src/Data/Binary/FloatCast.hs

    {-# LANGUAGE FlexibleContexts #-}
    {-# LANGUAGE Trustworthy #-}

    -- | This module was written based on
    --   <http://hackage.haskell.org/package/reinterpret-cast-0.1.0/docs/src/Data-ReinterpretCast-Internal-ImplArray.html>.
    --
    --   Implements casting via a 1-elemnt STUArray, as described in
    --   <http://stackoverflow.com/a/7002812/263061>.
    module Data.Binary.FloatCast
      ( floatToWord
      , wordToFloat
      , doubleToWord
      , wordToDouble
      ) where

    import Data.Word (Word32, Word64)
    import Data.Array.ST (newArray, readArray, MArray, STUArray)
    import Data.Array.Unsafe (castSTUArray)
    import GHC.ST (runST, ST)

    -- | Reinterpret-casts a `Float` to a `Word32`.
    floatToWord :: Float -> Word32
    floatToWord x = runST (cast x)
    {-# INLINE floatToWord #-}

    -- | Reinterpret-casts a `Word32` to a `Float`.
    wordToFloat :: Word32 -> Float
    wordToFloat x = runST (cast x)
    {-# INLINE wordToFloat #-}

    -- | Reinterpret-casts a `Double` to a `Word64`.
    doubleToWord :: Double -> Word64
    doubleToWord x = runST (cast x)
    {-# INLINE doubleToWord #-}

    -- | Reinterpret-casts a `Word64` to a `Double`.
    wordToDouble :: Word64 -> Double
    wordToDouble x = runST (cast x)
    {-# INLINE wordToDouble #-}

    cast :: (MArray (STUArray s) a (ST s),
             MArray (STUArray s) b (ST s)) => a -> ST s b
    cast x = newArray (0 :: Int, 0) x >>= castSTUArray >>= flip readArray 0
    {-# INLINE cast #-}