50 lines
1.5 KiB
Haskell
50 lines
1.5 KiB
Haskell
module Data.ByteString.Char8.Util (
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decodeHex
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, fromInt
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, hexString
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, previous
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, subBS
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, toInt
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, toBytes
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, utf16BEToutf8
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) where
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import Data.ByteString (ByteString, snoc)
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import qualified Data.ByteString as BS (empty, foldl, pack, singleton)
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import qualified Data.ByteString.Char8 as Char8 (drop, index, take, unpack)
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import Data.Text.Encoding (encodeUtf8, decodeUtf16BE)
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import Prelude hiding (length)
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previous :: Char -> Int -> ByteString -> Int
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previous char position byteString
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| Char8.index byteString position == char = position
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| otherwise = previous char (position - 1) byteString
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subBS :: Int -> Int -> ByteString -> ByteString
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subBS offset length = Char8.take length . Char8.drop offset
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hexString :: (Num a, Read a) => String -> a
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hexString s = read $ "0x" ++ s
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fromInt :: Int -> ByteString
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fromInt n
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| n < 0x100 = BS.singleton $ toEnum n
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| otherwise = fromInt (n `div` 0x100) `snoc` (toEnum (n `mod` 0x100))
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toBytes :: Int -> Int -> ByteString
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toBytes 0 _ = BS.empty
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toBytes size n = toBytes (size - 1) (n `div` 0x100) `snoc` (toEnum (n `mod` 0x100))
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toInt :: ByteString -> Int
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toInt = BS.foldl (\n w -> 0x100*n + fromEnum w) 0
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decodeHex :: ByteString -> ByteString
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decodeHex = BS.pack . fmap hexString . pairDigits . Char8.unpack
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where
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pairDigits "" = []
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pairDigits [c] = [[c]]
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pairDigits (firstChar:secondChar:end) = (firstChar:[secondChar]):pairDigits end
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utf16BEToutf8 :: ByteString -> ByteString
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utf16BEToutf8 = encodeUtf8 . decodeUtf16BE
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