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49 lines
1.6 KiB
Haskell
49 lines
1.6 KiB
Haskell
----------------------------------------------------------------------
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-- |
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-- Module : UTF8
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-- Maintainer : AR
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-- Stability : (stable)
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-- Portability : (portable)
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--
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-- > CVS $Date: 2005/04/21 16:23:42 $
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-- > CVS $Author: bringert $
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-- > CVS $Revision: 1.5 $
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--
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-- From the Char module supplied with HBC.
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-- code by Thomas Hallgren (Jul 10 1999)
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-----------------------------------------------------------------------------
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module GF.Text.UTF8 (decodeUTF8, encodeUTF8) where
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-- | Take a Unicode string and encode it as a string
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-- with the UTF8 method.
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decodeUTF8 :: String -> String
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decodeUTF8 "" = ""
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decodeUTF8 (c:cs) | c < '\x80' = c : decodeUTF8 cs
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decodeUTF8 (c:c':cs) | '\xc0' <= c && c <= '\xdf' &&
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'\x80' <= c' && c' <= '\xbf' =
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toEnum ((fromEnum c `mod` 0x20) * 0x40 + fromEnum c' `mod` 0x40) : decodeUTF8 cs
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decodeUTF8 (c:c':c'':cs) | '\xe0' <= c && c <= '\xef' &&
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'\x80' <= c' && c' <= '\xbf' &&
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'\x80' <= c'' && c'' <= '\xbf' =
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toEnum ((fromEnum c `mod` 0x10 * 0x1000) + (fromEnum c' `mod` 0x40) * 0x40 + fromEnum c'' `mod` 0x40) : decodeUTF8 cs
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decodeUTF8 s = s ---- AR workaround 22/6/2006
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----decodeUTF8 _ = error "UniChar.decodeUTF8: bad data"
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encodeUTF8 :: String -> String
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encodeUTF8 "" = ""
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encodeUTF8 (c:cs) =
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if c > '\x0000' && c < '\x0080' then
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c : encodeUTF8 cs
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else if c < toEnum 0x0800 then
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let i = fromEnum c
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in toEnum (0xc0 + i `div` 0x40) :
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toEnum (0x80 + i `mod` 0x40) :
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encodeUTF8 cs
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else
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let i = fromEnum c
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in toEnum (0xe0 + i `div` 0x1000) :
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toEnum (0x80 + (i `mod` 0x1000) `div` 0x40) :
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toEnum (0x80 + i `mod` 0x40) :
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encodeUTF8 cs
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