`DriverProxy.add_subscription`

aeron-rs/src/driver_proxy.rs

@@ -6,6 +6,8 @@ use crate::concurrent::AtomicBuffer;
 use crate::control_protocol::ClientCommand;
 use crate::util::{AeronError, IndexT, Result};
 use std::mem::size_of;
+use crate::command::subscription_message::SubscriptionMessageDefn;
+use std::ops::Sub;
 
 /// High-level interface for issuing commands to a media driver
 pub struct DriverProxy<A>
@@ -42,8 +44,33 @@ where
         self.client_id
     }
 
+    /// Request the media driver subscribe to a new channel and stream.
+    pub fn add_subscription(&mut self, channel: &str, stream_id: i32) -> Result<i64> {
+        let correlation_id = self.to_driver.next_correlation_id();
+        if channel.len() > (COMMAND_BUFFER_SIZE - size_of::<SubscriptionMessageDefn>()) {
+            return Err(AeronError::InsufficientCapacity)
+        }
+
+        self.write_command_to_driver(|buffer: &mut [u8], length: &mut IndexT| {
+            // UNWRAP: `SubscriptionMessageDefn` guaranteed to be smaller than `COMMAND_BUFFER_SIZE`
+            let mut subscription_message = Flyweight::new::<SubscriptionMessageDefn>(buffer, 0).unwrap();
+
+            subscription_message.put_client_id(self.client_id)
+                .put_registration_correlation_id(-1)
+                .put_correlation_id(correlation_id)
+                .put_stream_id(stream_id);
+            // UNWRAP: Bounds check performed prior to attempting the write
+            subscription_message.put_channel(channel).unwrap();
+
+            *length = subscription_message.length();
+            ClientCommand::AddSubscription
+        });
+
+        Ok(correlation_id)
+    }
+
     /// Request termination of the media driver. Optionally supply a payload on the request
-    /// that will be available to the driver.
+    /// that the driver can use to decide whether or not to honor the request.
     pub fn terminate_driver(&mut self, token_buffer: Option<&[u8]>) -> Result<()> {
         let client_id = self.client_id;
         if token_buffer.is_some()