| /* 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 */ |