ares_process (3)

#include <ares.h>

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

void ares_process_fd(ares_channel 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 with a timeout no greater than the timeout given by ares_timeout(3) ).

The ares_process 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 of course provided to allow users of c-ares to void select() in their applications and within c-ares.

EXAMPLE

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.