Cyrus IMAP Server: Prot Events
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From an email exchange between Ken Murchison and Lawrence Greenfield,
dated 03 Feb 2002 (slightly redacted and formatted for your viewing
pleasure):

   From: Ken Murchison
   To: Lawrence Greenfield
   Subject: Re: prot events


   Lawrence Greenfield wrote:

      Can you give me some details on how the event API in the prot
      layer works?  I'm a little unclear about the memory management,
      what should be returned from the event callback,

   Either the event pointer (if the event is still active), or NULL
   (if the event has been removed by the callback).

      and how to reschedule an event.

   Simply set the 'mark' time in the event to the wall time you want
   it to run again.

      (I'd like to make an event called every X seconds of idle time;
      I know the API can't do exactly that but I suspect I can fake it
      well enough.)

   Look at backend_timeout() in proxyd.c and/or drac_ping() in
   contrib/drac_auth.patch, they do exactly this.

   The API is pretty simple:

   * use prot_addwaitevent() to add an event (linked list) callback
     onto a stream.  takes the stream, the 'mark' time at which to run
     the event (NOT an interval, but the future clock value), the
     function pointer, and a rock to pass to the callback as args, and
     returns a pointer to the event (to use for future removal).

   * use prot_removewaitevent() to remove an event.  takes the stream
     and a pointer to the event as args.

   * the event callback gets the stream, a pointer to the event and
     the rock as args.  To reschedule an event, simply set the 'mark'
     time and return the event pointer.  If the callback removes the
     event, then return NULL.

   If you see and flaws in this API, feel free to go ahead and change
   it.

   Ken
