[419] | 1 | /*! |
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| 2 | \file |
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| 3 | \brief BDM's own smart pointer. |
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| 4 | \author Vaclav Barta. |
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| 5 | |
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| 6 | ----------------------------------- |
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| 7 | BDM++ - C++ library for Bayesian Decision Making under Uncertainty |
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| 8 | |
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| 9 | Using IT++ for numerical operations |
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| 10 | ----------------------------------- |
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| 11 | */ |
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| 12 | |
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| 13 | #ifndef shared_ptr_h |
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| 14 | #define shared_ptr_h |
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| 15 | |
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| 16 | #include <limits.h> |
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| 17 | #include <algorithm> |
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| 18 | #include <stdexcept> |
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| 19 | #include <string> |
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[420] | 20 | #include "itpp_ext.h" |
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[419] | 21 | |
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| 22 | namespace bdm { |
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| 23 | |
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| 24 | //! A naive implementation of roughly a subset of the std::tr1:shared_ptr spec (really just roughly - it ignores memory exceptions, for example; also note I didn't read the spec). |
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| 25 | // The standard template would naturally be preferable, _if_ it was |
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| 26 | // included in the standard libraries of all supported compilers - but |
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| 27 | // that's exactly what remains to be seen... |
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| 28 | template <typename T> |
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| 29 | class shared_ptr { |
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| 30 | private: |
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| 31 | T *payload; |
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| 32 | unsigned *refCnt; |
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| 33 | |
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| 34 | public: |
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[420] | 35 | //! Creates an empty shared_ptr - one that doesn't point anywhere. |
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[419] | 36 | shared_ptr(): |
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| 37 | payload(0), |
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| 38 | refCnt(0) |
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| 39 | { |
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| 40 | } |
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| 41 | |
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[420] | 42 | //! Constructs a shared_ptr that owns the pointer p (unless p is |
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| 43 | //! null, in which case this constructor creates an empty |
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| 44 | //! shared_ptr). |
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[419] | 45 | shared_ptr(T *p): |
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| 46 | payload(p), |
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| 47 | refCnt(p ? new unsigned(1) : 0) |
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| 48 | { |
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| 49 | } |
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| 50 | |
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[420] | 51 | //! If other is empty, constructs an empty shared_ptr; otherwise, |
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| 52 | //! constructs a shared_ptr that shares ownership with other. |
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[419] | 53 | shared_ptr(const shared_ptr &other): |
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| 54 | payload(other.payload), |
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| 55 | refCnt(other.refCnt) |
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| 56 | { |
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| 57 | add_ref(); |
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| 58 | } |
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| 59 | |
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| 60 | ~shared_ptr() |
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| 61 | { |
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| 62 | del_ref(); |
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| 63 | } |
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| 64 | |
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| 65 | shared_ptr &operator=(const shared_ptr &other) |
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| 66 | { |
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| 67 | other.add_ref(); |
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| 68 | del_ref(); |
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| 69 | |
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| 70 | payload = other.payload; |
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| 71 | refCnt = other.refCnt; |
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| 72 | |
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| 73 | return *this; |
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| 74 | } |
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| 75 | |
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[420] | 76 | //! Returns the stored pointer (which remains owned by this |
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| 77 | //! instance). |
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[419] | 78 | T *get() { return payload; } |
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| 79 | |
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[420] | 80 | //! Returns the stored pointer (which remains owned by this |
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| 81 | //! instance). This method may only be called when the stored |
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| 82 | //! pointer isn't NULL. |
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[419] | 83 | T *operator->() |
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| 84 | { |
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[420] | 85 | it_assert_debug(payload, "dereferencing NULL"); |
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[419] | 86 | return payload; |
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| 87 | } |
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| 88 | |
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[420] | 89 | //! Returns a reference to the object pointed to by the stored |
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| 90 | //! pointer. This method may only be called when the stored pointer |
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| 91 | //! isn't NULL. |
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[419] | 92 | T &operator*() |
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| 93 | { |
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[420] | 94 | it_assert_debug(payload, "dereferencing NULL"); |
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[419] | 95 | return *payload; |
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| 96 | } |
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| 97 | |
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[420] | 98 | //! Returns the stored pointer (which remains owned by this |
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| 99 | //! instance). |
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[419] | 100 | const T* get() const { return payload; } |
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| 101 | |
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[420] | 102 | //! Returns the stored pointer (which remains owned by this |
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| 103 | //! instance). This method may only be called when the stored |
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| 104 | //! pointer isn't NULL. |
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[419] | 105 | const T *operator->() const |
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| 106 | { |
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[420] | 107 | it_assert_debug(payload, "dereferencing NULL"); |
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[419] | 108 | return payload; |
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| 109 | } |
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| 110 | |
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[420] | 111 | //! Returns a reference to the object pointed to by the stored |
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| 112 | //! pointer. This method may only be called when the stored pointer |
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| 113 | //! isn't NULL. |
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[419] | 114 | const T &operator*() const |
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| 115 | { |
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[420] | 116 | it_assert_debug(payload, "dereferencing NULL"); |
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[419] | 117 | return *payload; |
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| 118 | } |
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| 119 | |
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| 120 | bool unique() const |
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| 121 | { |
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| 122 | return refCnt && (*refCnt == 1); |
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| 123 | } |
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| 124 | |
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| 125 | long use_count() const |
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| 126 | { |
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| 127 | return refCnt ? *refCnt : 0; |
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| 128 | } |
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| 129 | |
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| 130 | operator bool() const |
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| 131 | { |
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| 132 | return payload; |
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| 133 | } |
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| 134 | |
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| 135 | void swap(shared_ptr &other) |
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| 136 | { |
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| 137 | std::swap(payload, other.payload); |
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| 138 | std::swap(refCnt, other.refCnt); |
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| 139 | } |
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| 140 | |
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| 141 | private: |
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| 142 | void add_ref() const |
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| 143 | { |
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| 144 | if (refCnt) { |
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| 145 | if (*refCnt == UINT_MAX) { |
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| 146 | throw std::overflow_error( |
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| 147 | std::string("Shared pointer has too many references.")); |
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| 148 | } |
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| 149 | |
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| 150 | ++*refCnt; |
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| 151 | } |
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| 152 | } |
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| 153 | |
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| 154 | void del_ref() |
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| 155 | { |
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| 156 | if (refCnt) { |
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| 157 | if (!(--*refCnt)) { |
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| 158 | delete payload; |
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| 159 | delete refCnt; |
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| 160 | } |
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| 161 | } |
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| 162 | } |
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| 163 | }; |
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| 164 | |
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| 165 | template<typename T, typename U> |
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| 166 | bool operator==(shared_ptr<T> const &a, shared_ptr<U> const &b) |
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| 167 | { |
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| 168 | return a.get() == b.get(); |
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| 169 | } |
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| 170 | |
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| 171 | template<typename T, typename U> |
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| 172 | bool operator!=(shared_ptr<T> const &a, shared_ptr<U> const &b) |
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| 173 | { |
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| 174 | return a.get() != b.get(); |
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| 175 | } |
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| 176 | |
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| 177 | template<typename T, typename U> |
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| 178 | bool operator<(shared_ptr<T> const &a, shared_ptr<U> const &b) |
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| 179 | { |
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| 180 | return a.get() < b.get(); |
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| 181 | } |
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| 182 | |
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| 183 | } |
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| 184 | |
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| 185 | #endif |
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