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platform/SingletonPtr.h
- Committer:
- <>
- Date:
- 2016-10-28
- Revision:
- 149:156823d33999
File content as of revision 149:156823d33999:
/** \addtogroup platform */ /** @{*/ /* mbed Microcontroller Library * Copyright (c) 2006-2013 ARM Limited * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ #ifndef SINGLETONPTR_H #define SINGLETONPTR_H #include <stdint.h> #include <new> #include "platform/mbed_assert.h" #ifdef MBED_CONF_RTOS_PRESENT #include "cmsis_os.h" #endif #ifdef MBED_CONF_RTOS_PRESENT extern osMutexId singleton_mutex_id; #endif /** Lock the singleton mutex * * This function is typically used to provide * exclusive access when initializing a * global object. */ inline static void singleton_lock(void) { #ifdef MBED_CONF_RTOS_PRESENT osMutexWait(singleton_mutex_id, osWaitForever); #endif } /** Unlock the singleton mutex * * This function is typically used to provide * exclusive access when initializing a * global object. */ inline static void singleton_unlock(void) { #ifdef MBED_CONF_RTOS_PRESENT osMutexRelease (singleton_mutex_id); #endif } /** Utility class for creating an using a singleton * * @Note Synchronization level: Thread safe * * @Note: This class must only be used in a static context - * this class must never be allocated or created on the * stack. * * @Note: This class is lazily initialized on first use. * This class is a POD type so if it is not used it will * be garbage collected. */ template <class T> struct SingletonPtr { /** Get a pointer to the underlying singleton * * @returns * A pointer to the singleton */ T* get() { if (NULL == _ptr) { singleton_lock(); if (NULL == _ptr) { _ptr = new (_data) T(); } singleton_unlock(); } // _ptr was not zero initialized or was // corrupted if this assert is hit MBED_ASSERT(_ptr == (T *)&_data); return _ptr; } /** Get a pointer to the underlying singleton * * @returns * A pointer to the singleton */ T* operator->() { return get(); } // This is zero initialized when in global scope T *_ptr; // Force data to be 4 byte aligned uint32_t _data[(sizeof(T) + sizeof(uint32_t) - 1) / sizeof(uint32_t)]; }; #endif /** @}*/