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1/* `fd_set' type and related macros, and `select'/`pselect' declarations.
2 Copyright (C) 1996-2025 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
9
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
14
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, see
17 <https://www.gnu.org/licenses/>. */
18
19/* POSIX 1003.1g: 6.2 Select from File Descriptor Sets <sys/select.h> */
20
21#ifndef _SYS_SELECT_H
22#define _SYS_SELECT_H 1
23
24#include <features.h>
25
26/* Get definition of needed basic types. */
27#include <bits/types.h>
28
29/* Get __FD_* definitions. */
30#include <bits/select.h>
31
32/* Get sigset_t. */
33#include <bits/types/sigset_t.h>
34
35/* Get definition of timer specification structures. */
36#include <bits/types/time_t.h>
37#include <bits/types/struct_timeval.h>
38#ifdef __USE_XOPEN2K
39# include <bits/types/struct_timespec.h>
40#endif
41
42#ifndef __suseconds_t_defined
43typedef __suseconds_t suseconds_t;
44# define __suseconds_t_defined
45#endif
46
47
48/* The fd_set member is required to be an array of longs. */
49typedef long int __fd_mask;
50
51/* Some versions of <linux/posix_types.h> define this macros. */
52#undef __NFDBITS
53/* It's easier to assume 8-bit bytes than to get CHAR_BIT. */
54#define __NFDBITS (8 * (int) sizeof (__fd_mask))
55#define __FD_ELT(d) ((d) / __NFDBITS)
56#define __FD_MASK(d) ((__fd_mask) (1UL << ((d) % __NFDBITS)))
57
58/* fd_set for select and pselect. */
59typedef struct
60 {
61 /* XPG4.2 requires this member name. Otherwise avoid the name
62 from the global namespace. */
63#ifdef __USE_XOPEN
64 __fd_mask fds_bits[__FD_SETSIZE / __NFDBITS];
65# define __FDS_BITS(set) ((set)->fds_bits)
66#else
67 __fd_mask __fds_bits[__FD_SETSIZE / __NFDBITS];
68# define __FDS_BITS(set) ((set)->__fds_bits)
69#endif
70 } fd_set;
71
72/* Maximum number of file descriptors in `fd_set'. */
73#define FD_SETSIZE __FD_SETSIZE
74
75#ifdef __USE_MISC
76/* Sometimes the fd_set member is assumed to have this type. */
77typedef __fd_mask fd_mask;
78
79/* Number of bits per word of `fd_set' (some code assumes this is 32). */
80# define NFDBITS __NFDBITS
81#endif
82
83
84/* Access macros for `fd_set'. */
85#define FD_SET(fd, fdsetp) __FD_SET (fd, fdsetp)
86#define FD_CLR(fd, fdsetp) __FD_CLR (fd, fdsetp)
87#define FD_ISSET(fd, fdsetp) __FD_ISSET (fd, fdsetp)
88#define FD_ZERO(fdsetp) __FD_ZERO (fdsetp)
89
90
91__BEGIN_DECLS
92
93/* Check the first NFDS descriptors each in READFDS (if not NULL) for read
94 readiness, in WRITEFDS (if not NULL) for write readiness, and in EXCEPTFDS
95 (if not NULL) for exceptional conditions. If TIMEOUT is not NULL, time out
96 after waiting the interval specified therein. Returns the number of ready
97 descriptors, or -1 for errors.
98
99 This function is a cancellation point and therefore not marked with
100 __THROW. */
101#ifndef __USE_TIME64_REDIRECTS
102extern int select (int __nfds, fd_set *__restrict __readfds,
103 fd_set *__restrict __writefds,
104 fd_set *__restrict __exceptfds,
105 struct timeval *__restrict __timeout);
106#else
107# ifdef __REDIRECT
108extern int __REDIRECT (select,
109 (int __nfds, fd_set *__restrict __readfds,
110 fd_set *__restrict __writefds,
111 fd_set *__restrict __exceptfds,
112 struct timeval *__restrict __timeout),
113 __select64);
114# else
115# define select __select64
116# endif
117#endif
118
119#ifdef __USE_XOPEN2K
120/* Same as above only that the TIMEOUT value is given with higher
121 resolution and a sigmask which is been set temporarily. This version
122 should be used.
123
124 This function is a cancellation point and therefore not marked with
125 __THROW. */
126# ifndef __USE_TIME64_REDIRECTS
127extern int pselect (int __nfds, fd_set *__restrict __readfds,
128 fd_set *__restrict __writefds,
129 fd_set *__restrict __exceptfds,
130 const struct timespec *__restrict __timeout,
131 const __sigset_t *__restrict __sigmask);
132# else
133# ifdef __REDIRECT
134extern int __REDIRECT (pselect,
135 (int __nfds, fd_set *__restrict __readfds,
136 fd_set *__restrict __writefds,
137 fd_set *__restrict __exceptfds,
138 const struct timespec *__restrict __timeout,
139 const __sigset_t *__restrict __sigmask),
140 __pselect64);
141# else
142# define pselect __pselect64
143# endif
144# endif
145#endif
146
147
148/* Define some inlines helping to catch common problems. */
149#if __USE_FORTIFY_LEVEL > 0 && defined __GNUC__
150# include <bits/select2.h>
151#endif
152
153__END_DECLS
154
155#endif /* sys/select.h */