pool_allocator.h

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/**********************************************************\
 
  This file is part of the
  https://github.com/morzhovets/momo
  project, distributed under the MIT License. See
  https://github.com/morzhovets/momo/blob/branch_cpp11/LICENSE
  for details.
 
  momo/stdish/pool_allocator.h
 
  namespace momo::stdish:
    class unsynchronized_pool_allocator
 
\**********************************************************/
 
#ifndef MOMO_INCLUDE_GUARD_STDISH_POOL_ALLOCATOR
#define MOMO_INCLUDE_GUARD_STDISH_POOL_ALLOCATOR
 
#ifdef __has_include
# if __has_include(<momo/Utility.h>)
#  include <momo/Utility.h>
# endif
#endif
#ifndef MOMO_PARENT_HEADER
# include "../Utility.h"
#endif
 
#include MOMO_PARENT_HEADER(MemPool)
 
namespace momo
{
 
namespace stdish
{
 
template<typename TValue,
    typename TBaseAllocator = std::allocator<unsigned char>,
    typename TMemPoolParams = MemPoolParams<>>
class unsynchronized_pool_allocator
{
public:
    typedef TValue value_type;
 
    typedef TBaseAllocator base_allocator_type;
    typedef TMemPoolParams mem_pool_params;
 
    typedef value_type* pointer;
    typedef const value_type* const_pointer;
 
    typedef size_t size_type;
    typedef ptrdiff_t difference_type;
 
    typedef std::false_type propagate_on_container_copy_assignment;
    typedef std::true_type propagate_on_container_move_assignment;
    typedef std::true_type propagate_on_container_swap;
 
private:
    typedef MemManagerStd<base_allocator_type> MemManager;
    typedef momo::internal::MemManagerProxy<MemManager> MemManagerProxy;
 
    typedef mem_pool_params MemPoolParams;
    typedef momo::MemPool<MemPoolParams, MemManager> MemPool;
 
public:
    explicit unsynchronized_pool_allocator(const base_allocator_type& alloc = base_allocator_type())
        : mMemPool(std::allocate_shared<MemPool>(alloc, pvGetMemPoolParams(), MemManager(alloc)))   //?
    {
    }
 
    unsynchronized_pool_allocator(const unsynchronized_pool_allocator& alloc) noexcept
        : mMemPool(alloc.mMemPool)
    {
    }
 
    ~unsynchronized_pool_allocator() = default;
 
    unsynchronized_pool_allocator& operator=(const unsynchronized_pool_allocator& alloc) noexcept
    {
        mMemPool = alloc.mMemPool;
        return *this;
    }
 
    template<class Value>
    operator unsynchronized_pool_allocator<Value, base_allocator_type, mem_pool_params>() const
        noexcept
    {
        return momo::internal::ProxyConstructor<
            unsynchronized_pool_allocator<Value, base_allocator_type, mem_pool_params>>(mMemPool);
    }
 
    base_allocator_type get_base_allocator() const noexcept
    {
        return base_allocator_type(mMemPool->GetMemManager().GetByteAllocator());
    }
 
    unsynchronized_pool_allocator select_on_container_copy_construction() const noexcept
    {
        return unsynchronized_pool_allocator(get_base_allocator());
    }
 
    MOMO_NODISCARD pointer allocate(size_type count)
    {
        if (count == 1)
        {
            MemPoolParams memPoolParams = pvGetMemPoolParams();
            bool equal = pvIsEqual(memPoolParams, mMemPool->GetParams());
            if (!equal && mMemPool->GetAllocateCount() == 0)
            {
                *mMemPool = MemPool(memPoolParams, MemManager(get_base_allocator()));
                equal = true;
            }
            if (equal)
                return mMemPool->template Allocate<value_type>();
        }
        return MemManagerProxy::template Allocate<value_type>(mMemPool->GetMemManager(),
            count * sizeof(value_type));
    }
 
    void deallocate(pointer ptr, size_type count) noexcept
    {
        if (count == 1 && pvIsEqual(pvGetMemPoolParams(), mMemPool->GetParams()))
            return mMemPool->Deallocate(ptr);
        MemManagerProxy::Deallocate(mMemPool->GetMemManager(), ptr, count * sizeof(value_type));
    }
 
    template<typename Value, typename... ValueArgs>
    void construct(Value* ptr, ValueArgs&&... valueArgs)
    {
        typedef typename momo::internal::ObjectManager<Value, MemManager>
            ::template Creator<ValueArgs...> ValueCreator;
        ValueCreator(mMemPool->GetMemManager(), std::forward<ValueArgs>(valueArgs)...)(ptr);
    }
 
    template<class Value>
    void destroy(Value* ptr) noexcept
    {
        momo::internal::ObjectManager<Value, MemManager>::Destroy(mMemPool->GetMemManager(), *ptr);
    }
 
    friend bool operator==(const unsynchronized_pool_allocator& left,
        const unsynchronized_pool_allocator& right) noexcept
    {
        return left.mMemPool == right.mMemPool;
    }
 
    friend bool operator!=(const unsynchronized_pool_allocator& left,
        const unsynchronized_pool_allocator& right) noexcept
    {
        return !(left == right);
    }
 
protected:
    explicit unsynchronized_pool_allocator(const std::shared_ptr<MemPool>& memPool) noexcept
        : mMemPool(memPool)
    {
    }
 
private:
    static MemPoolParams pvGetMemPoolParams() noexcept
    {
        return MemPoolParams(sizeof(value_type),
            momo::internal::ObjectAlignmenter<value_type>::alignment);
    }
 
    static bool pvIsEqual(const MemPoolParams& memPoolParams1,
        const MemPoolParams& memPoolParams2) noexcept
    {
        return memPoolParams1.GetBlockSize() == memPoolParams2.GetBlockSize()
            && memPoolParams1.GetBlockAlignment() == memPoolParams2.GetBlockAlignment();
    }
 
private:
    std::shared_ptr<MemPool> mMemPool;
};
 
} // namespace stdish
 
} // namespace momo
 
#endif // MOMO_INCLUDE_GUARD_STDISH_POOL_ALLOCATOR