76c9a4a · binary-bits · git.iko.soy

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Implement putWord16be

76c9a4aLennart Kolmodin16 years ago

BitsPut.hs+16−1

@@ -1,6 +1,7 @@

1module BitsPut

2 ( putBool

3 , putWord8

4+ , putWord16be

4 , runBitPut

5 , runBitPut

5 )

6 )

6 where

7 where

@@ -43,7 +44,21 @@ putWord16be n w

43 | otherwise =

44 | otherwise =

44 BitPut $ \s -> PairS () $

45 BitPut $ \s -> PairS () $

45 case s of

46 case s of

47+ -- as n>=9, it's too big to fit into one single byte

48+ -- it'll either use 2 or 3 bytes

49+ -- it'll fit in 2 bytes

50+ (S b t o) | o + n <= 16 -> flush $

51+ let o' = o + n - 8

52+ w' = t .|. fromIntegral (w `shiftR` o')

53+ t' = fromIntegral (w `shiftL` (8-o'))

54+ in (S (b `mappend` B.singleton w') t' o')

55+ -- 3 bytes required

46− (S b t o) | otherwise -> undefined

56+ | otherwise -> flush $

57+ let o' = o + n - 16

58+ w' = t .|. fromIntegral (w `shiftR` (o' + 8))

59+ w'' = fromIntegral ((w `shiftR` o') .&. 0xff)

60+ t' = fromIntegral (w `shiftL` (8-o'))

61+ in (S (b `mappend` B.singleton w' `mappend` B.singleton w'') t' o')

48flush :: S -> S

63flush :: S -> S

49flush s@(S b w o)

64flush s@(S b w o)