[bluetooth_proxy] Eliminate heap allocations in connection state reporting (#10010)

esphome/components/bluetooth_proxy/__init__.py

@@ -87,6 +87,10 @@ async def to_code(config):
     cg.add(var.set_active(config[CONF_ACTIVE]))
     await esp32_ble_tracker.register_raw_ble_device(var, config)
 
+    # Define max connections for protobuf fixed array
+    connection_count = len(config.get(CONF_CONNECTIONS, []))
+    cg.add_define("BLUETOOTH_PROXY_MAX_CONNECTIONS", connection_count)
+
     for connection_conf in config.get(CONF_CONNECTIONS, []):
         connection_var = cg.new_Pvariable(connection_conf[CONF_ID])
         await cg.register_component(connection_var, connection_conf)

esphome/components/bluetooth_proxy/bluetooth_connection.cpp

@@ -78,6 +78,30 @@ void BluetoothConnection::dump_config() {
   BLEClientBase::dump_config();
 }
 
+void BluetoothConnection::update_allocated_slot_(uint64_t find_value, uint64_t set_value) {
+  auto &allocated = this->proxy_->connections_free_response_.allocated;
+  auto *it = std::find(allocated.begin(), allocated.end(), find_value);
+  if (it != allocated.end()) {
+    *it = set_value;
+  }
+}
+
+void BluetoothConnection::set_address(uint64_t address) {
+  // If we're clearing an address (disconnecting), update the pre-allocated message
+  if (address == 0 && this->address_ != 0) {
+    this->proxy_->connections_free_response_.free++;
+    this->update_allocated_slot_(this->address_, 0);
+  }
+  // If we're setting a new address (connecting), update the pre-allocated message
+  else if (address != 0 && this->address_ == 0) {
+    this->proxy_->connections_free_response_.free--;
+    this->update_allocated_slot_(0, address);
+  }
+
+  // Call parent implementation to actually set the address
+  BLEClientBase::set_address(address);
+}
+
 void BluetoothConnection::loop() {
   BLEClientBase::loop();
 

esphome/components/bluetooth_proxy/bluetooth_connection.h

@@ -24,12 +24,15 @@ class BluetoothConnection : public esp32_ble_client::BLEClientBase {
 
   esp_err_t notify_characteristic(uint16_t handle, bool enable);
 
+  void set_address(uint64_t address) override;
+
  protected:
   friend class BluetoothProxy;
 
   bool supports_efficient_uuids_() const;
   void send_service_for_discovery_();
   void reset_connection_(esp_err_t reason);
+  void update_allocated_slot_(uint64_t find_value, uint64_t set_value);
 
   // Memory optimized layout for 32-bit systems
   // Group 1: Pointers (4 bytes each, naturally aligned)

esphome/components/bluetooth_proxy/bluetooth_proxy.cpp

@@ -35,6 +35,9 @@ void BluetoothProxy::setup() {
   // Don't pre-allocate pool - let it grow only if needed in busy environments
   // Many devices in quiet areas will never need the overflow pool
 
+  this->connections_free_response_.limit = this->connections_.size();
+  this->connections_free_response_.free = this->connections_.size();
+
   this->parent_->add_scanner_state_callback([this](esp32_ble_tracker::ScannerState state) {
     if (this->api_connection_ != nullptr) {
       this->send_bluetooth_scanner_state_(state);
@@ -134,20 +137,6 @@ void BluetoothProxy::dump_config() {
                 YESNO(this->active_), this->connections_.size());
 }
 
-int BluetoothProxy::get_bluetooth_connections_free() {
-  int free = 0;
-  for (auto *connection : this->connections_) {
-    if (connection->address_ == 0) {
-      free++;
-      ESP_LOGV(TAG, "[%d] Free connection", connection->get_connection_index());
-    } else {
-      ESP_LOGV(TAG, "[%d] Used connection by [%s]", connection->get_connection_index(),
-               connection->address_str().c_str());
-    }
-  }
-  return free;
-}
-
 void BluetoothProxy::loop() {
   if (!api::global_api_server->is_connected() || this->api_connection_ == nullptr) {
     for (auto *connection : this->connections_) {
@@ -439,17 +428,13 @@ void BluetoothProxy::send_device_connection(uint64_t address, bool connected, ui
   this->api_connection_->send_message(call, api::BluetoothDeviceConnectionResponse::MESSAGE_TYPE);
 }
 void BluetoothProxy::send_connections_free() {
-  if (this->api_connection_ == nullptr)
-    return;
-  api::BluetoothConnectionsFreeResponse call;
-  call.free = this->get_bluetooth_connections_free();
-  call.limit = this->get_bluetooth_connections_limit();
-  for (auto *connection : this->connections_) {
-    if (connection->address_ != 0) {
-      call.allocated.push_back(connection->address_);
-    }
+  if (this->api_connection_ != nullptr) {
+    this->send_connections_free(this->api_connection_);
   }
-  this->api_connection_->send_message(call, api::BluetoothConnectionsFreeResponse::MESSAGE_TYPE);
+}
+
+void BluetoothProxy::send_connections_free(api::APIConnection *api_connection) {
+  api_connection->send_message(this->connections_free_response_, api::BluetoothConnectionsFreeResponse::MESSAGE_TYPE);
 }
 
 void BluetoothProxy::send_gatt_services_done(uint64_t address) {

esphome/components/bluetooth_proxy/bluetooth_proxy.h

@@ -49,6 +49,7 @@ enum BluetoothProxySubscriptionFlag : uint32_t {
 };
 
 class BluetoothProxy : public esp32_ble_tracker::ESPBTDeviceListener, public Component {
+  friend class BluetoothConnection;  // Allow connection to update connections_free_response_
  public:
   BluetoothProxy();
 #ifdef USE_ESP32_BLE_DEVICE
@@ -74,15 +75,13 @@ class BluetoothProxy : public esp32_ble_tracker::ESPBTDeviceListener, public Com
   void bluetooth_gatt_send_services(const api::BluetoothGATTGetServicesRequest &msg);
   void bluetooth_gatt_notify(const api::BluetoothGATTNotifyRequest &msg);
 
-  int get_bluetooth_connections_free();
-  int get_bluetooth_connections_limit() { return this->connections_.size(); }
-
   void subscribe_api_connection(api::APIConnection *api_connection, uint32_t flags);
   void unsubscribe_api_connection(api::APIConnection *api_connection);
   api::APIConnection *get_api_connection() { return this->api_connection_; }
 
   void send_device_connection(uint64_t address, bool connected, uint16_t mtu = 0, esp_err_t error = ESP_OK);
   void send_connections_free();
+  void send_connections_free(api::APIConnection *api_connection);
   void send_gatt_services_done(uint64_t address);
   void send_gatt_error(uint64_t address, uint16_t handle, esp_err_t error);
   void send_device_pairing(uint64_t address, bool paired, esp_err_t error = ESP_OK);
@@ -149,6 +148,9 @@ class BluetoothProxy : public esp32_ble_tracker::ESPBTDeviceListener, public Com
   // Group 3: 4-byte types
   uint32_t last_advertisement_flush_time_{0};
 
+  // Pre-allocated response message - always ready to send
+  api::BluetoothConnectionsFreeResponse connections_free_response_;
+
   // Group 4: 1-byte types grouped together
   bool active_;
   uint8_t advertisement_count_{0};