1 // Copyright 2024 The gRPC Authors 2 // 3 // Licensed under the Apache License, Version 2.0 (the "License"); 4 // you may not use this file except in compliance with the License. 5 // You may obtain a copy of the License at 6 // 7 // http://www.apache.org/licenses/LICENSE-2.0 8 // 9 // Unless required by applicable law or agreed to in writing, software 10 // distributed under the License is distributed on an "AS IS" BASIS, 11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12 // See the License for the specific language governing permissions and 13 // limitations under the License. 14 15 #ifndef GRPC_EVENT_ENGINE_EXTENSIBLE_H 16 #define GRPC_EVENT_ENGINE_EXTENSIBLE_H 17 18 #include <grpc/support/port_platform.h> 19 20 #include "absl/strings/string_view.h" 21 22 namespace grpc_event_engine { 23 namespace experimental { 24 25 class Extensible { 26 public: 27 /// A method which allows users to query whether an implementation supports a 28 /// specified extension. The name of the extension is provided as an input. 29 /// 30 /// An extension could be any type with a unique string id. Each extension may 31 /// support additional capabilities and if the implementation supports the 32 /// queried extension, it should return a valid pointer to the extension type. 33 /// 34 /// E.g., use case of an EventEngine::Endpoint supporting a custom extension. 35 /// 36 /// class CustomEndpointExtension { 37 /// public: 38 /// static std::string EndpointExtensionName() { 39 /// return "my.namespace.extension_name"; 40 /// } 41 /// virtual void Process() = 0; 42 /// } 43 /// 44 /// class CustomEndpoint : 45 /// public EventEngine::Endpoint, public CustomEndpointExtension { 46 /// public: 47 /// void* QueryExtension(absl::string_view id) override { 48 /// if (id == CustomEndpointExtension::EndpointExtensionName()) { 49 /// return static_cast<CustomEndpointExtension*>(this); 50 /// } 51 /// return nullptr; 52 /// } 53 /// void Process() override { ... } 54 /// ... 55 /// } 56 /// 57 /// auto endpoint = 58 /// static_cast<CustomEndpointExtension*>(endpoint->QueryExtension( 59 /// CustomEndpointExtension::EndpointExtensionName())); 60 /// if (endpoint != nullptr) endpoint->Process(); 61 /// QueryExtension(absl::string_view)62 virtual void* QueryExtension(absl::string_view /*id*/) { return nullptr; } 63 64 protected: 65 ~Extensible() = default; 66 }; 67 68 } // namespace experimental 69 } // namespace grpc_event_engine 70 71 #endif // GRPC_EVENT_ENGINE_EXTENSIBLE_H 72