Copyright 1998 by the Massachusetts Institute of Technology.
SPDX-License-Identifier: MIT

ares_process - Process events for name resolution

#include <ares.h>

void ares_process(ares_channel_t *channel,
 fd_set *read_fds,
 fd_set *write_fds)

void ares_process_fd(ares_channel_t *channel,
 ares_socket_t read_fd,
 ares_socket_t write_fd)

The ares_process(3) function handles input/output events and timeouts associated with queries pending on the name service channel identified by channel . The file descriptor sets pointed to by read_fds and write_fds should have file descriptors set in them according to whether the file descriptors specified by ares_fds(3) are ready for reading and writing. (The easiest way to determine this information is to invoke select(3) with a timeout no greater than the timeout given by ares_timeout(3)). The ares_process(3) function will invoke callbacks for pending queries if they complete successfully or fail. ares_process_fd(3) 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 avoid select(3) 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 read_fds and write_fds for ares_process(3), or ARES_SOCKET_BAD for both read_fd and write_fd for ares_process_fd(3). The following code fragment waits for all pending queries on a channel to complete:

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);
}

ares_fds (3), ares_timeout (3) Greg Hudson, MIT Information Systems

Copyright 1998 by the Massachusetts Institute of Technology.