objectpool.cpp

C++高级编程这本书所附的源代码

#include "ObjectPool.h"

template<typename T>
const int ObjectPool<T>::kDefaultChunkSize = 10;

template <typename T>
ObjectPool<T>::ObjectPool(int chunkSize) throw(invalid_argument, bad_alloc) :
  mChunkSize(chunkSize)
{
  if (mChunkSize <= 0) {
    throw invalid_argument("chunk size must be positive");
  }
  // Create mChunkSize objects to start
  allocateChunk();
}

  //
  // Allocates an array of mChunkSize objects because that's
  // more efficient than allocating each of them individually.
  // Stores a pointer to the first element of the array in the mAllObjects
  // vector. Adds a pointer to each new object to the mFreeList.
  //
template <typename T>
void ObjectPool<T>::allocateChunk()
{
  T *newObjects = new T[mChunkSize];
  mAllObjects.push_back(newObjects);
  for (int i = 0; i < mChunkSize; i++) {
    mFreeList.push(&newObjects[i]);
  }
}

  //
  // Freeing function for use in the for_each algorithm in the
  // destructor.
  //
template<typename T>
void ObjectPool<T>::arrayDeleteObject(T *obj)
{
  delete [] obj;
}

template <typename T>
ObjectPool<T>::~ObjectPool()
{
  // free each of the allocation chunks
  for_each(mAllObjects.begin(), mAllObjects.end(), arrayDeleteObject);
}

template <typename T>
T &ObjectPool<T>::acquireObject()
{
  if (mFreeList.empty()) {
    allocateChunk();
  }
  T *obj = mFreeList.front();
  mFreeList.pop();
  return (*obj);
}

template <typename T>
void ObjectPool<T>::releaseObject(T &obj)
{
  mFreeList.push(&obj);
}