Re: Foreign C with pointers
Thanks to all, that is the example that i need. I'll test the example.zip right now. -- Luis Cabellos ___ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
Re: Foreign C with pointers
On Dec 19, 2007 3:05 AM, John Vogel [EMAIL PROTECTED] wrote: Lol, I am surprised that the library even compiled without the return addr;. But, this definition is correct: Well, yeah, for some value of correct. It works in this case but it will most likely bite you if you use it in any other way. The other 2 definitions don't even compile. I posted two new type-signatures and two new definitions. I'm quite sure the right combination would work. -- Cheers, Lemmih ___ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
Foreign C with pointers
Hi, I am creating a binding to an existing library (lib*.a) from Haskell. How can i bind a function that get a pointer? e.g: I have in the c library. int GetData( Data * d ); The steps that i need are: 1 - create the Data in Haskell 2 - create the foreign import sentence in a lib*.hs 3 - use the Data after the call Where can i get a good tutorial about FFI? I try http://www.haskell.org/hdirect/ffi.html but it's too general (need i pair of examples, i think) -- Thanks a lot, Luis Cabellos ___ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
Re: Foreign C with pointers
zhen.sydow: Hi, I am creating a binding to an existing library (lib*.a) from Haskell. How can i bind a function that get a pointer? e.g: I have in the c library. int GetData( Data * d ); The steps that i need are: 1 - create the Data in Haskell 2 - create the foreign import sentence in a lib*.hs 3 - use the Data after the call Where can i get a good tutorial about FFI? I try [1]http://www.haskell.org/hdirect/ffi.html but it's too general (need i pair of examples, i think) Say we have: #include string.h void * memmove(void *dst, const void *src, size_t len); We can bind to that as: foreign import unsafe ccall string.h memmove c_memmove :: Ptr Word8 - Ptr Word8 - CSize - IO (Ptr Word8) You can use Foreign.Ptr.* and Foreign.ForeignPtr (or even, say, Data.ByteString) to get at Ptr on the Haskell side. ___ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
Re: Foreign C with pointers
You do realize that the example you gave is just as general as all the
tutorials.
Here is an example I was working, but it gives a *segmentation fault* for
some reason:
example.h
typedef struct
{
unsigned char a;
unsigned char b;
unsigned char c;
unsigned char d;
} IP;
IP* shiftIP(IP* addr);
example.c
#include example.h
IP* shiftIP(IP* addr){
unsigned char t;
t = addr-a;
addr-a = addr-b;
addr-b = addr-c;
addr-c = addr-d;
addr-d = t;
}
Example.hsc
{-# OPTIONS -ffi -fglasgow-exts #-}
module Example where
import Foreign
import Foreign.C.Types
import Control.Monad
#include buzz.h
data MyIP = MyIP
{ a :: CUChar
, b :: CUChar
, c :: CUChar
, d :: CUChar
} deriving (Show)
instance Storable MyIP where
sizeOf _ = #{size IP} -- 4
alignment _ = alignment (undefined :: CUChar) -- 1
peek p = return MyIP
`ap` (#{peek IP, a} p)
`ap` (#{peek IP, b} p)
`ap` (#{peek IP, c} p)
`ap` (#{peek IP, d} p)
poke p ip = do
#{poke IP, a} p $ a ip
#{poke IP, b} p $ b ip
#{poke IP, c} p $ c ip
#{poke IP, d} p $ d ip
foreign import ccall safe static buzzlib.h shiftIP
shiftIP :: Ptr MyIP - Ptr MyIP
shiftMyIP :: MyIP - MyIP
shiftMyIP ip = unsafePerformIO . alloca $ \ptr - poke ptr ip peek
(shiftIP ptr)
___
Glasgow-haskell-users mailing list
Glasgow-haskell-users@haskell.org
http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
Re: Foreign C with pointers
On Dec 19, 2007 1:06 AM, John Vogel [EMAIL PROTECTED] wrote:
You do realize that the example you gave is just as general as all the
tutorials.
Here is an example I was working, but it gives a segmentation fault for some
reason:
example.h
typedef struct
{
unsigned char a;
unsigned char b;
unsigned char c;
unsigned char d;
} IP;
IP* shiftIP(IP* addr);
example.c
#include example.h
IP* shiftIP(IP* addr){
unsigned char t;
t = addr-a;
addr-a = addr-b;
addr-b = addr-c;
addr-c = addr-d;
addr-d = t;
}
return addr; ?
or rather, void shiftIP.
Example.hsc
{-# OPTIONS -ffi -fglasgow-exts #-}
module Example where
import Foreign
import Foreign.C.Types
import Control.Monad
#include buzz.h
data MyIP = MyIP
{ a :: CUChar
, b :: CUChar
, c :: CUChar
, d :: CUChar
} deriving (Show)
instance Storable MyIP where
sizeOf _ = #{size IP} -- 4
alignment _ = alignment (undefined :: CUChar) -- 1
peek p = return MyIP
`ap` (#{peek IP, a} p)
`ap` (#{peek IP, b} p)
`ap` (#{peek IP, c} p)
`ap` (#{peek IP, d} p)
poke p ip = do
#{poke IP, a} p $ a ip
#{poke IP, b} p $ b ip
#{poke IP, c} p $ c ip
#{poke IP, d} p $ d ip
foreign import ccall safe static buzzlib.h shiftIP
shiftIP :: Ptr MyIP - Ptr MyIP
shiftIP isn't a pure function.
shiftIP :: Ptr MyIP - IO (Ptr MyIP) or
shiftIP :: Ptr MyIP - IO ()
shiftMyIP :: MyIP - MyIP
shiftMyIP ip = unsafePerformIO . alloca $ \ptr - poke ptr ip peek
(shiftIP ptr)
shiftMyIP ip = unsafePerformIO . alloca $ \ptr - poke ptr ip peek
= (shiftIP ptr) or
shiftMyIP ip = unsafePerformIO . alloca $ \ptr - poke ptr ip
shiftIP ptr peek ptr
--
Cheers,
Lemmih
___
Glasgow-haskell-users mailing list
Glasgow-haskell-users@haskell.org
http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
