Add throttle operator

Rx/v2/examples/doxygen/throttle.cpp

@@ -0,0 +1,20 @@
+#include "rxcpp/rx.hpp"
+
+#include "rxcpp/rx-test.hpp"
+#include "catch.hpp"
+
+SCENARIO("throttle sample"){
+    printf("//! [throttle sample]\n");
+    using namespace std::chrono;
+    auto scheduler = rxcpp::identity_current_thread();
+    auto start = scheduler.now();
+    auto period = milliseconds(10);
+    auto values = rxcpp::observable<>::interval(start, period, scheduler).
+        take(4).
+        throttle(period);
+    values.
+        subscribe(
+            [](long v) { printf("OnNext: %ld\n", v); },
+            []() { printf("OnCompleted\n"); });
+    printf("//! [throttle sample]\n");
+}

Rx/v2/src/rxcpp/operators/rx-throttle.hpp

@@ -0,0 +1,271 @@
+// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved. See License.txt in the project root for license information.
+
+#pragma once
+
+/*! \file rx-throttle.hpp
+
+    \brief  Return an observable that emits a value from the source and then ignores any following items until a particular timespan has passed before emitting another value.
+
+    \tparam Duration      the type of the time interval
+    \tparam Coordination  the type of the scheduler
+
+    \param period        the period of time to suppress any emitted items after the first emission
+    \param coordination  the scheduler to manage timeout for each event
+
+    \return  Observable that emits a value from the source and then ignores any following items until a particular timespan has passed before emitting another value.
+
+    \sample
+    \snippet throttle.cpp throttle sample
+    \snippet output.txt throttle sample
+*/
+
+#if !defined(RXCPP_OPERATORS_RX_THROTTLE_HPP)
+#define RXCPP_OPERATORS_RX_THROTTLE_HPP
+
+#include "../rx-includes.hpp"
+
+#include <iostream>
+
+namespace rxcpp {
+
+namespace operators {
+
+namespace detail {
+
+template<class... AN>
+struct throttle_invalid_arguments {};
+
+template<class... AN>
+struct throttle_invalid : public rxo::operator_base<throttle_invalid_arguments<AN...>> {
+    using type = observable<throttle_invalid_arguments<AN...>, throttle_invalid<AN...>>;
+};
+template<class... AN>
+using throttle_invalid_t = typename throttle_invalid<AN...>::type;
+
+template<class T, class Duration, class Coordination>
+struct throttle
+{
+    typedef rxu::decay_t<T> source_value_type;
+    typedef rxu::decay_t<Coordination> coordination_type;
+    typedef typename coordination_type::coordinator_type coordinator_type;
+    typedef rxu::decay_t<Duration> duration_type;
+
+    struct throttle_values
+    {
+        throttle_values(duration_type p, coordination_type c)
+            : period(p)
+            , coordination(c)
+        {
+        }
+
+        duration_type period;
+        coordination_type coordination;
+    };
+    throttle_values initial;
+
+    throttle(duration_type period, coordination_type coordination)
+        : initial(period, coordination)
+    {
+    }
+
+    template<class Subscriber>
+    struct throttle_observer
+    {
+        typedef throttle_observer<Subscriber> this_type;
+        typedef rxu::decay_t<T> value_type;
+        typedef rxu::decay_t<Subscriber> dest_type;
+        typedef observer<T, this_type> observer_type;
+
+        struct throttle_subscriber_values : public throttle_values
+        {
+            throttle_subscriber_values(composite_subscription cs, dest_type d, throttle_values v, coordinator_type c)
+                : throttle_values(v)
+                , cs(std::move(cs))
+                , dest(std::move(d))
+                , coordinator(std::move(c))
+                , worker(coordinator.get_worker())
+                , throttled(false)
+            {
+            }
+
+            composite_subscription cs;
+            dest_type dest;
+            coordinator_type coordinator;
+            rxsc::worker worker;
+            mutable bool throttled;
+        };
+        typedef std::shared_ptr<throttle_subscriber_values> state_type;
+        state_type state;
+
+        throttle_observer(composite_subscription cs, dest_type d, throttle_values v, coordinator_type c)
+            : state(std::make_shared<throttle_subscriber_values>(throttle_subscriber_values(std::move(cs), std::move(d), v, std::move(c))))
+        {
+            auto localState = state;
+
+            auto disposer = [=](const rxsc::schedulable&){
+                localState->cs.unsubscribe();
+                localState->dest.unsubscribe();
+                localState->worker.unsubscribe();
+            };
+            auto selectedDisposer = on_exception(
+                [&](){ return localState->coordinator.act(disposer); },
+                localState->dest);
+            if (selectedDisposer.empty()) {
+                return;
+            }
+
+            localState->dest.add([=](){
+                localState->worker.schedule(selectedDisposer.get());
+            });
+            localState->cs.add([=](){
+                localState->worker.schedule(selectedDisposer.get());
+            });
+        }
+
+        static std::function<void(const rxsc::schedulable&)> reset_throttle(state_type state) {
+            auto reset = [state](const rxsc::schedulable&) {
+                state->throttled = false;
+            };
+
+            auto selectedReset = on_exception(
+                    [&](){ return state->coordinator.act(reset); },
+                    state->dest);
+            if (selectedReset.empty()) {
+                return std::function<void(const rxsc::schedulable&)>();
+            }
+
+            return std::function<void(const rxsc::schedulable&)>(selectedReset.get());
