With this package you can build a Storable instance of a record type from
Storable instances of its elements in an elegant way. It does not do any magic,
just a bit arithmetic to compute the right offsets, that would be otherwise
done manually or by a preprocessor like C2HS. I cannot promise that the
generated memory layout is compatible with that of a corresponding C struct.
However, the module generates the smallest layout that is possible with respect
to the alignment of the record elements. If you encounter, that a record does
not have a compatible layout, we should fix that. But also without C
compatibility this package is useful e.g. in connection with StorableVector.
We provide Storable instance support for several cases:
If you wrap a type in a 'newtype', then you can lift its 'Storable' instance
to that 'newtype' with the module "Foreign.Storable.Newtype". This way you do
not need the 'GeneralizedNewtypeDeriving' feature of GHC.
If you have a type that is an instance of 'Traversable', you can use that
feature for implementation of 'Storable' methods. The module
"Foreign.Storable.Traversable" allows manipulation of the portion of your type,
that is accessible by 'Traversable' methods. For instance with the type 'data T
a = Cons Int [a]' and an according 'Traversable' implementation, you can load
and store the elements of the contained list. This may be part of a 'Storable'
implementation of the whole type.
If you have a record containing elements of various types, then you need
Note however that the Storable instances defined with this package are quite
slow in (up to) GHC-6.12.1. I'm afraid this is due to incomplete inlining, but
we have still to investigate the problem.
For examples see packages 'storable-tuple' and 'sample-frame'.