[Haskell-cafe] GHC.Ptr, Foreign.Storable, Data.Storable.Endian, looking for good examples of usage

[Aaron Gray]

On 10 January 2011 16:36, Antoine Latter <aslatter at gmail.com> wrote:

> On Mon, Jan 10, 2011 at 10:17 AM, Aaron Gray <aaronngray.lists at gmail.com>
> wrote:
> > On 10 January 2011 16:13, Daniel Fischer <
> daniel.is.fischer at googlemail.com>
> > wrote:
> >>
> >> On Monday 10 January 2011 16:45:36, Aaron Gray wrote:
> >> >
> >> > This is interesting, what does the following line do :-
> >> >
> >> >     data Int24 = I24# Int# deriving (Eq, Ord)
> >> >
> >> > regarding the I24# and Int#, are these inbuilt ?
> >>
> >> Int# is the raw machine int (4 or 8 bytes) and I24# is the constructor.
> >> GHC
> >> uses the magic hash '#' to denote raw unboxed types (and the
> constructors
> >> making ordinary boxed Haskell types from these, e.g. there's
> >>
> >> data Int = I# Int#
> >> data Word = W# Word#
> >> data Double = D# Double#
> >>
> >> and more defined in base [GHC.Types, GHC.Word]).
> >
> > So the 24 bit value is actually stored as a 32bit value. Meaning I will
> have
> > to do my own IO reader and writer code to a ByteString.
> > Thanks,
> > Aaron
> >
>
> I don't think so - the Storable instance provided for the Int24 type
> peeks and pokes 24-bit values. At least, that what I understand John's
> earlier message to mean.


Yes looking at the code it does support 24bit peeks and pokes.

Thanks,

Aaron
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