[api] Eliminate heap allocations when transmitting Event types (#11773)

esphome/components/api/api_connection.cpp

@@ -1294,11 +1294,11 @@ void APIConnection::alarm_control_panel_command(const AlarmControlPanelCommandRe
 #endif
 
 #ifdef USE_EVENT
-void APIConnection::send_event(event::Event *event, const std::string &event_type) {
+void APIConnection::send_event(event::Event *event, const char *event_type) {
   this->schedule_message_(event, MessageCreator(event_type), EventResponse::MESSAGE_TYPE,
                           EventResponse::ESTIMATED_SIZE);
 }
-uint16_t APIConnection::try_send_event_response(event::Event *event, const std::string &event_type, APIConnection *conn,
+uint16_t APIConnection::try_send_event_response(event::Event *event, const char *event_type, APIConnection *conn,
                                                 uint32_t remaining_size, bool is_single) {
   EventResponse resp;
   resp.set_event_type(StringRef(event_type));
@@ -1650,9 +1650,7 @@ void APIConnection::DeferredBatch::add_item(EntityBase *entity, MessageCreator c
   // O(n) but optimized for RAM and not performance.
   for (auto &item : items) {
     if (item.entity == entity && item.message_type == message_type) {
-      // Clean up old creator before replacing
+      // Replace with new creator
-      item.creator.cleanup(message_type);
-      // Move assign the new creator
       item.creator = std::move(creator);
       return;
     }
@@ -1822,7 +1820,7 @@ void APIConnection::process_batch_() {
 
   // Handle remaining items more efficiently
   if (items_processed < this->deferred_batch_.size()) {
-    // Remove processed items from the beginning with proper cleanup
+    // Remove processed items from the beginning
     this->deferred_batch_.remove_front(items_processed);
     // Reschedule for remaining items
     this->schedule_batch_();
@@ -1835,10 +1833,10 @@ void APIConnection::process_batch_() {
 uint16_t APIConnection::MessageCreator::operator()(EntityBase *entity, APIConnection *conn, uint32_t remaining_size,
                                                    bool is_single, uint8_t message_type) const {
 #ifdef USE_EVENT
-  // Special case: EventResponse uses string pointer
+  // Special case: EventResponse uses const char * pointer
   if (message_type == EventResponse::MESSAGE_TYPE) {
     auto *e = static_cast<event::Event *>(entity);
-    return APIConnection::try_send_event_response(e, *data_.string_ptr, conn, remaining_size, is_single);
+    return APIConnection::try_send_event_response(e, data_.const_char_ptr, conn, remaining_size, is_single);
   }
 #endif
 

esphome/components/api/api_connection.h

@@ -177,7 +177,7 @@ class APIConnection final : public APIServerConnection {
 #endif
 
 #ifdef USE_EVENT
-  void send_event(event::Event *event, const std::string &event_type);
+  void send_event(event::Event *event, const char *event_type);
 #endif
 
 #ifdef USE_UPDATE
@@ -450,7 +450,7 @@ class APIConnection final : public APIServerConnection {
                                                     bool is_single);
 #endif
 #ifdef USE_EVENT
-  static uint16_t try_send_event_response(event::Event *event, const std::string &event_type, APIConnection *conn,
+  static uint16_t try_send_event_response(event::Event *event, const char *event_type, APIConnection *conn,
                                           uint32_t remaining_size, bool is_single);
   static uint16_t try_send_event_info(EntityBase *entity, APIConnection *conn, uint32_t remaining_size, bool is_single);
 #endif
@@ -508,10 +508,8 @@ class APIConnection final : public APIServerConnection {
     // Constructor for function pointer
     MessageCreator(MessageCreatorPtr ptr) { data_.function_ptr = ptr; }
 
-    // Constructor for string state capture
+    // Constructor for const char * (Event types - no allocation needed)
-    explicit MessageCreator(const std::string &str_value) { data_.string_ptr = new std::string(str_value); }
+    explicit MessageCreator(const char *str_value) { data_.const_char_ptr = str_value; }
-
-    // No destructor - cleanup must be called explicitly with message_type
 
     // Delete copy operations - MessageCreator should only be moved
     MessageCreator(const MessageCreator &other) = delete;
@@ -523,8 +521,6 @@ class APIConnection final : public APIServerConnection {
     // Move assignment
     MessageCreator &operator=(MessageCreator &&other) noexcept {
       if (this != &other) {
-        // IMPORTANT: Caller must ensure cleanup() was called if this contains a string!
-        // In our usage, this happens in add_item() deduplication and vector::erase()
         data_ = other.data_;
         other.data_.function_ptr = nullptr;
       }
@@ -535,20 +531,10 @@ class APIConnection final : public APIServerConnection {
     uint16_t operator()(EntityBase *entity, APIConnection *conn, uint32_t remaining_size, bool is_single,
                         uint8_t message_type) const;
 
-    // Manual cleanup method - must be called before destruction for string types
-    void cleanup(uint8_t message_type) {
-#ifdef USE_EVENT
-      if (message_type == EventResponse::MESSAGE_TYPE && data_.string_ptr != nullptr) {
-        delete data_.string_ptr;
-        data_.string_ptr = nullptr;
-      }
-#endif
-    }
-
    private:
     union Data {
       MessageCreatorPtr function_ptr;
-      std::string *string_ptr;
+      const char *const_char_ptr;
     } data_;  // 4 bytes on 32-bit, 8 bytes on 64-bit - same as before
   };
 
@@ -568,42 +554,24 @@ class APIConnection final : public APIServerConnection {
     std::vector<BatchItem> items;
     uint32_t batch_start_time{0};
 
-   private:
-    // Helper to cleanup items from the beginning
-    void cleanup_items_(size_t count) {
-      for (size_t i = 0; i < count; i++) {
-        items[i].creator.cleanup(items[i].message_type);
-      }
-    }
-
-   public:
     DeferredBatch() {
       // Pre-allocate capacity for typical batch sizes to avoid reallocation
       items.reserve(8);
     }
 
-    ~DeferredBatch() {
-      // Ensure cleanup of any remaining items
-      clear();
-    }
-
     // Add item to the batch
     void add_item(EntityBase *entity, MessageCreator creator, uint8_t message_type, uint8_t estimated_size);
     // Add item to the front of the batch (for high priority messages like ping)
     void add_item_front(EntityBase *entity, MessageCreator creator, uint8_t message_type, uint8_t estimated_size);
 
-    // Clear all items with proper cleanup
+    // Clear all items
     void clear() {
-      cleanup_items_(items.size());
       items.clear();
       batch_start_time = 0;
     }
 
-    // Remove processed items from the front with proper cleanup
+    // Remove processed items from the front
-    void remove_front(size_t count) {
+    void remove_front(size_t count) { items.erase(items.begin(), items.begin() + count); }
-      cleanup_items_(count);
-      items.erase(items.begin(), items.begin() + count);
-    }
 
     bool empty() const { return items.empty(); }
     size_t size() const { return items.size(); }