text: // 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.
  
  #include "mediapipe/framework/calculator_framework.h"
  #include "mediapipe/framework/port/canonical_errors.h"
  
  namespace mediapipe {
  
  // A Calculator that simply passes its input Packets and header through,
  // unchanged.  The inputs may be specified by tag or index.  The outputs
  // must match the inputs exactly.  Any number of input side packets may
  // also be specified.  If output side packets are specified, they must
  // match the input side packets exactly and the Calculator passes its
  // input side packets through, unchanged.  Otherwise, the input side
  // packets will be ignored (allowing PassThroughCalculator to be used to
  // test internal behavior).  Any options may be specified and will be
  // ignored.
  class PassThroughCalculator : public CalculatorBase {
   public:
    static ::mediapipe::Status GetContract(CalculatorContract* cc) {
      if (!cc->Inputs().TagMap()->SameAs(*cc->Outputs().TagMap())) {
        return ::mediapipe::InvalidArgumentError(
            "Input and output streams to PassThroughCalculator must use "
            "matching tags and indexes.");
      }
      for (CollectionItemId id = cc->Inputs().BeginId();
           id < cc->Inputs().EndId(); ++id) {
        cc->Inputs().Get(id).SetAny();
        cc->Outputs().Get(id).SetSameAs(&cc->Inputs().Get(id));
      }
      for (CollectionItemId id = cc->InputSidePackets().BeginId();
           id < cc->InputSidePackets().EndId(); ++id) {
        cc->InputSidePackets().Get(id).SetAny();
      }
      if (cc->OutputSidePackets().NumEntries() != 0) {
        if (!cc->InputSidePackets().TagMap()->SameAs(
                *cc->OutputSidePackets().TagMap())) {
          return ::mediapipe::InvalidArgumentError(
              "Input and output side packets to PassThroughCalculator must use "
              "matching tags and indexes.");
        }
        for (CollectionItemId id = cc->InputSidePackets().BeginId();
             id < cc->InputSidePackets().EndId(); ++id) {
          cc->OutputSidePackets().Get(id).SetSameAs(
              &cc->InputSidePackets().Get(id));
        }
      }
      return ::mediapipe::OkStatus();
    }
  
    ::mediapipe::Status Open(CalculatorContext* cc) final {
      for (CollectionItemId id = cc->Inputs().BeginId();
           id < cc->Inputs().EndId(); ++id) {
        if (!cc->Inputs().Get(id).Header().IsEmpty()) {
          cc->Outputs().Get(id).SetHeader(cc->Inputs().Get(id).Header());
        }
      }
      if (cc->OutputSidePackets().NumEntries() != 0) {
        for (CollectionItemId id = cc->InputSidePackets().BeginId();
             id < cc->InputSidePackets().EndId(); ++id) {
          cc->OutputSidePackets().Get(id).Set(cc->InputSidePackets().Get(id));
        }
      }
      cc->SetOffset(TimestampDiff(0));
      return ::mediapipe::OkStatus();
    }
  
    ::mediapipe::Status Process(CalculatorContext* cc) final {
      cc->GetCounter("PassThrough")->Increment();
      if (cc->Inputs().NumEntries() == 0) {
        return tool::StatusStop();
      }
      for (CollectionItemId id = cc->Inputs().BeginId();
           id < cc->Inputs().EndId(); ++id) {
        if (!cc->Inputs().Get(id).IsEmpty()) {
          VLOG(3) << "Passing " << cc->Inputs().Get(id).Name() << " to "
                  << cc->Outputs().Get(id).Name() << " at "
                  << cc->InputTimestamp().DebugString();
          cc->Outputs().Get(id).AddPacket(cc->Inputs().Get(id).Value());
        }
      }
      return ::mediapipe::OkStatus();
    }
  };
  REGISTER_CALCULATOR(PassThroughCalculator);
  
  }  // namespace mediapipe
  