include/type_pool.h

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/*
    (C) Copyright Thierry Seegers 2012. Distributed under the following license:

    Boost Software License - Version 1.0 - August 17th, 2003

    Permission is hereby granted, free of charge, to any person or organization
    obtaining a copy of the software and accompanying documentation covered by
    this license (the "Software") to use, reproduce, display, distribute,
    execute, and transmit the Software, and to prepare derivative works of the
    Software, and to permit third-parties to whom the Software is furnished to
    do so, all subject to the following:

    The copyright notices in the Software and this entire statement, including
    the above license grant, this restriction and the following disclaimer,
    must be included in all copies of the Software, in whole or in part, and
    all derivative works of the Software, unless such copies or derivative
    works are solely in the form of machine-executable object code generated by
    a source language processor.

    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
    FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
    SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
    FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
    ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
    DEALINGS IN THE SOFTWARE.
*/

#if !defined(TYPEPOOL_H)
     #define TYPEPOOL_H

#include <algorithm>
#include <atomic>
#include <functional>
#include <future>
#include <list>
#include <memory>
#include <mutex>
#include <utility>

#define GCC_VERSION (__GNUC__ * 10000 + __GNUC_MINOR__ * 100 + __GNUC_PATCHLEVEL__)


template<size_t S, class Allocator = std::allocator<unsigned char[S]>>
class chunk_pool
{
    Allocator allocator;
    size_t cap;
    std::atomic<bool> empty;
    std::mutex m;
    std::future<void> preallocation;

    typedef std::list<typename Allocator::pointer> store_t;
    store_t store;
    
    // Disabled copy construction.
    chunk_pool(const chunk_pool&);
    chunk_pool(chunk_pool&&);

    // Disabled assignment.
    chunk_pool& operator=(const chunk_pool&);
    chunk_pool& operator=(chunk_pool&&);

protected:
    static size_t max_size()
    {
        store_t s;
        return s.max_size();
    }

public:
    typedef Allocator allocator_type;

    typedef typename allocator_type::pointer pointer;

    chunk_pool(size_t preallocate = 0, size_t cap = max_size()) : cap(std::min(cap, max_size()))
    {
        preallocate = std::min(preallocate, cap);

        empty = (preallocate == 0);

        preallocation = std::async([preallocate, this]() mutable -> void
        {
            try
            {
                while(preallocate--)
                {
                    store.push_back(this->allocator.allocate(1));
                }
            }
            catch(...) {}
        });
    }

    virtual ~chunk_pool()
    {
        preallocation.wait();
        std::for_each(store.begin(), store.end(), std::bind(&allocator_type::deallocate, allocator, std::placeholders::_1, S));
    }

    pointer allocate()
    {
        if(empty)
        {
            return allocator.allocate(1);
        }
        else
        {
            m.lock();

            preallocation.wait();
            empty = store.empty();
            
            if(!empty)
            {
                pointer p = store.back();
                store.pop_back();
                empty = store.empty();

                m.unlock();

                return p;
            }
            else
            {
                m.unlock();

                return allocator.allocate(1);
            }
        }
    }

   void release(typename Allocator::pointer p)
    {
        m.lock();

        if(store.size() < cap)
        {
            store.push_back(p);
            empty = false;
        }
        else
        {
            allocator.deallocate(p, S);
        }

        m.unlock();
    }
};

template<typename T, class Allocator = typename chunk_pool<sizeof(T)>::allocator_type>
class type_pool : public chunk_pool<sizeof(T), Allocator>
{
    void release(T* p)
    {
        p->~T();

        chunk_pool<sizeof(T), Allocator>::release(reinterpret_cast<typename chunk_pool<sizeof(T), Allocator>::pointer>(p));
    }

public:
    typedef typename std::unique_ptr<T, std::function<void (T*)>> unique_ptr;

    type_pool(size_t preallocate = 0, size_t cap = chunk_pool<sizeof(T), Allocator>::max_size()) : chunk_pool<sizeof(T), Allocator>(preallocate, cap)
    {}

    template<typename U>
    typename std::enable_if<std::is_same<T, U>::value, T*>::type get_ptr(U&& t)
    {
        return new(chunk_pool<sizeof(T), Allocator>::allocate()) T(std::move(t));
    }

#if (defined(__GNUG__) && (GCC_VERSION >= 40400))






    template<typename U, typename... Args>
    typename std::enable_if<std::is_same<T, U>::value, T*>::type get_ptr(Args&&... args)
    {
        return new(chunk_pool<sizeof(T), Allocator>::allocate()) T(std::forward<Args>(args)...);
    }
#endif

    template<typename U>
    typename std::enable_if<std::is_same<T, U>::value, std::shared_ptr<T>>::type get_shared(U&& t)
    {
        return std::shared_ptr<T>(get_ptr(std::move(t)), std::bind1st(std::mem_fun(&type_pool<T, Allocator>::release), this));
    }

#if (defined(__GNUG__) && (GCC_VERSION >= 40400))





    template<typename U, typename... Args>
    typename std::enable_if<std::is_same<T, U>::value, std::shared_ptr<T>>::type get_shared(Args&&... args)
    {
        return std::shared_ptr<T>(get_ptr<T>(std::forward<Args>(args)...), std::bind1st(std::mem_fun(&type_pool<T, Allocator>::release), this));
    }
#endif

    template<typename U>
    typename std::enable_if<std::is_same<T, U>::value, typename type_pool<T, Allocator>::unique_ptr>::type get_unique(U&& t)
    {
        return typename type_pool<T, Allocator>::unique_ptr(get_ptr(std::move(t)), std::bind1st(std::mem_fun(&type_pool<T, Allocator>::release), this));
    }

#if (defined(__GNUG__) && (GCC_VERSION >= 40400))






    template<typename U, typename... Args>
    typename std::enable_if<std::is_same<T, U>::value, typename type_pool<T, Allocator>::unique_ptr>::type get_unique(Args&&... args)
    {
        return typename type_pool<T, Allocator>::unique_ptr(get_ptr<T>(std::forward<Args>(args)...), std::bind1st(std::mem_fun(&type_pool<T, Allocator>::release), this));
    }
#endif
};

#endif