GHC/IO/Handle/Text.hs

{-# LANGUAGE Trustworthy #-}
{-# LANGUAGE CPP
 , NoImplicitPrelude
 , RecordWildCards
 , BangPatterns
 , PatternGuards
 , NondecreasingIndentation
 , MagicHash
 , ForeignFunctionInterface
 #-}
{-# OPTIONS_GHC -fno-warn-name-shadowing #-}
{-# OPTIONS_GHC -fno-warn-unused-matches #-}
{-# OPTIONS_HADDOCK hide #-}

-----------------------------------------------------------------------------
-- |
-- Module : GHC.IO.Text
-- Copyright : (c) The University of Glasgow, 1992-2008
-- License : see libraries/base/LICENSE
-- 
-- Maintainer : libraries@haskell.org
-- Stability : internal
-- Portability : non-portable
--
-- String I\/O functions
--
-----------------------------------------------------------------------------

-- #hide
module GHC.IO.Handle.Text ( 
 hWaitForInput, hGetChar, hGetLine, hGetContents, hPutChar, hPutStr,
 commitBuffer', -- hack, see below
 hGetBuf, hGetBufSome, hGetBufNonBlocking, hPutBuf, hPutBufNonBlocking,
 memcpy, hPutStrLn,
 ) where

import GHC.IO
import GHC.IO.FD
import GHC.IO.Buffer
import qualified GHC.IO.BufferedIO as Buffered
import GHC.IO.Exception
import GHC.Exception
import GHC.IO.Handle.Types
import GHC.IO.Handle.Internals
import qualified GHC.IO.Device as IODevice
import qualified GHC.IO.Device as RawIO

import Foreign
import Foreign.C

import qualified Control.Exception as Exception
import Data.Typeable
import System.IO.Error
import Data.Maybe
import Control.Monad

import GHC.IORef
import GHC.Base
import GHC.Real
import GHC.Num
import GHC.Show
import GHC.List

-- ---------------------------------------------------------------------------
-- Simple input operations

-- If hWaitForInput finds anything in the Handle's buffer, it
-- immediately returns. If not, it tries to read from the underlying
-- OS handle. Notice that for buffered Handles connected to terminals
-- this means waiting until a complete line is available.

-- | Computation 'hWaitForInput' @hdl t@
-- waits until input is available on handle @hdl@.
-- It returns 'True' as soon as input is available on @hdl@,
-- or 'False' if no input is available within @t@ milliseconds. Note that
-- 'hWaitForInput' waits until one or more full /characters/ are available,
-- which means that it needs to do decoding, and hence may fail
-- with a decoding error.
--
-- If @t@ is less than zero, then @hWaitForInput@ waits indefinitely.
--
-- This operation may fail with:
--
-- * 'isEOFError' if the end of file has been reached.
--
-- * a decoding error, if the input begins with an invalid byte sequence
-- in this Handle's encoding.
--
-- NOTE for GHC users: unless you use the @-threaded@ flag,
-- @hWaitForInput t@ where @t >= 0@ will block all other Haskell
-- threads for the duration of the call. It behaves like a
-- @safe@ foreign call in this respect.
--

hWaitForInput :: Handle -> Int -> IO Bool
hWaitForInput h msecs = do
 wantReadableHandle_ "hWaitForInput" h $ \ handle_@Handle__{..} -> do
 cbuf <- readIORef haCharBuffer

 if not (isEmptyBuffer cbuf) then return True else do

 if msecs < 0 
 then do cbuf' <- readTextDevice handle_ cbuf
 writeIORef haCharBuffer cbuf'
 return True
 else do
 -- there might be bytes in the byte buffer waiting to be decoded
 cbuf' <- decodeByteBuf handle_ cbuf
 writeIORef haCharBuffer cbuf'

 if not (isEmptyBuffer cbuf') then return True else do

 r <- IODevice.ready haDevice False{-read-} msecs
 if r then do -- Call hLookAhead' to throw an EOF
 -- exception if appropriate
 _ <- hLookAhead_ handle_
 return True
 else return False
 -- XXX we should only return when there are full characters
 -- not when there are only bytes. That would mean looping
 -- and re-running IODevice.ready if we don't have any full
 -- characters; but we don't know how long we've waited
 -- so far.

