Re: [Haskell-cafe] Detecting system endianness

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 wrote:

...

I think something like this might work:

Prelude GHC.Exts GHC.Word> let W64# x = 0x100000002 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.