1 // Copyright (c) Microsoft Open Technologies, Inc. All rights reserved. See License.txt in the project root for license information. 2 3 #pragma once 4 5 /*! \file rx-ref_count.hpp 6 7 \brief Make some \c connectable_observable behave like an ordinary \c observable. 8 Uses a reference count of the subscribers to control the connection to the published observable. 9 10 The first subscription will cause a call to \c connect(), and the last \c unsubscribe will unsubscribe the connection. 11 12 There are 2 variants of the operator: 13 \li \c ref_count(): calls \c connect on the \c source \c connectable_observable. 14 \li \c ref_count(other): calls \c connect on the \c other \c connectable_observable. 15 16 \tparam ConnectableObservable the type of the \c other \c connectable_observable (optional) 17 \param other \c connectable_observable to call \c connect on (optional) 18 19 If \c other is omitted, then \c source is used instead (which must be a \c connectable_observable). 20 Otherwise, \c source can be a regular \c observable. 21 22 \return An \c observable that emits the items from its \c source. 23 24 \sample 25 \snippet ref_count.cpp ref_count other diamond sample 26 \snippet output.txt ref_count other diamond sample 27 */ 28 29 #if !defined(RXCPP_OPERATORS_RX_REF_COUNT_HPP) 30 #define RXCPP_OPERATORS_RX_REF_COUNT_HPP 31 32 #include "../rx-includes.hpp" 33 34 namespace rxcpp { 35 36 namespace operators { 37 38 namespace detail { 39 40 template<class... AN> 41 struct ref_count_invalid_arguments {}; 42 43 template<class... AN> 44 struct ref_count_invalid : public rxo::operator_base<ref_count_invalid_arguments<AN...>> { 45 using type = observable<ref_count_invalid_arguments<AN...>, ref_count_invalid<AN...>>; 46 }; 47 template<class... AN> 48 using ref_count_invalid_t = typename ref_count_invalid<AN...>::type; 49 50 // ref_count(other) takes a regular observable source, not a connectable_observable. 51 // use template specialization to avoid instantiating 'subscribe' for two different types 52 // which would cause a compilation error. 53 template <typename connectable_type, typename observable_type> 54 struct ref_count_state_base { 55 ref_count_state_base(connectable_type other, observable_type source) 56 : connectable(std::move(other)) 57 , subscribable(std::move(source)) {} 58 59 connectable_type connectable; // connects to this. subscribes to this if subscribable empty. 60 observable_type subscribable; // subscribes to this if non-empty. 61 62 template <typename Subscriber> 63 void subscribe(Subscriber&& o) { 64 subscribable.subscribe(std::forward<Subscriber>(o)); 65 } 66 }; 67 68 // Note: explicit specializations have to be at namespace scope prior to C++17. 69 template <typename connectable_type> 70 struct ref_count_state_base<connectable_type, void> { 71 explicit ref_count_state_base(connectable_type c) 72 : connectable(std::move(c)) {} 73 74 connectable_type connectable; // connects to this. subscribes to this if subscribable empty. 75 76 template <typename Subscriber> 77 void subscribe(Subscriber&& o) { 78 connectable.subscribe(std::forward<Subscriber>(o)); 79 } 80 }; 81 82 template<class T, 83 class ConnectableObservable, 84 class Observable = void> // note: type order flipped versus the operator. 85 struct ref_count : public operator_base<T> 86 { 87 typedef rxu::decay_t<Observable> observable_type; 88 typedef rxu::decay_t<ConnectableObservable> connectable_type; 89 90 // ref_count() == false 91 // ref_count(other) == true 92 using has_observable_t = rxu::negation<std::is_same<void, Observable>>; 93 static constexpr bool has_observable_v = has_observable_t::value; 94 95 struct ref_count_state : public std::enable_shared_from_this<ref_count_state>, 96 public ref_count_state_base<ConnectableObservable, Observable> 97 { 98 template <class HasObservable = has_observable_t, 99 class Enabled = rxu::enable_if_all_true_type_t< 100 rxu::negation<HasObservable>>> 101 