Optimize bluetooth_proxy memory usage on ESP32 (#9114)

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

esphome/components/bluetooth_proxy/bluetooth_connection.h

@@ -26,10 +26,17 @@ class BluetoothConnection : public esp32_ble_client::BLEClientBase {
 
  protected:
   friend class BluetoothProxy;
-  bool seen_mtu_or_services_{false};
 
-  int16_t send_service_{-2};
+  // Memory optimized layout for 32-bit systems
+  // Group 1: Pointers (4 bytes each, naturally aligned)
   BluetoothProxy *proxy_;
+
+  // Group 2: 2-byte types
+  int16_t send_service_{-2};  // Needs to handle negative values and service count
+
+  // Group 3: 1-byte types
+  bool seen_mtu_or_services_{false};
+  // 1 byte used, 1 byte padding
 };
 
 }  // namespace bluetooth_proxy

esphome/components/bluetooth_proxy/bluetooth_proxy.h

@@ -134,11 +134,17 @@ class BluetoothProxy : public esp32_ble_tracker::ESPBTDeviceListener, public Com
 
   BluetoothConnection *get_connection_(uint64_t address, bool reserve);
 
-  bool active_;
-
-  std::vector<BluetoothConnection *> connections_{};
+  // Memory optimized layout for 32-bit systems
+  // Group 1: Pointers (4 bytes each, naturally aligned)
   api::APIConnection *api_connection_{nullptr};
+
+  // Group 2: Container types (typically 12 bytes on 32-bit)
+  std::vector<BluetoothConnection *> connections_{};
+
+  // Group 3: 1-byte types grouped together
+  bool active_;
   bool raw_advertisements_{false};
+  // 2 bytes used, 2 bytes padding
 };
 
 extern BluetoothProxy *global_bluetooth_proxy;  // NOLINT(cppcoreguidelines-avoid-non-const-global-variables)

esphome/components/esp32_ble_client/ble_client_base.h

@@ -96,21 +96,34 @@ class BLEClientBase : public espbt::ESPBTClient, public Component {
   void set_state(espbt::ClientState st) override;
 
  protected:
-  int gattc_if_;
-  esp_bd_addr_t remote_bda_;
-  esp_ble_addr_type_t remote_addr_type_{BLE_ADDR_TYPE_PUBLIC};
-  uint16_t conn_id_{UNSET_CONN_ID};
+  // Memory optimized layout for 32-bit systems
+  // Group 1: 8-byte types
   uint64_t address_{0};
-  bool auto_connect_{false};
+
+  // Group 2: Container types (grouped for memory optimization)
   std::string address_str_{};
-  uint8_t connection_index_;
-  int16_t service_count_{0};
-  uint16_t mtu_{23};
-  bool paired_{false};
-  espbt::ConnectionType connection_type_{espbt::ConnectionType::V1};
   std::vector<BLEService *> services_;
+
+  // Group 3: 4-byte types
+  int gattc_if_;
   esp_gatt_status_t status_{ESP_GATT_OK};
 
+  // Group 4: Arrays (6 bytes)
+  esp_bd_addr_t remote_bda_;
+
+  // Group 5: 2-byte types
+  uint16_t conn_id_{UNSET_CONN_ID};
+  uint16_t mtu_{23};
+
+  // Group 6: 1-byte types and small enums
+  esp_ble_addr_type_t remote_addr_type_{BLE_ADDR_TYPE_PUBLIC};
+  espbt::ConnectionType connection_type_{espbt::ConnectionType::V1};
+  uint8_t connection_index_;
+  uint8_t service_count_{0};  // ESP32 has max handles < 255, typical devices have < 50 services
+  bool auto_connect_{false};
+  bool paired_{false};
+  // 6 bytes used, 2 bytes padding
+
   void log_event_(const char *name);
 };
 

esphome/components/esp32_ble_tracker/esp32_ble_tracker.h

@@ -129,7 +129,7 @@ class ESPBTDeviceListener {
   ESP32BLETracker *parent_{nullptr};
 };
 
-enum class ClientState {
+enum class ClientState : uint8_t {
   // Connection is allocated
   INIT,
   // Client is disconnecting
@@ -165,7 +165,7 @@ enum class ScannerState {
   STOPPED,
 };
 
-enum class ConnectionType {
+enum class ConnectionType : uint8_t {
   // The default connection type, we hold all the services in ram
   // for the duration of the connection.
   V1,
@@ -193,15 +193,19 @@ class ESPBTClient : public ESPBTDeviceListener {
     }
   }
   ClientState state() const { return state_; }
-  int app_id;
+
+  // Memory optimized layout
+  uint8_t app_id;  // App IDs are small integers assigned sequentially
 
  protected:
+  // Group 1: 1-byte types
   ClientState state_{ClientState::INIT};
   // want_disconnect_ is set to true when a disconnect is requested
   // while the client is connecting. This is used to disconnect the
   // client as soon as we get the connection id (conn_id_) from the
   // ESP_GATTC_OPEN_EVT event.
   bool want_disconnect_{false};
+  // 2 bytes used, 2 bytes padding
 };
 
 class ESP32BLETracker : public Component,
@@ -262,7 +266,7 @@ class ESP32BLETracker : public Component,
   /// Called to set the scanner state. Will also call callbacks to let listeners know when state is changed.
   void set_scanner_state_(ScannerState state);
 
-  int app_id_{0};
+  uint8_t app_id_{0};
 
   /// Vector of addresses that have already been printed in print_bt_device_info
   std::vector<uint64_t> already_discovered_;