1 files changed, 45 insertions, 0 deletions
diff --git a/Text/Pandoc/UTF8.hs b/Text/Pandoc/UTF8.hs
new file mode 100644
index 000000000..16bdb9218
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+++ b/Text/Pandoc/UTF8.hs
@@ -0,0 +1,45 @@
+-- | Functions for converting Unicode strings to UTF-8 and vice versa.
+-- 
+-- Taken from <http://www.cse.ogi.edu/~hallgren/Talks/LHiH/base/lib/UTF8.hs>.
+-- (c) 2003, OGI School of Science & Engineering, Oregon Health and
+-- Science University.  
+--
+-- Modified by Martin Norbaeck
+-- to pass illegal UTF-8 sequences through unchanged.
+module Text.Pandoc.UTF8 ( 
+             fromUTF8, 
+             toUTF8 
+            ) where
+
+-- From the Char module supplied with HBC.
+
+-- | Take a UTF-8 string and decode it into a Unicode string.
+fromUTF8 :: String -> String
+fromUTF8 "" = ""
+fromUTF8 ('\xef':'\xbb':'\xbf':cs) = fromUTF8 cs -- skip BOM (byte order marker)
+fromUTF8 (c:c':cs) | '\xc0' <= c  && c  <= '\xdf' && 
+		             '\x80' <= c' && c' <= '\xbf' =
+	toEnum ((fromEnum c `mod` 0x20) * 0x40 + fromEnum c' `mod` 0x40) : fromUTF8 cs
+fromUTF8 (c:c':c'':cs) | '\xe0' <= c   && c   <= '\xef' && 
+		          '\x80' <= c'  && c'  <= '\xbf' &&
+		          '\x80' <= c'' && c'' <= '\xbf' =
+	toEnum ((fromEnum c `mod` 0x10 * 0x1000) + (fromEnum c' `mod` 0x40) * 0x40 + fromEnum c'' `mod` 0x40) : fromUTF8 cs
+fromUTF8 (c:cs) = c : fromUTF8 cs
+
+-- | Take a Unicode string and encode it as a UTF-8 string.
+toUTF8 :: String -> String
+toUTF8 "" = ""
+toUTF8 (c:cs) =
+	if c > '\x0000' && c < '\x0080' then
+	    c : toUTF8 cs
+	else if c < toEnum 0x0800 then
+	    let i = fromEnum c
+	    in  toEnum (0xc0 + i `div` 0x40) : 
+	        toEnum (0x80 + i `mod` 0x40) : 
+		toUTF8 cs
+	else
+	    let i = fromEnum c
+	    in  toEnum (0xe0 + i `div` 0x1000) : 
+	        toEnum (0x80 + (i `mod` 0x1000) `div` 0x40) : 
+		toEnum (0x80 + i `mod` 0x40) : 
+		toUTF8 cs