[api] Inline ProtoVarInt::parse fast path and return consumed in struct

Replace optional<ProtoVarInt> + consumed pointer with ProtoVarIntResult
struct that returns value + consumed count directly. This eliminates
memory stores through a pointer on the fast path (single-byte varints
< 128), keeping everything in registers.

The parse() method is now ESPHOME_ALWAYS_INLINE with the multi-byte
slow path outlined to parse_slow_(). The common case for protobuf
field tags, small enums, booleans, and typical message sizes/types
is a simple high-bit check + register return with no function call.

Measured on ESP32 (Xtensa): try_read_frame_ grows only +12 bytes
(320 → 332) for two inlined parse sites, while eliminating two
function calls per message on the hot path.

esphome/components/api/api_frame_helper_plaintext.cpp

@@ -128,37 +128,36 @@ APIError APIPlaintextFrameHelper::try_read_frame_() {
 
     // Skip indicator byte at position 0
     uint8_t varint_pos = 1;
-    uint32_t consumed = 0;
 
-    auto msg_size_varint = ProtoVarInt::parse(&rx_header_buf_[varint_pos], rx_header_buf_pos_ - varint_pos, &consumed);
+    auto msg_size_varint = ProtoVarInt::parse(&rx_header_buf_[varint_pos], rx_header_buf_pos_ - varint_pos);
     if (!msg_size_varint.has_value()) {
       // not enough data there yet
       continue;
     }
 
-    if (msg_size_varint->as_uint32() > MAX_MESSAGE_SIZE) {
+    if (msg_size_varint.as_uint32() > MAX_MESSAGE_SIZE) {
       state_ = State::FAILED;
-      HELPER_LOG("Bad packet: message size %" PRIu32 " exceeds maximum %u", msg_size_varint->as_uint32(),
+      HELPER_LOG("Bad packet: message size %" PRIu32 " exceeds maximum %u", msg_size_varint.as_uint32(),
                  MAX_MESSAGE_SIZE);
       return APIError::BAD_DATA_PACKET;
     }
-    rx_header_parsed_len_ = msg_size_varint->as_uint16();
+    rx_header_parsed_len_ = msg_size_varint.as_uint16();
 
     // Move to next varint position
-    varint_pos += consumed;
+    varint_pos += msg_size_varint.consumed;
 
-    auto msg_type_varint = ProtoVarInt::parse(&rx_header_buf_[varint_pos], rx_header_buf_pos_ - varint_pos, &consumed);
+    auto msg_type_varint = ProtoVarInt::parse(&rx_header_buf_[varint_pos], rx_header_buf_pos_ - varint_pos);
     if (!msg_type_varint.has_value()) {
       // not enough data there yet
       continue;
     }
-    if (msg_type_varint->as_uint32() > std::numeric_limits<uint16_t>::max()) {
+    if (msg_type_varint.as_uint32() > std::numeric_limits<uint16_t>::max()) {
       state_ = State::FAILED;
-      HELPER_LOG("Bad packet: message type %" PRIu32 " exceeds maximum %u", msg_type_varint->as_uint32(),
+      HELPER_LOG("Bad packet: message type %" PRIu32 " exceeds maximum %u", msg_type_varint.as_uint32(),
                  std::numeric_limits<uint16_t>::max());
       return APIError::BAD_DATA_PACKET;
     }
-    rx_header_parsed_type_ = msg_type_varint->as_uint16();
+    rx_header_parsed_type_ = msg_type_varint.as_uint16();
     rx_header_parsed_ = true;
   }
   // header reading done

