); // strip '>'
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dbg(2, `operand references '${arg_str}'`);
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arg_str = constants[arg_str];
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dbg(2, `arg_str from '${arg_str}'`);
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// Handle references to constants in indirect mode
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} else if (arg_str.startsWith(`(${CONSTANT_PREFIX}`)) {
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addressingMode = "indirect";
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arg_str = arg_str.replace(`(${CONSTANT_PREFIX}`, "");
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arg_str = arg_str.replace(")", "");
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// FIXME - a quick hack to get around problems caused by another use of lower-casing to sanitize input:
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arg_str = arg_str.toLowerCase();
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dbg(2, `INDY - operand references '${arg_str}'`);
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arg_str = constants[arg_str];
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// Handle indirect expressions
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} else if (arg_str.startsWith("(")) {
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addressingMode = "indirect";
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arg_str = arg_str.replace("(", "");
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arg_str = arg_str.replace(")", "");
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}
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// Handle numeric operands
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if (arg_num === null) {
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if (arg_str.startsWith("$")) {
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// Handle hex
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arg_str = arg_str.replace("$", "");
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arg_num = hex2num(arg_str);
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} else {
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// Accept decimal i guess
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arg_num = parseInt(arg_str);
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}
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}
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// DECODE!
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const op = mnemonics2opcodes[opName][addressingMode];
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machineCode.push(op);
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machineCode.push(arg_num);
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dbg(3, `IP: $${num2hex(IP)}, new code: $${num2hex(op)} $${num2hex(arg_num)}`);
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IP += 2;
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dbgGroupEnd(1, 'Input line');
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};
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dbg(1, '');
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dbgGroup(1, 'Memory before filling in label constants');
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dbgExec(1, () => logMemory(new Uint8Array(machineCode)));
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dbgGroupEnd(1, 'Memory before filling in label constants');
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// Backfill label references
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for (let k of Object.keys(labels)) {
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dbgGroup(2, `${LABEL_PREFIX}${k}`);
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let label = labels[k];
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dbg(2, `pointsToByte: ${label.pointsToByte}`);
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dbg(2, `bytesToReplace: ${label.bytesToReplace}`);
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dbgGroupEnd(2, `label`);
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for (let j = 0; j < label.bytesToReplace.length; j++) {
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machineCode[label.bytesToReplace[j]] = label.pointsToByte;
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}
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}
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return new Uint8Array(machineCode);
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}
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function stripComments(line) {
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return line.replace(/;.+/,"");
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}
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function stripWhitespaceFromEnds(line) {
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line = line.replace(/^\s+/,"");
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line = line.replace(/\s+$/,"");
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return line;
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}
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function hex2num(hex) { return parseInt(hex, 16) };
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// Debug helpers
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const dbg = (lvl, s) => { if (DEBUG && (lvl >= DEBUG_LEVEL)) console.log(s) };
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const dbgGroup = (lvl, s) => { if (DEBUG && (lvl >= DEBUG_LEVEL)) console.group(s) };
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const dbgGroupEnd = (lvl, s) => { if (DEBUG && (lvl >= DEBUG_LEVEL)) console.groupEnd() };
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const dbgExec = (lvl, func) => { if (DEBUG && (lvl >= DEBUG_LEVEL)) func(); } |