1 /* 2 * libjingle 3 * Copyright 2004--2005, Google Inc. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions are met: 7 * 8 * 1. Redistributions of source code must retain the above copyright notice, 9 * this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright notice, 11 * this list of conditions and the following disclaimer in the documentation 12 * and/or other materials provided with the distribution. 13 * 3. The name of the author may not be used to endorse or promote products 14 * derived from this software without specific prior written permission. 15 * 16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED 17 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF 18 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO 19 * EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 20 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, 21 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; 22 * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, 23 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR 24 * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF 25 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 26 */ 27 28 /* 29 * linked_ptr - simple reference linked pointer 30 * (like reference counting, just using a linked list of the references 31 * instead of their count.) 32 * 33 * The implementation stores three pointers for every linked_ptr, but 34 * does not allocate anything on the free store. 35 */ 36 37 #ifndef TALK_BASE_LINKED_PTR_H__ 38 #define TALK_BASE_LINKED_PTR_H__ 39 40 namespace talk_base { 41 42 /* For ANSI-challenged compilers, you may want to #define 43 * NO_MEMBER_TEMPLATES, explicit or mutable */ 44 #define NO_MEMBER_TEMPLATES 45 46 template <class X> class linked_ptr 47 { 48 public: 49 50 #ifndef NO_MEMBER_TEMPLATES 51 # define TEMPLATE_FUNCTION template <class Y> 52 TEMPLATE_FUNCTION friend class linked_ptr<Y>; 53 #else 54 # define TEMPLATE_FUNCTION 55 typedef X Y; 56 #endif 57 58 typedef X element_type; 59 60 explicit linked_ptr(X* p = 0) throw() 61 : itsPtr(p) {itsPrev = itsNext = this;} 62 ~linked_ptr() 63 {release();} 64 linked_ptr(const linked_ptr& r) throw() 65 {acquire(r);} 66 linked_ptr& operator=(const linked_ptr& r) 67 { 68 if (this != &r) { 69 release(); 70 acquire(r); 71 } 72 return *this; 73 } 74 75 #ifndef NO_MEMBER_TEMPLATES 76 template <class Y> friend class linked_ptr<Y>; 77 template <class Y> linked_ptr(const linked_ptr<Y>& r) throw() 78 {acquire(r);} 79 template <class Y> linked_ptr& operator=(const linked_ptr<Y>& r) 80 { 81 if (this != &r) { 82 release(); 83 acquire(r); 84 } 85 return *this; 86 } 87 #endif // NO_MEMBER_TEMPLATES 88 89 X& operator*() const throw() {return *itsPtr;} 90 X* operator->() const throw() {return itsPtr;} 91 X* get() const throw() {return itsPtr;} 92 bool unique() const throw() {return itsPrev ? itsPrev==this : true;} 93 94 private: 95 X* itsPtr; 96 mutable const linked_ptr* itsPrev; 97 mutable const linked_ptr* itsNext; 98 99 void acquire(const linked_ptr& r) throw() 100 { // insert this to the list 101 itsPtr = r.itsPtr; 102 itsNext = r.itsNext; 103 itsNext->itsPrev = this; 104 itsPrev = &r; 105 #ifndef mutable 106 r.itsNext = this; 107 #else // for ANSI-challenged compilers 108 (const_cast<linked_ptr<X>*>(&r))->itsNext = this; 109 #endif 110 } 111 112 #ifndef NO_MEMBER_TEMPLATES 113 template <class Y> void acquire(const linked_ptr<Y>& r) throw() 114 { // insert this to the list 115 itsPtr = r.itsPtr; 116 itsNext = r.itsNext; 117 itsNext->itsPrev = this; 118 itsPrev = &r; 119 #ifndef mutable 120 r.itsNext = this; 121 #else // for ANSI-challenged compilers 122 (const_cast<linked_ptr<X>*>(&r))->itsNext = this; 123 #endif 124 } 125 #endif // NO_MEMBER_TEMPLATES 126 127 void release() 128 { // erase this from the list, delete if unique 129 if (unique()) delete itsPtr; 130 else { 131 itsPrev->itsNext = itsNext; 132 itsNext->itsPrev = itsPrev; 133 itsPrev = itsNext = 0; 134 } 135 itsPtr = 0; 136 } 137 }; 138 139 } // namespace talk_base 140 141 #endif // TALK_BASE_LINKED_PTR_H__ 142 143