esphome/components/api/api_pb2.cpp

@@ -7,7 +7,7 @@
 
 namespace esphome::api {
 
-bool HelloRequest::decode_varint(uint32_t field_id, ProtoVarInt value) {
+bool HelloRequest::decode_varint(uint32_t field_id, ProtoVarIntResult value) {
   switch (field_id) {
     case 2:
       this->api_version_major = value.as_uint32();
@@ -316,7 +316,7 @@ uint32_t CoverStateResponse::calculate_size() const {
 #endif
   return size;
 }
-bool CoverCommandRequest::decode_varint(uint32_t field_id, ProtoVarInt value) {
+bool CoverCommandRequest::decode_varint(uint32_t field_id, ProtoVarIntResult value) {
   switch (field_id) {
     case 4:
       this->has_position = value.as_bool();
@@ -423,7 +423,7 @@ uint32_t FanStateResponse::calculate_size() const {
 #endif
   return size;
 }
-bool FanCommandRequest::decode_varint(uint32_t field_id, ProtoVarInt value) {
+bool FanCommandRequest::decode_varint(uint32_t field_id, ProtoVarIntResult value) {
   switch (field_id) {
     case 2:
       this->has_state = value.as_bool();
@@ -571,7 +571,7 @@ uint32_t LightStateResponse::calculate_size() const {
 #endif
   return size;
 }
-bool LightCommandRequest::decode_varint(uint32_t field_id, ProtoVarInt value) {
+bool LightCommandRequest::decode_varint(uint32_t field_id, ProtoVarIntResult value) {
   switch (field_id) {
     case 2:
       this->has_state = value.as_bool();
@@ -787,7 +787,7 @@ uint32_t SwitchStateResponse::calculate_size() const {
 #endif
   return size;
 }
-bool SwitchCommandRequest::decode_varint(uint32_t field_id, ProtoVarInt value) {
+bool SwitchCommandRequest::decode_varint(uint32_t field_id, ProtoVarIntResult value) {
   switch (field_id) {
     case 2:
       this->state = value.as_bool();
@@ -863,7 +863,7 @@ uint32_t TextSensorStateResponse::calculate_size() const {
   return size;
 }
 #endif
-bool SubscribeLogsRequest::decode_varint(uint32_t field_id, ProtoVarInt value) {
+bool SubscribeLogsRequest::decode_varint(uint32_t field_id, ProtoVarIntResult value) {
   switch (field_id) {
     case 1:
       this->level = static_cast<enums::LogLevel>(value.as_uint32());
@@ -971,7 +971,7 @@ uint32_t HomeassistantActionRequest::calculate_size() const {
 }
 #endif
 #ifdef USE_API_HOMEASSISTANT_ACTION_RESPONSES
-bool HomeassistantActionResponse::decode_varint(uint32_t field_id, ProtoVarInt value) {
+bool HomeassistantActionResponse::decode_varint(uint32_t field_id, ProtoVarIntResult value) {
   switch (field_id) {
     case 1:
       this->call_id = value.as_uint32();
@@ -1036,7 +1036,7 @@ bool HomeAssistantStateResponse::decode_length(uint32_t field_id, ProtoLengthDel
   return true;
 }
 #endif
-bool DSTRule::decode_varint(uint32_t field_id, ProtoVarInt value) {
+bool DSTRule::decode_varint(uint32_t field_id, ProtoVarIntResult value) {
   switch (field_id) {
     case 1:
       this->time_seconds = value.as_sint32();
@@ -1061,7 +1061,7 @@ bool DSTRule::decode_varint(uint32_t field_id, ProtoVarInt value) {
   }
   return true;
 }
-bool ParsedTimezone::decode_varint(uint32_t field_id, ProtoVarInt value) {
+bool ParsedTimezone::decode_varint(uint32_t field_id, ProtoVarIntResult value) {
   switch (field_id) {
     case 1:
       this->std_offset_seconds = value.as_sint32();
@@ -1142,7 +1142,7 @@ uint32_t ListEntitiesServicesResponse::calculate_size() const {
   size += ProtoSize::calc_uint32(1, static_cast<uint32_t>(this->supports_response));
   return size;
 }
-bool ExecuteServiceArgument::decode_varint(uint32_t field_id, ProtoVarInt value) {
+bool ExecuteServiceArgument::decode_varint(uint32_t field_id, ProtoVarIntResult value) {
   switch (field_id) {
     case 1:
       this->bool_ = value.as_bool();
@@ -1202,7 +1202,7 @@ void ExecuteServiceArgument::decode(const uint8_t *buffer, size_t length) {
   this->string_array.init(count_string_array);
   ProtoDecodableMessage::decode(buffer, length);
 }
-bool ExecuteServiceRequest::decode_varint(uint32_t field_id, ProtoVarInt value) {
+bool ExecuteServiceRequest::decode_varint(uint32_t field_id, ProtoVarIntResult value) {
   switch (field_id) {
 #ifdef USE_API_USER_DEFINED_ACTION_RESPONSES
     case 3:
@@ -1313,7 +1313,7 @@ uint32_t CameraImageResponse::calculate_size() const {
 #endif
   return size;
 }
-bool CameraImageRequest::decode_varint(uint32_t field_id, ProtoVarInt value) {
+bool CameraImageRequest::decode_varint(uint32_t field_id, ProtoVarIntResult value) {
   switch (field_id) {
     case 1:
       this->single = value.as_bool();
@@ -1468,7 +1468,7 @@ uint32_t ClimateStateResponse::calculate_size() const {
 #endif
   return size;
 }
-bool ClimateCommandRequest::decode_varint(uint32_t field_id, ProtoVarInt value) {
+bool ClimateCommandRequest::decode_varint(uint32_t field_id, ProtoVarIntResult value) {
   switch (field_id) {
     case 2:
       this->has_mode = value.as_bool();
@@ -1631,7 +1631,7 @@ uint32_t WaterHeaterStateResponse::calculate_size() const {
   size += ProtoSize::calc_float(1, this->target_temperature_high);
   return size;
 }
-bool WaterHeaterCommandRequest::decode_varint(uint32_t field_id, ProtoVarInt value) {
+bool WaterHeaterCommandRequest::decode_varint(uint32_t field_id, ProtoVarIntResult value) {
   switch (field_id) {
     case 2:
       this->has_fields = value.as_uint32();
@@ -1731,7 +1731,7 @@ uint32_t NumberStateResponse::calculate_size() const {
 #endif
   return size;
 }
-bool NumberCommandRequest::decode_varint(uint32_t field_id, ProtoVarInt value) {
+bool NumberCommandRequest::decode_varint(uint32_t field_id, ProtoVarIntResult value) {
   switch (field_id) {
 #ifdef USE_DEVICES
     case 3:
@@ -1812,7 +1812,7 @@ uint32_t SelectStateResponse::calculate_size() const {
 #endif
   return size;
 }
-bool SelectCommandRequest::decode_varint(uint32_t field_id, ProtoVarInt value) {
+bool SelectCommandRequest::decode_varint(uint32_t field_id, ProtoVarIntResult value) {
   switch (field_id) {
 #ifdef USE_DEVICES
     case 3:
@@ -1903,7 +1903,7 @@ uint32_t SirenStateResponse::calculate_size() const {
 #endif
   return size;
 }
-bool SirenCommandRequest::decode_varint(uint32_t field_id, ProtoVarInt value) {
+bool SirenCommandRequest::decode_varint(uint32_t field_id, ProtoVarIntResult value) {
   switch (field_id) {
     case 2:
       this->has_state = value.as_bool();
@@ -2011,7 +2011,7 @@ uint32_t LockStateResponse::calculate_size() const {
 #endif
   return size;
 }
-bool LockCommandRequest::decode_varint(uint32_t field_id, ProtoVarInt value) {
+bool LockCommandRequest::decode_varint(uint32_t field_id, ProtoVarIntResult value) {
   switch (field_id) {
     case 2:
       this->command = static_cast<enums::LockCommand>(value.as_uint32());
@@ -2082,7 +2082,7 @@ uint32_t ListEntitiesButtonResponse::calculate_size() const {
 #endif
   return size;
 }
-bool ButtonCommandRequest::decode_varint(uint32_t field_id, ProtoVarInt value) {
+bool ButtonCommandRequest::decode_varint(uint32_t field_id, ProtoVarIntResult value) {
   switch (field_id) {
 #ifdef USE_DEVICES
     case 2:
@@ -2182,7 +2182,7 @@ uint32_t MediaPlayerStateResponse::calculate_size() const {
 #endif
   return size;
 }
-bool MediaPlayerCommandRequest::decode_varint(uint32_t field_id, ProtoVarInt value) {
+bool MediaPlayerCommandRequest::decode_varint(uint32_t field_id, ProtoVarIntResult value) {
   switch (field_id) {
     case 2:
       this->has_command = value.as_bool();
@@ -2238,7 +2238,7 @@ bool MediaPlayerCommandRequest::decode_32bit(uint32_t field_id, Proto32Bit value
 }
 #endif
 #ifdef USE_BLUETOOTH_PROXY
-bool SubscribeBluetoothLEAdvertisementsRequest::decode_varint(uint32_t field_id, ProtoVarInt value) {
+bool SubscribeBluetoothLEAdvertisementsRequest::decode_varint(uint32_t field_id, ProtoVarIntResult value) {
   switch (field_id) {
     case 1:
       this->flags = value.as_uint32();
@@ -2274,7 +2274,7 @@ uint32_t BluetoothLERawAdvertisementsResponse::calculate_size() const {
   }
   return size;
 }
-bool BluetoothDeviceRequest::decode_varint(uint32_t field_id, ProtoVarInt value) {
+bool BluetoothDeviceRequest::decode_varint(uint32_t field_id, ProtoVarIntResult value) {
   switch (field_id) {
     case 1:
       this->address = value.as_uint64();
@@ -2307,7 +2307,7 @@ uint32_t BluetoothDeviceConnectionResponse::calculate_size() const {
   size += ProtoSize::calc_int32(1, this->error);
   return size;
 }
-bool BluetoothGATTGetServicesRequest::decode_varint(uint32_t field_id, ProtoVarInt value) {
+bool BluetoothGATTGetServicesRequest::decode_varint(uint32_t field_id, ProtoVarIntResult value) {
   switch (field_id) {
     case 1:
       this->address = value.as_uint64();
@@ -2413,7 +2413,7 @@ uint32_t BluetoothGATTGetServicesDoneResponse::calculate_size() const {
   size += ProtoSize::calc_uint64(1, this->address);
   return size;
 }
-bool BluetoothGATTReadRequest::decode_varint(uint32_t field_id, ProtoVarInt value) {
+bool BluetoothGATTReadRequest::decode_varint(uint32_t field_id, ProtoVarIntResult value) {
   switch (field_id) {
     case 1:
       this->address = value.as_uint64();
@@ -2438,7 +2438,7 @@ uint32_t BluetoothGATTReadResponse::calculate_size() const {
   size += ProtoSize::calc_length(1, this->data_len_);
   return size;
 }
-bool BluetoothGATTWriteRequest::decode_varint(uint32_t field_id, ProtoVarInt value) {
+bool BluetoothGATTWriteRequest::decode_varint(uint32_t field_id, ProtoVarIntResult value) {
   switch (field_id) {
     case 1:
       this->address = value.as_uint64();
@@ -2466,7 +2466,7 @@ bool BluetoothGATTWriteRequest::decode_length(uint32_t field_id, ProtoLengthDeli
   }
   return true;
 }
-bool BluetoothGATTReadDescriptorRequest::decode_varint(uint32_t field_id, ProtoVarInt value) {
+bool BluetoothGATTReadDescriptorRequest::decode_varint(uint32_t field_id, ProtoVarIntResult value) {
   switch (field_id) {
     case 1:
       this->address = value.as_uint64();
