[Haskell-cafe] Re: POSIX AIO (asych I/O) ...
vigalchin at gmail.com
Wed Jul 2 01:42:20 EDT 2008
Haskell 101 question! I discovered that aio_error returns "errno" rather
-1. Of course, my aio_error binding is called before my aio_return binding
(aio calling sequence "protocol"). I have worked on Posix OS's for quite a
while but am unhappy with non-consistent errno handling ;^(. In any case, I
modified my aio_error binding implementation to have a "AIOCB -> IO Errno"
aioError :: AIOCB -> IO Errno
aioError aiocb = do
allocaBytes (#const sizeof(struct aiocb)) $ \ p_aiocb -> do
poke p_aiocb aiocb
errno <- throwErrnoIfMinus1 "aioError" (c_aio_error p_aiocb)
foreign import ccall safe "aio.h aio_error"
c_aio_error :: Ptr AIOCB -> IO Errno
"ghc" thinks that "Errno" should be an instance of "Num":
No instance for (Num Errno)
On Tue, Jul 1, 2008 at 2:42 AM, Galchin, Vasili <vigalchin at gmail.com> wrote:
> I am also testing my aio support. The aio_write binding seems to
> work ok .. as well as aio_error, Aio_return is a problem child. I think I
> wrote a really simple binding. I always receive nbytes as 0. I have been
> staring at the code hoping to catch a stupid mistake. I put putStrLn's in
> the code. .....Here is the code ...
> aioReturn :: AIOCB -> IO (AIOCB, ByteCount)
> aioReturn aiocb = do
> allocaBytes (#const sizeof(struct aiocb)) $ \ p_aiocb -> do
> poke p_aiocb aiocb
> count <- throwErrnoIfMinus1 "aioReturn" (c_aio_return p_aiocb)
> aiocb <- peek p_aiocb
> return (aiocb, fromIntegral count)
> foreign import ccall safe "aio.h aio_return"
> c_aio_return :: Ptr AIOCB -> IO CInt
> Maybe someone can spot something that I haven't.
> Thanks, Vasili
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