packet_generator.h | Explore in Territory

// 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_PACKET_GENERATOR_H_
#define MEDIAPIPE_FRAMEWORK_PACKET_GENERATOR_H_

#include <memory>
#include <string>
#include <type_traits>

#include "absl/base/attributes.h"
#include "absl/base/macros.h"
#include "mediapipe/framework/deps/registration.h"
#include "mediapipe/framework/packet_generator.pb.h"
#include "mediapipe/framework/packet_set.h"
#include "mediapipe/framework/packet_type.h"
#include "mediapipe/framework/port.h"
#include "mediapipe/framework/port/status.h"

namespace mediapipe {

// Pure virtual base class for packet generators.  These classes take any
// number of input side packet packets and produce some number of external
// output packets.  Those packets then become input side packets to other
// PacketGenerator's or to Calculators within the calculator graph.
//
// ***NOTE*** It is vital that the public interfaces for all classes
// included in packets be thread safe if the packet is meant
// to be used concurrently (e.g., with the PacketManager).
class PacketGenerator { … };

// Details for the registration of a PacketGenerator follow.  A user of
// PacketGenerator does not need to know about the following code.
namespace internal {

// Gives access to the static functions within subclasses of PacketGenerator.
// This adds functionality akin to virtual static functions.
class StaticAccessToGenerator { … };

using StaticAccessToGeneratorRegistry =
    GlobalFactoryRegistry<std::unique_ptr<StaticAccessToGenerator>>;

// Functions for checking that the PacketGenerator has the proper
// functions defined.
template <class T>
constexpr bool PacketGeneratorHasFillExpectations(
    decltype(&T::FillExpectations) /*unused*/) { … }
template <class T>
constexpr bool PacketGeneratorHasFillExpectations(...) { … }
template <class T>
constexpr bool PacketGeneratorHasGenerate(decltype(&T::Generate) /*unused*/) { … }
template <class T>
constexpr bool PacketGeneratorHasGenerate(...) { … }

// Provides access to the static functions within a specific subclass
// of PacketGenerator.  See thee same mechanism in calculator.h for a
// more detailed explanation.
template <typename PacketGeneratorSubclass>
class StaticAccessToGeneratorTyped : public StaticAccessToGenerator { … };

}  // namespace internal

// Macro for registering PacketGenerators.  It actually just registers
// the StaticAccessToGeneratorTyped class.
#define REGISTER_PACKET_GENERATOR(name) …

}  // namespace mediapipe

#endif  // MEDIAPIPE_FRAMEWORK_PACKET_GENERATOR_H_
chromium/third_party/mediapipe/src/mediapipe/framework/packet_generator.h
