On Tue, Oct 26, 2010 at 12:21 AM, Johan Tibell <johan.tib...@gmail.com> wrote: > On Sun, Oct 24, 2010 at 2:02 AM, Johan Tibell <johan.tib...@gmail.com> wrote: >> I noticed that indexWordArray# only allows for aligned reads (by >> forcing the offset to be in words, rather than in bytes.) Is it >> possible to perform unaligned reads on a ByteArray# e.g. going via >> Addr#? There's the byteArrayContent# primitive but I don't know how to >> force the ByteArray# to stay pinned in memory while performing my >> reads. The ByteArray# is not guaranteed to be pinned in my case. > > It seems like I should be able to use (the undocumented) touch# > function to achieve this. Is that the case? >
I don't know much about GHC internals, but in the interest of keeping the conversation going I'll respond. I had thought that touch# prevented it from being collected - that is, it forces the GC to believe there is a reference to the region in memory so it doesn't disappear out from under the foreign call. So it is necessary for what you want, but I do not think sufficient. Whenever folks need a region to remain pinned in memory during a call use the various 'pined' allocation functions. All of the functions in Foreign.Marshal.Alloc use the pinned byte array allocation functions (aside from the ones which call malloc), which I take as the prototype of creating buffers to pass to foreign calls. Antoine _______________________________________________ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
