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platform/SharedPtr.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 171:3a7713b1edbc 1 /* mbed Microcontroller Library
AnnaBridge 171:3a7713b1edbc 2 * Copyright (c) 2006-2018 ARM Limited
AnnaBridge 172:65be27845400 3 * SPDX-License-Identifier: Apache-2.0
AnnaBridge 171:3a7713b1edbc 4 *
AnnaBridge 171:3a7713b1edbc 5 * Licensed under the Apache License, Version 2.0 (the "License");
AnnaBridge 171:3a7713b1edbc 6 * you may not use this file except in compliance with the License.
AnnaBridge 171:3a7713b1edbc 7 * You may obtain a copy of the License at
AnnaBridge 171:3a7713b1edbc 8 *
AnnaBridge 171:3a7713b1edbc 9 * http://www.apache.org/licenses/LICENSE-2.0
AnnaBridge 171:3a7713b1edbc 10 *
AnnaBridge 171:3a7713b1edbc 11 * Unless required by applicable law or agreed to in writing, software
AnnaBridge 171:3a7713b1edbc 12 * distributed under the License is distributed on an "AS IS" BASIS,
AnnaBridge 171:3a7713b1edbc 13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
AnnaBridge 171:3a7713b1edbc 14 * See the License for the specific language governing permissions and
AnnaBridge 171:3a7713b1edbc 15 * limitations under the License.
AnnaBridge 171:3a7713b1edbc 16 */
AnnaBridge 171:3a7713b1edbc 17
AnnaBridge 171:3a7713b1edbc 18 #ifndef __SHAREDPTR_H__
AnnaBridge 171:3a7713b1edbc 19 #define __SHAREDPTR_H__
AnnaBridge 171:3a7713b1edbc 20
AnnaBridge 171:3a7713b1edbc 21 #include <stdlib.h>
AnnaBridge 171:3a7713b1edbc 22
AnnaBridge 171:3a7713b1edbc 23 #include <stdint.h>
AnnaBridge 171:3a7713b1edbc 24 #include <stddef.h>
AnnaBridge 171:3a7713b1edbc 25
AnnaBridge 171:3a7713b1edbc 26 #include "platform/mbed_critical.h"
AnnaBridge 171:3a7713b1edbc 27
AnnaBridge 172:65be27845400 28 namespace mbed {
AnnaBridge 172:65be27845400 29
AnnaBridge 171:3a7713b1edbc 30 /** Shared pointer class.
AnnaBridge 171:3a7713b1edbc 31 *
AnnaBridge 171:3a7713b1edbc 32 * A shared pointer is a "smart" pointer that retains ownership of an object using
AnnaBridge 172:65be27845400 33 * reference counting across all smart pointers referencing that object.
AnnaBridge 171:3a7713b1edbc 34 *
AnnaBridge 171:3a7713b1edbc 35 * @code
AnnaBridge 171:3a7713b1edbc 36 * #include "platform/SharedPtr.h"
AnnaBridge 171:3a7713b1edbc 37 *
AnnaBridge 171:3a7713b1edbc 38 * void test() {
AnnaBridge 171:3a7713b1edbc 39 * struct MyStruct { int a; };
AnnaBridge 171:3a7713b1edbc 40 *
AnnaBridge 171:3a7713b1edbc 41 * // Create shared pointer
AnnaBridge 171:3a7713b1edbc 42 * SharedPtr<MyStruct> ptr( new MyStruct );
AnnaBridge 171:3a7713b1edbc 43 *
AnnaBridge 171:3a7713b1edbc 44 * // Increase reference count
AnnaBridge 171:3a7713b1edbc 45 * SharedPtr<MyStruct> ptr2( ptr );
AnnaBridge 171:3a7713b1edbc 46 *
AnnaBridge 171:3a7713b1edbc 47 * ptr = NULL; // Reference to the struct instance is still held by ptr2
AnnaBridge 171:3a7713b1edbc 48 *
AnnaBridge 171:3a7713b1edbc 49 * ptr2 = NULL; // The raw pointer is freed
AnnaBridge 171:3a7713b1edbc 50 * }
AnnaBridge 171:3a7713b1edbc 51 * @endcode
AnnaBridge 171:3a7713b1edbc 52 *
AnnaBridge 171:3a7713b1edbc 53 *
AnnaBridge 171:3a7713b1edbc 54 * It is similar to the std::shared_ptr class introduced in C++11;
AnnaBridge 171:3a7713b1edbc 55 * however, this is not a compatible implementation (no weak pointer, no make_shared, no custom deleters and so on.)