@@ -2479,7 +2479,7 @@ bool BluetoothGATTReadDescriptorRequest::decode_varint(uint32_t field_id, ProtoV
   }
   return true;
 }
-bool BluetoothGATTWriteDescriptorRequest::decode_varint(uint32_t field_id, ProtoVarInt value) {
+bool BluetoothGATTWriteDescriptorRequest::decode_varint(uint32_t field_id, ProtoVarIntResult value) {
   switch (field_id) {
     case 1:
       this->address = value.as_uint64();
@@ -2504,7 +2504,7 @@ bool BluetoothGATTWriteDescriptorRequest::decode_length(uint32_t field_id, Proto
   }
   return true;
 }
-bool BluetoothGATTNotifyRequest::decode_varint(uint32_t field_id, ProtoVarInt value) {
+bool BluetoothGATTNotifyRequest::decode_varint(uint32_t field_id, ProtoVarIntResult value) {
   switch (field_id) {
     case 1:
       this->address = value.as_uint64();
@@ -2632,7 +2632,7 @@ uint32_t BluetoothScannerStateResponse::calculate_size() const {
   size += ProtoSize::calc_uint32(1, static_cast<uint32_t>(this->configured_mode));
   return size;
 }
-bool BluetoothScannerSetModeRequest::decode_varint(uint32_t field_id, ProtoVarInt value) {
+bool BluetoothScannerSetModeRequest::decode_varint(uint32_t field_id, ProtoVarIntResult value) {
   switch (field_id) {
     case 1:
       this->mode = static_cast<enums::BluetoothScannerMode>(value.as_uint32());
@@ -2644,7 +2644,7 @@ bool BluetoothScannerSetModeRequest::decode_varint(uint32_t field_id, ProtoVarIn
 }
 #endif
 #ifdef USE_VOICE_ASSISTANT
-bool SubscribeVoiceAssistantRequest::decode_varint(uint32_t field_id, ProtoVarInt value) {
+bool SubscribeVoiceAssistantRequest::decode_varint(uint32_t field_id, ProtoVarIntResult value) {
   switch (field_id) {
     case 1:
       this->subscribe = value.as_bool();
@@ -2685,7 +2685,7 @@ uint32_t VoiceAssistantRequest::calculate_size() const {
   size += ProtoSize::calc_length(1, this->wake_word_phrase.size());
   return size;
 }
-bool VoiceAssistantResponse::decode_varint(uint32_t field_id, ProtoVarInt value) {
+bool VoiceAssistantResponse::decode_varint(uint32_t field_id, ProtoVarIntResult value) {
   switch (field_id) {
     case 1:
       this->port = value.as_uint32();
@@ -2713,7 +2713,7 @@ bool VoiceAssistantEventData::decode_length(uint32_t field_id, ProtoLengthDelimi
   }
   return true;
 }
-bool VoiceAssistantEventResponse::decode_varint(uint32_t field_id, ProtoVarInt value) {
+bool VoiceAssistantEventResponse::decode_varint(uint32_t field_id, ProtoVarIntResult value) {
   switch (field_id) {
     case 1:
       this->event_type = static_cast<enums::VoiceAssistantEvent>(value.as_uint32());
@@ -2734,7 +2734,7 @@ bool VoiceAssistantEventResponse::decode_length(uint32_t field_id, ProtoLengthDe
   }
   return true;
 }
-bool VoiceAssistantAudio::decode_varint(uint32_t field_id, ProtoVarInt value) {
+bool VoiceAssistantAudio::decode_varint(uint32_t field_id, ProtoVarIntResult value) {
   switch (field_id) {
     case 2:
       this->end = value.as_bool();
@@ -2766,7 +2766,7 @@ uint32_t VoiceAssistantAudio::calculate_size() const {
   size += ProtoSize::calc_bool(1, this->end);
   return size;
 }
-bool VoiceAssistantTimerEventResponse::decode_varint(uint32_t field_id, ProtoVarInt value) {
+bool VoiceAssistantTimerEventResponse::decode_varint(uint32_t field_id, ProtoVarIntResult value) {
   switch (field_id) {
     case 1:
       this->event_type = static_cast<enums::VoiceAssistantTimerEvent>(value.as_uint32());
@@ -2800,7 +2800,7 @@ bool VoiceAssistantTimerEventResponse::decode_length(uint32_t field_id, ProtoLen
   }
   return true;
 }
-bool VoiceAssistantAnnounceRequest::decode_varint(uint32_t field_id, ProtoVarInt value) {
+bool VoiceAssistantAnnounceRequest::decode_varint(uint32_t field_id, ProtoVarIntResult value) {
   switch (field_id) {
     case 4:
       this->start_conversation = value.as_bool();
@@ -2853,7 +2853,7 @@ uint32_t VoiceAssistantWakeWord::calculate_size() const {
   }
   return size;
 }
-bool VoiceAssistantExternalWakeWord::decode_varint(uint32_t field_id, ProtoVarInt value) {
+bool VoiceAssistantExternalWakeWord::decode_varint(uint32_t field_id, ProtoVarIntResult value) {
   switch (field_id) {
     case 5:
       this->model_size = value.as_uint32();
@@ -2990,7 +2990,7 @@ uint32_t AlarmControlPanelStateResponse::calculate_size() const {
 #endif
   return size;
 }
-bool AlarmControlPanelCommandRequest::decode_varint(uint32_t field_id, ProtoVarInt value) {
+bool AlarmControlPanelCommandRequest::decode_varint(uint32_t field_id, ProtoVarIntResult value) {
   switch (field_id) {
     case 2:
       this->command = static_cast<enums::AlarmControlPanelStateCommand>(value.as_uint32());
@@ -3082,7 +3082,7 @@ uint32_t TextStateResponse::calculate_size() const {
 #endif
   return size;
 }
-bool TextCommandRequest::decode_varint(uint32_t field_id, ProtoVarInt value) {
+bool TextCommandRequest::decode_varint(uint32_t field_id, ProtoVarIntResult value) {
   switch (field_id) {
 #ifdef USE_DEVICES
     case 3:
@@ -3167,7 +3167,7 @@ uint32_t DateStateResponse::calculate_size() const {
 #endif
   return size;
 }
-bool DateCommandRequest::decode_varint(uint32_t field_id, ProtoVarInt value) {
+bool DateCommandRequest::decode_varint(uint32_t field_id, ProtoVarIntResult value) {
   switch (field_id) {
     case 2:
       this->year = value.as_uint32();
@@ -3250,7 +3250,7 @@ uint32_t TimeStateResponse::calculate_size() const {
 #endif
   return size;
 }
-bool TimeCommandRequest::decode_varint(uint32_t field_id, ProtoVarInt value) {
+bool TimeCommandRequest::decode_varint(uint32_t field_id, ProtoVarIntResult value) {
   switch (field_id) {
     case 2:
       this->hour = value.as_uint32();
@@ -3393,7 +3393,7 @@ uint32_t ValveStateResponse::calculate_size() const {
 #endif
   return size;
 }
-bool ValveCommandRequest::decode_varint(uint32_t field_id, ProtoVarInt value) {
+bool ValveCommandRequest::decode_varint(uint32_t field_id, ProtoVarIntResult value) {
   switch (field_id) {
     case 2:
       this->has_position = value.as_bool();
@@ -3472,7 +3472,7 @@ uint32_t DateTimeStateResponse::calculate_size() const {
 #endif
   return size;
 }
-bool DateTimeCommandRequest::decode_varint(uint32_t field_id, ProtoVarInt value) {
+bool DateTimeCommandRequest::decode_varint(uint32_t field_id, ProtoVarIntResult value) {
   switch (field_id) {
 #ifdef USE_DEVICES
     case 3:
@@ -3561,7 +3561,7 @@ uint32_t UpdateStateResponse::calculate_size() const {
 #endif
   return size;
 }
-bool UpdateCommandRequest::decode_varint(uint32_t field_id, ProtoVarInt value) {
+bool UpdateCommandRequest::decode_varint(uint32_t field_id, ProtoVarIntResult value) {
   switch (field_id) {
     case 2:
       this->command = static_cast<enums::UpdateCommand>(value.as_uint32());
@@ -3606,7 +3606,7 @@ uint32_t ZWaveProxyFrame::calculate_size() const {
   size += ProtoSize::calc_length(1, this->data_len);
   return size;
 }
-bool ZWaveProxyRequest::decode_varint(uint32_t field_id, ProtoVarInt value) {
+bool ZWaveProxyRequest::decode_varint(uint32_t field_id, ProtoVarIntResult value) {
   switch (field_id) {
     case 1:
       this->type = static_cast<enums::ZWaveProxyRequestType>(value.as_uint32());
@@ -3672,7 +3672,7 @@ uint32_t ListEntitiesInfraredResponse::calculate_size() const {
 }
 #endif
 #ifdef USE_IR_RF
-bool InfraredRFTransmitRawTimingsRequest::decode_varint(uint32_t field_id, ProtoVarInt value) {
+bool InfraredRFTransmitRawTimingsRequest::decode_varint(uint32_t field_id, ProtoVarIntResult value) {
   switch (field_id) {
 #ifdef USE_DEVICES
     case 1:
@@ -3737,7 +3737,7 @@ uint32_t InfraredRFReceiveEvent::calculate_size() const {
 }
 #endif
 #ifdef USE_SERIAL_PROXY
-bool SerialProxyConfigureRequest::decode_varint(uint32_t field_id, ProtoVarInt value) {
+bool SerialProxyConfigureRequest::decode_varint(uint32_t field_id, ProtoVarIntResult value) {
   switch (field_id) {
     case 1:
       this->instance = value.as_uint32();
@@ -3772,7 +3772,7 @@ uint32_t SerialProxyDataReceived::calculate_size() const {
   size += ProtoSize::calc_length(1, this->data_len_);
   return size;
 }
-bool SerialProxyWriteRequest::decode_varint(uint32_t field_id, ProtoVarInt value) {
+bool SerialProxyWriteRequest::decode_varint(uint32_t field_id, ProtoVarIntResult value) {
   switch (field_id) {
     case 1:
       this->instance = value.as_uint32();
@@ -3794,7 +3794,7 @@ bool SerialProxyWriteRequest::decode_length(uint32_t field_id, ProtoLengthDelimi
   }
   return true;
 }
-bool SerialProxySetModemPinsRequest::decode_varint(uint32_t field_id, ProtoVarInt value) {
+bool SerialProxySetModemPinsRequest::decode_varint(uint32_t field_id, ProtoVarIntResult value) {
   switch (field_id) {
     case 1:
       this->instance = value.as_uint32();
@@ -3807,7 +3807,7 @@ bool SerialProxySetModemPinsRequest::decode_varint(uint32_t field_id, ProtoVarIn
   }
   return true;
 }
-bool SerialProxyGetModemPinsRequest::decode_varint(uint32_t field_id, ProtoVarInt value) {
+bool SerialProxyGetModemPinsRequest::decode_varint(uint32_t field_id, ProtoVarIntResult value) {
   switch (field_id) {
     case 1:
       this->instance = value.as_uint32();
@@ -3827,7 +3827,7 @@ uint32_t SerialProxyGetModemPinsResponse::calculate_size() const {
   size += ProtoSize::calc_uint32(1, this->line_states);
   return size;
 }
-bool SerialProxyRequest::decode_varint(uint32_t field_id, ProtoVarInt value) {
+bool SerialProxyRequest::decode_varint(uint32_t field_id, ProtoVarIntResult value) {
   switch (field_id) {
     case 1:
       this->instance = value.as_uint32();
@@ -3856,7 +3856,7 @@ uint32_t SerialProxyRequestResponse::calculate_size() const {
 }
 #endif
 #ifdef USE_BLUETOOTH_PROXY
-bool BluetoothSetConnectionParamsRequest::decode_varint(uint32_t field_id, ProtoVarInt value) {
+bool BluetoothSetConnectionParamsRequest::decode_varint(uint32_t field_id, ProtoVarIntResult value) {
   switch (field_id) {
     case 1:
       this->address = value.as_uint64();

