module GHC.IO.Encoding (
BufferCodec(..), TextEncoding(..), TextEncoder, TextDecoder,
latin1, latin1_encode, latin1_decode,
- utf8,
+ utf8, utf8_bom,
utf16, utf16le, utf16be,
utf32, utf32le, utf32be,
localeEncoding,
utf8 :: TextEncoding
utf8 = UTF8.utf8
+-- | The UTF-8 Unicode encoding, with a byte-order-mark (BOM; the byte
+-- sequence 0xEF 0xBB 0xBF). This encoding behaves like 'utf8',
+-- except that on input, the BOM sequence is ignored at the beginning
+-- of the stream, and on output, the BOM sequence is prepended.
+--
+-- The byte-order-mark is strictly unnecessary in UTF-8, but is
+-- sometimes used to identify the encoding of a file.
+--
+utf8_bom :: TextEncoding
+utf8_bom = UTF8.utf8_bom
+
-- | The UTF-16 Unicode encoding (a byte-order-mark should be used to
-- indicate endianness).
utf16 :: TextEncoding
module GHC.IO.Encoding.UTF8 (
utf8,
- utf8_decode,
- utf8_encode,
+ utf8_bom,
) where
import GHC.Base
import GHC.Real
import GHC.Num
+import GHC.IORef
-- import GHC.IO
import GHC.IO.Exception
import GHC.IO.Buffer
setState = const $ return ()
})
+utf8_bom :: TextEncoding
+utf8_bom = TextEncoding { mkTextDecoder = utf8_bom_DF,
+ mkTextEncoder = utf8_bom_EF }
+
+utf8_bom_DF :: IO (TextDecoder Bool)
+utf8_bom_DF = do
+ ref <- newIORef True
+ return (BufferCodec {
+ encode = utf8_bom_decode ref,
+ close = return (),
+ getState = readIORef ref,
+ setState = writeIORef ref
+ })
+
+utf8_bom_EF :: IO (TextEncoder Bool)
+utf8_bom_EF = do
+ ref <- newIORef True
+ return (BufferCodec {
+ encode = utf8_bom_encode ref,
+ close = return (),
+ getState = readIORef ref,
+ setState = writeIORef ref
+ })
+
+utf8_bom_decode :: IORef Bool -> DecodeBuffer
+utf8_bom_decode ref
+ input@Buffer{ bufRaw=iraw, bufL=ir, bufR=iw, bufSize=_ }
+ output
+ = do
+ first <- readIORef ref
+ if not first
+ then utf8_decode input output
+ else do
+ let no_bom = do writeIORef ref False; utf8_decode input output
+ if iw - ir < 1 then return (input,output) else do
+ c0 <- readWord8Buf iraw ir
+ if (c0 /= bom0) then no_bom else do
+ if iw - ir < 2 then return (input,output) else do
+ c1 <- readWord8Buf iraw (ir+1)
+ if (c1 /= bom1) then no_bom else do
+ if iw - ir < 3 then return (input,output) else do
+ c2 <- readWord8Buf iraw (ir+2)
+ if (c2 /= bom2) then no_bom else do
+ -- found a BOM, ignore it and carry on
+ writeIORef ref False
+ utf8_decode input{ bufL = ir + 3 } output
+
+utf8_bom_encode :: IORef Bool -> EncodeBuffer
+utf8_bom_encode ref input
+ output@Buffer{ bufRaw=oraw, bufL=_, bufR=ow, bufSize=os }
+ = do
+ b <- readIORef ref
+ if not b then utf8_encode input output
+ else if os - ow < 3
+ then return (input,output)
+ else do
+ writeIORef ref False
+ writeWord8Buf oraw ow bom0
+ writeWord8Buf oraw (ow+1) bom1
+ writeWord8Buf oraw (ow+2) bom2
+ utf8_encode input output{ bufR = ow+3 }
+
+bom0, bom1, bom2 :: Word8
+bom0 = 0xef
+bom1 = 0xbb
+bom2 = 0xbf
+
utf8_decode :: DecodeBuffer
utf8_decode
input@Buffer{ bufRaw=iraw, bufL=ir0, bufR=iw, bufSize=_ }