text: /*
   * Util.h
   *
   * This source file is part of the FoundationDB open source project
   *
   * Copyright 2013-2018 Apple Inc. and the FoundationDB project 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 _FLOW_UTIL_H_
  #define _FLOW_UTIL_H_
  #pragma once
  
  #include <algorithm>
  
  template <typename C>
  void swapAndPop(C* container, int index) {
  	if (index != container->size() - 1) {
  		using std::swap;
  		swap((*container)[index], container->back());
  	}
  
  	container->pop_back();
  }
  
  // Adds n to pCount upon construction, subtracts in upon destruction
  template <typename T>
  struct Hold {
  	Hold(T* pCount = nullptr, T n = 1) : pCount(pCount), n(n) {
  		if (pCount != nullptr) {
  			*pCount += n;
  		}
  	}
  	~Hold() {
  		if (pCount != nullptr) {
  			*pCount -= n;
  		}
  	}
  
  	Hold(Hold&& other) {
  		pCount = other.pCount;
  		other.pCount = nullptr;
  		n = other.n;
  	}
  
  	Hold& operator=(Hold&& other) {
  		if (pCount != nullptr) {
  			*pCount -= n;
  		}
  		pCount = other.pCount;
  		other.pCount = nullptr;
  		n = other.n;
  		return *this;
  	};
  
  	void release() {
  		if (pCount != nullptr) {
  			*pCount -= n;
  			pCount = nullptr;
  		}
  	}
  
  	T* pCount;
  	T n;
  
  	void operator=(const Hold& other) = delete;
  };
  
  #endif // _FLOW_UTIL_H_
  