{-# LANGUAGE FlexibleInstances     #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE ScopedTypeVariables   #-}
{-# LANGUAGE TypeFamilies          #-}

module HaskellWorks.Data.Bits.Broadword.Word16
  ( h
  , l
  , kBitDiff
  , kBitDiffPos
  , kBitDiffUnsafe
  ) where

import Data.Word
import HaskellWorks.Data.Bits.BitWise

-- | Initialise all sub-words of size k where 'k' ∈ { 2, 4, 8, 16 } such that the lowest bit is set to 1 and all other bits are cleared.
--
-- >>> import Numeric(showHex)
-- >>> showHex (l 2) ""
-- "5555"
-- >>> showHex (l 4) ""
-- "1111"
-- >>> showHex (l 8) ""
-- "101"
-- >>> showHex (l 16) ""
-- "1"
l :: Int -> Word16
l :: Int -> Word16
l Int
2  = Word16
0x5555
l Int
4  = Word16
0x1111
l Int
8  = Word16
0x0101
l Int
16 = Word16
0x0001
l Int
k  = [Char] -> Word16
forall a. HasCallStack => [Char] -> a
error ([Char]
"Invalid h k where k = " [Char] -> [Char] -> [Char]
forall a. [a] -> [a] -> [a]
++ Int -> [Char]
forall a. Show a => a -> [Char]
show Int
k)
{-# INLINE l #-}

-- | Initialise all sub-words of size k where 'k' ∈ { 2, 4, 8, 16 } such that the highest bit is set to 1 and all other bits are cleared.
--
-- >>> import Numeric(showHex)
-- >>> showHex (h 2) ""
-- "aaaa"
-- >>> showHex (h 4) ""
-- "8888"
-- >>> showHex (h 8) ""
-- "8080"
-- >>> showHex (h 16) ""
-- "8000"
h :: Int -> Word16
h :: Int -> Word16
h Int
2  = Word16
0xaaaa
h Int
4  = Word16
0x8888
h Int
8  = Word16
0x8080
h Int
16 = Word16
0x8000
h Int
k  = [Char] -> Word16
forall a. HasCallStack => [Char] -> a
error ([Char]
"Invalid h k where k = " [Char] -> [Char] -> [Char]
forall a. [a] -> [a] -> [a]
++ Int -> [Char]
forall a. Show a => a -> [Char]
show Int
k)
{-# INLINE h #-}

-- | Broadword subtraction of sub-words of size 'k' where 'k' ∈ { 2, 4, 8, 16 }.
--
-- The subtraction respects 2's complement so sub-words may be regarded as signed or unsigned words.
--
-- >>> import Numeric(showHex)
-- >>> showHex (kBitDiff 8 0x0201 0x0101) ""
-- "100"
-- >>> showHex (kBitDiff 8 0x0201 0x0102) ""
-- "1ff"
-- >>> showHex (kBitDiff 8 0x20ff 0x10ff) ""
-- "1000"
kBitDiff :: Int -> Word16 -> Word16 -> Word16
kBitDiff :: Int -> Word16 -> Word16 -> Word16
kBitDiff Int
k Word16
x Word16
y = ((Word16
x Word16 -> Word16 -> Word16
forall a. BitWise a => a -> a -> a
.|. Int -> Word16
h Int
k) Word16 -> Word16 -> Word16
forall a. Num a => a -> a -> a
- (Word16
y Word16 -> Word16 -> Word16
forall a. BitWise a => a -> a -> a
.&. Word16 -> Word16
forall a. BitWise a => a -> a
comp (Int -> Word16
h Int
k))) Word16 -> Word16 -> Word16
forall a. BitWise a => a -> a -> a
.^. ((Word16
x Word16 -> Word16 -> Word16
forall a. BitWise a => a -> a -> a
.^. Word16 -> Word16
forall a. BitWise a => a -> a
comp Word16
y) Word16 -> Word16 -> Word16
forall a. BitWise a => a -> a -> a
.&. Int -> Word16
h Int
k)
{-# INLINE kBitDiff #-}

-- | Broadword subtraction of sub-words of size 'k' where 'k' ∈ { 2, 4, 8, 16 } where results are bounded from below by 0.
--
-- >>> import Numeric(showHex)
-- >>> showHex (kBitDiffPos 8 0x0201 0x0101) ""
-- "100"
-- >>> showHex (kBitDiffPos 8 0x0201 0x0102) ""
-- "100"
-- >>> showHex (kBitDiffPos 8 0x20ff 0x10ff) ""
-- "1000"
kBitDiffPos :: Int -> Word16 -> Word16 -> Word16
kBitDiffPos :: Int -> Word16 -> Word16 -> Word16
kBitDiffPos Int
k Word16
x Word16
y =
                                                                        -- let !_ = trace (">> x = " <> bitShow x) x in
                                                                        -- let !_ = trace (">> y = " <> bitShow y) y in
  let d :: Word16
d = Int -> Word16 -> Word16 -> Word16
kBitDiff Int
k Word16
x Word16
y                                            in  -- let !_ = trace (">> d = " <> bitShow d) d in
  let s :: Word16
s = Int -> Word16 -> Word16 -> Word16
kBitDiff Int
k Word16
0 ((Word16 -> Word16
forall a. BitWise a => a -> a
comp Word16
d Word16 -> Word16 -> Word16
forall a. BitWise a => a -> a -> a
.&. Int -> Word16
h Int
k) Word16 -> Count -> Word16
forall a. Shift a => a -> Count -> a
.>. Int -> Count
forall a b. (Integral a, Num b) => a -> b
fromIntegral (Int
k Int -> Int -> Int
forall a. Num a => a -> a -> a
- Int
1))  in  -- let !_ = trace (">> s = " <> bitShow s) s in
  let r :: Word16
r = Word16
d Word16 -> Word16 -> Word16
forall a. BitWise a => a -> a -> a
.&. Word16
s                                                   in  -- let !_ = trace (">> r = " <> bitShow r) r in
  Word16
r
{-# INLINE kBitDiffPos #-}

-- | Broadword subtraction of sub-words of size 'k' where 'k' ∈ { 2, 4, 8, 16, 32, 64 } where all the sub-words of 'x' and 'y' must
-- not have the signed bit set for the result to be meaningful.
--
-- >>> import Numeric(showHex)
-- >>> showHex (kBitDiffUnsafe 8 0x0201 0x0101) ""
-- "100"
-- >>> showHex (kBitDiffUnsafe 8 0x0201 0x0102) ""
-- "1ff"
-- >>> showHex (kBitDiffUnsafe 8 0x20ff 0x10ff) "" -- produces nonsense in the last sub-word
-- "1080"
kBitDiffUnsafe :: Int -> Word16 -> Word16 -> Word16
kBitDiffUnsafe :: Int -> Word16 -> Word16 -> Word16
kBitDiffUnsafe Int
k Word16
x Word16
y = ((Word16
x Word16 -> Word16 -> Word16
forall a. BitWise a => a -> a -> a
.|. Int -> Word16
h Int
k) Word16 -> Word16 -> Word16
forall a. Num a => a -> a -> a
- Word16
y) Word16 -> Word16 -> Word16
forall a. BitWise a => a -> a -> a
.^. Int -> Word16
h Int
k
{-# INLINE kBitDiffUnsafe #-}