| /* |
| * Copyright (C) 2014-2019 Apple Inc. All rights reserved. |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions |
| * are met: |
| * 1. Redistributions of source code must retain the above copyright |
| * notice, this list of conditions and the following disclaimer. |
| * 2. Redistributions in binary form must reproduce the above copyright |
| * notice, this list of conditions and the following disclaimer in the |
| * documentation and/or other materials provided with the distribution. |
| * |
| * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY |
| * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
| * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR |
| * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR |
| * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, |
| * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, |
| * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR |
| * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY |
| * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE |
| * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| */ |
| |
| #pragma once |
| |
| #include "BExport.h" |
| #include "BInline.h" |
| #include "Mutex.h" |
| #include "Sizes.h" |
| |
| namespace bmalloc { |
| |
| // StaticPerProcess<T> behaves like PerProcess<T>, but we need to explicitly define storage for T with EXTERN. |
| // In this way, we allocate storage for a per-process object statically instead of allocating memory at runtime. |
| // To enforce this, we have DECLARE and DEFINE macros. If you do not know about T of StaticPerProcess<T>, you should use PerProcess<T> instead. |
| // |
| // Usage: |
| // In Object.h |
| // class Object : public StaticPerProcess<Object> { |
| // ... |
| // }; |
| // DECLARE_STATIC_PER_PROCESS_STORAGE(Object); |
| // |
| // In Object.cpp |
| // DEFINE_STATIC_PER_PROCESS_STORAGE(Object); |
| // |
| // Object* object = Object::get(); |
| // x = object->field->field; |
| // |
| // Object will be instantiated only once, even in the presence of concurrency. |
| // |
| template<typename T> struct StaticPerProcessStorageTraits; |
| |
| template<typename T> |
| class StaticPerProcess { |
| public: |
| static T* get() |
| { |
| T* object = getFastCase(); |
| if (!object) |
| return getSlowCase(); |
| return object; |
| } |
| |
| static T* getFastCase() |
| { |
| using Storage = typename StaticPerProcessStorageTraits<T>::Storage; |
| return (Storage::s_object).load(std::memory_order_relaxed); |
| } |
| |
| static Mutex& mutex() |
| { |
| using Storage = typename StaticPerProcessStorageTraits<T>::Storage; |
| return Storage::s_mutex; |
| } |
| |
| private: |
| BNO_INLINE static T* getSlowCase() |
| { |
| using Storage = typename StaticPerProcessStorageTraits<T>::Storage; |
| LockHolder lock(Storage::s_mutex); |
| if (!Storage::s_object.load(std::memory_order_consume)) { |
| T* t = new (&Storage::s_memory) T(lock); |
| Storage::s_object.store(t, std::memory_order_release); |
| } |
| return Storage::s_object.load(std::memory_order_consume); |
| } |
| }; |
| |
| #define DECLARE_STATIC_PER_PROCESS_STORAGE(Type) \ |
| template<> struct StaticPerProcessStorageTraits<Type> { \ |
| using Memory = typename std::aligned_storage<sizeof(Type), std::alignment_of<Type>::value>::type; \ |
| struct BEXPORT Storage { \ |
| static std::atomic<Type*> s_object; \ |
| static Mutex s_mutex; \ |
| static Memory s_memory; \ |
| }; \ |
| }; |
| |
| #define DEFINE_STATIC_PER_PROCESS_STORAGE(Type) \ |
| std::atomic<Type*> StaticPerProcessStorageTraits<Type>::Storage::s_object { nullptr }; \ |
| Mutex StaticPerProcessStorageTraits<Type>::Storage::s_mutex { }; \ |
| StaticPerProcessStorageTraits<Type>::Memory StaticPerProcessStorageTraits<Type>::Storage::s_memory { }; |
| |
| } // namespace bmalloc |