text: #ifndef CAFFE2_OPERATORS_WHILE_OP_H_
  #define CAFFE2_OPERATORS_WHILE_OP_H_
  
  #include "caffe2/core/context.h"
  #include "caffe2/core/logging.h"
  #include "caffe2/core/operator.h"
  
  namespace caffe2 {
  
  template <class Context>
  class WhileOp final : public Operator<Context> {
   public:
    WhileOp(const OperatorDef& operator_def, Workspace* ws)
        : Operator<Context>(operator_def, ws) {
      CAFFE_ENFORCE(
          this->template HasSingleArgumentOfType<NetDef>("loop_net"),
          "loop_net must be specified in While operator");
      loop_net_def_ =
          this->template GetSingleArgument<NetDef>("loop_net", NetDef());
      loop_net_ = CreateNet(loop_net_def_, ws);
      CAFFE_ENFORCE(loop_net_, "Failed to initialize loop subnet");
  
      cond_net_ = nullptr;
      bool has_cond_net =
          this->template HasSingleArgumentOfType<NetDef>("cond_net");
      if (has_cond_net) {
        cond_net_def_ =
            this->template GetSingleArgument<NetDef>("cond_net", NetDef());
        cond_net_ = CreateNet(cond_net_def_, ws);
        CAFFE_ENFORCE(cond_net_, "Failed to initialize condition subnet");
      }
    }
  
    USE_OPERATOR_CONTEXT_FUNCTIONS;
  
    bool RunOnDevice() override {
      CAFFE_ENFORCE(
          this->InputIsTensorType(0, Context::GetDeviceType()),
          "Invalid condition in While operator: tensor expected");
  
      const auto& condition = Input(0);
      CAFFE_ENFORCE_EQ(
          condition.numel(),
          1,
          "Invalid condition tensor in While operator: single value expected");
  
      while (true) {
        if (cond_net_ && !cond_net_->Run()) {
          return false;
        }
        if (!*condition.template data<bool>()) {
          return true;
        }
        if (!loop_net_->Run()) {
          return false;
        }
      }
  
      return true;
    }
  
   private:
    NetDef loop_net_def_;
    std::unique_ptr<NetBase> loop_net_;
  
    NetDef cond_net_def_;
    std::unique_ptr<NetBase> cond_net_;
  };
  
  } // namespace caffe2
  
  #endif // CAFFE2_OPERATORS_WHILE_OP_H_
  