first poc for a web runtime

web/src/main.js

@@ -0,0 +1,45 @@
+import wasmDataUrl from "data-url:./trainride.uw8";
+
+async function main() {
+    let wasm_module = await (await fetch(wasmDataUrl)).arrayBuffer();
+    let compiled_module = await WebAssembly.compile(wasm_module);
+
+    let import_object = {
+        uw8: {
+            ram: new WebAssembly.Memory({ initial: 8, maximum: 8 }),
+            time: new WebAssembly.Global({value: 'i32', mutable: true}, 0),
+        }
+    };
+
+    let instance = new WebAssembly.Instance(compiled_module, import_object);
+
+    let canvasCtx = document.getElementById('screen').getContext('2d');
+    let imageData = canvasCtx.createImageData(320, 256);
+
+    let buffer = imageData.data;
+    for(let i = 0; i < 320*256; ++i) {
+        buffer[i * 4 + 3] = 255;
+    }
+
+    let startTime = Date.now();
+
+    function mainloop() {
+        import_object.uw8.time.value = Date.now() - startTime;
+
+        instance.exports.tic();
+
+        let framebuffer = new Uint8Array(import_object.uw8.ram.buffer.slice(120, 120 + 320*256));
+        for(let i = 0; i < 320*256; ++i) {
+            buffer[i * 4] = framebuffer[i];
+            buffer[i * 4 + 1] = framebuffer[i];
+            buffer[i * 4 + 2] = framebuffer[i];
+        }
+        canvasCtx.putImageData(imageData, 0, 0);
+
+        window.requestAnimationFrame(mainloop);
+    }
+
+    mainloop();
+}
+
+main();