selector.h revision 4f6e8d7a00cbeda1e70cc15be9c4af1018bdad53 
1/*
2 * Copyright (C) 2007 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/**
18 * Framework for multiplexing I/O. A selector manages a set of file
19 * descriptors and calls out to user-provided callback functions to read and
20 * write data and handle errors.
21 */
22
23#ifndef __SELECTOR_H
24#define __SELECTOR_H
25
26#ifdef __cplusplus
27extern "C" {
28#endif
29
30#include <stdbool.h>
31
32/**
33 * Manages SelectableFds and invokes their callbacks at appropriate times.
34 */
35typedef struct Selector Selector;
36
37/**
38 * A selectable descriptor. Contains callbacks which the selector can invoke
39 * before calling select(), when the descriptor is readable or writable, and
40 * when the descriptor contains out-of-band data. Simply set a callback to
41 * NULL if you're not interested in that particular event.
42 *
43 * A selectable descriptor can indicate that it needs to be removed from the
44 * selector by setting the 'remove' flag. The selector will remove the
45 * descriptor at a later time and invoke the onRemove() callback.
46 *
47 * SelectableFd fields should only be modified from the selector loop.
48 */
49typedef struct SelectableFd SelectableFd;
50struct SelectableFd {
51
52    /** The file descriptor itself. */
53    int fd;
54
55    /** Pointer to user-specific data. Can be NULL. */
56    void* data;
57
58    /**
59     * Set this flag when you no longer wish to be selected. The selector
60     * will invoke onRemove() when the descriptor is actually removed.
61     */
62    bool remove;
63
64    /**
65     * Invoked by the selector before calling select. You can set up other
66     * callbacks from here as necessary.
67     */
68    void (*beforeSelect)(SelectableFd* self);
69
70    /**
71     * Invoked by the selector when the descriptor has data available. Set to
72     * NULL to indicate that you're not interested in reading.
73     */
74    void (*onReadable)(SelectableFd* self);
75
76    /**
77     * Invoked by the selector when the descriptor can accept data. Set to
78     * NULL to indicate that you're not interested in writing.
79     */
80    void (*onWritable)(SelectableFd* self);
81
82    /**
83     * Invoked by the selector when out-of-band (OOB) data is available. Set to
84     * NULL to indicate that you're not interested in OOB data.
85     */
86    void (*onExcept)(SelectableFd* self);
87
88    /**
89     * Invoked by the selector after the descriptor is removed from the
90     * selector but before the selector frees the SelectableFd memory.
91     */
92    void (*onRemove)(SelectableFd* self);
93
94    /**
95     * The selector which selected this fd. Set by the selector itself.
96     */
97    Selector* selector;
98};
99
100/**
101 * Creates a new selector.
102 */
103Selector* selectorCreate(void);
104
105/**
106 * Creates a new selectable fd, adds it to the given selector and returns a
107 * pointer. Outside of 'selector' and 'fd', all fields are set to 0 or NULL
108 * by default.
109 *
110 * The selectable fd should only be modified from the selector loop thread.
111 */
112SelectableFd* selectorAdd(Selector* selector, int fd);
113
114/**
115 * Wakes up the selector even though no I/O events occurred. Use this
116 * to indicate that you're ready to write to a descriptor.
117 */
118void selectorWakeUp(Selector* selector);
119
120/**
121 * Loops continuously selecting file descriptors and firing events.
122 * Does not return.
123 */
124void selectorLoop(Selector* selector);
125
126#ifdef __cplusplus
127}
128#endif
129
130#endif /* __SELECTOR_H */
131