Implement MQTT outbox limits and get_outbox_size()

CHANGELOG.md

@@ -7,6 +7,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Breaking
+- Implement MQTT outbox limit and get_outbox_size()
+
 ### Fixed
 - Fix wrong BT configuration version on the c6 (issue #556)
 

src/mqtt/client.rs

@@ -67,6 +67,7 @@ pub struct MqttClientConfiguration<'a> {
     pub task_stack: usize,
     pub buffer_size: usize,
     pub out_buffer_size: usize,
+    pub outbox_limit: Option<usize>,
 
     pub username: Option<&'a str>,
     pub password: Option<&'a str>,
@@ -108,6 +109,7 @@ impl Default for MqttClientConfiguration<'_> {
             task_stack: 0,
             buffer_size: 0,
             out_buffer_size: 0,
+            outbox_limit: None,
 
             username: None,
             password: None,
@@ -316,6 +318,10 @@ impl<'a> TryFrom<&'a MqttClientConfiguration<'a>>
             }
         }
 
+        if let Some(outbox_limit) = conf.outbox_limit {
+            c_conf.outbox.limit = outbox_limit as _;
+        }
+
         #[cfg(all(esp_idf_esp_tls_psk_verification, feature = "alloc"))]
         let tls_psk_conf = conf.psk.as_ref().map(|psk| psk.try_into()).transpose()?;
         #[cfg(not(all(esp_idf_esp_tls_psk_verification, feature = "alloc")))]
@@ -625,6 +631,12 @@ impl<'a> EspMqttClient<'a> {
         Self::check(unsafe { esp_mqtt_client_set_uri(self.raw_client, uri.as_ptr()) })
     }
 
+    pub fn get_outbox_size(&self) -> usize {
+        // this is always positive as internally this is converting uint64_t to int (defaults to 0)
+        let outbox_size = unsafe { esp_mqtt_client_get_outbox_size(self.raw_client) };
+        outbox_size.max(0) as usize
+    }
+
     extern "C" fn handle(
         event_handler_arg: *mut c_void,
         _event_base: esp_event_base_t,