+        }
+
+        void on_next(T v) const {
+            auto localState = state;
+
+            const auto tp = localState->worker.now().time_since_epoch();
+            std::cout << "on_next(" << v << ") at " << tp.count() / 1000000 << " throttled: " << (localState->throttled ? "true" : "false") << std::endl;
+
+            if (!localState->throttled) {
+                localState->throttled = true;
+
+                state->dest.on_next(v);
+
+                auto work = [v, localState](const rxsc::schedulable&) {
+                    auto produce_time = localState->worker.now() + localState->period;
+
+                    std::cout << "scheduling unthrottle for " << (produce_time.time_since_epoch().count() / 1000000) << std::endl;
+
+                    localState->worker.schedule(produce_time, reset_throttle(localState));
+                };
+                auto selectedWork = on_exception(
+                    [&](){return localState->coordinator.act(work);},
+                    localState->dest);
+                if (selectedWork.empty()) {
+                    return;
+                }
+                localState->worker.schedule(selectedWork.get());
+            }
+        }
+
+        void on_error(rxu::error_ptr e) const {
+            auto localState = state;
+            auto work = [e, localState](const rxsc::schedulable&) {
+                localState->dest.on_error(e);
+            };
+            auto selectedWork = on_exception(
+                [&](){ return localState->coordinator.act(work); },
+                localState->dest);
+            if (selectedWork.empty()) {
+                return;
+            }
+            localState->worker.schedule(selectedWork.get());
+        }
+
+        void on_completed() const {
+            auto localState = state;
+            auto work = [localState](const rxsc::schedulable&) {
+                localState->dest.on_completed();
+            };
+            auto selectedWork = on_exception(
+                [&](){ return localState->coordinator.act(work); },
+                localState->dest);
+            if (selectedWork.empty()) {
+                return;
+            }
+            localState->worker.schedule(selectedWork.get());
+        }
+
+        static subscriber<T, observer_type> make(dest_type d, throttle_values v) {
+            auto cs = composite_subscription();
+            auto coordinator = v.coordination.create_coordinator();
+
+            return make_subscriber<T>(cs, observer_type(this_type(cs, std::move(d), std::move(v), std::move(coordinator))));
+        }
+    };
+
+    template<class Subscriber>
+    auto operator()(Subscriber dest) const
+        -> decltype(throttle_observer<Subscriber>::make(std::move(dest), initial)) {
+        return      throttle_observer<Subscriber>::make(std::move(dest), initial);
+    }
+};
+
+}
+
+/*! @copydoc rx-throttle.hpp
+*/
+template<class... AN>
+auto throttle(AN&&... an)
+    ->      operator_factory<throttle_tag, AN...> {
+     return operator_factory<throttle_tag, AN...>(std::make_tuple(std::forward<AN>(an)...));
+}
+
+}
+
+template<>
+struct member_overload<throttle_tag>
+{
+    template<class Observable, class Duration,
+        class Enabled = rxu::enable_if_all_true_type_t<
+            is_observable<Observable>,
+            rxu::is_duration<Duration>>,
+        class SourceValue = rxu::value_type_t<Observable>,
+        class Throttle = rxo::detail::throttle<SourceValue, rxu::decay_t<Duration>, identity_one_worker>>
+    static auto member(Observable&& o, Duration&& d)
+        -> decltype(o.template lift<SourceValue>(Throttle(std::forward<Duration>(d), identity_current_thread()))) {
+        return      o.template lift<SourceValue>(Throttle(std::forward<Duration>(d), identity_current_thread()));
+    }
+
+    template<class Observable, class Coordination, class Duration,
+        class Enabled = rxu::enable_if_all_true_type_t<
+            is_observable<Observable>,
+            is_coordination<Coordination>,
+            rxu::is_duration<Duration>>,
+        class SourceValue = rxu::value_type_t<Observable>,
+        class Throttle = rxo::detail::throttle<SourceValue, rxu::decay_t<Duration>, rxu::decay_t<Coordination>>>
+    static auto member(Observable&& o, Coordination&& cn, Duration&& d)
+        -> decltype(o.template lift<SourceValue>(Throttle(std::forward<Duration>(d), std::forward<Coordination>(cn)))) {
+        return      o.template lift<SourceValue>(Throttle(std::forward<Duration>(d), std::forward<Coordination>(cn)));
+    }
+
+    template<class Observable, class Coordination, class Duration,
+        class Enabled = rxu::enable_if_all_true_type_t<
+            is_observable<Observable>,
+            is_coordination<Coordination>,
+            rxu::is_duration<Duration>>,
+        class SourceValue = rxu::value_type_t<Observable>,
+        class Throttle = rxo::detail::throttle<SourceValue, rxu::decay_t<Duration>, rxu::decay_t<Coordination>>>
+    static auto member(Observable&& o, Duration&& d, Coordination&& cn)
+        -> decltype(o.template lift<SourceValue>(Throttle(std::forward<Duration>(d), std::forward<Coordination>(cn)))) {
+        return      o.template lift<SourceValue>(Throttle(std::forward<Duration>(d), std::forward<Coordination>(cn)));
+    }
+
+    template<class... AN>
+    static operators::detail::throttle_invalid_t<AN...> member(const AN&...) {
+        std::terminate();
+        return {};
+        static_assert(sizeof...(AN) == 10000, "throttle takes (optional Coordination, required Duration) or (required Duration, optional Coordination)");
+    }
+};
+
+}
+
+#endif