-- ---------------------------------------------------------------------------
-- hGetChar

-- | Computation 'hGetChar' @hdl@ reads a character from the file or
-- channel managed by @hdl@, blocking until a character is available.
--
-- This operation may fail with:
--
-- * 'isEOFError' if the end of file has been reached.

hGetChar :: Handle -> IO Char
hGetChar handle =
 wantReadableHandle_ "hGetChar" handle $ \handle_@Handle__{..} -> do

 -- buffering mode makes no difference: we just read whatever is available
 -- from the device (blocking only if there is nothing available), and then
 -- return the first character.
 -- See [note Buffered Reading] in GHC.IO.Handle.Types
 buf0 <- readIORef haCharBuffer

 buf1 <- if isEmptyBuffer buf0
 then readTextDevice handle_ buf0
 else return buf0

 (c1,i) <- readCharBuf (bufRaw buf1) (bufL buf1)
 let buf2 = bufferAdjustL i buf1

 if haInputNL == CRLF && c1 == '\r'
 then do
 mbuf3 <- if isEmptyBuffer buf2
 then maybeFillReadBuffer handle_ buf2
 else return (Just buf2)

 case mbuf3 of
 -- EOF, so just return the '\r' we have
 Nothing -> do
 writeIORef haCharBuffer buf2
 return '\r'
 Just buf3 -> do
 (c2,i2) <- readCharBuf (bufRaw buf2) (bufL buf2)
 if c2 == '\n'
 then do
 writeIORef haCharBuffer (bufferAdjustL i2 buf3)
 return '\n'
 else do
 -- not a \r\n sequence, so just return the \r
 writeIORef haCharBuffer buf3
 return '\r'
 else do
 writeIORef haCharBuffer buf2
 return c1

-- ---------------------------------------------------------------------------
-- hGetLine

-- | Computation 'hGetLine' @hdl@ reads a line from the file or
-- channel managed by @hdl@.
--
-- This operation may fail with:
--
-- * 'isEOFError' if the end of file is encountered when reading
-- the /first/ character of the line.
--
-- If 'hGetLine' encounters end-of-file at any other point while reading
-- in a line, it is treated as a line terminator and the (partial)
-- line is returned.

hGetLine :: Handle -> IO String
hGetLine h =
 wantReadableHandle_ "hGetLine" h $ \ handle_ -> do
 hGetLineBuffered handle_

hGetLineBuffered :: Handle__ -> IO String
hGetLineBuffered handle_@Handle__{..} = do
 buf <- readIORef haCharBuffer
 hGetLineBufferedLoop handle_ buf []

hGetLineBufferedLoop :: Handle__
 -> CharBuffer -> [String]
 -> IO String
hGetLineBufferedLoop handle_@Handle__{..}
 buf@Buffer{ bufL=r0, bufR=w, bufRaw=raw0 } xss =
 let
 -- find the end-of-line character, if there is one
 loop raw r
 | r == w = return (False, w)
 | otherwise = do
 (c,r') <- readCharBuf raw r
 if c == '\n'
 then return (True, r) -- NB. not r': don't include the '\n'
 else loop raw r'
 in do
 (eol, off) <- loop raw0 r0

 debugIO ("hGetLineBufferedLoop: r=" ++ show r0 ++ ", w=" ++ show w ++ ", off=" ++ show off)

 (xs,r') <- if haInputNL == CRLF
 then unpack_nl raw0 r0 off ""
 else do xs <- unpack raw0 r0 off ""
 return (xs,off)

