Add WaitSet::new_for_node() (#276)

This function is important for users who directly use wait sets, since the live_subscriptions() etc. functions are not public.

rclrs/src/lib.rs

@@ -46,39 +46,7 @@ pub use wait::*;
 ///
 /// [1]: crate::RclReturnCode
 pub fn spin_once(node: &Node, timeout: Option<Duration>) -> Result<(), RclrsError> {
-    let live_subscriptions = node.live_subscriptions();
-    let live_clients = node.live_clients();
-    let live_guard_conditions = node.live_guard_conditions();
-    let live_services = node.live_services();
-    let ctx = Context {
-        rcl_context_mtx: node.rcl_context_mtx.clone(),
-    };
-    let mut wait_set = WaitSet::new(
-        live_subscriptions.len(),
-        live_guard_conditions.len(),
-        0,
-        live_clients.len(),
-        live_services.len(),
-        0,
-        &ctx,
-    )?;
-
-    for live_subscription in &live_subscriptions {
-        wait_set.add_subscription(live_subscription.clone())?;
-    }
-
-    for live_client in &live_clients {
-        wait_set.add_client(live_client.clone())?;
-    }
-
-    for live_guard_condition in &live_guard_conditions {
-        wait_set.add_guard_condition(live_guard_condition.clone())?;
-    }
-
-    for live_service in &live_services {
-        wait_set.add_service(live_service.clone())?;
-    }
-
+    let mut wait_set = WaitSet::new_for_node(node)?;
     let ready_entities = wait_set.wait(timeout)?;
 
     for ready_subscription in ready_entities.subscriptions {

rclrs/src/wait.rs

@@ -21,7 +21,7 @@ use std::vec::Vec;
 
 use crate::error::{to_rclrs_result, RclReturnCode, RclrsError, ToResult};
 use crate::rcl_bindings::*;
-use crate::{ClientBase, Context, ServiceBase, SubscriptionBase};
+use crate::{ClientBase, Context, Node, ServiceBase, SubscriptionBase};
 
 mod exclusivity_guard;
 mod guard_condition;
@@ -117,6 +117,45 @@ impl WaitSet {
         })
     }
 
+    /// Creates a new wait set and adds all waitable entities in the node to it.
+    ///
+    /// The wait set is sized to fit the node exactly, so there is no capacity for adding other entities.
+    pub fn new_for_node(node: &Node) -> Result<Self, RclrsError> {
+        let live_subscriptions = node.live_subscriptions();
+        let live_clients = node.live_clients();
+        let live_guard_conditions = node.live_guard_conditions();
+        let live_services = node.live_services();
+        let ctx = Context {
+            rcl_context_mtx: node.rcl_context_mtx.clone(),
+        };
+        let mut wait_set = WaitSet::new(
+            live_subscriptions.len(),
+            live_guard_conditions.len(),
+            0,
+            live_clients.len(),
+            live_services.len(),
+            0,
+            &ctx,
+        )?;
+
+        for live_subscription in &live_subscriptions {
+            wait_set.add_subscription(live_subscription.clone())?;
+        }
+
+        for live_client in &live_clients {
+            wait_set.add_client(live_client.clone())?;
+        }
+
+        for live_guard_condition in &live_guard_conditions {
+            wait_set.add_guard_condition(live_guard_condition.clone())?;
+        }
+
+        for live_service in &live_services {
+            wait_set.add_service(live_service.clone())?;
+        }
+        Ok(wait_set)
+    }
+
     /// Removes all entities from the wait set.
     ///
     /// This effectively resets the wait set to the state it was in after being created by