[api] Split ProtoVarInt::parse into 32-bit and 64-bit phases (#14039)

esphome/components/api/api_pb2.h

@@ -2,7 +2,6 @@
 // See script/api_protobuf/api_protobuf.py
 #pragma once
 
-#include "esphome/core/defines.h"
 #include "esphome/core/string_ref.h"
 
 #include "proto.h"

esphome/components/api/api_pb2_defines.h

@@ -0,0 +1,12 @@
+// This file was automatically generated with a tool.
+// See script/api_protobuf/api_protobuf.py
+#pragma once
+
+#include "esphome/core/defines.h"
+#ifdef USE_BLUETOOTH_PROXY
+#ifndef USE_API_VARINT64
+#define USE_API_VARINT64
+#endif
+#endif
+
+namespace esphome::api {}  // namespace esphome::api

esphome/components/api/proto.cpp

@@ -7,6 +7,23 @@ namespace esphome::api {
 
 static const char *const TAG = "api.proto";
 
+#ifdef USE_API_VARINT64
+optional<ProtoVarInt> ProtoVarInt::parse_wide(const uint8_t *buffer, uint32_t len, uint32_t *consumed,
+                                              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 {};
+}
+#endif
+
 uint32_t ProtoDecodableMessage::count_repeated_field(const uint8_t *buffer, size_t length, uint32_t target_field_id) {
   uint32_t count = 0;
   const uint8_t *ptr = buffer;

esphome/components/api/proto.h

@@ -1,5 +1,6 @@
 #pragma once
 
+#include "api_pb2_defines.h"
 #include "esphome/core/component.h"
 #include "esphome/core/helpers.h"
 #include "esphome/core/log.h"
@@ -110,59 +111,78 @@ class ProtoVarInt {
 #endif
     if (len == 0)
       return {};
-
-    // Most common case: single-byte varint (values 0-127)
+    // 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]);
     }
-
-    // General case for multi-byte varints
-    // Since we know buffer[0]'s high bit is set, initialize with its value
-    uint64_t result = buffer[0] & 0x7F;
-    uint8_t bitpos = 7;
-
-    // A 64-bit varint is at most 10 bytes (ceil(64/7)). Reject overlong encodings
-    // to avoid undefined behavior from shifting uint64_t by >= 64 bits.
-    uint32_t max_len = std::min(len, uint32_t(10));
-
-    // Start from the second byte since we've already processed the first
-    for (uint32_t i = 1; i < max_len; i++) {
+    // 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];
-      result |= uint64_t(val & 0x7F) << uint64_t(bitpos);
-      bitpos += 7;
+      result32 |= uint32_t(val & 0x7F) << (i * 7);
       if ((val & 0x80) == 0) {
         *consumed = i + 1;
-        return ProtoVarInt(result);
+        return ProtoVarInt(result32);
       }
     }
-
-    return {};  // Incomplete or invalid varint
+    // 64-bit phase for remaining bytes (BLE addresses etc.)
+#ifdef USE_API_VARINT64
+    return parse_wide(buffer, len, consumed, result32);
+#else
+    return {};
+#endif
   }
 
+#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));
+
+ public:
+#endif
+
   constexpr uint16_t as_uint16() const { return this->value_; }
   constexpr uint32_t as_uint32() const { return this->value_; }
-  constexpr uint64_t as_uint64() const { return this->value_; }
   constexpr bool as_bool() const { return this->value_; }
   constexpr int32_t as_int32() const {
     // Not ZigZag encoded
-    return static_cast<int32_t>(this->as_int64());
-  }
-  constexpr int64_t as_int64() const {
-    // Not ZigZag encoded
-    return static_cast<int64_t>(this->value_);
+    return static_cast<int32_t>(this->value_);
   }
   constexpr int32_t as_sint32() const {
     // with ZigZag encoding
     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 {
+    // Not ZigZag encoded
+    return static_cast<int64_t>(this->value_);
+  }
   constexpr int64_t as_sint64() const {
     // with ZigZag encoding
     return decode_zigzag64(this->value_);
   }
+#endif
 
  protected:
+#ifdef USE_API_VARINT64
   uint64_t value_;
+#else
+  uint32_t value_;
+#endif
 };
 
 // Forward declarations for decode_to_message, encode_message and encode_packed_sint32

esphome/core/defines.h

@@ -144,6 +144,7 @@
 #define USE_API_HOMEASSISTANT_SERVICES
 #define USE_API_HOMEASSISTANT_STATES
 #define USE_API_NOISE
+#define USE_API_VARINT64
 #define USE_API_PLAINTEXT
 #define USE_API_USER_DEFINED_ACTIONS
 #define USE_API_CUSTOM_SERVICES

script/api_protobuf/api_protobuf.py

@@ -1913,6 +1913,37 @@ def build_type_usage_map(
     )
 