esphome/components/api/api_pb2.h

@@ -399,7 +399,7 @@ class HelloRequest final : public ProtoDecodableMessage {
 
  protected:
   bool decode_length(uint32_t field_id, ProtoLengthDelimited value) override;
-  bool decode_varint(uint32_t field_id, ProtoVarInt value) override;
+  bool decode_varint(uint32_t field_id, ProtoVarIntResult value) override;
 };
 class HelloResponse final : public ProtoMessage {
  public:
@@ -688,7 +688,7 @@ class CoverCommandRequest final : public CommandProtoMessage {
 
  protected:
   bool decode_32bit(uint32_t field_id, Proto32Bit value) override;
-  bool decode_varint(uint32_t field_id, ProtoVarInt value) override;
+  bool decode_varint(uint32_t field_id, ProtoVarIntResult value) override;
 };
 #endif
 #ifdef USE_FAN
@@ -756,7 +756,7 @@ class FanCommandRequest final : public CommandProtoMessage {
  protected:
   bool decode_32bit(uint32_t field_id, Proto32Bit value) override;
   bool decode_length(uint32_t field_id, ProtoLengthDelimited value) override;
-  bool decode_varint(uint32_t field_id, ProtoVarInt value) override;
+  bool decode_varint(uint32_t field_id, ProtoVarIntResult value) override;
 };
 #endif
 #ifdef USE_LIGHT
@@ -846,7 +846,7 @@ class LightCommandRequest final : public CommandProtoMessage {
  protected:
   bool decode_32bit(uint32_t field_id, Proto32Bit value) override;
   bool decode_length(uint32_t field_id, ProtoLengthDelimited value) override;
-  bool decode_varint(uint32_t field_id, ProtoVarInt value) override;
+  bool decode_varint(uint32_t field_id, ProtoVarIntResult value) override;
 };
 #endif
 #ifdef USE_SENSOR
@@ -936,7 +936,7 @@ class SwitchCommandRequest final : public CommandProtoMessage {
 
  protected:
   bool decode_32bit(uint32_t field_id, Proto32Bit value) override;
-  bool decode_varint(uint32_t field_id, ProtoVarInt value) override;
+  bool decode_varint(uint32_t field_id, ProtoVarIntResult value) override;
 };
 #endif
 #ifdef USE_TEXT_SENSOR
@@ -988,7 +988,7 @@ class SubscribeLogsRequest final : public ProtoDecodableMessage {
 #endif
 
  protected:
-  bool decode_varint(uint32_t field_id, ProtoVarInt value) override;
+  bool decode_varint(uint32_t field_id, ProtoVarIntResult value) override;
 };
 class SubscribeLogsResponse final : public ProtoMessage {
  public:
@@ -1110,7 +1110,7 @@ class HomeassistantActionResponse final : public ProtoDecodableMessage {
 
  protected:
   bool decode_length(uint32_t field_id, ProtoLengthDelimited value) override;
-  bool decode_varint(uint32_t field_id, ProtoVarInt value) override;
+  bool decode_varint(uint32_t field_id, ProtoVarIntResult value) override;
 };
 #endif
 #ifdef USE_API_HOMEASSISTANT_STATES
@@ -1176,7 +1176,7 @@ class DSTRule final : public ProtoDecodableMessage {
 #endif
 
  protected:
-  bool decode_varint(uint32_t field_id, ProtoVarInt value) override;
+  bool decode_varint(uint32_t field_id, ProtoVarIntResult value) override;
 };
 class ParsedTimezone final : public ProtoDecodableMessage {
  public:
@@ -1190,7 +1190,7 @@ class ParsedTimezone final : public ProtoDecodableMessage {
 
