From: Ramakrishnan Muthukrishnan Date: Mon, 5 Dec 2016 16:22:37 +0000 (+0530) Subject: remove the older versions of checksum and checksumupdate X-Git-Url: https://git.rkrishnan.org/pf/content//%22%3C?a=commitdiff_plain;p=hs-rsync.git remove the older versions of checksum and checksumupdate --- diff --git a/src/Lib.hs b/src/Lib.hs index 596d94d..3f9aa00 100644 --- a/src/Lib.hs +++ b/src/Lib.hs @@ -90,17 +90,8 @@ recreate f0 blockSize ins = RBlk i -> (f0blocks !! i) `mappend` go f0blocks insts RChar w -> BL.singleton w `mappend` go f0blocks insts -rollingChecksum :: Int -> Int -> BL.ByteString -> Word32 -rollingChecksum strtIdx endIdx bs = a `mod` m + ((fromIntegral b) `mod` m) `shiftL` mb - where a = BL.foldl (\acc x -> acc + (fromIntegral x)) 0 bs' - b = BL.foldl (\acc x -> acc + x) 0 (BL.pack wbs') - bs' = BL.take (fromIntegral (endIdx - strtIdx + 1)) bs - m = 2^16 - mb = 16 - wbs' = BL.zipWith (*) (BL.pack (reverse (map fromIntegral [1..(endIdx - strtIdx + 1)]))) bs' - -checksum :: BL.ByteString -> Int -> Int -> Checksum -checksum bs strtIdx endIdx = (csval, strtIdx, endIdx) +rollingChecksum :: BL.ByteString -> Int -> Int -> Checksum +rollingChecksum bs strtIdx endIdx = (csval, strtIdx, endIdx) where csval = a `mod` m + ((fromIntegral b) `mod` m) `shiftL` size buffer = map fromIntegral $ take (endIdx - strtIdx) $ drop strtIdx $ BL.unpack bs indices = map fromIntegral [1..(endIdx - strtIdx + 1)] @@ -110,8 +101,8 @@ checksum bs strtIdx endIdx = (csval, strtIdx, endIdx) size = 16 -- given the checksum a(k, l) and b(k, l), find checksum a(k+1, l+1), b(k+1, l+1) -checksumUpdate :: Checksum -> BL.ByteString -> Checksum -checksumUpdate curCheckSum bs = (csval, oldStrtIdx + 1, oldEndIdx + 1) +rollingChecksumUpdate :: Checksum -> BL.ByteString -> Checksum +rollingChecksumUpdate curCheckSum bs = (csval, oldStrtIdx + 1, oldEndIdx + 1) where (oldChecksum, oldStrtIdx, oldEndIdx) = curCheckSum csval = a `mod` m + ((fromIntegral b) `mod` m) `shiftL` size m = 2^size @@ -122,15 +113,3 @@ checksumUpdate curCheckSum bs = (csval, oldStrtIdx + 1, oldEndIdx + 1) xlPlus1 = head $ drop (oldEndIdx + 1) $BL.unpack bs a = aold - fromIntegral xk + fromIntegral xlPlus1 b = a + bold - (fromIntegral (oldEndIdx - oldStrtIdx + 1)) - --- given the checksum of bytes from index: startIdx to endIdx, find --- the checksum for the block from (startIdx + 1 .. endIdx + 1) -rollingChecksumUpdate :: Word32 -> Word8 -> Word8 -> Integer -> Integer -> Word32 -rollingChecksumUpdate oldChecksum old new strtIdx endIdx = - let b_Old = (oldChecksum `shiftR` 16) .&. 0xff - a_Old = (oldChecksum .&. 0xff) - a_New = (a_Old - (fromIntegral old) + (fromIntegral new)) `mod` m - b_New = (b_Old - ((fromIntegral endIdx) - (fromIntegral strtIdx) + 1) * (fromIntegral old) + a_New) `mod` m - m = 2^16 - in - a_New `mod` m + (b_New `mod` m) * m