On 2008 Jul 28, at 2:41, Galchin, Vasili wrote:

So based on what you are saying I kind of need a Haskell AIO "imperative"/monadic function that basically returns a handle that is associated with this AIOCB chunk-of-memory .... This handle gets passed around during an AIO I/O session?? Sorry for talking too "imperatively" ;^) <<< smiley face ;^)

I/O *is* monadic in Haskell, so you're kinda there anyway. I would in fact use a custom state (AIO = StateT ForeignPtr IO) if I were doing it; I would hide the constructor so that the only way to alter values is to call specific function(s) returning filled-in aiocbs as initialized and passed to aio_read/aio_write, then provide accessors for the contents (which if necessary can call aio_return, aio_suspend, or aio_error). Returning from the monad would invoke aio_suspend to wait for completion or aio_cancel to abort. (Hm. Could be argued that we want ContT here to represent the two possibilities.)

I note from my local documentation that (a) indeed you must not modify the aiocb after passing it to aio_read/aio_write and (b) the offset value should not be read, much less modified, because it could change during the async I/O (and not in a reliably useful fashion; consider buffering). And as I said earlier, the exact same memory block (not merely a copy of it) must be used for the same aiocb.