with.h

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/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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 TVM_SUPPORT_WITH_H_
#define TVM_SUPPORT_WITH_H_

#include <dmlc/common.h>

#include <functional>
#include <utility>

namespace tvm {

template <typename ContextType>
class With {
 public:
  template <typename... Args>
  explicit With(Args&&... args) : ctx_(std::forward<Args>(args)...) {
    ctx_.EnterWithScope();
  }
  ~With() DMLC_THROW_EXCEPTION { ctx_.ExitWithScope(); }

  ContextType* get() { return &ctx_; }
  const ContextType* get() const { return &ctx_; }

  ContextType* operator->() { return get(); }
  const ContextType* operator->() const { return get(); }
  ContextType& operator*() { return *get(); }
  const ContextType* operator*() const { return *get(); }

  ContextType operator()() { return ctx_; }

 private:
  ContextType ctx_;
};

class ContextManager {
 public:
  template <class FEnter, class FExit>
  explicit ContextManager(FEnter f_enter, FExit f_exit) : f_enter_(f_enter), f_exit_(f_exit) {}

 private:
  void EnterWithScope() {
    if (f_enter_) f_enter_();
  }
  void ExitWithScope() {
    if (f_exit_) f_exit_();
  }
  std::function<void()> f_enter_;
  std::function<void()> f_exit_;
  template <typename>
  friend class With;
};

}  // namespace tvm
#endif  // TVM_SUPPORT_WITH_H_