 -- if eol == True, then off is the offset of the '\n'
 -- otherwise off == w and the buffer is now empty.
 if eol -- r' == off
 then do writeIORef haCharBuffer (bufferAdjustL (off+1) buf)
 return (concat (reverse (xs:xss)))
 else do
 let buf1 = bufferAdjustL r' buf
 maybe_buf <- maybeFillReadBuffer handle_ buf1
 case maybe_buf of
 -- Nothing indicates we caught an EOF, and we may have a
 -- partial line to return.
 Nothing -> do
 -- we reached EOF. There might be a lone \r left
 -- in the buffer, so check for that and
 -- append it to the line if necessary.
 -- 
 let pre = if not (isEmptyBuffer buf1) then "\r" else ""
 writeIORef haCharBuffer buf1{ bufL=0, bufR=0 }
 let str = concat (reverse (pre:xs:xss))
 if not (null str)
 then return str
 else ioe_EOF
 Just new_buf ->
 hGetLineBufferedLoop handle_ new_buf (xs:xss)

maybeFillReadBuffer :: Handle__ -> CharBuffer -> IO (Maybe CharBuffer)
maybeFillReadBuffer handle_ buf
 = Exception.catch
 (do buf' <- getSomeCharacters handle_ buf
 return (Just buf')
 )
 (\e -> do if isEOFError e
 then return Nothing
 else ioError e)

-- See GHC.IO.Buffer
#define CHARBUF_UTF32
-- #define CHARBUF_UTF16

-- NB. performance-critical code: eyeball the Core.
unpack :: RawCharBuffer -> Int -> Int -> [Char] -> IO [Char]
unpack !buf !r !w acc0
 | r == w = return acc0
 | otherwise = 
 withRawBuffer buf $ \pbuf -> 
 let
 unpackRB acc !i
 | i < r = return acc
 | otherwise = do
 -- Here, we are rather careful to only put an *evaluated* character
 -- in the output string. Due to pointer tagging, this allows the consumer
 -- to avoid ping-ponging between the actual consumer code and the thunk code
#ifdef CHARBUF_UTF16
 -- reverse-order decoding of UTF-16
 c2 <- peekElemOff pbuf i
 if (c2 < 0xdc00 || c2 > 0xdffff)
 then unpackRB (unsafeChr (fromIntegral c2) : acc) (i-1)
 else do c1 <- peekElemOff pbuf (i-1)
 let c = (fromIntegral c1 - 0xd800) * 0x400 +
 (fromIntegral c2 - 0xdc00) + 0x10000
 case desurrogatifyRoundtripCharacter (unsafeChr c) of
 { C# c# -> unpackRB (C# c# : acc) (i-2) }
#else
 c <- peekElemOff pbuf i
 unpackRB (c : acc) (i-1)
#endif
 in
 unpackRB acc0 (w-1)

-- NB. performance-critical code: eyeball the Core.
unpack_nl :: RawCharBuffer -> Int -> Int -> [Char] -> IO ([Char],Int)
unpack_nl !buf !r !w acc0
 | r == w = return (acc0, 0)
 | otherwise =
 withRawBuffer buf $ \pbuf ->
 let
 unpackRB acc !i
 | i < r = return acc
 | otherwise = do
 c <- peekElemOff pbuf i
 if (c == '\n' && i > r)
 then do
 c1 <- peekElemOff pbuf (i-1)
 if (c1 == '\r')
 then unpackRB ('\n':acc) (i-2)
 else unpackRB ('\n':acc) (i-1)
 else do
 unpackRB (c : acc) (i-1)
 in do
 c <- peekElemOff pbuf (w-1)
 if (c == '\r')
 then do 
 -- If the last char is a '\r', we need to know whether or
 -- not it is followed by a '\n', so leave it in the buffer
 -- for now and just unpack the rest.
 str <- unpackRB acc0 (w-2)
 return (str, w-1)
 else do
 str <- unpackRB acc0 (w-1)
 return (str, w)

-- Note [#5536]
--
-- We originally had
--
-- let c' = desurrogatifyRoundtripCharacter c in
-- c' `seq` unpackRB (c':acc) (i-1)
--
-- but this resulted in Core like
--
-- case (case x <# y of True -> C# e1; False -> C# e2) of c
-- C# _ -> unpackRB (c:acc) (i-1)
--
-- which compiles into a continuation for the outer case, with each
-- branch of the inner case building a C# and then jumping to the
-- continuation. We'd rather not have this extra jump, which makes
-- quite a difference to performance (see #5536) It turns out that
-- matching on the C# directly causes GHC to do the case-of-case,
-- giving much straighter code.

