Add support for loaned messages (#212)

Author: nnmm

rclrs/minimal_pub_sub/Cargo.toml

@@ -13,6 +13,14 @@ path = "src/minimal_subscriber.rs"
 name = "minimal_publisher"
 path = "src/minimal_publisher.rs"
 
+[[bin]]
+name = "zero_copy_subscriber"
+path = "src/zero_copy_subscriber.rs"
+
+[[bin]]
+name = "zero_copy_publisher"
+path = "src/zero_copy_publisher.rs"
+
 [dependencies]
 anyhow = {version = "1", features = ["backtrace"]}
 

rclrs/minimal_pub_sub/src/zero_copy_publisher.rs

@@ -0,0 +1,23 @@
+use anyhow::{Error, Result};
+use std::env;
+
+fn main() -> Result<(), Error> {
+    let context = rclrs::Context::new(env::args())?;
+
+    let node = rclrs::create_node(&context, "minimal_publisher")?;
+
+    let publisher =
+        node.create_publisher::<std_msgs::msg::rmw::UInt32>("topic", rclrs::QOS_PROFILE_DEFAULT)?;
+
+    let mut publish_count: u32 = 1;
+
+    while context.ok() {
+        let mut message = publisher.borrow_loaned_message()?;
+        message.data = publish_count;
+        println!("Publishing: {}", message.data);
+        message.publish()?;
+        publish_count += 1;
+        std::thread::sleep(std::time::Duration::from_millis(500));
+    }
+    Ok(())
+}

rclrs/minimal_pub_sub/src/zero_copy_subscriber.rs

@@ -0,0 +1,23 @@
+use std::env;
+
+use anyhow::{Error, Result};
+
+fn main() -> Result<(), Error> {
+    let context = rclrs::Context::new(env::args())?;
+
+    let mut node = rclrs::create_node(&context, "minimal_subscriber")?;
+
+    let mut num_messages: usize = 0;
+
+    let _subscription = node.create_subscription::<std_msgs::msg::UInt32, _>(
+        "topic",
+        rclrs::QOS_PROFILE_DEFAULT,
+        move |msg: std_msgs::msg::UInt32| {
+            num_messages += 1;
+            println!("I heard: '{}'", msg.data);
+            println!("(Got {} messages so far)", num_messages);
+        },
+    )?;
+
+    rclrs::spin(&node).map_err(|err| err.into())
+}