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-skip_last.hpp
6
7 \brief Make new observable with skipped last count items from this observable.
8
9 \tparam Count the type of the items counter.
10
11 \param t the number of last items to skip.
12
13 \return An observable that is identical to the source observable except that it does not emit the last t items that the source observable emits.
14
15 \sample
16 \snippet skip_last.cpp skip_last sample
17 \snippet output.txt skip_last sample
18 */
19
20 #if !defined(RXCPP_OPERATORS_RX_SKIP_LAST_HPP)
21 #define RXCPP_OPERATORS_RX_SKIP_LAST_HPP
22
23 #include "../rx-includes.hpp"
24
25 namespace rxcpp {
26
27 namespace operators {
28
29 namespace detail {
30
31 template<class... AN>
32 struct skip_last_invalid_arguments {};
33
34 template<class... AN>
35 struct skip_last_invalid : public rxo::operator_base<skip_last_invalid_arguments<AN...>> {
36 using type = observable<skip_last_invalid_arguments<AN...>, skip_last_invalid<AN...>>;
37 };
38 template<class... AN>
39 using skip_last_invalid_t = typename skip_last_invalid<AN...>::type;
40
41 template<class T, class Observable, class Count>
42 struct skip_last : public operator_base<T>
43 {
44 typedef rxu::decay_t<Observable> source_type;
45 typedef rxu::decay_t<Count> count_type;
46
47 typedef std::queue<T> queue_type;
48 typedef typename queue_type::size_type queue_size_type;
49
50 struct values
51 {
valuesrxcpp::operators::detail::skip_last::values52 values(source_type s, count_type t)
53 : source(std::move(s))
54 , count(static_cast<queue_size_type>(t))
55 {
56 }
57 source_type source;
58 queue_size_type count;
59 };
60 values initial;
61
skip_lastrxcpp::operators::detail::skip_last62 skip_last(source_type s, count_type t)
63 : initial(std::move(s), std::move(t))
64 {
65 }
66
67 template<class Subscriber>
on_subscriberxcpp::operators::detail::skip_last68 void on_subscribe(const Subscriber& s) const {
69
70 typedef Subscriber output_type;
71 struct state_type
72 : public std::enable_shared_from_this<state_type>
73 , public values
74 {
75 state_type(const values& i, const output_type& oarg)
76 : values(i)
77 , out(oarg)
78 {
79 }
80 queue_type items;
81 output_type out;
82 };
83 // take a copy of the values for each subscription
84 auto state = std::make_shared<state_type>(initial, s);
85
86 composite_subscription source_lifetime;
87
88 s.add(source_lifetime);
89
90 state->source.subscribe(
91 // split subscription lifetime
92 source_lifetime,
93 // on_next
94 [state](T t) {
95 if(state->count > 0) {
96 if (state->items.size() == state->count) {
97 state->out.on_next(std::move(state->items.front()));
98 state->items.pop();
99 }
100 state->items.push(t);
101 } else {
102 state->out.on_next(t);
103 }
104 },
105 // on_error
106 [state](rxu::error_ptr e) {
107 state->out.on_error(e);
108 },
109 // on_completed
110 [state]() {
111 state->out.on_completed();
112 }
113 );
114 }
115 };
116
117 }
118
119 /*! @copydoc rx-skip_last.hpp
120 */
121 template<class... AN>
skip_last(AN &&...an)122 auto skip_last(AN&&... an)
123 -> operator_factory<skip_last_tag, AN...> {
124 return operator_factory<skip_last_tag, AN...>(std::make_tuple(std::forward<AN>(an)...));
125 }
126
127 }
128
129 template<>
130 struct member_overload<skip_last_tag>
131 {
132 template<class Observable, class Count,
133 class Enabled = rxu::enable_if_all_true_type_t<
134 is_observable<Observable>>,
135 class SourceValue = rxu::value_type_t<Observable>,
136 class SkipLast = rxo::detail::skip_last<SourceValue, rxu::decay_t<Observable>, rxu::decay_t<Count>>,
137 class Value = rxu::value_type_t<SkipLast>,
138 class Result = observable<Value, SkipLast>>
memberrxcpp::member_overload139 static Result member(Observable&& o, Count&& c) {
140 return Result(SkipLast(std::forward<Observable>(o), std::forward<Count>(c)));
141 }
142
143 template<class... AN>
memberrxcpp::member_overload144 static operators::detail::skip_last_invalid_t<AN...> member(AN...) {
145 std::terminate();
146 return {};
147 static_assert(sizeof...(AN) == 10000, "skip_last takes (Count)");
148 }
149 };
150
151 }
152
153 #endif
154