AnnaBridge 171:3a7713b1edbc 56 *
AnnaBridge 171:3a7713b1edbc 57 * Usage: SharedPtr<Class> ptr(new Class())
AnnaBridge 171:3a7713b1edbc 58 *
AnnaBridge 171:3a7713b1edbc 59 * When ptr is passed around by value, the copy constructor and
AnnaBridge 171:3a7713b1edbc 60 * destructor manages the reference count of the raw pointer.
AnnaBridge 171:3a7713b1edbc 61 * If the counter reaches zero, delete is called on the raw pointer.
AnnaBridge 171:3a7713b1edbc 62 *
AnnaBridge 171:3a7713b1edbc 63 * To avoid loops, use "weak" references by calling the original
AnnaBridge 171:3a7713b1edbc 64 * pointer directly through ptr.get().
AnnaBridge 171:3a7713b1edbc 65 */
AnnaBridge 171:3a7713b1edbc 66
AnnaBridge 171:3a7713b1edbc 67 template <class T>
AnnaBridge 171:3a7713b1edbc 68 class SharedPtr {
AnnaBridge 171:3a7713b1edbc 69 public:
AnnaBridge 171:3a7713b1edbc 70 /**
AnnaBridge 171:3a7713b1edbc 71 * @brief Create empty SharedPtr not pointing to anything.
AnnaBridge 171:3a7713b1edbc 72 * @details Used for variable declaration.
AnnaBridge 171:3a7713b1edbc 73 */
AnnaBridge 171:3a7713b1edbc 74 SharedPtr(): _ptr(NULL), _counter(NULL)
AnnaBridge 171:3a7713b1edbc 75 {
AnnaBridge 171:3a7713b1edbc 76 }
AnnaBridge 171:3a7713b1edbc 77
AnnaBridge 171:3a7713b1edbc 78 /**
AnnaBridge 171:3a7713b1edbc 79 * @brief Create new SharedPtr
AnnaBridge 171:3a7713b1edbc 80 * @param ptr Pointer to take control over
AnnaBridge 171:3a7713b1edbc 81 */
AnnaBridge 171:3a7713b1edbc 82 SharedPtr(T *ptr): _ptr(ptr), _counter(NULL)
AnnaBridge 171:3a7713b1edbc 83 {
AnnaBridge 171:3a7713b1edbc 84 // Allocate counter on the heap, so it can be shared
AnnaBridge 171:3a7713b1edbc 85 if (_ptr != NULL) {
AnnaBridge 171:3a7713b1edbc 86 _counter = new uint32_t;
AnnaBridge 171:3a7713b1edbc 87 *_counter = 1;
AnnaBridge 171:3a7713b1edbc 88 }
AnnaBridge 171:3a7713b1edbc 89 }
AnnaBridge 171:3a7713b1edbc 90
AnnaBridge 171:3a7713b1edbc 91 /**
AnnaBridge 171:3a7713b1edbc 92 * @brief Destructor.
AnnaBridge 171:3a7713b1edbc 93 * @details Decrement reference counter, and delete object if no longer pointed to.
