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/* Non-blocking I/O for pipe or socket descriptors.
Copyright (C) 2011-2020 Free Software Foundation, Inc.
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <https://www.gnu.org/licenses/>. */
#ifndef _NONBLOCKING_H
#define _NONBLOCKING_H
#include <stdbool.h>
/* Non-blocking I/O is an I/O mode by which read(), write() calls avoid
blocking the current thread. When non-blocking is enabled:
- A read() call returns -1 with errno set to EAGAIN when no data or EOF
information is immediately available.
- A write() call returns -1 with errno set to EAGAIN when it cannot
transport the requested amount of data (but at most one pipe buffer)
without blocking.
Non-blocking I/O is most useful for character devices, pipes, and sockets.
Whether it also works on regular files and block devices is platform
dependent.
There are three modern alternatives to non-blocking I/O:
- use select() or poll() followed by read() or write() if the descriptor
is ready,
- call read() or write() in separate threads,
- use <aio.h> interfaces. */
#ifdef __cplusplus
extern "C" {
#endif
/* Return 1 if I/O to the descriptor DESC is currently non-blocking, 0
it is blocking, or -1 with errno set if fd is invalid or blocking
status cannot be determined (such as with sockets on mingw). */
extern int get_nonblocking_flag (int desc);
/* Specify the non-blocking flag for the descriptor DESC.
Return 0 upon success, or -1 with errno set upon failure.
The default depends on the presence of the O_NONBLOCK flag for files
or pipes opened with open() or on the presence of the SOCK_NONBLOCK
flag for sockets. */
extern int set_nonblocking_flag (int desc, bool value);
#ifdef __cplusplus
}
#endif
#endif /* _NONBLOCKING_H */
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