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platform/SingletonPtr.h@172:65be27845400, 2019-02-20 (annotated)

Committer:
AnnaBridge
Date:
Wed Feb 20 20:53:29 2019 +0000
Revision:
172:65be27845400
Parent:
171:3a7713b1edbc 
mbed library release version 165

Who changed what in which revision?

UserRevisionLine numberNew contents of line
AnnaBridge 156:ff21514d8981 1
AnnaBridge 156:ff21514d8981 2 /** \addtogroup platform */
AnnaBridge 156:ff21514d8981 3 /** @{*/
AnnaBridge 158:1c57384330a6 4 /**
AnnaBridge 158:1c57384330a6 5 * \defgroup platform_SingletonPtr SingletonPtr class
AnnaBridge 158:1c57384330a6 6 * @{
AnnaBridge 158:1c57384330a6 7 */
AnnaBridge 156:ff21514d8981 8 /* mbed Microcontroller Library
AnnaBridge 156:ff21514d8981 9 * Copyright (c) 2006-2013 ARM Limited
AnnaBridge 172:65be27845400 10 * SPDX-License-Identifier: Apache-2.0
AnnaBridge 156:ff21514d8981 11 *
AnnaBridge 156:ff21514d8981 12 * Licensed under the Apache License, Version 2.0 (the "License");
AnnaBridge 156:ff21514d8981 13 * you may not use this file except in compliance with the License.
AnnaBridge 156:ff21514d8981 14 * You may obtain a copy of the License at
AnnaBridge 156:ff21514d8981 15 *
AnnaBridge 156:ff21514d8981 16 * http://www.apache.org/licenses/LICENSE-2.0
AnnaBridge 156:ff21514d8981 17 *
AnnaBridge 156:ff21514d8981 18 * Unless required by applicable law or agreed to in writing, software
AnnaBridge 156:ff21514d8981 19 * distributed under the License is distributed on an "AS IS" BASIS,
AnnaBridge 156:ff21514d8981 20 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
AnnaBridge 156:ff21514d8981 21 * See the License for the specific language governing permissions and
AnnaBridge 156:ff21514d8981 22 * limitations under the License.
AnnaBridge 156:ff21514d8981 23 */
AnnaBridge 156:ff21514d8981 24 #ifndef SINGLETONPTR_H
AnnaBridge 156:ff21514d8981 25 #define SINGLETONPTR_H
AnnaBridge 156:ff21514d8981 26
AnnaBridge 172:65be27845400 27 #include <stdlib.h>
AnnaBridge 156:ff21514d8981 28 #include <stdint.h>
AnnaBridge 156:ff21514d8981 29 #include <new>
AnnaBridge 156:ff21514d8981 30 #include "platform/mbed_assert.h"
AnnaBridge 156:ff21514d8981 31 #ifdef MBED_CONF_RTOS_PRESENT
AnnaBridge 156:ff21514d8981 32 #include "cmsis_os2.h"
AnnaBridge 156:ff21514d8981 33 #endif
AnnaBridge 156:ff21514d8981 34
AnnaBridge 156:ff21514d8981 35 #ifdef MBED_CONF_RTOS_PRESENT
AnnaBridge 156:ff21514d8981 36 extern osMutexId_t singleton_mutex_id;
AnnaBridge 156:ff21514d8981 37 #endif
AnnaBridge 156:ff21514d8981 38
AnnaBridge 156:ff21514d8981 39 /** Lock the singleton mutex
AnnaBridge 156:ff21514d8981 40 *
AnnaBridge 156:ff21514d8981 41 * This function is typically used to provide
AnnaBridge 156:ff21514d8981 42 * exclusive access when initializing a
AnnaBridge 156:ff21514d8981 43 * global object.
AnnaBridge 156:ff21514d8981 44 */
AnnaBridge 156:ff21514d8981 45 inline static void singleton_lock(void)
AnnaBridge 156:ff21514d8981 46 {
AnnaBridge 156:ff21514d8981 47 #ifdef MBED_CONF_RTOS_PRESENT
AnnaBridge 171:3a7713b1edbc 48 if (!singleton_mutex_id) {
AnnaBridge 171:3a7713b1edbc 49 // RTOS has not booted yet so no mutex is needed
AnnaBridge 171:3a7713b1edbc 50 return;
AnnaBridge 171:3a7713b1edbc 51 }
AnnaBridge 156:ff21514d8981 52 osMutexAcquire(singleton_mutex_id, osWaitForever);
AnnaBridge 156:ff21514d8981 53 #endif
AnnaBridge 156:ff21514d8981 54 }
AnnaBridge 156:ff21514d8981 55
AnnaBridge 156:ff21514d8981 56 /** Unlock the singleton mutex
AnnaBridge 156:ff21514d8981 57 *
AnnaBridge 156:ff21514d8981 58 * This function is typically used to provide
AnnaBridge 156:ff21514d8981 59 * exclusive access when initializing a
AnnaBridge 156:ff21514d8981 60 * global object.
AnnaBridge 156:ff21514d8981 61 */
AnnaBridge 156:ff21514d8981 62 inline static void singleton_unlock(void)
AnnaBridge 156:ff21514d8981 63 {
AnnaBridge 156:ff21514d8981 64 #ifdef MBED_CONF_RTOS_PRESENT
