{-# LANGUAGE MagicHash #-} -- | -- Module : Data.Text.Internal.Unsafe.Shift -- Copyright : (c) Bryan O'Sullivan 2009 -- -- License : BSD-style -- Maintainer : bos@serpentine.com -- Stability : experimental -- Portability : GHC -- -- /Warning/: this is an internal module, and does not have a stable -- API or name. Functions in this module may not check or enforce -- preconditions expected by public modules. Use at your own risk! -- -- Fast, unchecked bit shifting functions. module Data.Text.Internal.Unsafe.Shift ( UnsafeShift(..) ) where -- import qualified Data.Bits as Bits import GHC.Base import GHC.Word -- | This is a workaround for poor optimisation in GHC 6.8.2. It -- fails to notice constant-width shifts, and adds a test and branch -- to every shift. This imposes about a 10% performance hit. -- -- These functions are undefined when the amount being shifted by is -- greater than the size in bits of a machine Int#. class UnsafeShift a where shiftL :: a -> Int -> a shiftR :: a -> Int -> a instance UnsafeShift Word16 where {-# INLINE shiftL #-} shiftL (W16# x#) (I# i#) = W16# (narrow16Word# (x# `uncheckedShiftL#` i#)) {-# INLINE shiftR #-} shiftR (W16# x#) (I# i#) = W16# (x# `uncheckedShiftRL#` i#) instance UnsafeShift Word32 where {-# INLINE shiftL #-} shiftL (W32# x#) (I# i#) = W32# (narrow32Word# (x# `uncheckedShiftL#` i#)) {-# INLINE shiftR #-} shiftR (W32# x#) (I# i#) = W32# (x# `uncheckedShiftRL#` i#) instance UnsafeShift Word64 where {-# INLINE shiftL #-} shiftL (W64# x#) (I# i#) = W64# (x# `uncheckedShiftL64#` i#) {-# INLINE shiftR #-} shiftR (W64# x#) (I# i#) = W64# (x# `uncheckedShiftRL64#` i#) instance UnsafeShift Int where {-# INLINE shiftL #-} shiftL (I# x#) (I# i#) = I# (x# `iShiftL#` i#) {-# INLINE shiftR #-} shiftR (I# x#) (I# i#) = I# (x# `iShiftRA#` i#) {- instance UnsafeShift Integer where {-# INLINE shiftL #-} shiftL = Bits.shiftL {-# INLINE shiftR #-} shiftR = Bits.shiftR -}