146 lines
3.0 KiB
C++
146 lines
3.0 KiB
C++
/*
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* Copyright (C) 2026 Josh Holtrop
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the “Software”), to
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* deal in the Software without restriction, including without limitation the
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* rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
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* sell copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
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* IN THE SOFTWARE.
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*/
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#pragma once
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#include <atomic>
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namespace rcp_internal
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{
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class root
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{
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private:
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mutable std::atomic<int> ref_count{0};
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rcp<root> root_rcp;
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protected:
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root()
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{
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root_rcp = rcp<root>(this);
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}
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virtual ~root() = default;
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public:
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void rcp_inc() const
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{
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ref_count.fetch_add(1, std::memory_order_relaxed);
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}
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void rcp_dec() const
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{
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if (ref_count.fetch_sub(1, std::memory_order_acq_rel) == 0)
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{
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delete this;
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}
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}
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rcp<root> & get_root_rcp()
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{
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return root_rcp;
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}
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}
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template <typename T>
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class managed
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{
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public:
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static_assert(std::is_base_of<root, T>::value,
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"T must inherit from rcp::root to use rcp::managed<T>");
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rcp<T> get_rcp()
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{
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root * r = (root *)this;
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return rcp<T>(r->get_root_ref());
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}
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}
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}
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/**
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* Reference-counting pointer.
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*/
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template <typename T>
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class rcp
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{
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private:
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T * ptr = nullptr;
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explicit rcp(T * p) : ptr(p)
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{
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if (p)
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{
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ptr->rcp_inc();
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}
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}
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friend T;
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public:
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rcp() = default;
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rcp(const rcp & other) : ptr(other.ptr)
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{
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if (ptr)
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{
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ptr->rcp_inc();
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}
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}
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~rcp()
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{
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if (ptr)
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{
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ptr->rcp_dec();
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}
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}
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/* Casting constructor: allows rcp<Base> -> rcp<Derived> */
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template <typename U>
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rcp(const rcp<U> & other) : ptr(static_cast<T *>(other.get_raw()))
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{
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if (ptr)
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{
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ptr->rcp_inc();
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}
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}
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T * get_raw() const
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{
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return ptr;
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}
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T * operator->() const
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{
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return ptr;
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}
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bool operator!() const
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{
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return !ptr;
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}
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using root = rcp_internal::root;
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using managed = rcp_internal::managed;
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}
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