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| 1 /* |
| 2 * Copyright 2004 The WebRTC Project Authors. All rights reserved. |
| 3 * |
| 4 * Use of this source code is governed by a BSD-style license |
| 5 * that can be found in the LICENSE file in the root of the source |
| 6 * tree. An additional intellectual property rights grant can be found |
| 7 * in the file PATENTS. All contributing project authors may |
| 8 * be found in the AUTHORS file in the root of the source tree. |
| 9 */ |
| 10 |
| 11 /* |
| 12 * linked_ptr - simple reference linked pointer |
| 13 * (like reference counting, just using a linked list of the references |
| 14 * instead of their count.) |
| 15 * |
| 16 * The implementation stores three pointers for every linked_ptr, but |
| 17 * does not allocate anything on the free store. |
| 18 */ |
| 19 |
| 20 #ifndef WEBRTC_BASE_LINKED_PTR_H__ |
| 21 #define WEBRTC_BASE_LINKED_PTR_H__ |
| 22 |
| 23 namespace rtc { |
| 24 |
| 25 /* For ANSI-challenged compilers, you may want to #define |
| 26 * NO_MEMBER_TEMPLATES, explicit or mutable */ |
| 27 #define NO_MEMBER_TEMPLATES |
| 28 |
| 29 template <class X> class linked_ptr |
| 30 { |
| 31 public: |
| 32 |
| 33 #ifndef NO_MEMBER_TEMPLATES |
| 34 # define TEMPLATE_FUNCTION template <class Y> |
| 35 TEMPLATE_FUNCTION friend class linked_ptr<Y>; |
| 36 #else |
| 37 # define TEMPLATE_FUNCTION |
| 38 typedef X Y; |
| 39 #endif |
| 40 |
| 41 typedef X element_type; |
| 42 |
| 43 explicit linked_ptr(X* p = 0) throw() |
| 44 : itsPtr(p) {itsPrev = itsNext = this;} |
| 45 ~linked_ptr() |
| 46 {release();} |
| 47 linked_ptr(const linked_ptr& r) throw() |
| 48 {acquire(r);} |
| 49 linked_ptr& operator=(const linked_ptr& r) |
| 50 { |
| 51 if (this != &r) { |
| 52 release(); |
| 53 acquire(r); |
| 54 } |
| 55 return *this; |
| 56 } |
| 57 |
| 58 #ifndef NO_MEMBER_TEMPLATES |
| 59 template <class Y> friend class linked_ptr<Y>; |
| 60 template <class Y> linked_ptr(const linked_ptr<Y>& r) throw() |
| 61 {acquire(r);} |
| 62 template <class Y> linked_ptr& operator=(const linked_ptr<Y>& r) |
| 63 { |
| 64 if (this != &r) { |
| 65 release(); |
| 66 acquire(r); |
| 67 } |
| 68 return *this; |
| 69 } |
| 70 #endif // NO_MEMBER_TEMPLATES |
| 71 |
| 72 X& operator*() const throw() {return *itsPtr;} |
| 73 X* operator->() const throw() {return itsPtr;} |
| 74 X* get() const throw() {return itsPtr;} |
| 75 bool unique() const throw() {return itsPrev ? itsPrev==this : true;} |
| 76 |
| 77 private: |
| 78 X* itsPtr; |
| 79 mutable const linked_ptr* itsPrev; |
| 80 mutable const linked_ptr* itsNext; |
| 81 |
| 82 void acquire(const linked_ptr& r) throw() |
| 83 { // insert this to the list |
| 84 itsPtr = r.itsPtr; |
| 85 itsNext = r.itsNext; |
| 86 itsNext->itsPrev = this; |
| 87 itsPrev = &r; |
| 88 #ifndef mutable |
| 89 r.itsNext = this; |
| 90 #else // for ANSI-challenged compilers |
| 91 (const_cast<linked_ptr<X>*>(&r))->itsNext = this; |
| 92 #endif |
| 93 } |
| 94 |
| 95 #ifndef NO_MEMBER_TEMPLATES |
| 96 template <class Y> void acquire(const linked_ptr<Y>& r) throw() |
| 97 { // insert this to the list |
| 98 itsPtr = r.itsPtr; |
| 99 itsNext = r.itsNext; |
| 100 itsNext->itsPrev = this; |
| 101 itsPrev = &r; |
| 102 #ifndef mutable |
| 103 r.itsNext = this; |
| 104 #else // for ANSI-challenged compilers |
| 105 (const_cast<linked_ptr<X>*>(&r))->itsNext = this; |
| 106 #endif |
| 107 } |
| 108 #endif // NO_MEMBER_TEMPLATES |
| 109 |
| 110 void release() |
| 111 { // erase this from the list, delete if unique |
| 112 if (unique()) delete itsPtr; |
| 113 else { |
| 114 itsPrev->itsNext = itsNext; |
| 115 itsNext->itsPrev = itsPrev; |
| 116 itsPrev = itsNext = 0; |
| 117 } |
| 118 itsPtr = 0; |
| 119 } |
| 120 }; |
| 121 |
| 122 } // namespace rtc |
| 123 |
| 124 #endif // WEBRTC_BASE_LINKED_PTR_H__ |
| 125 |
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