mirror of https://github.com/CGAL/cgal
143 lines
3.3 KiB
C++
143 lines
3.3 KiB
C++
// Copyright (c) 1999
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// Utrecht University (The Netherlands),
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// ETH Zurich (Switzerland),
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// INRIA Sophia-Antipolis (France),
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// Max-Planck-Institute Saarbruecken (Germany),
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// and Tel-Aviv University (Israel). All rights reserved.
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//
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// This file is part of CGAL (www.cgal.org)
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//
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// $URL$
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// $Id$
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// SPDX-License-Identifier: LGPL-3.0-or-later OR LicenseRef-Commercial
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//
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//
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// Author(s) : Sylvain Pion
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#ifndef CGAL_HANDLE_H
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#define CGAL_HANDLE_H
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#include <cstddef>
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#include <cstdint>
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#include <atomic>
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#include <CGAL/Handle_for.h>
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#include <CGAL/assertions.h>
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namespace CGAL {
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class Rep
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{
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friend class Handle;
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protected:
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Rep(int count = 1)
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: count(count)
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{}
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virtual ~Rep() {}
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std::atomic_int count;
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};
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class Handle
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{
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public:
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typedef std::ptrdiff_t Id_type ;
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Handle() noexcept
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: PTR(static_cast<Rep*>(0)) {}
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Handle(const Handle& x) noexcept(!(CGAL_PRECONDITIONS_ENABLED || CGAL_ASSERTIONS_ENABLED))
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{
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CGAL_precondition( x.PTR != static_cast<Rep*>(0) );
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PTR = x.PTR;
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//CGAL_assume (PTR->count > 0);
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incref();
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}
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Handle(Handle&& x) noexcept : PTR(x.PTR) { x.PTR = 0; }
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~Handle() { reset(); }
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Handle&
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operator=(const Handle& x) noexcept(!CGAL_PRECONDITIONS_ENABLED)
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{
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CGAL_precondition( x.PTR != static_cast<Rep*>(0) );
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x.incref();
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if(PTR) decref(); // not reset() in case this==&x
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PTR = x.PTR;
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return *this;
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}
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Handle&
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operator=(Handle&& x) noexcept
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{
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swap(*this, x);
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return *this;
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}
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friend void swap(Handle& a, Handle& b) noexcept { std::swap(a.PTR, b.PTR); }
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private:
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void incref() const noexcept
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{
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if (is_currently_single_threaded()) {
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PTR->count.store(PTR->count.load(std::memory_order_relaxed) + 1, std::memory_order_relaxed);
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} else {
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PTR->count.fetch_add(1, std::memory_order_relaxed);
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}
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}
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void decref()
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{
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if (is_currently_single_threaded()) {
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auto c = PTR->count.load(std::memory_order_relaxed);
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if (c == 1)
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delete PTR;
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else
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PTR->count.store(c - 1, std::memory_order_relaxed);
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} else {
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// TSAN does not support fences :-(
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#if !defined __SANITIZE_THREAD__ && !__has_feature(thread_sanitizer)
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if (PTR->count.load(std::memory_order_relaxed) == 1
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|| PTR->count.fetch_sub(1, std::memory_order_release) == 1) {
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std::atomic_thread_fence(std::memory_order_acquire);
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#else
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if (PTR->count.fetch_sub(1, std::memory_order_acq_rel) == 1) {
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#endif
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delete PTR;
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}
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}
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}
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public:
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void reset()
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{
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if (PTR)
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{
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decref();
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PTR=0;
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}
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}
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int
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refs() const noexcept { return PTR->count.load(std::memory_order_relaxed); }
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Id_type id() const noexcept { return static_cast<Id_type>(reinterpret_cast<std::intptr_t>(static_cast<void*>(PTR)) / sizeof(Rep)); }
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bool identical(const Handle& h) const noexcept { return PTR == h.PTR; }
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void * for_compact_container() const { return PTR; }
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void for_compact_container(void* p) { PTR = static_cast<Rep*>(p); }
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protected:
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Rep* PTR;
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};
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//inline Handle::Id_type id(const Handle& x) { return x.id() ; }
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inline bool identical(const Handle &h1, const Handle &h2) noexcept { return h1.identical(h2); }
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} //namespace CGAL
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#endif // CGAL_HANDLE_H
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