Feature (CPU): Implement a simple single-stepping mode

cpu.js

@@ -1,3 +1,5 @@
+const readlineSync = require('readline-sync');
+
 const { INITIAL_IP_ADDRESS, CYCLE_LIMIT } = require('./machine.config');
 const { num2hex, num2bin_4bit } = require('./logging.js');
 const display = require('./display.js');
@@ -311,6 +313,23 @@ exports.runProgram = (code, debug = false, clockSpeed = 10) => {
   }, clockSpeed);
 }
 
+/**
+ * @param {Uint8Array} code   - Machine code to run
+ * @param {Boolean}   [debug] - Enable/disable debugging printouts
+ **/
+exports.singleStepProgram = (code, debug = false) => {
+  startCPU(code);
+  while (CPU.running) {
+    stepCPU(debug);
+    // FIXME: this prevents exiting with Ctrl+C:
+    let key = readlineSync.keyIn('S to step, Q to quit > ', {
+      limit: ['s', 'S', 'q', 'Q'],
+    });
+    if (key.toLowerCase() === 'q') { process.exit(); }
+    console.log();
+  }
+}
+
 
 // FUNCTIONS THAT PULL INFO FROM STATE TO DISPLAY
 

notes/2023-08-16--dev-notes.md

@@ -8,7 +8,7 @@
 - [ ] Notes re: ROM and/or tape loader
 - [ ] CPU updates
   - [x] Rename to CPU
-  - [ ] Implement single-stepping
+  - [x] Implement single-stepping
   - [ ] Implement keypad input
     - [ ] Look at KIM-1 and VIP buttons for memory editing
 

package-lock.json

@@ -5,6 +5,9 @@
   "packages": {
     "": {
       "name": "paper-computer",
+      "dependencies": {
+        "readline-sync": "^1.4.10"
+      },
       "devDependencies": {
         "jsdoc": "^4.0.2",
         "jsdoc-to-markdown": "^8.0.0"
@@ -720,6 +723,14 @@
         "node": ">=0.10.0"
       }
     },
+    "node_modules/readline-sync": {
+      "version": "1.4.10",
+      "resolved": "https://registry.npmjs.org/readline-sync/-/readline-sync-1.4.10.tgz",
+      "integrity": "sha512-gNva8/6UAe8QYepIQH/jQ2qn91Qj0B9sYjMBBs3QOB8F2CXcKgLxQaJRP76sWVRQt+QU+8fAkCbCvjjMFu7Ycw==",
+      "engines": {
+        "node": ">= 0.8.0"
+      }
+    },
     "node_modules/reduce-extract": {
       "version": "1.0.0",
       "resolved": "https://registry.npmjs.org/reduce-extract/-/reduce-extract-1.0.0.tgz",

package.json

@@ -1,10 +1,13 @@
 {
   "name": "paper-computer",
   "scripts": {
-    "jsdoc":      "./node_modules/.bin/jsdoc"
+    "jsdoc": "./node_modules/.bin/jsdoc"
   },
   "devDependencies": {
     "jsdoc": "^4.0.2",
     "jsdoc-to-markdown": "^8.0.0"
+  },
+  "dependencies": {
+    "readline-sync": "^1.4.10"
   }
 }

readme.md

@@ -25,6 +25,12 @@ With animated display of screen memory:
 With verbose debugging output:  
 ```./run-cpu debug source_code.asm```
 
+With single stepping + pretty-printed display:  
+```./run-cpu step source_code.asm```
+
+With single stepping + verbose debugging output:  
+```./run-cpu stepdebug source_code.asm```
+
 ## Instruction set
 
     00   END

run-cpu.js

@@ -2,6 +2,8 @@
 
 // Run:   `./run-cpu.js run assembly.asm`
 // Debug: `./run-cpu.js debug assembly.asm`
+// Run with single-stepping: `./run-cpu.js step assembly.asm`
+// Debug with single-stepping: `./run-cpu.js stepdebug assembly.asm`
 
 // TODO: allow running pre-compiled machine code.
 //
@@ -22,12 +24,15 @@ const mode = process.argv[2];
 const filename = process.argv[3];
 const inputFile_str = fs.readFileSync(filename, 'utf8');
 
-let machineCode;
+let machineCode = assembler.assemble(inputFile_str);
 if (mode === "debug") {
   logRunningHeader();
-  machineCode = assembler.assemble(inputFile_str);
   computer.runProgram(machineCode, true);
+} else if (mode === "stepdebug") {
+  logRunningHeader();
+  computer.singleStepProgram(machineCode, true);
+} else if (mode === "step") {
+  computer.singleStepProgram(machineCode, false);
 } else {
-  machineCode = assembler.assemble(inputFile_str);
   computer.runProgram(machineCode, false, 200);
 }

sketches/stdin.js

@@ -0,0 +1,23 @@
+const readlineSync = require('readline-sync');
+
+let key = readlineSync.keyIn('? ')
+console.log(key);
+
+/* This works without external dependencies,
+ * but it's for a full line at a time
+const readline = require('readline/promises');
+
+const rl = readline.createInterface({
+  input: process.stdin,
+  output: process.stdout
+});
+
+async function getInput(prompt) {
+  let input = await rl.question(prompt)
+  console.log(input);
+  console.log("Later");
+  rl.close();
+}
+
+getInput('?');
+*/