| /* |
| * Copyright (C) 2014-2018 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 "BInline.h" |
| #include "Mutex.h" |
| #include "Sizes.h" |
| |
| namespace bmalloc { |
| |
| // Usage: |
| // Object* object = PerProcess<Object>::get(); |
| // x = object->field->field; |
| // |
| // Object will be instantiated only once, even in the face of concurrency. |
| // |
| // NOTE: If you observe global side-effects of the Object constructor, be |
| // sure to lock the Object mutex. For example: |
| // |
| // Object() : m_field(...) { globalFlag = true } |
| // |
| // Object* object = PerProcess<Object>::get(); |
| // x = object->m_field; // OK |
| // if (globalFlag) { ... } // Undefined behavior. |
| // |
| // std::lock_guard<Mutex> lock(PerProcess<Object>::mutex()); |
| // Object* object = PerProcess<Object>::get(lock); |
| // if (globalFlag) { ... } // OK. |
| |
| struct PerProcessData { |
| const char* disambiguator; |
| void* memory; |
| size_t size; |
| size_t alignment; |
| Mutex mutex; |
| bool isInitialized; |
| PerProcessData* next; |
| }; |
| |
| constexpr unsigned stringHash(const char* string) |
| { |
| unsigned result = 5381; |
| while (char c = *string++) |
| result = result * 33 + c; |
| return result; |
| } |
| |
| BEXPORT PerProcessData* getPerProcessData(unsigned disambiguatorHash, const char* disambiguator, size_t size, size_t alignment); |
| |
| template<typename T> |
| class PerProcess { |
| public: |
| static T* get() |
| { |
| T* object = getFastCase(); |
| if (!object) |
| return getSlowCase(); |
| return object; |
| } |
| |
| static T* getFastCase() |
| { |
| return s_object.load(std::memory_order_relaxed); |
| } |
| |
| static Mutex& mutex() |
| { |
| if (!s_data) |
| coalesce(); |
| return s_data->mutex; |
| } |
| |
| private: |
| static void coalesce() |
| { |
| if (s_data) |
| return; |
| |
| const char* disambiguator = __PRETTY_FUNCTION__; |
| s_data = getPerProcessData(stringHash(disambiguator), disambiguator, sizeof(T), std::alignment_of<T>::value); |
| } |
| |
| BNO_INLINE static T* getSlowCase() |
| { |
| std::lock_guard<Mutex> lock(mutex()); |
| if (!s_object.load()) { |
| if (s_data->isInitialized) |
| s_object.store(static_cast<T*>(s_data->memory)); |
| else { |
| T* t = new (s_data->memory) T(lock); |
| s_object.store(t); |
| s_data->isInitialized = true; |
| } |
| } |
| return s_object.load(); |
| } |
| |
| static std::atomic<T*> s_object; |
| static PerProcessData* s_data; |
| }; |
| |
| template<typename T> |
| std::atomic<T*> PerProcess<T>::s_object { nullptr }; |
| |
| template<typename T> |
| PerProcessData* PerProcess<T>::s_data { nullptr }; |
| |
| } // namespace bmalloc |