mirror of https://github.com/ARMmbed/mbed-os.git
147 lines
3.5 KiB
C++
147 lines
3.5 KiB
C++
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/** \addtogroup platform */
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/** @{*/
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/**
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* \defgroup platform_SingletonPtr SingletonPtr class
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* @{
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*/
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/* mbed Microcontroller Library
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* Copyright (c) 2006-2013 ARM Limited
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* SPDX-License-Identifier: Apache-2.0
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef SINGLETONPTR_H
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#define SINGLETONPTR_H
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#include <stdlib.h>
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#include <stdint.h>
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#include <new>
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#include "platform/mbed_assert.h"
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#include "platform/mbed_critical.h"
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#ifdef MBED_CONF_RTOS_PRESENT
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#include "cmsis_os2.h"
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#endif
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#ifdef MBED_CONF_RTOS_PRESENT
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extern osMutexId_t singleton_mutex_id;
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#endif
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/** Lock the singleton mutex
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*
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* This function is typically used to provide
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* exclusive access when initializing a
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* global object.
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*/
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inline static void singleton_lock(void)
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{
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#ifdef MBED_CONF_RTOS_PRESENT
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if (!singleton_mutex_id) {
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// RTOS has not booted yet so no mutex is needed
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return;
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}
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osMutexAcquire(singleton_mutex_id, osWaitForever);
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#endif
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}
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/** Unlock the singleton mutex
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*
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* This function is typically used to provide
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* exclusive access when initializing a
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* global object.
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*/
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inline static void singleton_unlock(void)
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{
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#ifdef MBED_CONF_RTOS_PRESENT
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if (!singleton_mutex_id) {
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// RTOS has not booted yet so no mutex is needed
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return;
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}
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osMutexRelease(singleton_mutex_id);
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#endif
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}
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/** Utility class for creating an using a singleton
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*
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* @note Synchronization level: Thread safe
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*
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* @note: This class must only be used in a static context -
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* this class must never be allocated or created on the
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* stack.
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*
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* @note: This class is lazily initialized on first use.
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* This class is a POD type so if it is not used it will
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* be garbage collected.
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*/
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template <class T>
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struct SingletonPtr {
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/** Get a pointer to the underlying singleton
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*
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* @returns
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* A pointer to the singleton
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*/
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T *get() const
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{
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T *p = static_cast<T *>(core_util_atomic_load_ptr(&_ptr));
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if (p == NULL) {
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singleton_lock();
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p = static_cast<T *>(_ptr);
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if (p == NULL) {
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p = new (_data) T();
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core_util_atomic_store_ptr(&_ptr, p);
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}
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singleton_unlock();
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}
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// _ptr was not zero initialized or was
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// corrupted if this assert is hit
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MBED_ASSERT(p == reinterpret_cast<T *>(&_data));
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return p;
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}
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/** Get a pointer to the underlying singleton
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*
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* @returns
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* A pointer to the singleton
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*/
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T *operator->() const
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{
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return get();
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}
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/** Get a reference to the underlying singleton
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*
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* @returns
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* A reference to the singleton
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*/
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T &operator*() const
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{
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return *get();
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}
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// This is zero initialized when in global scope
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mutable void *_ptr;
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#if __cplusplus >= 201103L
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// Align data appropriately
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alignas(T) mutable char _data[sizeof(T)];
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#else
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// Force data to be 8 byte aligned
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mutable uint64_t _data[(sizeof(T) + sizeof(uint64_t) - 1) / sizeof(uint64_t)];
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#endif
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};
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#endif
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/**@}*/
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/**@}*/
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