RE: Wanted: mmap or other fast IO
Manuel M. T. Chakravarty [EMAIL PROTECTED] writes: Sven Panne [EMAIL PROTECTED] wrote, [ Simply can't resist... ;-) ] Simon Marlow wrote: The easiest way is to declare mmap as a foreign function using foreign import, then build a little wrapper around it. A problem will be: What Haskell types should be used for size_t and off_t? Getting this done properly would require autoconf or something similar. Perhaps some more Haskell types (Size, Off, ...) should be added to the FFI module. I'm not sure which ones exactly and if FFI is the right place for it. Opinions? I don't think that the standard FFI is the right place for that. If you are programming the FFI by hand, autoconf is the right thing to use. Otherwise, a tool can help. C-Haskell can compute the right type by analysing the C headers, ie, feeding it `sys/mman.h'. H/Direct when fed `mman.h' might also do the right thing. I don't see why HDirect shouldn't. This request is not a new one - having a module that provides a Haskell mapping for the various 'abstract' types that ISO/ANSI C defines (and POSIX.1 doesn't.) It was a bit painful to introduce such a thing at the time (it very easily led to mutual dep. between the 'posix' and 'misc' syslibs), but perhaps the new library organization has untied the knot. --sigbjorn
RE: Wanted: mmap or other fast IO
Title: RE: Wanted: mmap or other fast IO Is there any interface to mmap(2) available? Something that behaves like an immutable array would be great. An mmap may have a signature like mmap :: Ix a, ?? b = Handle - IO (Array a b) I've no idea what types should be allowed for b. It has to be some fixed size type, e.g. Int, but this would require the mmapped file's size to be a multiple of the size of Ints. The easiest way is to declare mmap as a foreign function using foreign import, then build a little wrapper around it. Unfortunately you won't be able to turn the resulting memory into an array (even a ByteArray), since these are assumed to live in GHC's heap, but you'll be able to return an Addr and use writeXXXOffAddr/readXXXOffAddr to access it(*). Cheers, Simon (*) the readXXXOffAddr functions are known to be broken at the moment (see recent discussion on ghc-bugs), we're currently working on fixing them.
Re: Wanted: mmap or other fast IO
[ Simply can't resist... ;-) ] Simon Marlow wrote: The easiest way is to declare mmap as a foreign function using foreign import, then build a little wrapper around it. A problem will be: What Haskell types should be used for size_t and off_t? Getting this done properly would require autoconf or something similar. Perhaps some more Haskell types (Size, Off, ...) should be added to the FFI module. I'm not sure which ones exactly and if FFI is the right place for it. Opinions? [...] but you'll be able to return an Addr and use writeXXXOffAddr/ readXXXOffAddr to access it(*). If you are using GHC 4.06 you should better use the Storable class in the module FFI. For an idea what a slightly higher-level module layered upon FFI could look like, see http://www.informatik.uni-muenchen.de/~Sven.Panne/haskell_libs/ffi/Marshal.hs or Manuel's http://www.informatik.uni-muenchen.de/~Sven.Panne/haskell_libs/ffi/C2HSMarsh.hs from his C-HS tool. Both should be merged and improved somehow, suggestions welcome. (*) the readXXXOffAddr functions are known to be broken at the moment (see recent discussion on ghc-bugs), we're currently working on fixing them. A workaround is not using -O for modules using FFI or readXXXOffAddr. Cheers, Sven -- Sven PanneTel.: +49/89/2178-2235 LMU, Institut fuer Informatik FAX : +49/89/2178-2211 LFE Programmier- und Modellierungssprachen Oettingenstr. 67 mailto:[EMAIL PROTECTED]D-80538 Muenchen http://www.informatik.uni-muenchen.de/~Sven.Panne
Re: Wanted: mmap or other fast IO
Sven Panne [EMAIL PROTECTED] wrote, [ Simply can't resist... ;-) ] Simon Marlow wrote: The easiest way is to declare mmap as a foreign function using foreign import, then build a little wrapper around it. A problem will be: What Haskell types should be used for size_t and off_t? Getting this done properly would require autoconf or something similar. Perhaps some more Haskell types (Size, Off, ...) should be added to the FFI module. I'm not sure which ones exactly and if FFI is the right place for it. Opinions? I don't think that the standard FFI is the right place for that. If you are programming the FFI by hand, autoconf is the right thing to use. Otherwise, a tool can help. C-Haskell can compute the right type by analysing the C headers, ie, feeding it `sys/mman.h'. H/Direct when fed `mman.h' might also do the right thing. It might of course be nice to provide some libraries in hslibs/ that define access to some of the often used types and functions. Manuel
