Replace 3-call sequence (write_raw_byte + write_raw_byte + encode_raw)
with single inlined encode_raw_short_string call for forced string
fields with max_data_length < 128. The compiler can hoist the pos
pointer across all three writes in one function boundary.
Add max_data_length field option for string/bytes fields. When
max_data_length < 128, the codegen emits constant-size length varint
calculations and direct byte writes.
Annotate all entity name and object_id fields with
(max_data_length) = 120 and (force) = true across all 25
ListEntities*Response messages (50 fields).
Generated code changes:
- calculate_size: `calc_length(1, size)` -> `2 + size` (constant)
- encode: `encode_string(N, ref)` -> `write_raw_byte(tag) + write_raw_byte(len) + encode_raw(data, len)`
Eliminates 2 function calls per field per entity list response,
removes zero-check branches, and removes varint size computation.
Refactor the constant-size varint pattern into a reusable helper
method on the TypeInfo base class, used by both UInt32Type (max_value)
and FixedArrayBytesType (fixed_array_size < 128).
Add a max_value field option to api_options.proto that tells the code
generator the maximum value a field can have. When max_value < 128,
the generated calculate_size() uses constant arithmetic instead of
calling varint size functions, and encode() uses direct byte writes
instead of varint encoding.
Also optimize FixedArrayBytesType: when fixed_array_size < 128, the
length varint is always 1 byte, so calculate_size() uses constant
arithmetic and encode() uses write_raw_byte for the length.
Applied to BluetoothLERawAdvertisement.address_type (max_value=4).
Measured on ESP32 (upstairsdesk89proxy):
- BluetoothLERawAdvertisement::calculate_size: 88 → 71 bytes (-19%)
- BluetoothLERawAdvertisement::encode: 199 → 179 bytes (-10%)
- Total BLE proxy hot path: 1807 → 1770 bytes (-37 bytes)
Add encode_varint_raw_short() and ProtoSize::varint_short() that
inline both the 1-byte and 2-byte varint paths, falling back to
the noinline slow path for 3+ bytes.
Use these for sint32 fields (zigzag encoding), where values like
RSSI (-100 to 0) produce zigzag values that are 1-2 bytes. This
avoids a function call for the common case without bloating the
generic encode_varint_raw fast path.
Add CodSpeed benchmarks for BluetoothLERawAdvertisementsResponse
(12 advertisements) covering calculate_size, encode, calc+encode,
and fresh-buffer paths.
Includes a lightweight bluetooth_proxy stub header in
tests/benchmarks/stubs/ so the api component can compile with
USE_BLUETOOTH_PROXY on the host platform without pulling in
ESP32 BLE dependencies.
decode() is never called polymorphically - all call sites in
read_message_() use concrete types. The only indirect call site was
decode_to_message(), which also always knows the concrete type.
Convert decode_to_message() to a template so the concrete type is
preserved, allowing decode() to be non-virtual. The two classes that
override decode() (ExecuteServiceArgument, ExecuteServiceRequest) now
hide the base method, which works since all calls use concrete types.
This removes one vtable slot (4 bytes) from each decodable message
class vtable, saving ~148 bytes of flash.
Extend the precomputed-tag approach from fixed32 key fields to all forced
fields with single-byte tags (field IDs 1-15). The code generator now
emits write_raw_byte(tag) followed by the raw encode primitive instead
of calling the full encode_* method.
For varint types (uint32, uint64, sint32, sint64, int64, bool, enum),
this eliminates the zero-check branch and encode_field_raw indirection.
For length-delimited types (bytes, string), it additionally skips the
encode_string wrapper.
Benchmarked on real hardware with BluetoothLERawAdvertisementsResponse
(12 advertisements per message, 10000 iterations):
ESP32 (Xtensa dual-core 240MHz):
encode: 38498 -> 30460 ns/op (-20.9%)
calc+encode: 48479 -> 40458 ns/op (-16.6%)
ESP32-C3 (RISC-V single-core 160MHz):
encode: 54199 -> 40342 ns/op (-25.6%)
calc+encode: 57800 -> 51365 ns/op (-11.1%)
- Combine tag byte + fixed32 value into single write_tag_and_fixed32()
method: pos[0] = tag, memcpy(pos+1, &value, 4), pos += 5
- Extract calculate_tag() from duplicated computation in
calculate_field_id_size() and encode_content
- Combine tag byte + fixed32 value into single write_tag_and_fixed32()
method: pos[0] = tag, memcpy(pos+1, &value, 4), pos += 5
- Extract calculate_tag() from duplicated computation in
calculate_field_id_size() and encode_content
Instead of ALWAYS_INLINE on encode_field_raw (which bloated all
callers), have the code generator precompute the tag byte and emit
write_raw_byte(tag) + write_fixed32_raw(value) directly.
This gives the same tight codegen (single byte store + memcpy) for
key fields without inflating encode_bool/encode_uint32/etc.
+108 bytes flash vs baseline, -48 bytes vs the ALWAYS_INLINE approach.
- Update comments to reflect that ProtoService methods moved to
APIConnection, not APIServerConnectionBase
- Fix comment referring to read_message as "override"
- Wrap #include "api_connection.h" and read_message_ implementation
in #ifdef USE_API guards
J. Nick Koston