122 lines
2.8 KiB
C++
Executable file
122 lines
2.8 KiB
C++
Executable file
/*
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* Copyright (c) 2018 Samsung Electronics Co., Ltd. All rights reserved.
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#ifndef VCOWPTR_H
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#define VCOWPTR_H
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#include <assert.h>
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#include "vglobal.h"
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template <typename T>
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class vcow_ptr {
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struct model {
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std::atomic<std::size_t> mRef{1};
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model() = default;
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template <class... Args>
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explicit model(Args&&... args) : mValue(std::forward<Args>(args)...)
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{
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}
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T mValue;
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};
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model* mModel;
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public:
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using element_type = T;
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vcow_ptr()
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{
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static model default_s;
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mModel = &default_s;
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++mModel->mRef;
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}
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~vcow_ptr()
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{
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if (mModel && (--mModel->mRef == 0)) delete mModel;
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}
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template <class... Args>
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vcow_ptr(Args&&... args) : mModel(new model(std::forward<Args>(args)...))
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{
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}
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vcow_ptr(const vcow_ptr& x) noexcept : mModel(x.mModel)
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{
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assert(mModel);
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++mModel->mRef;
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}
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vcow_ptr(vcow_ptr&& x) noexcept : mModel(x.mModel)
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{
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assert(mModel);
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x.mModel = nullptr;
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}
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auto operator=(const vcow_ptr& x) noexcept -> vcow_ptr&
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{
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return *this = vcow_ptr(x);
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}
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auto operator=(vcow_ptr&& x) noexcept -> vcow_ptr&
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{
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auto tmp = std::move(x);
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swap(*this, tmp);
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return *this;
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}
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auto operator*() const noexcept -> const element_type& { return read(); }
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auto operator-> () const noexcept -> const element_type* { return &read(); }
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int refCount() const noexcept
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{
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assert(mModel);
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return mModel->mRef;
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}
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bool unique() const noexcept
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{
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assert(mModel);
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return mModel->mRef == 1;
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}
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auto write() -> element_type&
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{
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if (!unique()) *this = vcow_ptr(read());
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return mModel->mValue;
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}
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auto read() const noexcept -> const element_type&
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{
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assert(mModel);
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return mModel->mValue;
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}
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friend inline void swap(vcow_ptr& x, vcow_ptr& y) noexcept
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{
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std::swap(x.mModel, y.mModel);
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}
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};
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#endif // VCOWPTR_H
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