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#pragma once
#include <memory>
template<class T, size_t NumElementsInReserve>
class cAllocationPool
{
public:
class cStarvationCallbacks
{
public:
virtual ~cStarvationCallbacks() {}
virtual void OnStartingUsingBuffer() = 0;
virtual void OnStopUsingBuffer() = 0;
virtual void OnBufferEmpty() = 0;
};
cAllocationPool(std::auto_ptr<cStarvationCallbacks> a_Callbacks) :
m_Callbacks(a_Callbacks)
{
for (size_t i = 0; i < NumElementsInReserve; i++)
{
void * space = malloc(sizeof(T));
if (space == NULL)
{
m_Callbacks->OnStartingUsingBuffer();
break;
}
m_FreeList.push_front(space);
}
}
~cAllocationPool()
{
while (!m_FreeList.empty())
{
free (m_FreeList.front());
m_FreeList.pop_front();
}
}
T * Allocate()
{
if (m_FreeList.size() <= NumElementsInReserve)
{
void * space = malloc(sizeof(T));
if (space != NULL)
{
return new(space) T;
}
else if (m_FreeList.size() == NumElementsInReserve)
{
m_Callbacks->OnStartingUsingBuffer();
}
else if (m_FreeList.empty())
{
m_Callbacks->OnBufferEmpty();
// Try again until the memory is avalable
return Allocate();
}
}
// placement new, used to initalize the object
T * ret = new (m_FreeList.front()) T;
m_FreeList.pop_front();
return ret;
}
void Free(T * ptr)
{
if (ptr == NULL)
{
return;
}
// placement destruct.
ptr->~T();
m_FreeList.push_front(ptr);
if (m_FreeList.size() == NumElementsInReserve)
{
m_Callbacks->OnStopUsingBuffer();
}
}
private:
std::list<void *> m_FreeList;
std::auto_ptr<cStarvationCallbacks> m_Callbacks;
};
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