On Tue, Dec 8, 2009 at 3:22 AM, Magicloud Magiclouds
<magicloud.magiclo...@gmail.com> wrote:
> Hi,
> I am warping some C libs. In one function, I do this:
> 183 allocaBytes bufLen $ \buf -> do
> 184 ret <- {# call buf_read #}
> 185 bluh
> 186 bala
> 187 buf
> 188 bufLen
> 189 if ret < 0
> 190 then userError "bufRead error"
> 191 else -- what should I do here?
>
> I am thinking about bytestring, to pass the content of the buf to
> the outside of the function. But I am not sure.
> What should I do?
See: Data.ByteString.Internal.createAndTrim:
http://hackage.haskell.org/packages/archive/bytestring/0.9.1.4/doc/html/Data-ByteString-Internal.html#v:createAndTrim
With that your program becomes something like:
createAndTrim bufLen $ \buf ->
ret <- {# call buf_read #}
bluh
bala
buf
bufLen
if ret < 0
then userError "bufRead error"
else return ret -- if ret indicates the number of bytes read
regards,
Bas
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