  protected:
   bool decode_length(uint32_t field_id, ProtoLengthDelimited value) override;
-  bool decode_varint(uint32_t field_id, ProtoVarInt value) override;
+  bool decode_varint(uint32_t field_id, ProtoVarIntResult value) override;
 };
 class GetTimeResponse final : public ProtoDecodableMessage {
  public:
@@ -1261,7 +1261,7 @@ class ExecuteServiceArgument final : public ProtoDecodableMessage {
  protected:
   bool decode_32bit(uint32_t field_id, Proto32Bit value) override;
   bool decode_length(uint32_t field_id, ProtoLengthDelimited value) override;
-  bool decode_varint(uint32_t field_id, ProtoVarInt value) override;
+  bool decode_varint(uint32_t field_id, ProtoVarIntResult value) override;
 };
 class ExecuteServiceRequest final : public ProtoDecodableMessage {
  public:
@@ -1286,7 +1286,7 @@ class ExecuteServiceRequest final : public ProtoDecodableMessage {
  protected:
   bool decode_32bit(uint32_t field_id, Proto32Bit value) override;
   bool decode_length(uint32_t field_id, ProtoLengthDelimited value) override;
-  bool decode_varint(uint32_t field_id, ProtoVarInt value) override;
+  bool decode_varint(uint32_t field_id, ProtoVarIntResult value) override;
 };
 #endif
 #ifdef USE_API_USER_DEFINED_ACTION_RESPONSES
@@ -1365,7 +1365,7 @@ class CameraImageRequest final : public ProtoDecodableMessage {
 #endif
 
  protected:
-  bool decode_varint(uint32_t field_id, ProtoVarInt value) override;
+  bool decode_varint(uint32_t field_id, ProtoVarIntResult value) override;
 };
 #endif
 #ifdef USE_CLIMATE
@@ -1464,7 +1464,7 @@ class ClimateCommandRequest final : public CommandProtoMessage {
  protected:
   bool decode_32bit(uint32_t field_id, Proto32Bit value) override;
   bool decode_length(uint32_t field_id, ProtoLengthDelimited value) override;
-  bool decode_varint(uint32_t field_id, ProtoVarInt value) override;
+  bool decode_varint(uint32_t field_id, ProtoVarIntResult value) override;
 };
 #endif
 #ifdef USE_WATER_HEATER
@@ -1528,7 +1528,7 @@ class WaterHeaterCommandRequest final : public CommandProtoMessage {
 
  protected:
   bool decode_32bit(uint32_t field_id, Proto32Bit value) override;
-  bool decode_varint(uint32_t field_id, ProtoVarInt value) override;
+  bool decode_varint(uint32_t field_id, ProtoVarIntResult value) override;
 };
 #endif
 #ifdef USE_NUMBER
@@ -1584,7 +1584,7 @@ class NumberCommandRequest final : public CommandProtoMessage {
 
  protected:
   bool decode_32bit(uint32_t field_id, Proto32Bit value) override;
-  bool decode_varint(uint32_t field_id, ProtoVarInt value) override;
+  bool decode_varint(uint32_t field_id, ProtoVarIntResult value) override;
 };
 #endif
 #ifdef USE_SELECT
@@ -1636,7 +1636,7 @@ class SelectCommandRequest final : public CommandProtoMessage {
  protected:
   bool decode_32bit(uint32_t field_id, Proto32Bit value) override;
   bool decode_length(uint32_t field_id, ProtoLengthDelimited value) override;
-  bool decode_varint(uint32_t field_id, ProtoVarInt value) override;
+  bool decode_varint(uint32_t field_id, ProtoVarIntResult value) override;
 };
 #endif
 #ifdef USE_SIREN
@@ -1696,7 +1696,7 @@ class SirenCommandRequest final : public CommandProtoMessage {
  protected:
   bool decode_32bit(uint32_t field_id, Proto32Bit value) override;
   bool decode_length(uint32_t field_id, ProtoLengthDelimited value) override;
-  bool decode_varint(uint32_t field_id, ProtoVarInt value) override;
+  bool decode_varint(uint32_t field_id, ProtoVarIntResult value) override;
 };
 #endif
 #ifdef USE_LOCK
@@ -1752,7 +1752,7 @@ class LockCommandRequest final : public CommandProtoMessage {
  protected:
   bool decode_32bit(uint32_t field_id, Proto32Bit value) override;
   bool decode_length(uint32_t field_id, ProtoLengthDelimited value) override;
-  bool decode_varint(uint32_t field_id, ProtoVarInt value) override;
+  bool decode_varint(uint32_t field_id, ProtoVarIntResult value) override;
 };
 #endif
 #ifdef USE_BUTTON
@@ -1785,7 +1785,7 @@ class ButtonCommandRequest final : public CommandProtoMessage {
 
  protected:
   bool decode_32bit(uint32_t field_id, Proto32Bit value) override;
-  bool decode_varint(uint32_t field_id, ProtoVarInt value) override;
+  bool decode_varint(uint32_t field_id, ProtoVarIntResult value) override;
 };
 #endif
 #ifdef USE_MEDIA_PLAYER
@@ -1862,7 +1862,7 @@ class MediaPlayerCommandRequest final : public CommandProtoMessage {
  protected:
   bool decode_32bit(uint32_t field_id, Proto32Bit value) override;
   bool decode_length(uint32_t field_id, ProtoLengthDelimited value) override;
-  bool decode_varint(uint32_t field_id, ProtoVarInt value) override;
+  bool decode_varint(uint32_t field_id, ProtoVarIntResult value) override;
 };
 #endif
 #ifdef USE_BLUETOOTH_PROXY
@@ -1879,7 +1879,7 @@ class SubscribeBluetoothLEAdvertisementsRequest final : public ProtoDecodableMes
 #endif
 
  protected:
-  bool decode_varint(uint32_t field_id, ProtoVarInt value) override;
+  bool decode_varint(uint32_t field_id, ProtoVarIntResult value) override;
 };
 class BluetoothLERawAdvertisement final : public ProtoMessage {
  public:
@@ -1929,7 +1929,7 @@ class BluetoothDeviceRequest final : public ProtoDecodableMessage {
 #endif
 
  protected:
-  bool decode_varint(uint32_t field_id, ProtoVarInt value) override;
+  bool decode_varint(uint32_t field_id, ProtoVarIntResult value) override;
 };
 class BluetoothDeviceConnectionResponse final : public ProtoMessage {
  public:
@@ -1963,7 +1963,7 @@ class BluetoothGATTGetServicesRequest final : public ProtoDecodableMessage {
 #endif
 
  protected:
-  bool decode_varint(uint32_t field_id, ProtoVarInt value) override;
+  bool decode_varint(uint32_t field_id, ProtoVarIntResult value) override;
 };
 class BluetoothGATTDescriptor final : public ProtoMessage {
  public:
@@ -2054,7 +2054,7 @@ class BluetoothGATTReadRequest final : public ProtoDecodableMessage {
 #endif
 
  protected:
-  bool decode_varint(uint32_t field_id, ProtoVarInt value) override;
+  bool decode_varint(uint32_t field_id, ProtoVarIntResult value) override;
 };
 class BluetoothGATTReadResponse final : public ProtoMessage {
  public:
@@ -2097,7 +2097,7 @@ class BluetoothGATTWriteRequest final : public ProtoDecodableMessage {
 
  protected:
   bool decode_length(uint32_t field_id, ProtoLengthDelimited value) override;
-  bool decode_varint(uint32_t field_id, ProtoVarInt value) override;
+  bool decode_varint(uint32_t field_id, ProtoVarIntResult value) override;
 };
 class BluetoothGATTReadDescriptorRequest final : public ProtoDecodableMessage {
  public:
@@ -2113,7 +2113,7 @@ class BluetoothGATTReadDescriptorRequest final : public ProtoDecodableMessage {
 #endif
 
  protected:
-  bool decode_varint(uint32_t field_id, ProtoVarInt value) override;
+  bool decode_varint(uint32_t field_id, ProtoVarIntResult value) override;
 };
 class BluetoothGATTWriteDescriptorRequest final : public ProtoDecodableMessage {
  public:
@@ -2132,7 +2132,7 @@ class BluetoothGATTWriteDescriptorRequest final : public ProtoDecodableMessage {
 
  protected:
   bool decode_length(uint32_t field_id, ProtoLengthDelimited value) override;
-  bool decode_varint(uint32_t field_id, ProtoVarInt value) override;
+  bool decode_varint(uint32_t field_id, ProtoVarIntResult value) override;
 };
 class BluetoothGATTNotifyRequest final : public ProtoDecodableMessage {
  public:
@@ -2149,7 +2149,7 @@ class BluetoothGATTNotifyRequest final : public ProtoDecodableMessage {
 #endif
 
