add basic infrastructure of javascript example

example/provider/javascript/js/webfuse/messagereader.js

@@ -0,0 +1,59 @@
+class MessageReader {
+    
+    constructor(data) {
+        // console.log(new Uint8Array(data));
+        this.raw = data;
+        this.data = new DataView(data);
+        this.pos = 0;
+        this.decoder = new TextDecoder('utf-8');
+    }
+
+    read_u8() {
+        const result = this.data.getUint8(this.pos);
+        this.pos++;
+        return result;
+    }
+
+    read_bool() {
+        return this.read_u8() == 1;
+    }
+
+    read_u32() {
+        const result = this.data.getUint32(this.pos);
+        this.pos += 4;
+        return result;
+    }
+
+    read_u64() {
+        const result = this.data.getBigUint64(this.pos);
+        this.pos += 8;
+        return Number(result);
+    }
+
+    read_str() {
+        const length = this.read_u32();
+        if (length > 0) {
+            const view = new Uint8Array(this.raw, this.pos, length);
+            this.pos += length;
+            return this.decoder.decode(view);
+        }
+        else {
+            return "";
+        }
+    }
+
+    read_bytes() {
+        const length = this.read_u32();
+        if (length > 0) {
+            const view = new Uint8Array(this.raw, this.pos, length);
+            this.pos += length;
+            return view;
+        }
+        else {
+            return [];
+        }
+    }
+
+}
+
+export { MessageReader }