 
+def get_varint64_ifdef(
+    file_desc: descriptor.FileDescriptorProto,
+    message_ifdef_map: dict[str, str | None],
+) -> tuple[bool, str | None]:
+    """Check if 64-bit varint fields exist and get their common ifdef guard.
+
+    Returns:
+        (has_varint64, ifdef_guard) - has_varint64 is True if any fields exist,
+        ifdef_guard is the common guard or None if unconditional.
+    """
+    varint64_types = {
+        FieldDescriptorProto.TYPE_INT64,
+        FieldDescriptorProto.TYPE_UINT64,
+        FieldDescriptorProto.TYPE_SINT64,
+    }
+    ifdefs: set[str | None] = {
+        message_ifdef_map.get(msg.name)
+        for msg in file_desc.message_type
+        if not msg.options.deprecated
+        for field in msg.field
+        if not field.options.deprecated and field.type in varint64_types
+    }
+    if not ifdefs:
+        return False, None
+    if None in ifdefs:
+        # At least one 64-bit varint field is unconditional, so the guard must be unconditional.
+        return True, None
+    ifdefs.discard(None)
+    return True, ifdefs.pop() if len(ifdefs) == 1 else None
+
+
 def build_enum_type(desc, enum_ifdef_map) -> tuple[str, str, str]:
     """Builds the enum type.
 
@@ -2567,11 +2598,38 @@ def main() -> None:
 
     file = d.file[0]
 
+    # Build dynamic ifdef mappings early so we can emit USE_API_VARINT64 before includes
+    enum_ifdef_map, message_ifdef_map, message_source_map, used_messages = (
+        build_type_usage_map(file)
+    )
+
+    # Find the ifdef guard for 64-bit varint fields (int64/uint64/sint64).
+    # Generated into api_pb2_defines.h so proto.h can include it, ensuring
+    # consistent ProtoVarInt layout across all translation units.
+    has_varint64, varint64_guard = get_varint64_ifdef(file, message_ifdef_map)
+
+    # Generate api_pb2_defines.h — included by proto.h to ensure all translation
+    # units see USE_API_VARINT64 consistently (avoids ODR violations in ProtoVarInt).
+    defines_content = FILE_HEADER
+    defines_content += "#pragma once\n\n"
+    defines_content += '#include "esphome/core/defines.h"\n'
+    if has_varint64:
+        lines = [
+            "#ifndef USE_API_VARINT64",
+            "#define USE_API_VARINT64",
+            "#endif",
+        ]
+        defines_content += "\n".join(wrap_with_ifdef(lines, varint64_guard))
+        defines_content += "\n"
+    defines_content += "\nnamespace esphome::api {}  // namespace esphome::api\n"
+
+    with open(root / "api_pb2_defines.h", "w", encoding="utf-8") as f:
+        f.write(defines_content)
+
     content = FILE_HEADER
     content += """\
 #pragma once
 
-#include "esphome/core/defines.h"
 #include "esphome/core/string_ref.h"
 
 #include "proto.h"
@@ -2702,11 +2760,6 @@ static void dump_bytes_field(DumpBuffer &out, const char *field_name, const uint
 
     content += "namespace enums {\n\n"
 
-    # Build dynamic ifdef mappings for both enums and messages
-    enum_ifdef_map, message_ifdef_map, message_source_map, used_messages = (
-        build_type_usage_map(file)
-    )
-
     # Simple grouping of enums by ifdef
     current_ifdef = None
 

tests/integration/fixtures/varint_five_byte_device_id.yaml

@@ -0,0 +1,47 @@
+esphome:
+  name: varint-5byte-test
+  # Define areas and devices - device_ids will be FNV hashes > 2^28,
+  # requiring 5-byte varint encoding that exercises the 32-bit parse boundary.
+  areas:
+    - id: test_area
+      name: Test Area
+  devices:
+    - id: sub_device_one
+      name: Sub Device One
+      area_id: test_area
+    - id: sub_device_two
+      name: Sub Device Two
+      area_id: test_area
+
+host:
+api:
+logger:
+
+# Switches on sub-devices so we can send commands with large device_id varints
+switch:
+  - platform: template
+    name: Device Switch
+    device_id: sub_device_one
+    id: device_switch_one
+    optimistic: true
+    turn_on_action:
+      - logger.log: "Switch one on"
+    turn_off_action:
+      - logger.log: "Switch one off"
+
+  - platform: template
+    name: Device Switch
+    device_id: sub_device_two
+    id: device_switch_two
+    optimistic: true
+    turn_on_action:
+      - logger.log: "Switch two on"
+    turn_off_action:
+      - logger.log: "Switch two off"
+
+sensor:
+  - platform: template
+    name: Device Sensor
+    device_id: sub_device_one
+    lambda: return 42.0;
+    update_interval: 0.1s

