Hello, I want to model an I/O read/write buffer in Haskell and marshall down into ANSI C. 1) ByteString? Or Ptr Word8? 2) What are example values of the types in 1)? Kind regards, Vasili
Basically I want to model POSIX async io "aiocb"( http://uw714doc.sco.com/en/man/html.5/aiocb.5.html) in Haskell .. in particular the aiocb field "aio_buf"! Kind regards, Vasili On Sun, Jun 22, 2008 at 1:47 AM, Galchin, Vasili <vigalchin@gmail.com> wrote:
Hello,
I want to model an I/O read/write buffer in Haskell and marshall down into ANSI C.
1) ByteString? Or Ptr Word8?
2) What are example values of the types in 1)?
Kind regards, Vasili
2008/6/23 Galchin, Vasili <vigalchin@gmail.com>:
Basically I want to model POSIX async io "aiocb"( http://uw714doc.sco.com/en/man/html.5/aiocb.5.html) in Haskell .. in particular the aiocb field "aio_buf"!
That's a mutable buffer, so this has to be pretty low level in your wrapping of the AIO interface. I would keep it as a Ptr Word8 at that point. ByteStrings are probably the correct type for the user visible interface, but I would guess not here. Plus, ByteString data lives in the Haskell heap so could get moved about by the collector. Since an AIO interface is probably going to return while the IO is still in progress, you don't want to stop the collector, but nor do you want the data moving because the kernel's pointer isn't going to move with it. AGL -- Adam Langley agl@imperialviolet.org http://www.imperialviolet.org
On Mon, Jun 23, 2008 at 12:07 PM, Adam Langley <agl@imperialviolet.org> wrote:
2008/6/23 Galchin, Vasili <vigalchin@gmail.com>:
Basically I want to model POSIX async io "aiocb"( http://uw714doc.sco.com/en/man/html.5/aiocb.5.html) in Haskell .. in particular the aiocb field "aio_buf"!
That's a mutable buffer, so this has to be pretty low level in your wrapping of the AIO interface. I would keep it as a Ptr Word8 at that point. ByteStrings are probably the correct type for the user visible interface, but I would guess not here.
I tried to write a test value of Word8 without success. Can you give an example?
Plus, ByteString data lives in the Haskell heap so could get moved about by the collector. Since an AIO interface is probably going to return while the IO is still in progress, you don't want to stop the collector, but nor do you want the data moving because the kernel's pointer isn't going to move with it.
^^ Interesting about moving around in the heap. I cannot use it for AIO.
AGL
-- Adam Langley agl@imperialviolet.org http://www.imperialviolet.org
On Mon, Jun 23, 2008 at 1:15 PM, Galchin, Vasili <vigalchin@gmail.com> wrote:
I tried to write a test value of Word8 without success. Can you give an example?
I'm not quite sure what you would want in such an example. See [1] for the malloc function. Then you take the result and wrap it with [2]: fp <- mallocBytes nbytes >>= newForeignPtr finalizerFree When you want to use it, use [3] to unwrap fp and get a raw Ptr Word8. You can pass these to foreign functions any place they expect a uint8_t *, char * etc. [1] http://www.haskell.org/hoogle/hoodoc.cgi?module=Foreign.Marshal.Alloc&name=m... [2] http://www.haskell.org/hoogle/hoodoc.cgi?module=Foreign.ForeignPtr&name=newF... [3] http://www.haskell.org/hoogle/hoodoc.cgi?module=Foreign.ForeignPtr&name=with... -- Adam Langley agl@imperialviolet.org http://www.imperialviolet.org
agl:
2008/6/23 Galchin, Vasili <vigalchin@gmail.com>:
Basically I want to model POSIX async io "aiocb"( http://uw714doc.sco.com/en/man/html.5/aiocb.5.html) in Haskell .. in particular the aiocb field "aio_buf"!
That's a mutable buffer, so this has to be pretty low level in your wrapping of the AIO interface. I would keep it as a Ptr Word8 at that point. ByteStrings are probably the correct type for the user visible interface, but I would guess not here.