  protected:
-  bool decode_varint(uint32_t field_id, ProtoVarInt value) override;
+  bool decode_varint(uint32_t field_id, ProtoVarIntResult value) override;
 };
 class BluetoothGATTNotifyDataResponse final : public ProtoMessage {
  public:
@@ -2329,7 +2329,7 @@ class BluetoothScannerSetModeRequest final : public ProtoDecodableMessage {
 #endif
 
  protected:
-  bool decode_varint(uint32_t field_id, ProtoVarInt value) override;
+  bool decode_varint(uint32_t field_id, ProtoVarIntResult value) override;
 };
 #endif
 #ifdef USE_VOICE_ASSISTANT
@@ -2347,7 +2347,7 @@ class SubscribeVoiceAssistantRequest final : public ProtoDecodableMessage {
 #endif
 
  protected:
-  bool decode_varint(uint32_t field_id, ProtoVarInt value) override;
+  bool decode_varint(uint32_t field_id, ProtoVarIntResult value) override;
 };
 class VoiceAssistantAudioSettings final : public ProtoMessage {
  public:
@@ -2396,7 +2396,7 @@ class VoiceAssistantResponse final : public ProtoDecodableMessage {
 #endif
 
  protected:
-  bool decode_varint(uint32_t field_id, ProtoVarInt value) override;
+  bool decode_varint(uint32_t field_id, ProtoVarIntResult value) override;
 };
 class VoiceAssistantEventData final : public ProtoDecodableMessage {
  public:
@@ -2424,7 +2424,7 @@ class VoiceAssistantEventResponse final : public ProtoDecodableMessage {
 
  protected:
   bool decode_length(uint32_t field_id, ProtoLengthDelimited value) override;
-  bool decode_varint(uint32_t field_id, ProtoVarInt value) override;
+  bool decode_varint(uint32_t field_id, ProtoVarIntResult value) override;
 };
 class VoiceAssistantAudio final : public ProtoDecodableMessage {
  public:
@@ -2444,7 +2444,7 @@ class VoiceAssistantAudio final : public ProtoDecodableMessage {
 
  protected:
   bool decode_length(uint32_t field_id, ProtoLengthDelimited value) override;
-  bool decode_varint(uint32_t field_id, ProtoVarInt value) override;
+  bool decode_varint(uint32_t field_id, ProtoVarIntResult value) override;
 };
 class VoiceAssistantTimerEventResponse final : public ProtoDecodableMessage {
  public:
@@ -2465,7 +2465,7 @@ class VoiceAssistantTimerEventResponse final : public ProtoDecodableMessage {
 
  protected:
   bool decode_length(uint32_t field_id, ProtoLengthDelimited value) override;
-  bool decode_varint(uint32_t field_id, ProtoVarInt value) override;
+  bool decode_varint(uint32_t field_id, ProtoVarIntResult value) override;
 };
 class VoiceAssistantAnnounceRequest final : public ProtoDecodableMessage {
  public:
@@ -2484,7 +2484,7 @@ class VoiceAssistantAnnounceRequest final : public ProtoDecodableMessage {
 
  protected:
   bool decode_length(uint32_t field_id, ProtoLengthDelimited value) override;
-  bool decode_varint(uint32_t field_id, ProtoVarInt value) override;
+  bool decode_varint(uint32_t field_id, ProtoVarIntResult value) override;
 };
 class VoiceAssistantAnnounceFinished final : public ProtoMessage {
  public:
@@ -2530,7 +2530,7 @@ class VoiceAssistantExternalWakeWord final : public ProtoDecodableMessage {
 
  protected:
   bool decode_length(uint32_t field_id, ProtoLengthDelimited value) override;
-  bool decode_varint(uint32_t field_id, ProtoVarInt value) override;
+  bool decode_varint(uint32_t field_id, ProtoVarIntResult value) override;
 };
 class VoiceAssistantConfigurationRequest final : public ProtoDecodableMessage {
  public:
@@ -2632,7 +2632,7 @@ class AlarmControlPanelCommandRequest final : public CommandProtoMessage {
  protected:
   bool decode_32bit(uint32_t field_id, Proto32Bit value) override;
   bool decode_length(uint32_t field_id, ProtoLengthDelimited value) override;
-  bool decode_varint(uint32_t field_id, ProtoVarInt value) override;
+  bool decode_varint(uint32_t field_id, ProtoVarIntResult value) override;
 };
 #endif
 #ifdef USE_TEXT
@@ -2687,7 +2687,7 @@ class TextCommandRequest final : public CommandProtoMessage {
  protected:
   bool decode_32bit(uint32_t field_id, Proto32Bit value) override;
   bool decode_length(uint32_t field_id, ProtoLengthDelimited value) override;
-  bool decode_varint(uint32_t field_id, ProtoVarInt value) override;
+  bool decode_varint(uint32_t field_id, ProtoVarIntResult value) override;
 };
 #endif
 #ifdef USE_DATETIME_DATE
@@ -2741,7 +2741,7 @@ class DateCommandRequest final : public CommandProtoMessage {
 
  protected:
   bool decode_32bit(uint32_t field_id, Proto32Bit value) override;
-  bool decode_varint(uint32_t field_id, ProtoVarInt value) override;
+  bool decode_varint(uint32_t field_id, ProtoVarIntResult value) override;
 };
 #endif
 #ifdef USE_DATETIME_TIME
@@ -2795,7 +2795,7 @@ class TimeCommandRequest final : public CommandProtoMessage {
 
  protected:
   bool decode_32bit(uint32_t field_id, Proto32Bit value) override;
-  bool decode_varint(uint32_t field_id, ProtoVarInt value) override;
+  bool decode_varint(uint32_t field_id, ProtoVarIntResult value) override;
 };
 #endif
 #ifdef USE_EVENT
@@ -2886,7 +2886,7 @@ class ValveCommandRequest final : public CommandProtoMessage {
 
  protected:
   bool decode_32bit(uint32_t field_id, Proto32Bit value) override;
-  bool decode_varint(uint32_t field_id, ProtoVarInt value) override;
+  bool decode_varint(uint32_t field_id, ProtoVarIntResult value) override;
 };
 #endif
 #ifdef USE_DATETIME_DATETIME
@@ -2936,7 +2936,7 @@ class DateTimeCommandRequest final : public CommandProtoMessage {
 
  protected:
   bool decode_32bit(uint32_t field_id, Proto32Bit value) override;
-  bool decode_varint(uint32_t field_id, ProtoVarInt value) override;
+  bool decode_varint(uint32_t field_id, ProtoVarIntResult value) override;
 };
 #endif
 #ifdef USE_UPDATE
@@ -2994,7 +2994,7 @@ class UpdateCommandRequest final : public CommandProtoMessage {
 
  protected:
   bool decode_32bit(uint32_t field_id, Proto32Bit value) override;
-  bool decode_varint(uint32_t field_id, ProtoVarInt value) override;
+  bool decode_varint(uint32_t field_id, ProtoVarIntResult value) override;
 };
 #endif
 #ifdef USE_ZWAVE_PROXY
@@ -3034,7 +3034,7 @@ class ZWaveProxyRequest final : public ProtoDecodableMessage {
 
  protected:
   bool decode_length(uint32_t field_id, ProtoLengthDelimited value) override;
-  bool decode_varint(uint32_t field_id, ProtoVarInt value) override;
+  bool decode_varint(uint32_t field_id, ProtoVarIntResult value) override;
 };
 #endif
 #ifdef USE_INFRARED
@@ -3079,7 +3079,7 @@ class InfraredRFTransmitRawTimingsRequest final : public ProtoDecodableMessage {
  protected:
   bool decode_32bit(uint32_t field_id, Proto32Bit value) override;
   bool decode_length(uint32_t field_id, ProtoLengthDelimited value) override;
-  bool decode_varint(uint32_t field_id, ProtoVarInt value) override;
+  bool decode_varint(uint32_t field_id, ProtoVarIntResult value) override;
 };
 class InfraredRFReceiveEvent final : public ProtoMessage {
  public:
@@ -3121,7 +3121,7 @@ class SerialProxyConfigureRequest final : public ProtoDecodableMessage {
 #endif
 
