ISO2022JP encoding

Ignore-this: fa857024fa249fff451f5c024962484e

darcs-hash:20090303125641-a4fee-ac96e5788bb6b3cdf61f2e19f4bd19ece710e24b

Data/Encoding/ISO2022JP.hs

@@ -0,0 +1,52 @@
+{-# LANGUAGE DeriveDataTypeable #-}
+{- | Implements the japanese character encoding ISO 2022-JP.
+     See http://tools.ietf.org/html/rfc1468 for reference.
+ -}
+module Data.Encoding.ISO2022JP where
+
+import Data.Typeable
+
+import Data.Encoding.Base
+import Data.Encoding.Exception
+import Data.Encoding.ByteSource
+import Data.Encoding.ISO2022
+import Data.Encoding.ASCII
+import Data.Encoding.JISX0201
+import Data.Encoding.JISX0208
+
+import Control.Throws
+
+data ISO2022JP = ISO2022JP deriving (Eq,Show,Typeable)
+
+instance Encoding ISO2022JP where
+    encodeChar = encodeCharISO2022
+    decodeChar = decodeCharISO2022
+    encode = encodeISO2022
+    decode = decodeISO2022
+    encodeable _ c = encodeable ASCII c || encodeable JISX0201 c || encodeable JISX0208 c
+
+instance ISO2022 ISO2022JP where
+    readEscape _ = do
+      w <- fetchAhead fetchWord8
+      if w == 27
+        then (do
+               fetchWord8
+               w2 <- fetchWord8
+               w3 <- fetchWord8
+               case w2 of
+                 40 -> case w3 of
+                        66 -> return $ Just $ DynEncoding ASCII
+                        74 -> return $ Just $ DynEncoding JISX0201
+                        _ -> throwException (IllegalCharacter w3)
+                 36 -> case w3 of
+                        64 -> return $ Just $ DynEncoding JISX0208 -- XXX: this actually has to be the 1978 version of the standard... too bad I can't find it
+                        66 -> return $ Just $ DynEncoding JISX0208
+                        _ -> throwException (IllegalCharacter w3)
+                 _ -> throwException (IllegalCharacter w2)
+             )
+        else return Nothing
+    encodingForChar _ c
+        | encodeable ASCII c = Just (DynEncoding ASCII,[27,40,66])
+        | encodeable JISX0201 c = Just (DynEncoding JISX0201,[27,40,74])
+        | encodeable JISX0208 c = Just (DynEncoding JISX0208,[27,36,66])
+        | otherwise  = Nothing