AnnaBridge 171:3a7713b1edbc 94 */
AnnaBridge 171:3a7713b1edbc 95 ~SharedPtr()
AnnaBridge 171:3a7713b1edbc 96 {
AnnaBridge 171:3a7713b1edbc 97 decrement_counter();
AnnaBridge 171:3a7713b1edbc 98 }
AnnaBridge 171:3a7713b1edbc 99
AnnaBridge 171:3a7713b1edbc 100 /**
AnnaBridge 171:3a7713b1edbc 101 * @brief Copy constructor.
AnnaBridge 171:3a7713b1edbc 102 * @details Create new SharedPtr from other SharedPtr by
AnnaBridge 171:3a7713b1edbc 103 * copying pointer to original object and pointer to counter.
AnnaBridge 171:3a7713b1edbc 104 * @param source Object being copied from.
AnnaBridge 171:3a7713b1edbc 105 */
AnnaBridge 171:3a7713b1edbc 106 SharedPtr(const SharedPtr &source): _ptr(source._ptr), _counter(source._counter)
AnnaBridge 171:3a7713b1edbc 107 {
AnnaBridge 171:3a7713b1edbc 108 // Increment reference counter
AnnaBridge 171:3a7713b1edbc 109 if (_ptr != NULL) {
AnnaBridge 171:3a7713b1edbc 110 core_util_atomic_incr_u32(_counter, 1);
AnnaBridge 171:3a7713b1edbc 111 }
AnnaBridge 171:3a7713b1edbc 112 }
AnnaBridge 171:3a7713b1edbc 113
AnnaBridge 171:3a7713b1edbc 114 /**
AnnaBridge 171:3a7713b1edbc 115 * @brief Assignment operator.
AnnaBridge 171:3a7713b1edbc 116 * @details Cleanup previous reference and assign new pointer and counter.
AnnaBridge 171:3a7713b1edbc 117 * @param source Object being assigned from.
AnnaBridge 171:3a7713b1edbc 118 * @return Object being assigned.
AnnaBridge 171:3a7713b1edbc 119 */
AnnaBridge 171:3a7713b1edbc 120 SharedPtr operator=(const SharedPtr &source)
AnnaBridge 171:3a7713b1edbc 121 {
AnnaBridge 171:3a7713b1edbc 122 if (this != &source) {
AnnaBridge 171:3a7713b1edbc 123 // Clean up by decrementing counter
AnnaBridge 171:3a7713b1edbc 124 decrement_counter();
AnnaBridge 171:3a7713b1edbc 125
AnnaBridge 171:3a7713b1edbc 126 // Assign new values
AnnaBridge 171:3a7713b1edbc 127 _ptr = source.get();
AnnaBridge 171:3a7713b1edbc 128 _counter = source.get_counter();
AnnaBridge 171:3a7713b1edbc 129
AnnaBridge 171:3a7713b1edbc 130 // Increment new counter
AnnaBridge 171:3a7713b1edbc 131 if (_ptr != NULL) {
AnnaBridge 171:3a7713b1edbc 132 core_util_atomic_incr_u32(_counter, 1);
AnnaBridge 171:3a7713b1edbc 133 }
AnnaBridge 171:3a7713b1edbc 134 }
AnnaBridge 171:3a7713b1edbc 135
AnnaBridge 171:3a7713b1edbc 136 return *this;
AnnaBridge 171:3a7713b1edbc 137 }
AnnaBridge 171:3a7713b1edbc 138
AnnaBridge 171:3a7713b1edbc 139 /**
AnnaBridge 171:3a7713b1edbc 140 * @brief Replaces the managed pointer with a new unmanaged pointer.
AnnaBridge 171:3a7713b1edbc 141 * @param[in] ptr the new raw pointer to manage.
