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// 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
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// KIND, either express or implied.  See the License for the
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#ifndef IMPALA_UTIL_SCOPE_EXIT_TRIGGER_H
#define IMPALA_UTIL_SCOPE_EXIT_TRIGGER_H

namespace impala {

/// Utility class that calls a client-supplied function when it is destroyed.
///
/// Use judiciously - scope exits can be hard to reason about, and this class should not
/// act as proxy for work-performing d'tors, which we try to avoid.
template <typename T>
class ScopeExitTrigger;

// The only way to construct ScopeExitTriggers is with MakeScopeExitTrigger, to enable
// lambdas, which have indescribable types, to be the contained trigger, like
//
//   const auto foo = MakeScopeExitTrigger([](){});
template <typename T>
ScopeExitTrigger<T> MakeScopeExitTrigger(const T& trigger);

template <typename T>
class ScopeExitTrigger {
 public:
  ~ScopeExitTrigger() { trigger_(); }

  friend ScopeExitTrigger<T> MakeScopeExitTrigger<>(const T& trigger);

 private:
  explicit ScopeExitTrigger(const T& trigger) : trigger_(trigger) {}
  T trigger_;
};

template <typename T>
ScopeExitTrigger<T> MakeScopeExitTrigger(const T& trigger) {
  return ScopeExitTrigger<T>(trigger);
}
}

#endif