2020-11-16 14:47:43 +08:00
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.\"
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.\" Copyright 1998 by the Massachusetts Institute of Technology.
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.\"
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.\" Permission to use, copy, modify, and distribute this
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.\" software and its documentation for any purpose and without
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.\" fee is hereby granted, provided that the above copyright
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.\" notice appear in all copies and that both that copyright
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.\" notice and this permission notice appear in supporting
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.\" documentation, and that the name of M.I.T. not be used in
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.\" advertising or publicity pertaining to distribution of the
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.\" software without specific, written prior permission.
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.\" M.I.T. makes no representations about the suitability of
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.\" this software for any purpose. It is provided "as is"
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.\" without express or implied warranty.
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.\"
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.TH ARES_PROCESS 3 "25 July 1998"
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.SH NAME
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ares_process \- Process events for name resolution
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.SH SYNOPSIS
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.nf
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#include <ares.h>
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void ares_process(ares_channel \fIchannel\fP,
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fd_set *\fIread_fds\fP,
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fd_set *\fIwrite_fds\fP)
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void ares_process_fd(ares_channel \fIchannel\fP,
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ares_socket_t \fIread_fd\fP,
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ares_socket_t \fIwrite_fd\fP)
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.fi
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.SH DESCRIPTION
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The \fBares_process(3)\fP function handles input/output events and timeouts
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associated with queries pending on the name service channel identified by
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.IR channel .
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The file descriptor sets pointed to by \fIread_fds\fP and \fIwrite_fds\fP
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should have file descriptors set in them according to whether the file
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descriptors specified by \fIares_fds(3)\fP are ready for reading and writing.
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(The easiest way to determine this information is to invoke \fBselect(3)\fP
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with a timeout no greater than the timeout given by \fIares_timeout(3)\fP).
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The \fBares_process(3)\fP function will invoke callbacks for pending queries
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if they complete successfully or fail.
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\fBares_process_fd(3)\fP works the same way but acts and operates only on the
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specific file descriptors (sockets) you pass in to the function. Use
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ARES_SOCKET_BAD for "no action". This function is provided to allow users of
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2023-02-04 15:03:54 +08:00
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c-ares to avoid \fIselect(3)\fP in their applications and within c-ares.
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2020-11-16 14:47:43 +08:00
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To only process possible timeout conditions without a socket event occurring,
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one may pass NULL as the values for both \fIread_fds\fP and \fIwrite_fds\fP for
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\fBares_process(3)\fP, or ARES_SOCKET_BAD for both \fIread_fd\fP and
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\fIwrite_fd\fP for \fBares_process_fd(3)\fP.
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.SH EXAMPLE
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The following code fragment waits for all pending queries on a channel
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to complete:
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.nf
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int nfds, count;
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fd_set readers, writers;
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struct timeval tv, *tvp;
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while (1) {
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FD_ZERO(&readers);
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FD_ZERO(&writers);
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nfds = ares_fds(channel, &readers, &writers);
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if (nfds == 0)
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break;
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tvp = ares_timeout(channel, NULL, &tv);
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count = select(nfds, &readers, &writers, NULL, tvp);
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ares_process(channel, &readers, &writers);
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}
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.fi
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.SH SEE ALSO
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.BR ares_fds (3),
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.BR ares_timeout (3)
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.SH AUTHOR
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Greg Hudson, MIT Information Systems
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.br
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Copyright 1998 by the Massachusetts Institute of Technology.
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