mirror of
https://github.com/libguestfs/libguestfs.git
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0f54df53d2
As part of our efforts to clean up and simplify libguestfs, removing gnulib deletes a large dependency that we mostly no longer use and causes problems for new users trying to build the library from source. A few modules from gnulib are still used (under a compatible license) and these are copied into gnulib/lib/
70 lines
2.6 KiB
C
70 lines
2.6 KiB
C
/* Non-blocking I/O for pipe or socket descriptors.
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Copyright (C) 2011-2021 Free Software Foundation, Inc.
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(NB: I modified the original GPL boilerplate here to LGPLv2+. This
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is because of the weird way that gnulib uses licenses, where the
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real license is covered in the modules/X file. The real license
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for this file is LGPLv2+, not GPL. - RWMJ)
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This library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2 of the License, or (at your option) any later version.
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This library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with this library; if not, write to the Free Software
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Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#ifndef _NONBLOCKING_H
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#define _NONBLOCKING_H
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#include <stdbool.h>
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/* Non-blocking I/O is an I/O mode by which read(), write() calls avoid
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blocking the current thread. When non-blocking is enabled:
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- A read() call returns -1 with errno set to EAGAIN when no data or EOF
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information is immediately available.
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- A write() call returns -1 with errno set to EAGAIN when it cannot
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transport the requested amount of data (but at most one pipe buffer)
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without blocking.
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Non-blocking I/O is most useful for character devices, pipes, and sockets.
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Whether it also works on regular files and block devices is platform
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dependent.
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There are three modern alternatives to non-blocking I/O:
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- use select() or poll() followed by read() or write() if the descriptor
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is ready,
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- call read() or write() in separate threads,
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- use <aio.h> interfaces. */
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#ifdef __cplusplus
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extern "C" {
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#endif
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/* Return 1 if I/O to the descriptor DESC is currently non-blocking, 0
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it is blocking, or -1 with errno set if fd is invalid or blocking
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status cannot be determined (such as with sockets on mingw). */
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extern int get_nonblocking_flag (int desc);
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/* Specify the non-blocking flag for the descriptor DESC.
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Return 0 upon success, or -1 with errno set upon failure.
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The default depends on the presence of the O_NONBLOCK flag for files
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or pipes opened with open() or on the presence of the SOCK_NONBLOCK
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flag for sockets. */
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extern int set_nonblocking_flag (int desc, bool value);
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#ifdef __cplusplus
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}
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#endif
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#endif /* _NONBLOCKING_H */
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