Plus, ByteString data lives in the Haskell heap so could get moved about by the collector. Since an AIO interface is probably going to
ByteStrings are allocated into pinned memory, so they're easy to pass to C and back. It uses the fast 'mallocPlainForeignPtr' api, -- GHC notes: 'mallocPlainForeignPtr' has a heavily optimised -- implementation in GHC. It uses pinned memory in the garbage -- collected heap, as for mallocForeignPtr. So heap allocated and collected, but not moved.
return while the IO is still in progress, you don't want to stop the collector, but nor do you want the data moving because the kernel's pointer isn't going to move with it.
-- Don
On Mon, Jun 23, 2008 at 2:27 PM, Don Stewart <dons@galois.com> wrote:
So heap allocated and collected, but not moved.
My bad. In that case, you might want to work with ByteStrings all the way since it might make building the visible interface (which probably should use ByteStrings) easier. AGL -- Adam Langley agl@imperialviolet.org http://www.imperialviolet.org
ok ..... 1) how do I marshall from ByteString to char * (poke)?? 2) how do I write let x =??? :: Word8 3) how do I write let y = ??? ::ByteString Kind regards, Vasili On Mon, Jun 23, 2008 at 6:13 PM, Adam Langley <agl@imperialviolet.org> wrote:
On Mon, Jun 23, 2008 at 2:27 PM, Don Stewart <dons@galois.com> wrote:
So heap allocated and collected, but not moved.
My bad. In that case, you might want to work with ByteStrings all the way since it might make building the visible interface (which probably should use ByteStrings) easier.
AGL
-- Adam Langley agl@imperialviolet.org http://www.imperialviolet.org
e.g. on Word8 ..... let aiocb = AIOCB{ aioFd=fd, aioLioOpcode=0, aioReqPrio=0, aioOffset=0, aioBuf=??, <<<<<<<<<<<<<<<<<<<<< Ptr Word8 aioBytes=128, aioSigevent=event} ??? Kind regards, Vasili On Mon, Jun 23, 2008 at 8:13 PM, Galchin, Vasili <vigalchin@gmail.com> wrote:
ok .....
1) how do I marshall from ByteString to char * (poke)??
2) how do I write
let x =??? :: Word8
3) how do I write
let y = ??? ::ByteString
Kind regards, Vasili
On Mon, Jun 23, 2008 at 6:13 PM, Adam Langley <agl@imperialviolet.org> wrote:
On Mon, Jun 23, 2008 at 2:27 PM, Don Stewart <dons@galois.com> wrote:
So heap allocated and collected, but not moved.
My bad. In that case, you might want to work with ByteStrings all the way since it might make building the visible interface (which probably should use ByteStrings) easier.
AGL
-- Adam Langley agl@imperialviolet.org http://www.imperialviolet.org
See the Data.ByteString.Internal docs: http://www.haskell.org/ghc/docs/latest/html/libraries/bytestring/Data-ByteSt... Of course, you'd better not write to the contents of that pointer, or bad things could happen... David On Mon, Jun 23, 2008 at 08:18:23PM -0500, Galchin, Vasili wrote:
e.g. on Word8 .....
let aiocb = AIOCB{ aioFd=fd, aioLioOpcode=0, aioReqPrio=0, aioOffset=0, aioBuf=??, <<<<<<<<<<<<<<<<<<<<< Ptr Word8 aioBytes=128, aioSigevent=event}
???
Kind regards, Vasili
On Mon, Jun 23, 2008 at 8:13 PM, Galchin, Vasili <vigalchin@gmail.com> wrote:
ok .....
1) how do I marshall from ByteString to char * (poke)??
2) how do I write
let x =??? :: Word8
3) how do I write
let y = ??? ::ByteString
Kind regards, Vasili
On Mon, Jun 23, 2008 at 6:13 PM, Adam Langley <agl@imperialviolet.org> wrote:
On Mon, Jun 23, 2008 at 2:27 PM, Don Stewart <dons@galois.com> wrote:
So heap allocated and collected, but not moved.
My bad. In that case, you might want to work with ByteStrings all the way since it might make building the visible interface (which probably should use ByteStrings) easier.
AGL
participants (4)
-
Adam Langley -
David Roundy -
Don Stewart -
Galchin, Vasili