Strip any Byte Order Mark (BOM) from the front of decoded streams.

When decoding to UTF-32, Solaris iconv inserts a BOM at the front
of the stream, but Linux iconv doesn't.

diff --git a/GHC/IO/Handle/Internals.hs b/GHC/IO/Handle/Internals.hs
index b8dc82a..cc9e3d3 100644 (file)
--- a/GHC/IO/Handle/Internals.hs
+++ b/GHC/IO/Handle/Internals.hs
@@ -727,7 +727,7 @@ readTextDevice h_@Handle__{..} cbuf = do
 
   debugIO ("readTextDevice after reading: bbuf=" ++ summaryBuffer bbuf1)
 
-  (bbuf2,cbuf2) <-
+  (bbuf2,cbuf') <- 
       case haDecoder of
           Nothing      -> do
                writeIORef haLastDecode (error "codec_state", bbuf1)
@@ -737,16 +737,13 @@ readTextDevice h_@Handle__{..} cbuf = do
                writeIORef haLastDecode (state, bbuf1)
                (encode decoder) bbuf1 cbuf
 
-  debugIO ("readTextDevice after decoding: cbuf=" ++ summaryBuffer cbuf2 ++ 
+  debugIO ("readTextDevice after decoding: cbuf=" ++ summaryBuffer cbuf' ++ 
         " bbuf=" ++ summaryBuffer bbuf2)
 
-  cbuf3 <- stripByteOrderMark cbuf2
-
   writeIORef haByteBuffer bbuf2
-  if bufR cbuf3 == bufR cbuf -- no new characters
+  if bufR cbuf' == bufR cbuf -- no new characters
      then readTextDevice' h_ bbuf2 cbuf -- we need more bytes to make a Char
-     else return cbuf3
-
+     else return cbuf'
 
 -- we have an incomplete byte sequence at the end of the buffer: try to
 -- read more bytes.
@@ -795,7 +792,7 @@ readTextDeviceNonBlocking h_@Handle__{..} cbuf = do
                    if isNothing r then ioe_EOF else do  -- raise EOF
                    return bbuf1
 
-  (bbuf2,cbuf2) <-
+  (bbuf2,cbuf') <-
       case haDecoder of
           Nothing      -> do
                writeIORef haLastDecode (error "codec_state", bbuf1)
@@ -805,23 +802,5 @@ readTextDeviceNonBlocking h_@Handle__{..} cbuf = do
                writeIORef haLastDecode (state, bbuf1)
                (encode decoder) bbuf1 cbuf
 
-  cbuf3        <- stripByteOrderMark cbuf2
-
   writeIORef haByteBuffer bbuf2
-  return cbuf3
-
-
--- | When converting from UTF-8 to UCS-4, Solaris iconv adds a Byte Order Mark (BOM)
---     of value 0xfeff to the start of the stream. We don't want to return this to
---     the caller, so strip it here. This is a safe operation for other platforms,
---     so always do it.
-stripByteOrderMark :: CharBuffer -> IO CharBuffer
-stripByteOrderMark cbuf
-  | isEmptyBuffer cbuf
-  = return cbuf
-  
-  | otherwise
-  = do firstChar <- peekCharBuf (bufRaw cbuf) 0
-       if firstChar == chr 0xfeff
-        then   return (bufferRemove 1 cbuf)
-        else   return cbuf
+  return cbuf'