spinlock.h

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/*
 * Copyright (C) 2017-2019 Robin Gareus <robin@gareus.org>
 *
 * 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; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */
 
#ifndef _pbd_spinlock_h_
#define _pbd_spinlock_h_
 
#include <boost/smart_ptr/detail/spinlock.hpp>
#include <cstring>
 
#include "pbd/libpbd_visibility.h"
 
namespace PBD {
 
/* struct boost::detail::spinlock {
 *   void lock();
 *   bool try_lock();
 *   void unlock();
 * };
 *
 * initialize with BOOST_DETAIL_SPINLOCK_INIT
 */
 
struct spinlock_t {
public:
#ifdef BOOST_SMART_PTR_DETAIL_SPINLOCK_STD_ATOMIC_HPP_INCLUDED
        /* C++11 non-static data member initialization,
         * with non-copyable std::atomic ATOMIC_FLAG_INIT
         */
        spinlock_t () {}
#else
        /* default C++ assign struct's first member */
        spinlock_t ()
        {
                boost::detail::spinlock init = BOOST_DETAIL_SPINLOCK_INIT;
                std::memcpy (&l, &init, sizeof (init));
        }
#endif
        void lock () { l.lock (); }
        void unlock () { l.unlock (); }
        bool try_lock () { return l.try_lock (); }
 
private:
#ifdef BOOST_SMART_PTR_DETAIL_SPINLOCK_STD_ATOMIC_HPP_INCLUDED
        boost::detail::spinlock l = BOOST_DETAIL_SPINLOCK_INIT;
#else
        boost::detail::spinlock l;
#endif
 
        /* prevent copy construction */
        spinlock_t (const spinlock_t&);
};
 
/* RAII wrapper */
class LIBPBD_API SpinLock {
 
public:
        SpinLock (spinlock_t&);
        ~SpinLock ();
 
private:
        spinlock_t& _lock;
};
 
} /* namespace */
 
#endif /* _pbd_spinlock_h__ */