[api] Use FixedVector for ExecuteServiceRequest/Argument arrays to eliminate reallocations (#11270)

script/api_protobuf/api_protobuf.py

@@ -11,6 +11,7 @@ from typing import Any
 
 import aioesphomeapi.api_options_pb2 as pb
 import google.protobuf.descriptor_pb2 as descriptor
+from google.protobuf.descriptor_pb2 import FieldDescriptorProto
 
 
 class WireType(IntEnum):
@@ -148,7 +149,7 @@ class TypeInfo(ABC):
     @property
     def repeated(self) -> bool:
         """Check if the field is repeated."""
-        return self._field.label == 3
+        return self._field.label == FieldDescriptorProto.LABEL_REPEATED
 
     @property
     def wire_type(self) -> WireType:
@@ -337,7 +338,7 @@ def create_field_type_info(
     needs_encode: bool = True,
 ) -> TypeInfo:
     """Create the appropriate TypeInfo instance for a field, handling repeated fields and custom options."""
-    if field.label == 3:  # repeated
+    if field.label == FieldDescriptorProto.LABEL_REPEATED:
         # Check if this repeated field has fixed_array_with_length_define option
         if (
             fixed_size := get_field_opt(field, pb.fixed_array_with_length_define)
@@ -1879,6 +1880,9 @@ def build_message_type(
         )
         public_content.append("#endif")
 
+    # Collect fixed_vector fields for custom decode generation
+    fixed_vector_fields = []
+
     for field in desc.field:
         # Skip deprecated fields completely
         if field.options.deprecated:
@@ -1887,7 +1891,7 @@ def build_message_type(
         # Validate that fixed_array_size is only used in encode-only messages
         if (
             needs_decode
-            and field.label == 3
+            and field.label == FieldDescriptorProto.LABEL_REPEATED
             and get_field_opt(field, pb.fixed_array_size) is not None
         ):
             raise ValueError(
@@ -1900,7 +1904,7 @@ def build_message_type(
         # Validate that fixed_array_with_length_define is only used in encode-only messages
         if (
             needs_decode
-            and field.label == 3
+            and field.label == FieldDescriptorProto.LABEL_REPEATED
             and get_field_opt(field, pb.fixed_array_with_length_define) is not None
         ):
             raise ValueError(
@@ -1910,6 +1914,14 @@ def build_message_type(
                 f"since we cannot trust or control the number of items received from clients."
             )
 
+        # Collect fixed_vector repeated fields for custom decode generation
+        if (
+            needs_decode
+            and field.label == FieldDescriptorProto.LABEL_REPEATED
+            and get_field_opt(field, pb.fixed_vector, False)
+        ):
+            fixed_vector_fields.append((field.name, field.number))
+
         ti = create_field_type_info(field, needs_decode, needs_encode)
 
         # Skip field declarations for fields that are in the base class
@@ -2018,6 +2030,22 @@ def build_message_type(
         prot = "bool decode_64bit(uint32_t field_id, Proto64Bit value) override;"
         protected_content.insert(0, prot)
 
+    # Generate custom decode() override for messages with FixedVector fields
+    if fixed_vector_fields:
+        # Generate the decode() implementation in cpp
+        o = f"void {desc.name}::decode(const uint8_t *buffer, size_t length) {{\n"
+        # Count and init each FixedVector field
+        for field_name, field_number in fixed_vector_fields:
+            o += f"  uint32_t count_{field_name} = ProtoDecodableMessage::count_repeated_field(buffer, length, {field_number});\n"
+            o += f"  this->{field_name}.init(count_{field_name});\n"
+        # Call parent decode to populate the fields
+        o += "  ProtoDecodableMessage::decode(buffer, length);\n"
+        o += "}\n"
+        cpp += o
+        # Generate the decode() declaration in header (public method)
+        prot = "void decode(const uint8_t *buffer, size_t length) override;"
+        public_content.append(prot)
+
     # Only generate encode method if this message needs encoding and has fields
     if needs_encode and encode:
         o = f"void {desc.name}::encode(ProtoWriteBuffer buffer) const {{"