1 files changed, 33 insertions, 0 deletions

diff --git a/src/js/tinyvm.ts b/src/js/tinyvm.ts
index ab1e4da..b6146fb 100644
--- a/src/js/tinyvm.ts
+++ b/src/js/tinyvm.ts
@@ -171,6 +171,9 @@ export class TinyVM {
 
     private inputBuffer: Uint8Array = new Uint8Array(0);
     private inputPos: number = 0;
+    /** true while a streaming run is suspended by a poll (syscall 42) rather than by a read: the host
+        should resume it after its event loop has run, whether or not input came. */
+    public polling: boolean = false;
     private outputBuffer: number[] = [];
     private onOutput?: (byte: number) => void;
     private onMessage?: (msg: string) => void;
@@ -429,6 +432,14 @@ export class TinyVM {
                 }
                 return -1n;
             }
+            case 42: // poll: input is waiting
+                return this.inputPos < this.inputBuffer.length ? 1n : 0n;
+            case 41: { // shortest float text into a word buffer
+                const text = formatFloat(a, 0n, 17n);
+                if (b < 0n || c <= BigInt(text.length) || b > BigInt(this.mw) || c > BigInt(this.mw) - b) return -1n;
+                for (let i = 0; i < text.length; i++) this.mem[Number(b) + i] = BigInt(text.charCodeAt(i));
+                this.mem[Number(b) + text.length] = 0n; return BigInt(text.length);
+            }
             case 18: { // fill heap words without running one vm store per word
                 if (a < BigInt(this.L.HEAP_LO) || c <= 0n || a > BigInt(this.mw) || c > BigInt(this.mw) - a) return -1n;
                 this.mem.fill(b, Number(a), Number(a + c)); return c;
@@ -721,6 +732,14 @@ export class TinyVM {
                     break;
                 case 2: // st
                     if (Number(a) === this.L.SYSGATE) {
+                        if (b === 42n && this.streaming) {
+                            // poll: suspend once so the host can deliver what has arrived, then say if input waits
+                            if (!this.polling) { this.polling = true; this.rp = p - 1; this.rs = s; this.rr = r; this.blocked = true; return BLOCKED; }
+                            this.polling = false;
+                            mem[Number(a)] = this.inputPos < this.inputBuffer.length ? 1n : 0n;
+                            s += 2;
+                            break;
+                        }
                         this.rs = s + 2; this.rr = r;
                         const result = this.syscall(b, mem[Number(a) + 1], mem[Number(a) + 2], mem[Number(a) + 3]);
                         mem = this.mem; bytes = this.bytes; view = this.view; mw = this.mw; // a grow may have moved them
@@ -898,6 +917,20 @@ export class TinyVM {
 
 // command line runner: node src/js/tinyvm.js <file.zc>, or the source on stdin
 if (typeof require === 'function' && typeof module !== 'undefined' && require.main === module) {
+    const option = process.argv[2];
+    if (option === '--help' || option === '-h') {
+        process.stdout.write('usage: node src/js/tinyvm.js [file.zc]\n' +
+            'compiles and runs the file, or reads source from stdin when no file is supplied.\n' +
+            'input after a backtick is program input.\n' +
+            'options:\n  --help, -h  show this help and exit\n' +
+            'environment:\n  TINYVM_MEMORY_WORDS      initial vm memory in words\n' +
+            '  TINYVM_MAX_MEMORY_WORDS  maximum vm memory in words\n');
+        process.exit(0);
+    }
+    if (option && option.startsWith('-')) {
+        process.stderr.write('tinyvm.js: unknown option ' + option + '; use --help for usage\n');
+        process.exit(2);
+    }
     const genomePath = path.join(__dirname, 'genome.json');
     if (!fs.existsSync(genomePath)) {
         console.error('Error: genome.json not found. Run extract_genome.js first.');