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platform/SingletonPtr.h@135:fce8a9387ed1, 2017-01-17 (annotated)

Committer:
kaoshen
Date:
Tue Jan 17 23:27:32 2017 +0000
Revision:
135:fce8a9387ed1
Parent:
128:9bcdf88f62b0 
333 ADS1115 ADC1

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<> 128:9bcdf88f62b0 1
<> 128:9bcdf88f62b0 2 /** \addtogroup platform */
<> 128:9bcdf88f62b0 3 /** @{*/
<> 128:9bcdf88f62b0 4 /* mbed Microcontroller Library
<> 128:9bcdf88f62b0 5 * Copyright (c) 2006-2013 ARM Limited
<> 128:9bcdf88f62b0 6 *
<> 128:9bcdf88f62b0 7 * Licensed under the Apache License, Version 2.0 (the "License");
<> 128:9bcdf88f62b0 8 * you may not use this file except in compliance with the License.
<> 128:9bcdf88f62b0 9 * You may obtain a copy of the License at
<> 128:9bcdf88f62b0 10 *
<> 128:9bcdf88f62b0 11 * http://www.apache.org/licenses/LICENSE-2.0
<> 128:9bcdf88f62b0 12 *
<> 128:9bcdf88f62b0 13 * Unless required by applicable law or agreed to in writing, software
<> 128:9bcdf88f62b0 14 * distributed under the License is distributed on an "AS IS" BASIS,
<> 128:9bcdf88f62b0 15 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
<> 128:9bcdf88f62b0 16 * See the License for the specific language governing permissions and
<> 128:9bcdf88f62b0 17 * limitations under the License.
<> 128:9bcdf88f62b0 18 */
<> 128:9bcdf88f62b0 19 #ifndef SINGLETONPTR_H
<> 128:9bcdf88f62b0 20 #define SINGLETONPTR_H
<> 128:9bcdf88f62b0 21
<> 128:9bcdf88f62b0 22 #include <stdint.h>
<> 128:9bcdf88f62b0 23 #include <new>
<> 128:9bcdf88f62b0 24 #include "platform/mbed_assert.h"
<> 128:9bcdf88f62b0 25 #ifdef MBED_CONF_RTOS_PRESENT
<> 128:9bcdf88f62b0 26 #include "cmsis_os.h"
<> 128:9bcdf88f62b0 27 #endif
<> 128:9bcdf88f62b0 28
<> 128:9bcdf88f62b0 29 #ifdef MBED_CONF_RTOS_PRESENT
<> 128:9bcdf88f62b0 30 extern osMutexId singleton_mutex_id;
<> 128:9bcdf88f62b0 31 #endif
<> 128:9bcdf88f62b0 32
<> 128:9bcdf88f62b0 33 /** Lock the singleton mutex
<> 128:9bcdf88f62b0 34 *
<> 128:9bcdf88f62b0 35 * This function is typically used to provide
<> 128:9bcdf88f62b0 36 * exclusive access when initializing a
<> 128:9bcdf88f62b0 37 * global object.
<> 128:9bcdf88f62b0 38 */
<> 128:9bcdf88f62b0 39 inline static void singleton_lock(void)
<> 128:9bcdf88f62b0 40 {
<> 128:9bcdf88f62b0 41 #ifdef MBED_CONF_RTOS_PRESENT
<> 128:9bcdf88f62b0 42 osMutexWait(singleton_mutex_id, osWaitForever);
<> 128:9bcdf88f62b0 43 #endif
<> 128:9bcdf88f62b0 44 }
<> 128:9bcdf88f62b0 45
<> 128:9bcdf88f62b0 46 /** Unlock the singleton mutex
<> 128:9bcdf88f62b0 47 *
<> 128:9bcdf88f62b0 48 * This function is typically used to provide
<> 128:9bcdf88f62b0 49 * exclusive access when initializing a
<> 128:9bcdf88f62b0 50 * global object.