  protected:
-  bool decode_varint(uint32_t field_id, ProtoVarInt value) override;
+  bool decode_varint(uint32_t field_id, ProtoVarIntResult value) override;
 };
 class SerialProxyDataReceived final : public ProtoMessage {
  public:
@@ -3161,7 +3161,7 @@ class SerialProxyWriteRequest final : public ProtoDecodableMessage {
 
  protected:
   bool decode_length(uint32_t field_id, ProtoLengthDelimited value) override;
-  bool decode_varint(uint32_t field_id, ProtoVarInt value) override;
+  bool decode_varint(uint32_t field_id, ProtoVarIntResult value) override;
 };
 class SerialProxySetModemPinsRequest final : public ProtoDecodableMessage {
  public:
@@ -3177,7 +3177,7 @@ class SerialProxySetModemPinsRequest final : public ProtoDecodableMessage {
 #endif
 
  protected:
-  bool decode_varint(uint32_t field_id, ProtoVarInt value) override;
+  bool decode_varint(uint32_t field_id, ProtoVarIntResult value) override;
 };
 class SerialProxyGetModemPinsRequest final : public ProtoDecodableMessage {
  public:
@@ -3192,7 +3192,7 @@ class SerialProxyGetModemPinsRequest final : public ProtoDecodableMessage {
 #endif
 
  protected:
-  bool decode_varint(uint32_t field_id, ProtoVarInt value) override;
+  bool decode_varint(uint32_t field_id, ProtoVarIntResult value) override;
 };
 class SerialProxyGetModemPinsResponse final : public ProtoMessage {
  public:
@@ -3225,7 +3225,7 @@ class SerialProxyRequest final : public ProtoDecodableMessage {
 #endif
 
  protected:
-  bool decode_varint(uint32_t field_id, ProtoVarInt value) override;
+  bool decode_varint(uint32_t field_id, ProtoVarIntResult value) override;
 };
 class SerialProxyRequestResponse final : public ProtoMessage {
  public:
@@ -3265,7 +3265,7 @@ class BluetoothSetConnectionParamsRequest final : public ProtoDecodableMessage {
 #endif
 
  protected:
-  bool decode_varint(uint32_t field_id, ProtoVarInt value) override;
+  bool decode_varint(uint32_t field_id, ProtoVarIntResult value) override;
 };
 class BluetoothSetConnectionParamsResponse final : public ProtoMessage {
  public:

esphome/components/api/proto.cpp

@@ -20,20 +20,40 @@ void ProtoWriteBuffer::encode_varint_raw_slow_(uint32_t value) {
   *this->pos_++ = static_cast<uint8_t>(value);
 }
 
+ProtoVarIntResult ProtoVarInt::parse_slow_(const uint8_t *buffer, uint32_t len) {
+  // Multi-byte varint: first byte already checked to have high bit set
+  uint32_t result32 = buffer[0] & 0x7F;
 #ifdef USE_API_VARINT64
-optional<ProtoVarInt> ProtoVarInt::parse_wide(const uint8_t *buffer, uint32_t len, uint32_t *consumed,
-                                              uint32_t result32) {
+  uint32_t limit = std::min(len, uint32_t(4));
+#else
+  uint32_t limit = std::min(len, uint32_t(5));
+#endif
+  for (uint32_t i = 1; i < limit; i++) {
+    uint8_t val = buffer[i];
+    result32 |= uint32_t(val & 0x7F) << (i * 7);
+    if ((val & 0x80) == 0) {
+      return {result32, i + 1};
+    }
+  }
+#ifdef USE_API_VARINT64
+  return parse_wide_(buffer, len, result32);
+#else
+  return {0, 0};
+#endif
+}
+
+#ifdef USE_API_VARINT64
+ProtoVarIntResult ProtoVarInt::parse_wide_(const uint8_t *buffer, uint32_t len, uint32_t result32) {
   uint64_t result64 = result32;
   uint32_t limit = std::min(len, uint32_t(10));
   for (uint32_t i = 4; i < limit; i++) {
     uint8_t val = buffer[i];
     result64 |= uint64_t(val & 0x7F) << (i * 7);
     if ((val & 0x80) == 0) {
-      *consumed = i + 1;
-      return ProtoVarInt(result64);
+      return {result64, i + 1};
     }
   }
-  return {};
+  return {0, 0};
 }
 #endif
 
@@ -43,18 +63,16 @@ uint32_t ProtoDecodableMessage::count_repeated_field(const uint8_t *buffer, size
   const uint8_t *end = buffer + length;
 
   while (ptr < end) {
-    uint32_t consumed;
-
     // Parse field header (tag)
-    auto res = ProtoVarInt::parse(ptr, end - ptr, &consumed);
+    auto res = ProtoVarInt::parse(ptr, end - ptr);
     if (!res.has_value()) {
       break;  // Invalid data, stop counting
     }
 
-    uint32_t tag = res->as_uint32();
+    uint32_t tag = res.as_uint32();
     uint32_t field_type = tag & WIRE_TYPE_MASK;
     uint32_t field_id = tag >> 3;
-    ptr += consumed;
+    ptr += res.consumed;
 
     // Count if this is the target field
     if (field_id == target_field_id) {
@@ -64,20 +82,20 @@ uint32_t ProtoDecodableMessage::count_repeated_field(const uint8_t *buffer, size
     // Skip field data based on wire type
     switch (field_type) {
       case WIRE_TYPE_VARINT: {  // VarInt - parse and skip
-        res = ProtoVarInt::parse(ptr, end - ptr, &consumed);
+        res = ProtoVarInt::parse(ptr, end - ptr);
         if (!res.has_value()) {
           return count;  // Invalid data, return what we have
         }
-        ptr += consumed;
+        ptr += res.consumed;
         break;
       }
       case WIRE_TYPE_LENGTH_DELIMITED: {  // Length-delimited - parse length and skip data
-        res = ProtoVarInt::parse(ptr, end - ptr, &consumed);
+        res = ProtoVarInt::parse(ptr, end - ptr);
         if (!res.has_value()) {
           return count;
         }
-        uint32_t field_length = res->as_uint32();
-        ptr += consumed;
+        uint32_t field_length = res.as_uint32();
+        ptr += res.consumed;
         if (field_length > static_cast<size_t>(end - ptr)) {
           return count;  // Out of bounds
         }
@@ -190,41 +208,39 @@ void ProtoDecodableMessage::decode(const uint8_t *buffer, size_t length) {
   const uint8_t *end = buffer + length;
 
   while (ptr < end) {
-    uint32_t consumed;
-
     // Parse field header
-    auto res = ProtoVarInt::parse(ptr, end - ptr, &consumed);
+    auto res = ProtoVarInt::parse(ptr, end - ptr);
     if (!res.has_value()) {
       ESP_LOGV(TAG, "Invalid field start at offset %ld", (long) (ptr - buffer));
       return;
     }
 