Rx/v2/src/rxcpp/rx-includes.hpp

@@ -259,6 +259,7 @@
 #include "operators/rx-take_until.hpp"
 #include "operators/rx-take_while.hpp"
 #include "operators/rx-tap.hpp"
+#include "operators/rx-throttle.hpp"
 #include "operators/rx-time_interval.hpp"
 #include "operators/rx-timeout.hpp"
 #include "operators/rx-timestamp.hpp"

Rx/v2/src/rxcpp/rx-observable.hpp

@@ -1417,6 +1417,17 @@ class observable
         return      observable_member(take_while_tag{},                *this, std::forward<AN>(an)...);
     }
 
+    /*! @copydoc rx-throttle.hpp
+     */
+    template<class... AN>
+    auto throttle(AN&&... an) const
+        /// \cond SHOW_SERVICE_MEMBERS
+        -> decltype(observable_member(throttle_tag{}, *(this_type*)nullptr, std::forward<AN>(an)...))
+        /// \endcond
+    {
+        return  observable_member(throttle_tag{},                *this, std::forward<AN>(an)...);
+    }
+
     /*! @copydoc rx-repeat.hpp
      */
     template<class... AN>

Rx/v2/src/rxcpp/rx-operators.hpp

@@ -462,6 +462,13 @@ struct tap_tag {
     };
 };
 
+struct throttle_tag {
+    template<class Included>
+    struct include_header{
+        static_assert(Included::value, "missing include: please #include <rxcpp/operators/rx-throttle.hpp>");
+    };
+};
+
 struct timeout_tag {
     template<class Included>
     struct include_header{

Rx/v2/test/CMakeLists.txt

@@ -79,6 +79,7 @@ set(TEST_SOURCES
     ${TEST_DIR}/operators/take_until.cpp
     ${TEST_DIR}/operators/take_while.cpp
     ${TEST_DIR}/operators/tap.cpp
+    ${TEST_DIR}/operators/throttle.cpp
     ${TEST_DIR}/operators/time_interval.cpp
     ${TEST_DIR}/operators/timeout.cpp
     ${TEST_DIR}/operators/timestamp.cpp