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Diff: platform/SingletonPtr.h
- Revision:
- 149:156823d33999
diff -r 21d94c44109e -r 156823d33999 platform/SingletonPtr.h --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/platform/SingletonPtr.h Fri Oct 28 11:17:30 2016 +0100 @@ -0,0 +1,110 @@ + +/** \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 + +/** @}*/