Merge pull request #28 from jprider63/master

Wraps bad character sets

src/Data/Serialize.hs

@@ -255,6 +255,14 @@ instance (Serialize a,Integral a) => Serialize (R.Ratio a) where
 
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+-- Safely wrap `chr` to avoid exceptions. 
+-- `chr` source: http://hackage.haskell.org/package/base-4.7.0.2/docs/src/GHC-Char.html#chr
+chrEither :: Int -> Either String Char
+chrEither i
+  | i <= 0x10FFFF = Right (chr i) -- Or: C# (chr# i#)
+  | otherwise =
+     Left ("bad argument: " ++ show i)
+
 -- Char is serialised as UTF-8
 instance Serialize Char where
     put a | c <= 0x7f     = put (fromIntegral c :: Word8)
@@ -296,7 +304,11 @@ instance Serialize Char where
                                 z <- liftM (xor 0x80) getByte
                                 return (z .|. shiftL6 (y .|. shiftL6
                                         (x .|. shiftL6 (xor 0xf0 w))))
-        return $! chr r
+        case chrEither r of
+            Right r' -> 
+                return $! r'
+            Left err ->
+                fail err
 
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 -- Instances for the first few tuples