1 /*
2  * Copyright 2018, The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *     http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 #pragma once
18 
19 #include <chrono>
20 #include <vector>
21 
22 #include <poll.h>
23 
24 /* An interface for pollable classes.
25  */
26 class Pollable {
27 public:
28     using Clock = std::chrono::steady_clock;
29     using Timestamp = Clock::time_point;
30     virtual ~Pollable() = default;
31 
32     /* Get the poll data for the next poll loop. The implementation can place
33      * as many fds as needed in |fds|.
34      */
35     virtual void getPollData(std::vector<pollfd>* fds) const = 0;
36     /* Get the timeout for the next poll loop. This should be a timestamp
37      * indicating when the timeout should be triggered. Note that this may
38      * be called at any time and any number of times for a poll loop so the
39      * deadline should not be adjusted in this call, a set deadline should
40      * just be returned. Note specifically that if a call to onReadAvailable
41      * modifies the deadline the timeout for the previous timestamp might not
42      * fire as the poller will check the timestamp AFTER onReadAvailable is
43      * called.
44      */
45     virtual Timestamp getTimeout() const = 0;
46     /* Called when there is data available to read on an fd associated with
47      * the pollable. |fd| indicates which fd to read from. If the call returns
48      * false the poller will exit its poll loop with a return code of |status|.
49      */
50     virtual bool onReadAvailable(int fd, int* status) = 0;
51     /* Called when an fd associated with the pollable is closed. |fd| indicates
52      * which fd was closed. If the call returns false the poller will exit its
53      * poll loop with a return code of |status|.
54      */
55     virtual bool onClose(int fd, int* status) = 0;
56     /* Called when the timeout returned by getPollData has been reached. If
57      * the call returns false the poller will exit its poll loop with a return
58      * code of |status|.
59      */
60     virtual bool onTimeout(int* status) = 0;
61 };
62 
63