tests/integration/test_varint_five_byte_device_id.py

@@ -0,0 +1,120 @@
+"""Integration test for 5-byte varint parsing of device_id fields.
+
+Device IDs are FNV hashes (uint32) that frequently exceed 2^28 (268435456),
+requiring 5 varint bytes. This test verifies that:
+1. The firmware correctly decodes 5-byte varint device_id in incoming commands
+2. The firmware correctly encodes large device_id values in state responses
+3. Switch commands with large device_id reach the correct entity
+"""
+
+from __future__ import annotations
+
+import asyncio
+
+from aioesphomeapi import EntityState, SwitchInfo, SwitchState
+import pytest
+
+from .types import APIClientConnectedFactory, RunCompiledFunction
+
+
+@pytest.mark.asyncio
+async def test_varint_five_byte_device_id(
+    yaml_config: str,
+    run_compiled: RunCompiledFunction,
+    api_client_connected: APIClientConnectedFactory,
+) -> None:
+    """Test that device_id values requiring 5-byte varints parse correctly."""
+    async with run_compiled(yaml_config), api_client_connected() as client:
+        device_info = await client.device_info()
+        devices = device_info.devices
+        assert len(devices) >= 2, f"Expected at least 2 devices, got {len(devices)}"
+
+        # Verify at least one device_id exceeds the 4-byte varint boundary (2^28)
+        large_ids = [d for d in devices if d.device_id >= (1 << 28)]
+        assert len(large_ids) > 0, (
+            "Expected at least one device_id >= 2^28 to exercise 5-byte varint path. "
+            f"Got device_ids: {[d.device_id for d in devices]}"
+        )
+
+        # Get entities
+        all_entities, _ = await client.list_entities_services()
+        switch_entities = [e for e in all_entities if isinstance(e, SwitchInfo)]
+
+        # Find switches named "Device Switch" — one per sub-device
+        device_switches = [e for e in switch_entities if e.name == "Device Switch"]
+        assert len(device_switches) == 2, (
+            f"Expected 2 'Device Switch' entities, got {len(device_switches)}"
+        )
+
+        # Verify switches have different device_ids matching the sub-devices
+        switch_device_ids = {s.device_id for s in device_switches}
+        assert len(switch_device_ids) == 2, "Switches should have different device_ids"
+
+        # Subscribe to states and wait for initial states
+        loop = asyncio.get_running_loop()
+        states: dict[tuple[int, int], EntityState] = {}
+        switch_futures: dict[tuple[int, int], asyncio.Future[EntityState]] = {}
+        initial_done: asyncio.Future[bool] = loop.create_future()
+
+        def on_state(state: EntityState) -> None:
+            key = (state.device_id, state.key)
+            states[key] = state
+
+            if len(states) >= 3 and not initial_done.done():
+                initial_done.set_result(True)
+
+            if initial_done.done() and key in switch_futures:
+                fut = switch_futures[key]
+                if not fut.done() and isinstance(state, SwitchState):
+                    fut.set_result(state)
+
+        client.subscribe_states(on_state)
+
+        try:
+            await asyncio.wait_for(initial_done, timeout=10.0)
+        except TimeoutError:
+            pytest.fail(
+                f"Timed out waiting for initial states. Got {len(states)} states"
+            )
+
+        # Verify state responses contain correct large device_id values
+        for device in devices:
+            device_states = [
+                s for (did, _), s in states.items() if did == device.device_id
+            ]
+            assert len(device_states) > 0, (
+                f"No states received for device '{device.name}' "
+                f"(device_id={device.device_id})"
+            )
+
+        # Test switch commands with large device_id varints —
+        # this is the critical path: the client encodes device_id as a varint
+        # in the SwitchCommandRequest, and the firmware must decode it correctly.
+        for switch in device_switches:
+            state_key = (switch.device_id, switch.key)
+
+            # Turn on
+            switch_futures[state_key] = loop.create_future()
+            client.switch_command(switch.key, True, device_id=switch.device_id)
+            try:
+                await asyncio.wait_for(switch_futures[state_key], timeout=2.0)
+            except TimeoutError:
+                pytest.fail(
+                    f"Timed out waiting for switch ON state "
+                    f"(device_id={switch.device_id}, key={switch.key}). "
+                    f"This likely means the firmware failed to decode the "
+                    f"5-byte varint device_id in SwitchCommandRequest."
+                )
+            assert states[state_key].state is True
+
+            # Turn off
+            switch_futures[state_key] = loop.create_future()
+            client.switch_command(switch.key, False, device_id=switch.device_id)
+            try:
+                await asyncio.wait_for(switch_futures[state_key], timeout=2.0)
+            except TimeoutError:
+                pytest.fail(
+                    f"Timed out waiting for switch OFF state "
+                    f"(device_id={switch.device_id}, key={switch.key})"
+                )
+            assert states[state_key].state is False