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mbed 2

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platform/SharedPtr.h@171:3a7713b1edbc, 2018-11-08 (annotated)

Committer:
AnnaBridge
Date:
Thu Nov 08 11:45:42 2018 +0000
Revision:
171:3a7713b1edbc
Child:
172:65be27845400
mbed library. Release version 164

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