AnnaBridge 171:3a7713b1edbc 65 if (!singleton_mutex_id) {
AnnaBridge 171:3a7713b1edbc 66 // RTOS has not booted yet so no mutex is needed
AnnaBridge 171:3a7713b1edbc 67 return;
AnnaBridge 171:3a7713b1edbc 68 }
AnnaBridge 170:e95d10626187 69 osMutexRelease(singleton_mutex_id);
AnnaBridge 156:ff21514d8981 70 #endif
AnnaBridge 156:ff21514d8981 71 }
AnnaBridge 156:ff21514d8981 72
AnnaBridge 156:ff21514d8981 73 /** Utility class for creating an using a singleton
AnnaBridge 156:ff21514d8981 74 *
AnnaBridge 156:ff21514d8981 75 * @note Synchronization level: Thread safe
AnnaBridge 156:ff21514d8981 76 *
AnnaBridge 156:ff21514d8981 77 * @note: This class must only be used in a static context -
AnnaBridge 156:ff21514d8981 78 * this class must never be allocated or created on the
AnnaBridge 156:ff21514d8981 79 * stack.
AnnaBridge 156:ff21514d8981 80 *
AnnaBridge 156:ff21514d8981 81 * @note: This class is lazily initialized on first use.
AnnaBridge 156:ff21514d8981 82 * This class is a POD type so if it is not used it will
AnnaBridge 156:ff21514d8981 83 * be garbage collected.
AnnaBridge 156:ff21514d8981 84 */
AnnaBridge 156:ff21514d8981 85 template <class T>
AnnaBridge 156:ff21514d8981 86 struct SingletonPtr {
AnnaBridge 156:ff21514d8981 87
AnnaBridge 156:ff21514d8981 88 /** Get a pointer to the underlying singleton
AnnaBridge 156:ff21514d8981 89 *
AnnaBridge 156:ff21514d8981 90 * @returns
AnnaBridge 156:ff21514d8981 91 * A pointer to the singleton
AnnaBridge 156:ff21514d8981 92 */
AnnaBridge 172:65be27845400 93 T *get() const
AnnaBridge 170:e95d10626187 94 {
AnnaBridge 156:ff21514d8981 95 if (NULL == _ptr) {
AnnaBridge 156:ff21514d8981 96 singleton_lock();
AnnaBridge 156:ff21514d8981 97 if (NULL == _ptr) {
AnnaBridge 156:ff21514d8981 98 _ptr = new (_data) T();
AnnaBridge 156:ff21514d8981 99 }
AnnaBridge 156:ff21514d8981 100 singleton_unlock();
AnnaBridge 156:ff21514d8981 101 }
AnnaBridge 156:ff21514d8981 102 // _ptr was not zero initialized or was
AnnaBridge 156:ff21514d8981 103 // corrupted if this assert is hit
AnnaBridge 156:ff21514d8981 104 MBED_ASSERT(_ptr == (T *)&_data);
AnnaBridge 156:ff21514d8981 105 return _ptr;
AnnaBridge 156:ff21514d8981 106 }
AnnaBridge 156:ff21514d8981 107
AnnaBridge 156:ff21514d8981 108 /** Get a pointer to the underlying singleton
AnnaBridge 156:ff21514d8981 109 *
AnnaBridge 156:ff21514d8981 110 * @returns
AnnaBridge 156:ff21514d8981 111 * A pointer to the singleton
AnnaBridge 156:ff21514d8981 112 */
AnnaBridge 172:65be27845400 113 T *operator->() const
AnnaBridge 170:e95d10626187 114 {
AnnaBridge 156:ff21514d8981 115 return get();
AnnaBridge 156:ff21514d8981 116 }
AnnaBridge 156:ff21514d8981 117
AnnaBridge 172:65be27845400 118 /** Get a reference to the underlying singleton
AnnaBridge 172:65be27845400 119 *
AnnaBridge 172:65be27845400 120 * @returns
AnnaBridge 172:65be27845400 121 * A reference to the singleton
AnnaBridge 172:65be27845400 122 */
AnnaBridge 172:65be27845400 123 T &operator*() const
AnnaBridge 172:65be27845400 124 {
AnnaBridge 172:65be27845400 125 return *get();
AnnaBridge 172:65be27845400 126 }
AnnaBridge 172:65be27845400 127
AnnaBridge 156:ff21514d8981 128 // This is zero initialized when in global scope
AnnaBridge 172:65be27845400 129 mutable T *_ptr;
AnnaBridge 172:65be27845400 130 #if __cplusplus >= 201103L
AnnaBridge 172:65be27845400 131 // Align data appropriately
AnnaBridge 172:65be27845400 132 alignas(T) mutable char _data[sizeof(T)];
AnnaBridge 172:65be27845400 133 #else
AnnaBridge 172:65be27845400 134 // Force data to be 8 byte aligned
AnnaBridge 172:65be27845400 135 mutable uint64_t _data[(sizeof(T) + sizeof(uint64_t) - 1) / sizeof(uint64_t)];
AnnaBridge 172:65be27845400 136 #endif
AnnaBridge 156:ff21514d8981 137 };
AnnaBridge 156:ff21514d8981 138
AnnaBridge 156:ff21514d8981 139 #endif
AnnaBridge 158:1c57384330a6 140 /**@}*/
AnnaBridge 156:ff21514d8981 141
AnnaBridge 158:1c57384330a6 142 /**@}*/