122 lines
3.7 KiB
C++
122 lines
3.7 KiB
C++
// Copyright 2019 The MediaPipe Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#ifndef MEDIAPIPE_FRAMEWORK_GRAPH_SERVICE_H_
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#define MEDIAPIPE_FRAMEWORK_GRAPH_SERVICE_H_
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#include <memory>
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#include <type_traits>
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#include <utility>
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#include "absl/strings/str_cat.h"
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#include "mediapipe/framework/packet.h"
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#include "mediapipe/framework/port/status.h"
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namespace mediapipe {
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// The GraphService API can be used to define extensions to a graph's execution
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// environment. These are, essentially, graph-level singletons, and are
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// available to all calculators in the graph (and in any subgraphs) without
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// requiring a manual connection.
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//
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// IMPORTANT: this is an experimental API. Get in touch with the MediaPipe team
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// if you want to use it. In most cases, you should use a side packet instead.
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class GraphServiceBase {
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public:
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// TODO: fix services for which default init is broken, remove
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// this setting.
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enum DefaultInitSupport {
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kAllowDefaultInitialization,
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kDisallowDefaultInitialization
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};
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constexpr GraphServiceBase(const char* key) : key(key) {}
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virtual ~GraphServiceBase() = default;
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inline virtual absl::StatusOr<Packet> CreateDefaultObject() const {
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return DefaultInitializationUnsupported();
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}
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const char* key;
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protected:
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absl::Status DefaultInitializationUnsupported() const {
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return absl::UnimplementedError(absl::StrCat(
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"Graph service '", key, "' does not support default initialization"));
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}
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};
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template <typename T>
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class GraphService : public GraphServiceBase {
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public:
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using type = T;
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using packet_type = std::shared_ptr<T>;
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constexpr GraphService(const char* my_key, DefaultInitSupport default_init =
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kDisallowDefaultInitialization)
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: GraphServiceBase(my_key), default_init_(default_init) {}
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absl::StatusOr<Packet> CreateDefaultObject() const override {
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if (default_init_ != kAllowDefaultInitialization) {
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return DefaultInitializationUnsupported();
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}
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auto packet_or = CreateDefaultObjectInternal();
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if (packet_or.ok()) {
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return MakePacket<std::shared_ptr<T>>(std::move(packet_or).value());
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} else {
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return packet_or.status();
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}
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}
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private:
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absl::StatusOr<std::shared_ptr<T>> CreateDefaultObjectInternal() const {
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auto call_create = [](auto x) -> decltype(decltype(x)::type::Create()) {
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return decltype(x)::type::Create();
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};
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if constexpr (std::is_invocable_r_v<absl::StatusOr<std::shared_ptr<T>>,
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decltype(call_create), type_tag<T>>) {
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return T::Create();
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}
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if constexpr (std::is_default_constructible_v<T>) {
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return std::make_shared<T>();
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}
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return DefaultInitializationUnsupported();
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}
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template <class U>
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struct type_tag {
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using type = U;
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};
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DefaultInitSupport default_init_;
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};
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template <typename T>
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class ServiceBinding {
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public:
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bool IsAvailable() { return service_ != nullptr; }
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T& GetObject() { return *service_; }
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ServiceBinding() {}
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explicit ServiceBinding(std::shared_ptr<T> service) : service_(service) {}
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private:
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std::shared_ptr<T> service_;
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};
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} // namespace mediapipe
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#endif // MEDIAPIPE_FRAMEWORK_GRAPH_SERVICE_H_
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