rwlock.h

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/*
 * Copyright (C) 2026 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.
 */
 
#pragma once
 
#include <shared_mutex>
 
#include "pbd/libpbd_visibility.h"
 
namespace PBD
{
 
class LIBPBD_API RWLock
{
public:
        enum LockFlags {
                Lock,
                NotLock,
                TryLock
        };
 
        class ReaderLock;
        class WriterLock;
 
        RWLock ();
        ~RWLock ();
 
        inline void reader_lock ()
        {
                _rw_lock.lock_shared ();
        }
        inline bool reader_trylock ()
        {
                return _rw_lock.try_lock_shared ();
        }
        inline void reader_unlock ()
        {
                _rw_lock.unlock_shared ();
        }
 
        inline void writer_lock ()
        {
                _rw_lock.lock ();
        }
        inline bool writer_trylock ()
        {
                return _rw_lock.try_lock ();
        }
        inline void writer_unlock ()
        {
                _rw_lock.unlock ();
        }
 
private:
        RWLock (const RWLock&)            = delete;
        RWLock& operator= (const RWLock&) = delete;
 
        std::shared_mutex _rw_lock;
};
 
class LIBPBD_API RWLock::ReaderLock
{
public:
        ReaderLock (RWLock& rwlock, RWLock::LockFlags m = Lock);
        ~ReaderLock ();
 
        inline void acquire ()
        {
                _rwlock.reader_lock ();
                _locked = true;
        }
 
        inline bool try_acquire ()
        {
                _locked = _rwlock.reader_trylock ();
                return _locked;
        };
 
        inline void release ()
        {
                _rwlock.reader_unlock ();
                _locked = false;
        }
 
        inline bool locked () const
        {
                return _locked;
        }
 
private:
        RWLock& _rwlock;
        bool    _locked;
 
        ReaderLock (RWLock::ReaderLock const&)                    = delete;
        RWLock::ReaderLock& operator= (RWLock::ReaderLock const&) = delete;
};
 
class LIBPBD_API RWLock::WriterLock
{
public:
        WriterLock (RWLock& rwlock, RWLock::LockFlags m = Lock);
        ~WriterLock ();
 
        inline void acquire ()
        {
                _rwlock.writer_lock ();
                _locked = true;
        }
 
        inline bool try_acquire ()
        {
                _locked = _rwlock.writer_trylock ();
                return _locked;
        }
 
        inline void release ()
        {
                _rwlock.writer_unlock ();
                _locked = false;
        }
 
        inline bool locked () const
        {
                return _locked;
        }
 
private:
        RWLock& _rwlock;
        bool    _locked;
 
        WriterLock (RWLock::WriterLock const&)                    = delete;
        RWLock::WriterLock& operator= (RWLock::WriterLock const&) = delete;
};
 
} // namespace PBD