c-ares/ares_process.3

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.\" Copyright 1998 by the Massachusetts Institute of Technology.
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.TH ARES_PROCESS 3 "25 July 1998"
.SH NAME
ares_process \- Process events for name resolution
.SH SYNOPSIS
.nf
#include <ares.h>

void ares_process(ares_channel \fIchannel\fP,
                  fd_set *\fIread_fds\fP,
                  fd_set *\fIwrite_fds\fP)

void ares_process_fd(ares_channel \fIchannel\fP,
                     ares_socket_t \fIread_fd\fP,
                     ares_socket_t \fIwrite_fd\fP)
.fi
.SH DESCRIPTION
The \fBares_process(3)\fP function handles input/output events and timeouts
associated with queries pending on the name service channel identified by
.IR channel .
The file descriptor sets pointed to by \fIread_fds\fP and \fIwrite_fds\fP
should have file descriptors set in them according to whether the file
descriptors specified by \fIares_fds(3)\fP are ready for reading and writing.
(The easiest way to determine this information is to invoke \fBselect(3)\fP
with a timeout no greater than the timeout given by \fIares_timeout(3)\fP).

The \fBares_process(3)\fP function will invoke callbacks for pending queries
if they complete successfully or fail.

\fBares_process_fd(3)\fP works the same way but acts and operates only on the
specific file descriptors (sockets) you pass in to the function. Use
ARES_SOCKET_BAD for "no action". This function is provided to allow users of
c-ares to void \fIselect(3)\fP in their applications and within c-ares.

To only process possible timeout conditions without a socket event occurring,
one may pass NULL as the values for both \fIread_fds\fP and \fIwrite_fds\fP for
\fBares_process(3)\fP, or ARES_SOCKET_BAD for both \fIread_fd\fP and
\fIwrite_fd\fP for \fBares_process_fd(3)\fP.
.SH EXAMPLE
The following code fragment waits for all pending queries on a channel
to complete:

.nf
int nfds, count;
fd_set readers, writers;
struct timeval tv, *tvp;

while (1) {
  FD_ZERO(&readers);
  FD_ZERO(&writers);
  nfds = ares_fds(channel, &readers, &writers);
  if (nfds == 0)
    break;
  tvp = ares_timeout(channel, NULL, &tv);
  count = select(nfds, &readers, &writers, NULL, tvp);
  ares_process(channel, &readers, &writers);
}
.fi
.SH SEE ALSO
.BR ares_fds (3),
.BR ares_timeout (3)
.SH AUTHOR
Greg Hudson, MIT Information Systems
.br
Copyright 1998 by the Massachusetts Institute of Technology.