AnnaBridge 171:3a7713b1edbc 142 */
AnnaBridge 171:3a7713b1edbc 143 void reset(T *ptr)
AnnaBridge 171:3a7713b1edbc 144 {
AnnaBridge 171:3a7713b1edbc 145 // Clean up by decrementing counter
AnnaBridge 171:3a7713b1edbc 146 decrement_counter();
AnnaBridge 171:3a7713b1edbc 147
AnnaBridge 172:65be27845400 148 _ptr = ptr;
AnnaBridge 171:3a7713b1edbc 149 if (ptr != NULL) {
AnnaBridge 171:3a7713b1edbc 150 // Allocate counter on the heap, so it can be shared
AnnaBridge 171:3a7713b1edbc 151 _counter = new uint32_t;
AnnaBridge 171:3a7713b1edbc 152 *_counter = 1;
AnnaBridge 172:65be27845400 153 } else {
AnnaBridge 172:65be27845400 154 _counter = NULL;
AnnaBridge 171:3a7713b1edbc 155 }
AnnaBridge 171:3a7713b1edbc 156 }
AnnaBridge 171:3a7713b1edbc 157
AnnaBridge 171:3a7713b1edbc 158 /**
AnnaBridge 171:3a7713b1edbc 159 * @brief Replace the managed pointer with a NULL pointer.
AnnaBridge 171:3a7713b1edbc 160 */
AnnaBridge 171:3a7713b1edbc 161 void reset()
AnnaBridge 171:3a7713b1edbc 162 {
AnnaBridge 171:3a7713b1edbc 163 reset(NULL);
AnnaBridge 171:3a7713b1edbc 164 }
AnnaBridge 171:3a7713b1edbc 165
AnnaBridge 171:3a7713b1edbc 166 /**
AnnaBridge 171:3a7713b1edbc 167 * @brief Raw pointer accessor.
AnnaBridge 171:3a7713b1edbc 168 * @details Get raw pointer to object pointed to.
AnnaBridge 171:3a7713b1edbc 169 * @return Pointer.
AnnaBridge 171:3a7713b1edbc 170 */
AnnaBridge 171:3a7713b1edbc 171 T *get() const
AnnaBridge 171:3a7713b1edbc 172 {
AnnaBridge 171:3a7713b1edbc 173 return _ptr;
AnnaBridge 171:3a7713b1edbc 174 }
AnnaBridge 171:3a7713b1edbc 175
AnnaBridge 171:3a7713b1edbc 176 /**
AnnaBridge 171:3a7713b1edbc 177 * @brief Reference count accessor.
AnnaBridge 171:3a7713b1edbc 178 * @return Reference count.
AnnaBridge 171:3a7713b1edbc 179 */
AnnaBridge 171:3a7713b1edbc 180 uint32_t use_count() const
AnnaBridge 171:3a7713b1edbc 181 {
AnnaBridge 171:3a7713b1edbc 182 if (_ptr != NULL) {
AnnaBridge 171:3a7713b1edbc 183 core_util_critical_section_enter();
AnnaBridge 171:3a7713b1edbc 184 uint32_t current_counter = *_counter;
AnnaBridge 171:3a7713b1edbc 185 core_util_critical_section_exit();
AnnaBridge 171:3a7713b1edbc 186 return current_counter;
AnnaBridge 171:3a7713b1edbc 187 } else {
AnnaBridge 171:3a7713b1edbc 188 return 0;
AnnaBridge 171:3a7713b1edbc 189 }
AnnaBridge 171:3a7713b1edbc 190 }
AnnaBridge 171:3a7713b1edbc 191
AnnaBridge 171:3a7713b1edbc 192 /**
AnnaBridge 171:3a7713b1edbc 193 * @brief Dereference object operator.
AnnaBridge 171:3a7713b1edbc 194 * @details Override to return the object pointed to.
AnnaBridge 171:3a7713b1edbc 195 */
AnnaBridge 171:3a7713b1edbc 196 T &operator*() const
AnnaBridge 171:3a7713b1edbc 197 {
AnnaBridge 171:3a7713b1edbc 198 return *_ptr;
AnnaBridge 171:3a7713b1edbc 199 }
AnnaBridge 171:3a7713b1edbc 200
AnnaBridge 171:3a7713b1edbc 201 /**
AnnaBridge 171:3a7713b1edbc 202 * @brief Dereference object member operator.
