1 files changed, 64 insertions, 0 deletions
diff --git a/pw_rpc/public/pw_rpc/internal/method_lookup.h b/pw_rpc/public/pw_rpc/internal/method_lookup.h
new file mode 100644
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+++ b/pw_rpc/public/pw_rpc/internal/method_lookup.h
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+// Copyright 2020 The Pigweed Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may not
+// use this file except in compliance with the License. You may obtain a copy of
+// the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+// License for the specific language governing permissions and limitations under
+// the License.
+#pragma once
+
+#include "pw_rpc/internal/method.h"
+
+namespace pw::rpc::internal {
+
+// Gets a Method object from a generated RPC service class. Getter functions are
+// provided for each supported method implementation. The
+//
+// To ensure the MethodUnion actually holds the requested method type, the
+// method ID is accessed in a static_assert. It is invalid to access an unset
+// union member in a constant expression, so this results in a compiler error.
+class MethodLookup {
+ public:
+  template <typename Service, uint32_t kMethodId>
+  static constexpr const auto& GetRawMethod() {
+    const auto& method = GetMethodUnion<Service, kMethodId>().raw_method();
+    static_assert(method.id() == kMethodId, "Incorrect method implementation");
+    return method;
+  }
+
+  template <typename Service, uint32_t kMethodId>
+  static constexpr const auto& GetNanopbMethod() {
+    const auto& method = GetMethodUnion<Service, kMethodId>().nanopb_method();
+    static_assert(method.id() == kMethodId, "Incorrect method implementation");
+    return method;
+  }
+
+ private:
+  template <typename Service, uint32_t kMethodId>
+  static constexpr const auto& GetMethodUnion() {
+    constexpr auto method = GetMethodUnionPointer<Service>(kMethodId);
+    static_assert(method != nullptr,
+                  "The selected function is not an RPC service method");
+    return *method;
+  }
+
+  template <typename Service>
+  static constexpr
+      typename decltype(GeneratedService<Service>::kMethods)::const_pointer
+      GetMethodUnionPointer(uint32_t kMethodId) {
+    for (size_t i = 0; i < GeneratedService<Service>::kMethodIds.size(); ++i) {
+      if (GeneratedService<Service>::kMethodIds[i] == kMethodId) {
+        return &GeneratedService<Service>::kMethods[i];
+      }
+    }
+    return nullptr;
+  }
+};
+
+}  // namespace pw::rpc::internal