CowRefCount.h

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/*
 * This file is a part of the Biology project by eons LLC.
 * Biology (aka Develop Biology) is a framework for approaching software
 * development from a natural sciences perspective.
 *
 * Copyright (C) 2026 Séon O'Shannon & eons LLC
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as
 * published by the Free Software Foundation, either version 3 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 Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */
 
#pragma once
 
#include "bio/common/macro/LanguageMacros.h"
 
#if BIO_CPP_VERSION >= 11
    #include <atomic>
#endif
 
namespace bio {
 
#if BIO_CPP_VERSION >= 11
 
typedef ::std::atomic< unsigned int > CowRefCount;
 
inline void CowInc(CowRefCount& count)
{
    count.fetch_add(1, ::std::memory_order_relaxed);
}
 
inline bool CowDecAndIsLast(CowRefCount& count)
{
    return count.fetch_sub(1, ::std::memory_order_acq_rel) == 1;
}
 
inline unsigned int CowLoad(const CowRefCount& count)
{
    return count.load(::std::memory_order_relaxed);
}
 
#else // cpp98: plain counter, caller-serialised (no __sync_* in-tree)
 
typedef unsigned int CowRefCount;
 
inline void CowInc(CowRefCount& count)
{
    ++count;
}
 
inline bool CowDecAndIsLast(CowRefCount& count)
{
    return (--count == 0);
}
 
inline unsigned int CowLoad(const CowRefCount& count)
{
    return count;
}
 
#endif
 
} // namespace bio