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+/* Non-blocking I/O for pipe or socket descriptors.
+ Copyright (C) 2011-2022 Free Software Foundation, Inc.
+
+ This file is free software: you can redistribute it and/or modify
+ it under the terms of the GNU Lesser General Public License as
+ published by the Free Software Foundation; either version 2.1 of the
+ License, or (at your option) any later version.
+
+ This file 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 Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser 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 */