AnnaBridge 171:3a7713b1edbc 203 * @details Override to return return member in object pointed to.
AnnaBridge 171:3a7713b1edbc 204 */
AnnaBridge 171:3a7713b1edbc 205 T *operator->() const
AnnaBridge 171:3a7713b1edbc 206 {
AnnaBridge 171:3a7713b1edbc 207 return _ptr;
AnnaBridge 171:3a7713b1edbc 208 }
AnnaBridge 171:3a7713b1edbc 209
AnnaBridge 171:3a7713b1edbc 210 /**
AnnaBridge 171:3a7713b1edbc 211 * @brief Boolean conversion operator.
AnnaBridge 171:3a7713b1edbc 212 * @return Whether or not the pointer is NULL.
AnnaBridge 171:3a7713b1edbc 213 */
AnnaBridge 171:3a7713b1edbc 214 operator bool() const
AnnaBridge 171:3a7713b1edbc 215 {
AnnaBridge 171:3a7713b1edbc 216 return (_ptr != NULL);
AnnaBridge 171:3a7713b1edbc 217 }
AnnaBridge 171:3a7713b1edbc 218
AnnaBridge 171:3a7713b1edbc 219 private:
AnnaBridge 171:3a7713b1edbc 220 /**
AnnaBridge 171:3a7713b1edbc 221 * @brief Get pointer to reference counter.
AnnaBridge 171:3a7713b1edbc 222 * @return Pointer to reference counter.
AnnaBridge 171:3a7713b1edbc 223 */
AnnaBridge 171:3a7713b1edbc 224 uint32_t *get_counter() const
AnnaBridge 171:3a7713b1edbc 225 {
AnnaBridge 171:3a7713b1edbc 226 return _counter;
AnnaBridge 171:3a7713b1edbc 227 }
AnnaBridge 171:3a7713b1edbc 228
AnnaBridge 171:3a7713b1edbc 229 /**
AnnaBridge 171:3a7713b1edbc 230 * @brief Decrement reference counter.
AnnaBridge 171:3a7713b1edbc 231 * @details If count reaches zero, free counter and delete object pointed to.
AnnaBridge 172:65be27845400 232 * Does not modify our own pointers - assumption is they will be overwritten
AnnaBridge 172:65be27845400 233 * or destroyed immediately afterwards.
AnnaBridge 171:3a7713b1edbc 234 */
AnnaBridge 171:3a7713b1edbc 235 void decrement_counter()
AnnaBridge 171:3a7713b1edbc 236 {
AnnaBridge 171:3a7713b1edbc 237 if (_ptr != NULL) {
AnnaBridge 171:3a7713b1edbc 238 uint32_t new_value = core_util_atomic_decr_u32(_counter, 1);
AnnaBridge 171:3a7713b1edbc 239 if (new_value == 0) {
AnnaBridge 171:3a7713b1edbc 240 delete _counter;
AnnaBridge 171:3a7713b1edbc 241 delete _ptr;
AnnaBridge 171:3a7713b1edbc 242 }
AnnaBridge 171:3a7713b1edbc 243 }
AnnaBridge 171:3a7713b1edbc 244 }
AnnaBridge 171:3a7713b1edbc 245
AnnaBridge 171:3a7713b1edbc 246 private:
AnnaBridge 171:3a7713b1edbc 247 // Pointer to shared object
AnnaBridge 171:3a7713b1edbc 248 T *_ptr;
AnnaBridge 171:3a7713b1edbc 249
AnnaBridge 171:3a7713b1edbc 250 // Pointer to shared reference counter
AnnaBridge 171:3a7713b1edbc 251 uint32_t *_counter;
AnnaBridge 171:3a7713b1edbc 252 };
AnnaBridge 171:3a7713b1edbc 253
AnnaBridge 171:3a7713b1edbc 254 /** Non-member relational operators.
