1/* 2 * Copyright (c) 2002-2005 The Regents of The University of Michigan 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions are 7 * met: redistributions of source code must retain the above copyright 8 * notice, this list of conditions and the following disclaimer; 9 * redistributions in binary form must reproduce the above copyright 10 * notice, this list of conditions and the following disclaimer in the 11 * documentation and/or other materials provided with the distribution; 12 * neither the name of the copyright holders nor the names of its 13 * contributors may be used to endorse or promote products derived from 14 * this software without specific prior written permission. 15 * 16 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 17 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 18 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 19 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 20 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 21 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 22 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 24 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 26 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 27 * 28 * Authors: Nathan Binkert 29 */ 30 31#ifndef __BASE_REFCNT_HH__ 32#define __BASE_REFCNT_HH__ 33
|
34/** 35 * @file base/refcnt.hh 36 * 37 * Classes for managing reference counted objects. 38 */ 39 40/** 41 * Derive from RefCounted if you want to enable reference counting of 42 * this class. If you want to use automatic reference counting, you 43 * should use RefCountingPtr<T> instead of regular pointers. 44 */ |
45class RefCounted 46{ 47 private:
|
48 // The reference count is mutable because one may want to 49 // reference count a const pointer. This really is OK because 50 // const is about logical constness of the object not really about 51 // strictly disallowing an object to change. |
52 mutable int count; 53 54 private: 55 // Don't allow a default copy constructor or copy operator on 56 // these objects because the default operation will copy the 57 // reference count as well and we certainly don't want that. 58 RefCounted(const RefCounted &); 59 RefCounted &operator=(const RefCounted &); 60 61 public:
|
62 /** 63 * We initialize the reference count to zero and the first object 64 * to take ownership of it must increment it to one. 65 * 66 * @attention A memory leak will occur if you never assign a newly 67 * constructed object to a reference counting pointer. 68 */ |
69 RefCounted() : count(0) {}
|
70 71 /** 72 * We make the destructor virtual because we're likely to have 73 * virtual functions on reference counted objects. 74 * 75 * @todo Even if this were true, does it matter? Shouldn't the 76 * derived class indicate this? This only matters if we would 77 * ever choose to delete a "RefCounted *" which I doubt we'd ever 78 * do. We don't ever delete a "void *". 79 */ |
80 virtual ~RefCounted() {} 81
|
82 /// Increment the reference count |
83 void incref() { ++count; }
|
84 85 /// Decrement the reference count and destroy the object if all 86 /// references are gone. |
87 void decref() { if (--count <= 0) delete this; } 88}; 89
|
90/** 91 * If you want a reference counting pointer to a mutable object, 92 * create it like this: 93 * @code 94 * typedef RefCountingPtr<Foo> FooPtr; 95 * @endcode 96 * 97 * @attention Do not use "const FooPtr" 98 * To create a reference counting pointer to a const object, use this: 99 * @code 100 * typedef RefCountingPtr<const Foo> ConstFooPtr; 101 * @endcode 102 * 103 * These two usages are analogous to iterator and const_iterator in the stl. 104 */ |
105template <class T> 106class RefCountingPtr 107{ 108 protected:
|
109 /// The stored pointer. 110 /// Arguably this should be private. |
111 T *data; 112
|
60 void copy(T *d)
|
113 /** 114 * Copy a new pointer value and increment the reference count if 115 * it is a valid pointer. Note, this does not delete the 116 * reference any existing object. 117 * @param d Pointer to store. 118 */ 119 void 120 copy(T *d) |
121 { 122 data = d; 123 if (data) 124 data->incref(); 125 }
|
66 void del()
|
126 127 /** 128 * Delete the reference to any existing object if it is non NULL. 129 * @attention this doesn't clear the pointer value, so a double 130 * decref could happen if not careful. 131 */ 132 void 133 del() |
134 { 135 if (data) 136 data->decref(); 137 }
|
71 void set(T *d)
72 {
73 if (data == d)
74 return;
|
138
|
76 del();
77 copy(d);
|
139 /** 140 * Drop the old reference and change it to something new. 141 */ 142 void 143 set(T *d) 144 { 145 // Need to check if we're actually changing because otherwise 146 // we could delete the last reference before adding the new 147 // reference. 148 if (data != d) { 149 del(); 150 copy(d); 151 } |
152 } 153
|
80
|
154 public:
|
155 /// Create an empty reference counting pointer. |
156 RefCountingPtr() : data(0) {}
|
157 158 /// Create a new reference counting pointer to some object 159 /// (probably something newly created). Adds a reference. |
160 RefCountingPtr(T *data) { copy(data); }
|
161 162 /// Create a new reference counting pointer by copying another 163 /// one. Adds a reference. |
164 RefCountingPtr(const RefCountingPtr &r) { copy(r.data); }
|
165 166 /// Destroy the pointer and any reference it may hold. |
167 ~RefCountingPtr() { del(); } 168
|
169 // The following pointer access functions are const because they 170 // don't actually change the pointer, though the user could change 171 // what is pointed to. This is analagous to a "Foo * const". 172 173 /// Access a member variable. |
174 T *operator->() const { return data; }
|
175 176 /// Dereference the pointer. |
177 T &operator*() const { return *data; }
|
178 179 /// Directly access the pointer itself without taking a reference. |
180 T *get() const { return data; } 181
|
182 /// Assign a new value to the pointer |
183 const RefCountingPtr &operator=(T *p) { set(p); return *this; }
|
184 185 /// Copy the pointer from another RefCountingPtr |
186 const RefCountingPtr &operator=(const RefCountingPtr &r) 187 { return operator=(r.data); } 188
|
189 /// Check if the pointer is empty |
190 bool operator!() const { return data == 0; }
|
191 192 /// Check if the pointer is non-empty |
193 operator bool() const { return data != 0; } 194}; 195
|
196/// Check for equality of two reference counting pointers. |
197template<class T> 198inline bool operator==(const RefCountingPtr<T> &l, const RefCountingPtr<T> &r) 199{ return l.get() == r.get(); } 200
|
201/// Check for equality of of a reference counting pointers and a 202/// regular pointer |
203template<class T> 204inline bool operator==(const RefCountingPtr<T> &l, const T *r) 205{ return l.get() == r; } 206
|
207/// Check for equality of of a reference counting pointers and a 208/// regular pointer |
209template<class T> 210inline bool operator==(const T *l, const RefCountingPtr<T> &r) 211{ return l == r.get(); } 212
|
213/// Check for inequality of two reference counting pointers. |
214template<class T> 215inline bool operator!=(const RefCountingPtr<T> &l, const RefCountingPtr<T> &r) 216{ return l.get() != r.get(); } 217
|
218/// Check for inequality of of a reference counting pointers and a 219/// regular pointer |
220template<class T> 221inline bool operator!=(const RefCountingPtr<T> &l, const T *r) 222{ return l.get() != r; } 223
|
224/// Check for inequality of of a reference counting pointers and a 225/// regular pointer |
226template<class T> 227inline bool operator!=(const T *l, const RefCountingPtr<T> &r) 228{ return l != r.get(); } 229 230#endif // __BASE_REFCNT_HH__
|