add queue size

src/MqttClient.cpp

@@ -194,6 +194,14 @@ const char* MqttClient::getClientId() const {
   return _clientId;
 }
 
+size_t MqttClient::queueSize() const {
+  size_t ret = 0;
+  EMC_SEMAPHORE_TAKE();
+  ret = _outbox.size();
+  EMC_SEMAPHORE_GIVE();
+  return ret;
+}
+
 void MqttClient::loop() {
   switch (_state) {
     case State::disconnected:

src/MqttClient.h

@@ -65,6 +65,7 @@ class MqttClient {
   uint16_t publish(const char* topic, uint8_t qos, bool retain, espMqttClientTypes::PayloadCallback callback, size_t length);
   void clearQueue(bool deleteSessionData = false);  // Not MQTT compliant and may cause unpredictable results when `deleteSessionData` = true!
   const char* getClientId() const;
+  size_t queueSize() const;
   void loop();
 
  protected:

src/Outbox.h

@@ -163,6 +163,16 @@ class Outbox {
     return false;
   }
 
+  size_t size() const {
+    Node* n = _first;
+    size_t count = 0;
+    while (n) {
+      n = n->next;
+      ++count;
+    }
+    return count;
+  }
+
  private:
   Node* _first;
   Node* _last;