Inspector+LibCore+rpcdump: Rework the RPC stuff to be request/response

RPC clients now send JSON-encoded requests to the RPC server.
The connection also stays alive instead of disconnecting automatically
after the initial CObject graph dump.

JSON payloads are preceded by a single host-order encoded 32-bit int
containing the length of the payload.

So far, we have three RPC commands:

    - Identify
    - GetAllObjects
    - Disconnect

We'll be adding more of these as we go along. :^)

DevTools/Inspector/RemoteProcess.cpp

@@ -11,10 +11,80 @@ RemoteProcess::RemoteProcess(pid_t pid)
 {
 }
 
+void RemoteProcess::handle_identify_response(const JsonObject& response)
+{
+    int pid = response.get("pid").to_int();
+    ASSERT(pid == m_pid);
+
+    m_process_name = response.get("process_name").as_string_or({});
+
+    if (on_update)
+        on_update();
+}
+
+void RemoteProcess::handle_get_all_objects_response(const JsonObject& response)
+{
+    // FIXME: It would be good if we didn't have to make a local copy of the array value here!
+    auto objects = response.get("objects");
+    auto& object_array = objects.as_array();
+
+    NonnullOwnPtrVector<RemoteObject> remote_objects;
+    HashMap<String, RemoteObject*> objects_by_address;
+
+    for (auto& value : object_array.values()) {
+        ASSERT(value.is_object());
+        auto& object = value.as_object();
+        auto remote_object = make<RemoteObject>();
+        remote_object->address = object.get("address").to_string();
+        remote_object->parent_address = object.get("parent").to_string();
+        remote_object->name = object.get("name").to_string();
+        remote_object->class_name = object.get("class_name").to_string();
+        remote_object->json = object;
+        objects_by_address.set(remote_object->address, remote_object);
+        remote_objects.append(move(remote_object));
+    }
+
+    for (int i = 0; i < remote_objects.size(); ++i) {
+        auto& remote_object = remote_objects.ptr_at(i);
+        auto* parent = objects_by_address.get(remote_object->parent_address).value_or(nullptr);
+        if (!parent) {
+            m_roots.append(move(remote_object));
+        } else {
+            remote_object->parent = parent;
+            parent->children.append(move(remote_object));
+        }
+    }
+
+    m_object_graph_model->update();
+
+    if (on_update)
+        on_update();
+}
+
+void RemoteProcess::send_request(const JsonObject& request)
+{
+    auto serialized = request.to_string();
+    i32 length = serialized.length();
+    m_socket.write((const u8*)&length, sizeof(length));
+    m_socket.write(serialized);
+}
+
 void RemoteProcess::update()
 {
     m_socket.on_connected = [this] {
         dbg() << "Connected to PID " << m_pid;
+
+        {
+            JsonObject request;
+            request.set("type", "Identify");
+            send_request(request);
+        }
+
+        {
+            JsonObject request;
+            request.set("type", "GetAllObjects");
+            send_request(request);
+        }
     };
 
     m_socket.on_ready_to_read = [this] {
@@ -24,39 +94,35 @@ void RemoteProcess::update()
             return;
         }
 
-        auto data = m_socket.read_all();
+        i32 length;
+        int nread = m_socket.read((u8*)&length, sizeof(length));
+        ASSERT(nread == sizeof(length));
+
+        auto data = m_socket.read(length);
+        ASSERT(data.size() == length);
+
+        dbg() << "Got packet size " << length << " and read that many bytes";
+
         auto json_value = JsonValue::from_string(data);
-        ASSERT(json_value.is_array());
-        auto& object_array = json_value.as_array();
+        ASSERT(json_value.is_object());
 
-        Vector<NonnullOwnPtr<RemoteObject>> remote_objects;
-        HashMap<String, RemoteObject*> objects_by_address;
+        dbg() << "Got JSON response " << json_value.to_string();
 
-        for (auto& value : object_array.values()) {
-            ASSERT(value.is_object());
-            auto& object = value.as_object();
-            auto remote_object = make<RemoteObject>();
-            remote_object->address = object.get("address").to_string();
-            remote_object->parent_address = object.get("parent").to_string();
-            remote_object->name = object.get("name").to_string();
-            remote_object->class_name = object.get("class_name").to_string();
-            remote_object->json = object;
-            objects_by_address.set(remote_object->address, remote_object);
-            remote_objects.append(move(remote_object));
+        auto& response = json_value.as_object();
+
+        auto response_type = response.get("type").as_string_or({});
+        if (response_type.is_null())
+            return;
+
+        if (response_type == "GetAllObjects") {
+            handle_get_all_objects_response(response);
+            return;
         }
 
-        for (int i = 0; i < remote_objects.size(); ++i) {
-            auto& remote_object = remote_objects[i];
-            auto* parent = objects_by_address.get(remote_object->parent_address).value_or(nullptr);
-            if (!parent) {
-                m_roots.append(move(remote_object));
-            } else {
-                remote_object->parent = parent;
-                parent->children.append(move(remote_object));
-            }
+        if (response_type == "Identify") {
+            handle_identify_response(response);
+            return;
         }
-
-        m_object_graph_model->update();
     };
 
     auto success = m_socket.connect(CSocketAddress::local(String::format("/tmp/rpc.%d", m_pid)));