Support to publish serialized messages

This patch implements the feature that a publisher can publish a raw
message, and an example is added.

Fix #646

example/publisher-raw-message.js

@@ -0,0 +1,43 @@
+// Copyright (c) 2020 Intel Corporation. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+'use strict';
+
+/* eslint-disable camelcase */
+
+const rclnodejs = require('../index.js');
+
+rclnodejs
+  .init()
+  .then(() => {
+    const node = rclnodejs.createNode('publisher_message_example_node');
+
+    // We have to make sure the message type of publisher and subscription is
+    // the same, although it seems meaningless when sending raw messages.
+    const publisher = node.createPublisher(
+      'test_msgs/msg/BasicTypes',
+      'chatter'
+    );
+    let count = 0;
+
+    setInterval(function () {
+      publisher.publish(Buffer.from('Hello ROS World'));
+      console.log(`Publish ${++count} messages.`);
+    }, 1000);
+
+    rclnodejs.spin(node);
+  })
+  .catch((e) => {
+    console.log(e);
+  });

lib/publisher.js

@@ -38,21 +38,27 @@ class Publisher extends Entity {
 
   /**
    * Publish a message
-   * @param {object} message - The message to be sent.
+   * @param {object|Buffer} message - The message to be sent, could be kind of JavaScript message generated from .msg
+   *                                                          or be a Buffer for a raw message.
    * @return {undefined}
    */
   publish(message) {
-    // Enables call by plain object/number/string argument
-    //  e.g. publisher.publish(3.14);
-    //       publisher.publish('The quick brown fox...');
-    //       publisher.publish({linear: {x: 0, y: 1, z: 2}, ...});
-    let messageToSend =
-      message instanceof this._typeClass
-        ? message
-        : new this._typeClass(message);
+    if (message instanceof Buffer) {
+      rclnodejs.publishRawMessage(this._handle, message);
+    } else {
+      // Enables call by plain object/number/string argument
+      //  e.g. publisher.publish(3.14);
+      //       publisher.publish('The quick brown fox...');
+      //       publisher.publish({linear: {x: 0, y: 1, z: 2}, ...});
+      let messageToSend =
+        message instanceof this._typeClass
+          ? message
+          : new this._typeClass(message);
+
+      let rawMessage = messageToSend.serialize();
+      rclnodejs.publish(this._handle, rawMessage);
+    }
 
-    let rawMessage = messageToSend.serialize();
-    rclnodejs.publish(this._handle, rawMessage);
     debug(`Message of topic ${this.topic} has been published.`);
   }
 

src/rcl_bindings.cpp

@@ -1692,6 +1692,27 @@ NAN_METHOD(ServiceServerIsAvailable) {
   info.GetReturnValue().Set(result);
 }
 
+NAN_METHOD(PublishRawMessage) {
+  rcl_publisher_t* publisher = reinterpret_cast<rcl_publisher_t*>(
+      RclHandle::Unwrap<RclHandle>(
+          Nan::To<v8::Object>(info[0]).ToLocalChecked())
+          ->ptr());
+
+  auto object = Nan::To<v8::Object>(info[1]).ToLocalChecked();
+  rcl_serialized_message_t serialized_msg =
+      rmw_get_zero_initialized_serialized_message();
+  serialized_msg.buffer_capacity = node::Buffer::Length(object);
+  serialized_msg.buffer_length = serialized_msg.buffer_capacity;
+  serialized_msg.buffer =
+      reinterpret_cast<uint8_t*>(node::Buffer::Data(object));
+
+  THROW_ERROR_IF_NOT_EQUAL(
+      rcl_publish_serialized_message(publisher, &serialized_msg, nullptr),
+      RCL_RET_OK, rcl_get_error_string().str);
+
+  info.GetReturnValue().Set(Nan::Undefined());
+}
+
 std::vector<BindingMethod> binding_methods = {
     {"init", Init},
     {"createNode", CreateNode},
@@ -1757,6 +1778,7 @@ std::vector<BindingMethod> binding_methods = {
     {"countPublishers", CountPublishers},
     {"countSubscribers", CountSubscribers},
     {"serviceServerIsAvailable", ServiceServerIsAvailable},
+    {"publishRawMessage", PublishRawMessage},
     {"", nullptr}};
 
 }  // namespace rclnodejs