ObjectPool.h

/*
 * Copyright (c) 2008-2014, Pedigree Developers
 *
 * Please see the CONTRIB file in the root of the source tree for a full
 * list of contributors.
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#ifndef KERNEL_UTILITY_OBJECT_POOL_H
#define KERNEL_UTILITY_OBJECT_POOL_H

#include "pedigree/kernel/processor/types.h"
#ifdef THREADS
#include "pedigree/kernel/LockGuard.h"
#include "pedigree/kernel/Spinlock.h"
#endif
#include "pedigree/kernel/utilities/Vector.h"
#include "pedigree/kernel/utilities/assert.h"


template <class T, size_t poolSize = 16>
class ObjectPool
{
  public:
    ObjectPool()
        : m_Pool()
#ifdef THREADS
          ,
          m_Spinlock()
#endif
    {
    }

    virtual ~ObjectPool()
    {
        for (auto it = m_Pool.begin(); it != m_Pool.end(); ++it)
        {
            delete *it;
        }
    }

    template <typename... Args>
    T *allocate(Args... args)
    {
        if (!poolSize)
        {
            return new T(args...);
        }

#ifdef THREADS
        LockGuard<Spinlock> guard(m_Spinlock);
#endif

        m_Pool.reserve(poolSize, true);
        if (m_Pool.count())
        {
            // popping from the rear of a vector is much faster
            return m_Pool.popBack();
        }
        else
        {
            return new T(args...);
        }
    }

    void deallocate(T *object)
    {
        if (!poolSize)
        {
            delete object;
            return;
        }

        assert(object != nullptr);
        if (!object)
        {
            return;
        }

#ifdef THREADS
        LockGuard<Spinlock> guard(m_Spinlock);
#endif

        // We only add the object back to the pool if we aren't already at
        // capacity (otherwise we'd resize the Vector).
        m_Pool.reserve(poolSize, true);
        if (m_Pool.count() < poolSize)
        {
            m_Pool.pushBack(object);
        }
        else
        {
            delete object;
        }
    }

  private:
    Vector<T *> m_Pool;
#ifdef THREADS
    Spinlock m_Spinlock;
#endif
};

#endif  // KERNEL_UTILITY_OBJECT_POOL_H