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mediapipe/framework/graph_service.h

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+// Copyright 2019 The MediaPipe 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
+//
+//      http://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.
+
+#ifndef MEDIAPIPE_FRAMEWORK_GRAPH_SERVICE_H_
+#define MEDIAPIPE_FRAMEWORK_GRAPH_SERVICE_H_
+
+#include <memory>
+
+namespace mediapipe {
+
+// The GraphService API can be used to define extensions to a graph's execution
+// environment. These are, essentially, graph-level singletons, and are
+// available to all calculators in the graph (and in any subgraphs) without
+// requiring a manual connection.
+//
+// IMPORTANT: this is an experimental API. Get in touch with the MediaPipe team
+// if you want to use it. In most cases, you should use a side packet instead.
+
+struct GraphServiceBase {
+  constexpr GraphServiceBase(const char* key) : key(key) {}
+
+  const char* key;
+};
+
+template <typename T>
+struct GraphService : public GraphServiceBase {
+  using type = T;
+  using packet_type = std::shared_ptr<T>;
+
+  constexpr GraphService(const char* key) : GraphServiceBase(key) {}
+};
+
+}  // namespace mediapipe
+
+#endif  // MEDIAPIPE_FRAMEWORK_GRAPH_SERVICE_H_