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SingletonPtr.h
00001 00002 /** \addtogroup platform */ 00003 /** @{*/ 00004 /** 00005 * \defgroup platform_SingletonPtr SingletonPtr class 00006 * @{ 00007 */ 00008 /* mbed Microcontroller Library 00009 * Copyright (c) 2006-2013 ARM Limited 00010 * 00011 * Licensed under the Apache License, Version 2.0 (the "License"); 00012 * you may not use this file except in compliance with the License. 00013 * You may obtain a copy of the License at 00014 * 00015 * http://www.apache.org/licenses/LICENSE-2.0 00016 * 00017 * Unless required by applicable law or agreed to in writing, software 00018 * distributed under the License is distributed on an "AS IS" BASIS, 00019 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 00020 * See the License for the specific language governing permissions and 00021 * limitations under the License. 00022 */ 00023 #ifndef SINGLETONPTR_H 00024 #define SINGLETONPTR_H 00025 00026 #include <stdint.h> 00027 #include <new> 00028 #include "platform/mbed_assert.h" 00029 #ifdef MBED_CONF_RTOS_PRESENT 00030 #include "cmsis_os2.h" 00031 #endif 00032 00033 #ifdef MBED_CONF_RTOS_PRESENT 00034 extern osMutexId_t singleton_mutex_id; 00035 #endif 00036 00037 /** Lock the singleton mutex 00038 * 00039 * This function is typically used to provide 00040 * exclusive access when initializing a 00041 * global object. 00042 */ 00043 inline static void singleton_lock(void) 00044 { 00045 #ifdef MBED_CONF_RTOS_PRESENT 00046 if (!singleton_mutex_id) { 00047 // RTOS has not booted yet so no mutex is needed 00048 return; 00049 } 00050 osMutexAcquire(singleton_mutex_id, osWaitForever); 00051 #endif 00052 } 00053 00054 /** Unlock the singleton mutex 00055 * 00056 * This function is typically used to provide 00057 * exclusive access when initializing a 00058 * global object. 00059 */ 00060 inline static void singleton_unlock(void) 00061 { 00062 #ifdef MBED_CONF_RTOS_PRESENT 00063 if (!singleton_mutex_id) { 00064 // RTOS has not booted yet so no mutex is needed 00065 return; 00066 } 00067 osMutexRelease(singleton_mutex_id); 00068 #endif 00069 } 00070 00071 /** Utility class for creating an using a singleton 00072 * 00073 * @note Synchronization level: Thread safe 00074 * 00075 * @note: This class must only be used in a static context - 00076 * this class must never be allocated or created on the 00077 * stack. 00078 * 00079 * @note: This class is lazily initialized on first use. 00080 * This class is a POD type so if it is not used it will 00081 * be garbage collected. 00082 */ 00083 template <class T> 00084 struct SingletonPtr { 00085 00086 /** Get a pointer to the underlying singleton 00087 * 00088 * @returns 00089 * A pointer to the singleton 00090 */ 00091 T *get() 00092 { 00093 if (NULL == _ptr) { 00094 singleton_lock(); 00095 if (NULL == _ptr) { 00096 _ptr = new (_data) T(); 00097 } 00098 singleton_unlock(); 00099 } 00100 // _ptr was not zero initialized or was 00101 // corrupted if this assert is hit 00102 MBED_ASSERT(_ptr == (T *)&_data); 00103 return _ptr; 00104 } 00105 00106 /** Get a pointer to the underlying singleton 00107 * 00108 * @returns 00109 * A pointer to the singleton 00110 */ 00111 T *operator->() 00112 { 00113 return get(); 00114 } 00115 00116 /** Get a reference to the underlying singleton 00117 * 00118 * @returns 00119 * A reference to the singleton 00120 */ 00121 T &operator*() 00122 { 00123 return *get(); 00124 } 00125 00126 // This is zero initialized when in global scope 00127 T *_ptr; 00128 // Force data to be 4 byte aligned 00129 uint32_t _data[(sizeof(T) + sizeof(uint32_t) - 1) / sizeof(uint32_t)]; 00130 }; 00131 00132 #endif 00133 /**@}*/ 00134 00135 /**@}*/
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