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https://github.com/SerenityOS/serenity
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0d934fc991
Alot of code is shared between i386/i686/x86 and x86_64 and a lot probably will be used for compatability modes. So we start by moving the headers into one Directory. We will probalby be able to move some cpp files aswell.
134 lines
3.7 KiB
C++
134 lines
3.7 KiB
C++
/*
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* Copyright (c) 2020, the SerenityOS developers.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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*
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* 1. Redistributions of source code must retain the above copyright notice, this
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* list of conditions and the following disclaimer.
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*
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* 2. Redistributions in binary form must reproduce the above copyright notice,
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* this list of conditions and the following disclaimer in the documentation
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* and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#pragma once
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#include <AK/Assertions.h>
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#include <AK/Atomic.h>
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#include <AK/Noncopyable.h>
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#ifdef KERNEL
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# include <Kernel/Arch/x86/CPU.h>
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#endif
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#ifndef __serenity__
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# include <new>
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#endif
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namespace AK {
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template<typename T>
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struct SingletonInstanceCreator {
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static T* create()
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{
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return new T();
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}
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};
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template<typename T, T* (*InitFunction)() = SingletonInstanceCreator<T>::create>
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class Singleton {
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AK_MAKE_NONCOPYABLE(Singleton);
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AK_MAKE_NONMOVABLE(Singleton);
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public:
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Singleton() = default;
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template<bool allow_create = true>
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static T* get(T*& obj_var)
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{
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T* obj = AK::atomic_load(&obj_var, AK::memory_order_acquire);
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if (FlatPtr(obj) <= 0x1) {
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// If this is the first time, see if we get to initialize it
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#ifdef KERNEL
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Kernel::ScopedCritical critical;
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#endif
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if constexpr (allow_create) {
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if (obj == nullptr && AK::atomic_compare_exchange_strong(&obj_var, obj, (T*)0x1, AK::memory_order_acq_rel)) {
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// We're the first one
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obj = InitFunction();
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AK::atomic_store(&obj_var, obj, AK::memory_order_release);
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return obj;
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}
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}
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// Someone else was faster, wait until they're done
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while (obj == (T*)0x1) {
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#ifdef KERNEL
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Kernel::Processor::wait_check();
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#else
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// TODO: yield
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#endif
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obj = AK::atomic_load(&obj_var, AK::memory_order_acquire);
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}
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if constexpr (allow_create) {
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// We should always return an instance if we allow creating one
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VERIFY(obj != nullptr);
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}
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VERIFY(obj != (T*)0x1);
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}
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return obj;
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}
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T* ptr() const
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{
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return get(m_obj);
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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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T& operator*() const
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{
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return *ptr();
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}
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operator T*() const
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{
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return ptr();
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}
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operator T&() const
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{
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return *ptr();
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}
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bool is_initialized() const
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{
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T* obj = AK::atomic_load(&m_obj, AK::memory_order_consume);
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return FlatPtr(obj) > 0x1;
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}
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void ensure_instance()
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{
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ptr();
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}
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private:
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mutable T* m_obj { nullptr }; // atomic
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};
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}
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