<> 128:9bcdf88f62b0 51 */
<> 128:9bcdf88f62b0 52 inline static void singleton_unlock(void)
<> 128:9bcdf88f62b0 53 {
<> 128:9bcdf88f62b0 54 #ifdef MBED_CONF_RTOS_PRESENT
<> 128:9bcdf88f62b0 55 osMutexRelease (singleton_mutex_id);
<> 128:9bcdf88f62b0 56 #endif
<> 128:9bcdf88f62b0 57 }
<> 128:9bcdf88f62b0 58
<> 128:9bcdf88f62b0 59 /** Utility class for creating an using a singleton
<> 128:9bcdf88f62b0 60 *
<> 128:9bcdf88f62b0 61 * @Note Synchronization level: Thread safe
<> 128:9bcdf88f62b0 62 *
<> 128:9bcdf88f62b0 63 * @Note: This class must only be used in a static context -
<> 128:9bcdf88f62b0 64 * this class must never be allocated or created on the
<> 128:9bcdf88f62b0 65 * stack.
<> 128:9bcdf88f62b0 66 *
<> 128:9bcdf88f62b0 67 * @Note: This class is lazily initialized on first use.
<> 128:9bcdf88f62b0 68 * This class is a POD type so if it is not used it will
<> 128:9bcdf88f62b0 69 * be garbage collected.
<> 128:9bcdf88f62b0 70 */
<> 128:9bcdf88f62b0 71 template <class T>
<> 128:9bcdf88f62b0 72 struct SingletonPtr {
<> 128:9bcdf88f62b0 73
<> 128:9bcdf88f62b0 74 /** Get a pointer to the underlying singleton
<> 128:9bcdf88f62b0 75 *
<> 128:9bcdf88f62b0 76 * @returns
<> 128:9bcdf88f62b0 77 * A pointer to the singleton
<> 128:9bcdf88f62b0 78 */
<> 128:9bcdf88f62b0 79 T* get() {
<> 128:9bcdf88f62b0 80 if (NULL == _ptr) {
<> 128:9bcdf88f62b0 81 singleton_lock();
<> 128:9bcdf88f62b0 82 if (NULL == _ptr) {
<> 128:9bcdf88f62b0 83 _ptr = new (_data) T();
<> 128:9bcdf88f62b0 84 }
<> 128:9bcdf88f62b0 85 singleton_unlock();
<> 128:9bcdf88f62b0 86 }
<> 128:9bcdf88f62b0 87 // _ptr was not zero initialized or was
<> 128:9bcdf88f62b0 88 // corrupted if this assert is hit
<> 128:9bcdf88f62b0 89 MBED_ASSERT(_ptr == (T *)&_data);
<> 128:9bcdf88f62b0 90 return _ptr;
<> 128:9bcdf88f62b0 91 }
<> 128:9bcdf88f62b0 92
<> 128:9bcdf88f62b0 93 /** Get a pointer to the underlying singleton
<> 128:9bcdf88f62b0 94 *
<> 128:9bcdf88f62b0 95 * @returns
<> 128:9bcdf88f62b0 96 * A pointer to the singleton
<> 128:9bcdf88f62b0 97 */
<> 128:9bcdf88f62b0 98 T* operator->() {
<> 128:9bcdf88f62b0 99 return get();
<> 128:9bcdf88f62b0 100 }
<> 128:9bcdf88f62b0 101
<> 128:9bcdf88f62b0 102 // This is zero initialized when in global scope
<> 128:9bcdf88f62b0 103 T *_ptr;
<> 128:9bcdf88f62b0 104 // Force data to be 4 byte aligned
<> 128:9bcdf88f62b0 105 uint32_t _data[(sizeof(T) + sizeof(uint32_t) - 1) / sizeof(uint32_t)];
<> 128:9bcdf88f62b0 106 };
<> 128:9bcdf88f62b0 107
<> 128:9bcdf88f62b0 108 #endif
<> 128:9bcdf88f62b0 109
<> 128:9bcdf88f62b0 110 /** @}*/