Seastar
High performance C++ framework for concurrent servers
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poll.hh
1/*
2 * This file is open source software, licensed to you under the terms
3 * of the Apache License, Version 2.0 (the "License"). See the NOTICE file
4 * distributed with this work for additional information regarding copyright
5 * ownership. You may not use this file except in compliance with the License.
6 *
7 * You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing,
12 * software distributed under the License is distributed on an
13 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
14 * KIND, either express or implied. See the License for the
15 * specific language governing permissions and limitations
16 * under the License.
17 */
18/*
19 * Copyright 2019 ScyllaDB
20 */
21
22#pragma once
23
24namespace seastar {
25
26struct pollfn {
27 virtual ~pollfn() {}
28 // Returns true if work was done (false = idle)
29 virtual bool poll() = 0;
30 // Checks if work needs to be done, but without actually doing any
31 // returns true if works needs to be done (false = idle)
32 virtual bool pure_poll() = 0;
33 // Tries to enter interrupt mode.
34 //
35 // If it returns true, then events from this poller will wake
36 // a sleeping idle loop, and exit_interrupt_mode() must be called
37 // to return to normal polling.
38 //
39 // If it returns false, the sleeping idle loop may not be entered.
40 virtual bool try_enter_interrupt_mode() = 0;
41 virtual void exit_interrupt_mode() = 0;
42};
43
44// The common case for poller -- do not make any difference between
45// poll() and pure_poll(), always/never agree to go to sleep and do
46// nothing on wakeup.
47template <bool Passive>
48struct simple_pollfn : public pollfn {
49 virtual bool pure_poll() override final {
50 return poll();
51 }
52 virtual bool try_enter_interrupt_mode() override final {
53 return Passive;
54 }
55 virtual void exit_interrupt_mode() override final {
56 }
57};
58
59namespace internal {
60
61template <typename Func>
62requires std::is_invocable_r_v<bool, Func>
63inline
64std::unique_ptr<seastar::pollfn> make_pollfn(Func&& func) {
65 struct the_pollfn : simple_pollfn<false> {
66 the_pollfn(Func&& func) : func(std::forward<Func>(func)) {}
67 Func func;
68 virtual bool poll() override final {
69 return func();
70 }
71 };
72 return std::make_unique<the_pollfn>(std::forward<Func>(func));
73}
74
75class poller {
76 std::unique_ptr<pollfn> _pollfn;
77 class registration_task;
78 class deregistration_task;
79 registration_task* _registration_task = nullptr;
80public:
81 template <typename Func>
82 requires std::is_invocable_r_v<bool, Func>
83 static poller simple(Func&& poll) {
84 return poller(make_pollfn(std::forward<Func>(poll)));
85 }
86 poller(std::unique_ptr<pollfn> fn)
87 : _pollfn(std::move(fn)) {
88 do_register();
89 }
90 ~poller();
91 poller(poller&& x) noexcept;
92 poller& operator=(poller&& x) noexcept;
93 void do_register() noexcept;
94 friend class reactor;
95};
96
97} // internal namespace
98
99}
Seastar API namespace.
Definition: abort_on_ebadf.hh:26
STL namespace.
Definition: poll.hh:26
Definition: poll.hh:48