-    uint32_t tag = res->as_uint32();
+    uint32_t tag = res.as_uint32();
     uint32_t field_type = tag & WIRE_TYPE_MASK;
     uint32_t field_id = tag >> 3;
-    ptr += consumed;
+    ptr += res.consumed;
 
     switch (field_type) {
       case WIRE_TYPE_VARINT: {  // VarInt
-        res = ProtoVarInt::parse(ptr, end - ptr, &consumed);
+        res = ProtoVarInt::parse(ptr, end - ptr);
         if (!res.has_value()) {
           ESP_LOGV(TAG, "Invalid VarInt at offset %ld", (long) (ptr - buffer));
           return;
         }
-        if (!this->decode_varint(field_id, *res)) {
-          ESP_LOGV(TAG, "Cannot decode VarInt field %" PRIu32 " with value %" PRIu32 "!", field_id, res->as_uint32());
+        if (!this->decode_varint(field_id, res)) {
+          ESP_LOGV(TAG, "Cannot decode VarInt field %" PRIu32 " with value %" PRIu32 "!", field_id, res.as_uint32());
         }
-        ptr += consumed;
+        ptr += res.consumed;
         break;
       }
       case WIRE_TYPE_LENGTH_DELIMITED: {  // Length-delimited
-        res = ProtoVarInt::parse(ptr, end - ptr, &consumed);
+        res = ProtoVarInt::parse(ptr, end - ptr);
         if (!res.has_value()) {
           ESP_LOGV(TAG, "Invalid Length Delimited at offset %ld", (long) (ptr - buffer));
           return;
         }
-        uint32_t field_length = res->as_uint32();
-        ptr += consumed;
+        uint32_t field_length = res.as_uint32();
+        ptr += res.consumed;
         if (field_length > static_cast<size_t>(end - ptr)) {
           ESP_LOGV(TAG, "Out-of-bounds Length Delimited at offset %ld", (long) (ptr - buffer));
           return;

esphome/components/api/proto.h

@@ -98,62 +98,57 @@ inline void encode_varint_to_buffer(uint32_t val, uint8_t *buffer) {
  * within the same function scope where temporaries are created.
  */
 
+/// Result of parsing a varint: value + number of bytes consumed.
+/// consumed == 0 indicates parse failure (not enough data or invalid).
+struct ProtoVarIntResult {
+#ifdef USE_API_VARINT64
+  uint64_t value;
+#else
+  uint32_t value;
+#endif
+  uint32_t consumed;  // 0 = parse failed
+
+  constexpr bool has_value() const { return this->consumed != 0; }
+  constexpr uint16_t as_uint16() const { return this->value; }
+  constexpr uint32_t as_uint32() const { return this->value; }
+  constexpr bool as_bool() const { return this->value; }
+  constexpr int32_t as_int32() const { return static_cast<int32_t>(this->value); }
+  constexpr int32_t as_sint32() const { return decode_zigzag32(static_cast<uint32_t>(this->value)); }
+#ifdef USE_API_VARINT64
+  constexpr uint64_t as_uint64() const { return this->value; }
+  constexpr int64_t as_int64() const { return static_cast<int64_t>(this->value); }
+  constexpr int64_t as_sint64() const { return decode_zigzag64(this->value); }
+#endif
+};
+
 /// Representation of a VarInt - in ProtoBuf should be 64bit but we only use 32bit
 class ProtoVarInt {
  public:
   ProtoVarInt() : value_(0) {}
   explicit ProtoVarInt(uint64_t value) : value_(value) {}
 
-  /// Parse a varint from buffer. consumed must be a valid pointer (not null).
-  static optional<ProtoVarInt> parse(const uint8_t *buffer, uint32_t len, uint32_t *consumed) {
-#ifdef ESPHOME_DEBUG_API
-    assert(consumed != nullptr);
-#endif
+  /// Parse a varint from buffer. Returns result with consumed=0 on failure.
+  static inline ProtoVarIntResult ESPHOME_ALWAYS_INLINE parse(const uint8_t *buffer, uint32_t len) {
     if (len == 0)
-      return {};
+      return {0, 0};
     // Fast path: single-byte varints (0-127) are the most common case
-    // (booleans, small enums, field tags). Avoid loop overhead entirely.
-    if ((buffer[0] & 0x80) == 0) {
-      *consumed = 1;
-      return ProtoVarInt(buffer[0]);
-    }
-    // 32-bit phase: process remaining bytes with native 32-bit shifts.
-    // Without USE_API_VARINT64: cover bytes 1-4 (shifts 7, 14, 21, 28) — the uint32_t
-    // shift at byte 4 (shift by 28) may lose bits 32-34, but those are always zero for valid uint32 values.
-    // With USE_API_VARINT64: cover bytes 1-3 (shifts 7, 14, 21) so parse_wide handles
-    // byte 4+ with full 64-bit arithmetic (avoids truncating values > UINT32_MAX).
-    uint32_t result32 = buffer[0] & 0x7F;
-#ifdef USE_API_VARINT64
-    uint32_t limit = std::min(len, uint32_t(4));
-#else
-    uint32_t limit = std::min(len, uint32_t(5));
-#endif
-    for (uint32_t i = 1; i < limit; i++) {
-      uint8_t val = buffer[i];
-      result32 |= uint32_t(val & 0x7F) << (i * 7);
-      if ((val & 0x80) == 0) {
-        *consumed = i + 1;
-        return ProtoVarInt(result32);
-      }
-    }
-    // 64-bit phase for remaining bytes (BLE addresses etc.)
-#ifdef USE_API_VARINT64
-    return parse_wide(buffer, len, consumed, result32);
-#else
-    return {};
-#endif
+    // (booleans, small enums, field tags, small message sizes/types).
+    if ((buffer[0] & 0x80) == 0) [[likely]]
+      return {buffer[0], 1};
+    return parse_slow_(buffer, len);
   }
 
-#ifdef USE_API_VARINT64
  protected:
-  /// Continue parsing varint bytes 4-9 with 64-bit arithmetic.
-  /// Separated to keep 64-bit shift code (__ashldi3 on 32-bit platforms) out of the common path.
-  static optional<ProtoVarInt> parse_wide(const uint8_t *buffer, uint32_t len, uint32_t *consumed, uint32_t result32)
-      __attribute__((noinline));
+  // Slow path for multi-byte varints (>= 128), outlined to keep fast path small
+  static ProtoVarIntResult parse_slow_(const uint8_t *buffer, uint32_t len) __attribute__((noinline));
 
- public:
+#ifdef USE_API_VARINT64
+  /// Continue parsing varint bytes 4-9 with 64-bit arithmetic.
+  static ProtoVarIntResult parse_wide_(const uint8_t *buffer, uint32_t len, uint32_t result32)
+      __attribute__((noinline));
 #endif
 
+ public:
   constexpr uint16_t as_uint16() const { return this->value_; }
   constexpr uint32_t as_uint32() const { return this->value_; }
   constexpr bool as_bool() const { return this->value_; }
@@ -499,7 +494,7 @@ class ProtoDecodableMessage : public ProtoMessage {
 
  protected:
   ~ProtoDecodableMessage() = default;
-  virtual bool decode_varint(uint32_t field_id, ProtoVarInt value) { return false; }
+  virtual bool decode_varint(uint32_t field_id, ProtoVarIntResult value) { return false; }
   virtual bool decode_length(uint32_t field_id, ProtoLengthDelimited value) { return false; }
   virtual bool decode_32bit(uint32_t field_id, Proto32Bit value) { return false; }
   // NOTE: decode_64bit removed - wire type 1 not supported

script/api_protobuf/api_protobuf.py

@@ -2205,7 +2205,7 @@ def build_message_type(
 
     cpp = ""
     if decode_varint:
-        o = f"bool {desc.name}::decode_varint(uint32_t field_id, ProtoVarInt value) {{\n"
+        o = f"bool {desc.name}::decode_varint(uint32_t field_id, ProtoVarIntResult value) {{\n"
         o += "  switch (field_id) {\n"
         o += indent("\n".join(decode_varint), "    ") + "\n"
         o += "    default: return false;\n"
@@ -2213,7 +2213,9 @@ def build_message_type(
         o += "  return true;\n"
         o += "}\n"
         cpp += o
-        prot = "bool decode_varint(uint32_t field_id, ProtoVarInt value) override;"
+        prot = (
+            "bool decode_varint(uint32_t field_id, ProtoVarIntResult value) override;"
+        )
         protected_content.insert(0, prot)
     if decode_length:
         o = f"bool {desc.name}::decode_length(uint32_t field_id, ProtoLengthDelimited value) {{\n"