henrike@webrtc.org | f7795df | 2014-05-13 18:00:26 +0000 | [diff] [blame^] | 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 | |