explicit ref_count_state(connectable_type source) 102 : ref_count_state_base<ConnectableObservable, Observable>(std::move(source)) 103 , subscribers(0) 104 { 105 } 106 107 template <bool HasObservableV = has_observable_v> 108 ref_count_state(connectable_type other, 109 typename std::enable_if<HasObservableV, observable_type>::type source) 110 : ref_count_state_base<ConnectableObservable, Observable>(std::move(other), 111 std::move(source)) 112 , subscribers(0) 113 { 114 } 115 116 std::mutex lock; 117 long subscribers; 118 composite_subscription connection; 119 }; 120 std::shared_ptr<ref_count_state> state; 121 122 // connectable_observable<T> source = ...; 123 // source.ref_count(); 124 // 125 // calls connect on source after the subscribe on source. 126 template <class HasObservable = has_observable_t, 127 class Enabled = rxu::enable_if_all_true_type_t< 128 rxu::negation<HasObservable>>> 129 explicit ref_count(connectable_type source) 130 : state(std::make_shared<ref_count_state>(std::move(source))) 131 { 132 } 133 134 // connectable_observable<?> other = ...; 135 // observable<T> source = ...; 136 // source.ref_count(other); 137 // 138 // calls connect on 'other' after the subscribe on 'source'. 139 template <bool HasObservableV = has_observable_v> 140 ref_count(connectable_type other, 141 typename std::enable_if<HasObservableV, observable_type>::type source) 142 : state(std::make_shared<ref_count_state>(std::move(other), std::move(source))) 143 { 144 } 145 146 template<class Subscriber> 147 void on_subscribe(Subscriber&& o) const { 148 std::unique_lock<std::mutex> guard(state->lock); 149 auto needConnect = ++state->subscribers == 1; 150 auto keepAlive = state; 151 guard.unlock(); 152 o.add( 153 [keepAlive](){ 154 std::unique_lock<std::mutex> guard_unsubscribe(keepAlive->lock); 155 if (--keepAlive->subscribers == 0) { 156 keepAlive->connection.unsubscribe(); 157 keepAlive->connection = composite_subscription(); 158 } 159 }); 160 keepAlive->subscribe(std::forward<Subscriber>(o)); 161 if (needConnect) { 162 keepAlive->connectable.connect(keepAlive->connection); 163 } 164 } 165 }; 166 167 } 168 169 /*! @copydoc rx-ref_count.hpp 170 */ 171 template<class... AN> 172 auto ref_count(AN&&... an) 173 -> operator_factory<ref_count_tag, AN...> { 174 return operator_factory<ref_count_tag, AN...>(std::make_tuple(std::forward<AN>(an)...)); 175 } 176 177 } 178 179 template<> 180 struct member_overload<ref_count_tag> 181 { 182 template<class ConnectableObservable, 183 class Enabled = rxu::enable_if_all_true_type_t< 184 is_connectable_observable<ConnectableObservable>>, 185 class SourceValue = rxu::value_type_t<ConnectableObservable>, 186 class RefCount = rxo::detail::ref_count<SourceValue, rxu::decay_t<ConnectableObservable>>, 187 class Value = rxu::value_type_t<RefCount>, 188 class Result = observable<Value, RefCount> 189 > 190 static Result member(ConnectableObservable&& o) { 191 return Result(RefCount(std::forward<ConnectableObservable>(o))); 192 } 193 194 template<class Observable, 195 class ConnectableObservable, 196 class Enabled = rxu::enable_if_all_true_type_t< 197 is_observable<Observable>, 198 is_connectable_observable<ConnectableObservable>>, 199 class SourceValue = rxu::value_type_t<Observable>, 200 class RefCount = rxo::detail::ref_count<SourceValue, 201 rxu::decay_t<ConnectableObservable>, 202 rxu::decay_t<Observable>>, 203 class Value = rxu::value_type_t<RefCount>, 204 class Result = observable<Value, RefCount> 205 > 206 static Result member(Observable&& o, ConnectableObservable&& other) { 207 return Result(RefCount(std::forward<ConnectableObservable>(other), 208 std::forward<Observable>(o))); 209 } 210 211 template<class... AN> 212 static operators::detail::ref_count_invalid_t<AN...> member(AN...) { 213 std::terminate(); 214 return {}; 215 static_assert(sizeof...(AN) == 10000, "ref_count takes (optional ConnectableObservable)"); 216 } 217 }; 218 219 } 220 221 #endif 222
