all: add WebAssembly backend

src/examples/wasm/wasm.js

@@ -0,0 +1,55 @@
+'use strict';
+
+const WASM_URL = '../../../wasm.wasm';
+
+var wasm;
+var logLine = [];
+var memory8;
+
+var importObject = {
+  env: {
+    io_get_stdout: function() {
+      return 1;
+    },
+    resource_write: function(fd, ptr, len) {
+      if (fd == 1) {
+        for (let i=0; i<len; i++) {
+          let c = memory8[ptr+i];
+          if (c == 13) { // CR
+            // ignore
+          } else if (c == 10) { // LF
+            // write line
+            let line = new TextDecoder("utf-8").decode(new Uint8Array(logLine));
+            logLine = [];
+            console.log(line);
+          } else {
+            logLine.push(c);
+          }
+        }
+      } else {
+        console.error('invalid file descriptor:', fd);
+      }
+    },
+  },
+};
+
+function updateResult() {
+  let a = parseInt(document.querySelector('#a').value);
+  let b = parseInt(document.querySelector('#b').value);
+  let result = wasm.exports.add(a, b);
+  document.querySelector('#result').value = result;
+}
+
+function init() {
+  document.querySelector('#a').oninput = updateResult;
+  document.querySelector('#b').oninput = updateResult;
+
+  WebAssembly.instantiateStreaming(fetch(WASM_URL), importObject).then(function(obj) {
+    wasm = obj.instance;
+    memory8 = new Uint8Array(wasm.exports.memory.buffer);
+    wasm.exports.cwa_main();
+    updateResult();
+  })
+}
+
+init();