[core] Add CodSpeed C++ benchmarks for protobuf, main loop, and helpers (#14878)

tests/benchmarks/components/api/bench_proto_decode.cpp

@@ -0,0 +1,93 @@
+#include <benchmark/benchmark.h>
+
+#include "esphome/components/api/api_pb2.h"
+#include "esphome/components/api/api_buffer.h"
+
+namespace esphome::api::benchmarks {
+
+// Inner iteration count to amortize CodSpeed instrumentation overhead.
+// Without this, the ~60ns per-iteration valgrind start/stop cost dominates
+// sub-microsecond benchmarks.
+static constexpr int kInnerIterations = 2000;
+
+// Helper: encode a message into a buffer and return it.
+// Benchmarks encode once in setup, then decode the resulting bytes in a loop.
+// This keeps decode benchmarks in sync with the actual protobuf schema —
+// hand-encoded byte arrays would silently break when fields change.
+template<typename T> static APIBuffer encode_message(const T &msg) {
+  APIBuffer buffer;
+  uint32_t size = msg.calculate_size();
+  buffer.resize(size);
+  ProtoWriteBuffer writer(&buffer, 0);
+  msg.encode(writer);
+  return buffer;
+}
+
+// --- HelloRequest decode (string + varint fields) ---
+
+static void Decode_HelloRequest(benchmark::State &state) {
+  HelloRequest source;
+  source.client_info = StringRef::from_lit("aioesphomeapi");
+  source.api_version_major = 1;
+  source.api_version_minor = 10;
+  auto encoded = encode_message(source);
+
+  for (auto _ : state) {
+    HelloRequest msg;
+    for (int i = 0; i < kInnerIterations; i++) {
+      msg.decode(encoded.data(), encoded.size());
+    }
+    benchmark::DoNotOptimize(msg.api_version_major);
+  }
+  state.SetItemsProcessed(state.iterations() * kInnerIterations);
+}
+BENCHMARK(Decode_HelloRequest);
+
+// --- SwitchCommandRequest decode (simple command) ---
+
+static void Decode_SwitchCommandRequest(benchmark::State &state) {
+  SwitchCommandRequest source;
+  source.key = 0x12345678;
+  source.state = true;
+  auto encoded = encode_message(source);
+
+  for (auto _ : state) {
+    SwitchCommandRequest msg;
+    for (int i = 0; i < kInnerIterations; i++) {
+      msg.decode(encoded.data(), encoded.size());
+    }
+    benchmark::DoNotOptimize(msg.state);
+  }
+  state.SetItemsProcessed(state.iterations() * kInnerIterations);
+}
+BENCHMARK(Decode_SwitchCommandRequest);
+
+// --- LightCommandRequest decode (complex command with many fields) ---
+
+static void Decode_LightCommandRequest(benchmark::State &state) {
+  LightCommandRequest source;
+  source.key = 0x11223344;
+  source.has_state = true;
+  source.state = true;
+  source.has_brightness = true;
+  source.brightness = 0.8f;
+  source.has_rgb = true;
+  source.red = 1.0f;
+  source.green = 0.5f;
+  source.blue = 0.2f;
+  source.has_effect = true;
+  source.effect = StringRef::from_lit("rainbow");
+  auto encoded = encode_message(source);
+
+  for (auto _ : state) {
+    LightCommandRequest msg;
+    for (int i = 0; i < kInnerIterations; i++) {
+      msg.decode(encoded.data(), encoded.size());
+    }
+    benchmark::DoNotOptimize(msg.brightness);
+  }
+  state.SetItemsProcessed(state.iterations() * kInnerIterations);
+}
+BENCHMARK(Decode_LightCommandRequest);
+
+}  // namespace esphome::api::benchmarks