AtomAs.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) 2023 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
 
// Out-of-line definitions of Atom::As< T >() / Atom::AsBonded< T >() /
// Atom::operator T(). <br />
//
// This is NOT a standalone header: it requires bio::chemical::Atom to be a
// COMPLETE type. It is #include'd at the very bottom of Atom.h, AFTER the Atom
// class is closed, so that the bonded copy-on-write handle Cow< T > -- which
// calls back into Atom -- is fully defined here; that ordering is what breaks
// the Atom <-> Cow include cycle. Do not #include this directly; include
// Atom.h, which pulls it in transparently (no call site needs an extra include).
 
#include "bio/chemical/wrapper/Cow.h"
 
namespace bio {
namespace chemical {
 
template < typename T >
Cow< T > Atom::AsBonded() const
{
    BIO_STATIC_ASSERT(!type::IsReference< T >())
    BIO_STATIC_ASSERT(!type::IsPointer< T >())
 
    // Resolve a snapshot of the bonded under a shared lock (the same lookup the pre-COW
    // AsBonded did), then hand out a DEFERRED handle: it shares the snapshot on read and
    // copy-on-write detaches the source bond on write. The shared lock is released when
    // this returns, so the handle's later Write takes a fresh exclusive (RFC §12).
    SafelyAccessShared< Atom > guard(const_cast< Atom* >(this));
    const AtomicNumber bondId = GetBondId< T >();
    const Valence position = GetBondPositionLocked(bondId);
    Pointer< physical::Wave > snapshot = NULL;
    if (position && mBonds.IsAllocated(position))
    {
        snapshot = mBonds.OptimizedAccess(position)->GetBonded();
    }
    return Cow< T >(const_cast< Atom* >(this), bondId, snapshot);
}
 
template < typename T >
typename atom_detail::AsResultType<
    T,
    type::IsWaveImplementation< typename type::RemovePointer< T >::Type >::sValue
>::Type
Atom::As() const
{
    // We store either a Wave-derived object or a Quantum<T> payload. T should be
    // the bonded type itself (As<int>(), As<const Surface>()). Pointer spelling
    // is still normalized here only so old template instantiations fail cleanly.
    BIO_STATIC_ASSERT(!type::IsPointer< typename type::RemovePointer< T >::Type >())
    return atom_detail::AsDispatcher<
        T,
        type::IsWaveImplementation< typename type::RemovePointer< T >::Type >::sValue
    >::As(*this);
}
 
template < typename T >
Atom::operator T() const
{
    return As< T >();
}
 
} //chemical namespace
} //bio namespace