[Haskell-cafe] Detecting system endianness

2008-12-18 Thread Mauricio 

Hi,

Is there some way I can check the endianness
of the machine my haskell code is running in?

Thanks,
Maurício

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Re: [Haskell-cafe] Detecting system endianness

2008-12-18 Thread Ryan Ingram 
I think something like this might work:

Prelude GHC.Exts GHC.Word let W64# x = 0x10002 in W32# (unsafeCoerce# x)
2

You should get 1 for big-endian and 2 for little-endian.

(Disclaimer: not particularily well-tested.)

  -- ryan

On Thu, Dec 18, 2008 at 3:27 AM, Mauricio briqueabra...@yahoo.com wrote:
 Hi,

 Is there some way I can check the endianness
 of the machine my haskell code is running in?

 Thanks,
 Maurício

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 Haskell-Cafe@haskell.org
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Re: [Haskell-cafe] Detecting system endianness

2008-12-18 Thread Ryan Ingram 
Actually, this is probably safer:

import Foreign.Marshal.Alloc
import Foreign.Ptr
import Foreign.Storable
import Data.Word
import System.IO.Unsafe

endianCheck = unsafePerformIO $ alloca $ \p - poke p (0x01020304 ::
Word32)  peek (castPtr p :: Ptr Word8)

littleEndian = endianCheck == 4
bigEndian = endianCheck == 1

  -- ryan

On Thu, Dec 18, 2008 at 4:33 AM, Ryan Ingram ryani.s...@gmail.com wrote:
 I think something like this might work:

 Prelude GHC.Exts GHC.Word let W64# x = 0x10002 in W32# (unsafeCoerce# x)
 2

 You should get 1 for big-endian and 2 for little-endian.

 (Disclaimer: not particularily well-tested.)

  -- ryan

 On Thu, Dec 18, 2008 at 3:27 AM, Mauricio briqueabra...@yahoo.com wrote:
 Hi,

 Is there some way I can check the endianness
 of the machine my haskell code is running in?

 Thanks,
 Maurício

 ___
 Haskell-Cafe mailing list
 Haskell-Cafe@haskell.org
 http://www.haskell.org/mailman/listinfo/haskell-cafe


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Re: [Haskell-cafe] Detecting system endianness

2008-12-18 Thread Holger Siegel 
On Thursday 18 December 2008 13:40:47 Ryan Ingram wrote:
 Actually, this is probably safer:

 import Foreign.Marshal.Alloc
 import Foreign.Ptr
 import Foreign.Storable
 import Data.Word
 import System.IO.Unsafe

 endianCheck = unsafePerformIO $ alloca $ \p - poke p (0x01020304 ::
 Word32)  peek (castPtr p :: Ptr Word8)

 littleEndian = endianCheck == 4
 bigEndian = endianCheck == 1

   -- ryan

 On Thu, Dec 18, 2008 at 4:33 AM, Ryan Ingram ryani.s...@gmail.com wrote:
  I think something like this might work:
 
  Prelude GHC.Exts GHC.Word let W64# x = 0x10002 in W32#
  (unsafeCoerce# x) 2
 
  You should get 1 for big-endian and 2 for little-endian.
 
  (Disclaimer: not particularily well-tested.)


Using modules Data.Binary, Data.Binary.Put and Data.Word, you can define

  littleEndian =  (decode $ runPut $ putWord16host 42 :: Word8) == 42

Under the hood, it also uses peek and poke, but it looks a bit more 
functional.


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Re: [Haskell-cafe] Detecting system endianness

2008-12-18 Thread wren ng thornton 
In a similar vein, is there already a function available to give the 
size of Word in bytes? Or should I write the usual Ptr conversion tricks 
to figure it out?




Holger Siegel wrote:

On Thursday 18 December 2008 13:40:47 Ryan Ingram wrote:

Actually, this is probably safer:

import Foreign.Marshal.Alloc
import Foreign.Ptr
import Foreign.Storable
import Data.Word
import System.IO.Unsafe

endianCheck = unsafePerformIO $ alloca $ \p - poke p (0x01020304 ::
Word32)  peek (castPtr p :: Ptr Word8)

littleEndian = endianCheck == 4
bigEndian = endianCheck == 1

  -- ryan



Using modules Data.Binary, Data.Binary.Put and Data.Word, you can define

  littleEndian =  (decode $ runPut $ putWord16host 42 :: Word8) == 42

Under the hood, it also uses peek and poke, but it looks a bit more 
functional.



--
Live well,
~wren
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Re: [Haskell-cafe] Detecting system endianness

2008-12-18 Thread Don Stewart 
Foreign.Storable.sizeOf

wren:
 In a similar vein, is there already a function available to give the 
 size of Word in bytes? Or should I write the usual Ptr conversion tricks 
 to figure it out?
 
 
 
 Holger Siegel wrote:
 On Thursday 18 December 2008 13:40:47 Ryan Ingram wrote:
 Actually, this is probably safer:
 
 import Foreign.Marshal.Alloc
 import Foreign.Ptr
 import Foreign.Storable
 import Data.Word
 import System.IO.Unsafe
 
 endianCheck = unsafePerformIO $ alloca $ \p - poke p (0x01020304 ::
 Word32)  peek (castPtr p :: Ptr Word8)
 
 littleEndian = endianCheck == 4
 bigEndian = endianCheck == 1
 
   -- ryan
 
 
 Using modules Data.Binary, Data.Binary.Put and Data.Word, you can define
 
   littleEndian =  (decode $ runPut $ putWord16host 42 :: Word8) == 42
 
 Under the hood, it also uses peek and poke, but it looks a bit more 
 functional.
 
 
 -- 
 Live well,
 ~wren
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Re: [Haskell-cafe] Detecting system endianness

2008-12-18 Thread George Pollard 
On Thu, 2008-12-18 at 22:35 -0500, wren ng thornton wrote:
 In a similar vein, is there already a function available to give the 
 size of Word in bytes? Or should I write the usual Ptr conversion tricks 
 to figure it out?

How about this:

(`div` 8) $ ceiling $ logBase 2 $ fromIntegral (maxBound :: Word)

Could write an integral log_2 function to make it nicer :)

- George


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