Async (no threads) resolver library?

[stenn at whimsy.udel.edu]

I need to provide gethostbyname() and gethostbyaddr() functionality in a
package (NTP) where the program cannot block; I'm happy to make a
sequence of calls and use an existing select() to catch/dispatch the
responses.  I cannot use threads.

Does anybody know where I might find an async (*not* threaded) resolver
library?

Harlan