CowControlBlock.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/chemical/wrapper/CowRefCount.h"
 
namespace bio {
 
template < typename T >
struct CowControlBlock
{
    CowRefCount mRefCount; // starts at 1
    T* mPayload;           // owned; deleted when refcount hits 0 (unless immutable)
    bool mImmutable;       // true = per-type prototype flyweight: forces detach on first write
 
    CowControlBlock(
        T* payload,
        bool immutable
    )
        :
        mRefCount(1),
        mPayload(payload),
        mImmutable(immutable)
    {
    }
 
private:
    // Non-copyable: control blocks are shared by pointer, never duplicated.
    CowControlBlock(const CowControlBlock&);
    CowControlBlock& operator=(const CowControlBlock&);
};
 
} // namespace bio