AnnaBridge 171:3a7713b1edbc 255 */
AnnaBridge 171:3a7713b1edbc 256 template <class T, class U>
AnnaBridge 171:3a7713b1edbc 257 bool operator== (const SharedPtr<T> &lhs, const SharedPtr<U> &rhs)
AnnaBridge 171:3a7713b1edbc 258 {
AnnaBridge 171:3a7713b1edbc 259 return (lhs.get() == rhs.get());
AnnaBridge 171:3a7713b1edbc 260 }
AnnaBridge 171:3a7713b1edbc 261
AnnaBridge 171:3a7713b1edbc 262 template <class T, typename U>
AnnaBridge 171:3a7713b1edbc 263 bool operator== (const SharedPtr<T> &lhs, U rhs)
AnnaBridge 171:3a7713b1edbc 264 {
AnnaBridge 171:3a7713b1edbc 265 return (lhs.get() == (T *) rhs);
AnnaBridge 171:3a7713b1edbc 266 }
AnnaBridge 171:3a7713b1edbc 267
AnnaBridge 171:3a7713b1edbc 268 template <class T, typename U>
AnnaBridge 171:3a7713b1edbc 269 bool operator== (U lhs, const SharedPtr<T> &rhs)
AnnaBridge 171:3a7713b1edbc 270 {
AnnaBridge 171:3a7713b1edbc 271 return ((T *) lhs == rhs.get());
AnnaBridge 171:3a7713b1edbc 272 }
AnnaBridge 171:3a7713b1edbc 273
AnnaBridge 171:3a7713b1edbc 274 /** Non-member relational operators.
AnnaBridge 171:3a7713b1edbc 275 */
AnnaBridge 171:3a7713b1edbc 276 template <class T, class U>
AnnaBridge 171:3a7713b1edbc 277 bool operator!= (const SharedPtr<T> &lhs, const SharedPtr<U> &rhs)
AnnaBridge 171:3a7713b1edbc 278 {
AnnaBridge 171:3a7713b1edbc 279 return (lhs.get() != rhs.get());
AnnaBridge 171:3a7713b1edbc 280 }
AnnaBridge 171:3a7713b1edbc 281
AnnaBridge 171:3a7713b1edbc 282 template <class T, typename U>
AnnaBridge 171:3a7713b1edbc 283 bool operator!= (const SharedPtr<T> &lhs, U rhs)
AnnaBridge 171:3a7713b1edbc 284 {
AnnaBridge 171:3a7713b1edbc 285 return (lhs.get() != (T *) rhs);
AnnaBridge 171:3a7713b1edbc 286 }
AnnaBridge 171:3a7713b1edbc 287
AnnaBridge 171:3a7713b1edbc 288 template <class T, typename U>
AnnaBridge 171:3a7713b1edbc 289 bool operator!= (U lhs, const SharedPtr<T> &rhs)
AnnaBridge 171:3a7713b1edbc 290 {
AnnaBridge 171:3a7713b1edbc 291 return ((T *) lhs != rhs.get());
AnnaBridge 171:3a7713b1edbc 292 }
AnnaBridge 171:3a7713b1edbc 293
AnnaBridge 172:65be27845400 294 } /* namespace mbed */
AnnaBridge 172:65be27845400 295
AnnaBridge 172:65be27845400 296 #ifndef MBED_NO_GLOBAL_USING_DIRECTIVE
AnnaBridge 172:65be27845400 297 using mbed::SharedPtr;
AnnaBridge 172:65be27845400 298 #endif
AnnaBridge 172:65be27845400 299
AnnaBridge 171:3a7713b1edbc 300 #endif // __SHAREDPTR_H__