LocklessList.h

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/*
 * LocklessList.h - list with lockless push and pop
 *
 * Copyright (c) 2016 Javier Serrano Polo <javier@jasp.net>
 *
 * This file is part of LMMS - https://lmms.io
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public
 * License along with this program (see COPYING); if not, write to the
 * Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
 * Boston, MA 02110-1301 USA.
 *
 */
 
#ifndef LMMS_LOCKLESS_LIST_H
#define LMMS_LOCKLESS_LIST_H
 
#include "LocklessAllocator.h"
 
#include <atomic>
 
namespace lmms
{
 
template<typename T>
class LocklessList
{
public:
    struct Element
    {
        T value;
        Element * next;
    } ;
 
    LocklessList( size_t size ) :
        m_first(nullptr),
        m_allocator(new LocklessAllocatorT<Element>(size))
    {
    }
 
    ~LocklessList()
    {
        delete m_allocator;
    }
 
    void push( T value )
    {
        Element * e = m_allocator->alloc();
        e->value = value;
        e->next = m_first.load(std::memory_order_relaxed);
 
        while (!m_first.compare_exchange_weak(e->next, e,
                std::memory_order_release,
                std::memory_order_relaxed))
        {
            // Empty loop (compare_exchange_weak updates e->next)
        }
    }
 
    Element * popList()
    {
        return m_first.exchange(nullptr);
    }
 
    Element * first()
    {
        return m_first.load(std::memory_order_acquire);
    }
 
    void setFirst( Element * e )
    {
        m_first.store(e, std::memory_order_release);
    }
 
    void free( Element * e )
    {
        m_allocator->free( e );
    }
 
 
private:
    std::atomic<Element*> m_first;
    LocklessAllocatorT<Element> * m_allocator;
 
} ;
 
 
} // namespace lmms
 
#endif // LMMS_LOCKLESS_LIST_H