-- -----------------------------------------------------------------------------
-- hGetContents

-- hGetContents on a DuplexHandle only affects the read side: you can
-- carry on writing to it afterwards.

-- | Computation 'hGetContents' @hdl@ returns the list of characters
-- corresponding to the unread portion of the channel or file managed
-- by @hdl@, which is put into an intermediate state, /semi-closed/.
-- In this state, @hdl@ is effectively closed,
-- but items are read from @hdl@ on demand and accumulated in a special
-- list returned by 'hGetContents' @hdl@.
--
-- Any operation that fails because a handle is closed,
-- also fails if a handle is semi-closed. The only exception is 'hClose'.
-- A semi-closed handle becomes closed:
--
-- * if 'hClose' is applied to it;
--
-- * if an I\/O error occurs when reading an item from the handle;
--
-- * or once the entire contents of the handle has been read.
--
-- Once a semi-closed handle becomes closed, the contents of the
-- associated list becomes fixed. The contents of this final list is
-- only partially specified: it will contain at least all the items of
-- the stream that were evaluated prior to the handle becoming closed.
--
-- Any I\/O errors encountered while a handle is semi-closed are simply
-- discarded.
--
-- This operation may fail with:
--
-- * 'isEOFError' if the end of file has been reached.

hGetContents :: Handle -> IO String
hGetContents handle = 
 wantReadableHandle "hGetContents" handle $ \handle_ -> do
 xs <- lazyRead handle
 return (handle_{ haType=SemiClosedHandle}, xs )

-- Note that someone may close the semi-closed handle (or change its
-- buffering), so each time these lazy read functions are pulled on,
-- they have to check whether the handle has indeed been closed.

lazyRead :: Handle -> IO String
lazyRead handle = 
 unsafeInterleaveIO $
 withHandle "hGetContents" handle $ \ handle_ -> do
 case haType handle_ of
 ClosedHandle -> return (handle_, "")
 SemiClosedHandle -> lazyReadBuffered handle handle_
 _ -> ioException 
 (IOError (Just handle) IllegalOperation "hGetContents"
 "illegal handle type" Nothing Nothing)

lazyReadBuffered :: Handle -> Handle__ -> IO (Handle__, [Char])
lazyReadBuffered h handle_@Handle__{..} = do
 buf <- readIORef haCharBuffer
 Exception.catch
 (do
 buf'@Buffer{..} <- getSomeCharacters handle_ buf
 lazy_rest <- lazyRead h
 (s,r) <- if haInputNL == CRLF
 then unpack_nl bufRaw bufL bufR lazy_rest
 else do s <- unpack bufRaw bufL bufR lazy_rest
 return (s,bufR)
 writeIORef haCharBuffer (bufferAdjustL r buf')
 return (handle_, s)
 )
 (\e -> do (handle_', _) <- hClose_help handle_
 debugIO ("hGetContents caught: " ++ show e)
 -- We might have a \r cached in CRLF mode. So we
 -- need to check for that and return it:
 let r = if isEOFError e
 then if not (isEmptyBuffer buf)
 then "\r"
 else ""
 else
 throw (augmentIOError e "hGetContents" h)

 return (handle_', r)
 )

-- ensure we have some characters in the buffer
getSomeCharacters :: Handle__ -> CharBuffer -> IO CharBuffer
getSomeCharacters handle_@Handle__{..} buf@Buffer{..} =
 case bufferElems buf of

 -- buffer empty: read some more
 0 -> readTextDevice handle_ buf

 -- if the buffer has a single '\r' in it and we're doing newline
 -- translation: read some more
 1 | haInputNL == CRLF -> do
 (c,_) <- readCharBuf bufRaw bufL
 if c == '\r'
 then do -- shuffle the '\r' to the beginning. This is only safe
 -- if we're about to call readTextDevice, otherwise it
 -- would mess up flushCharBuffer.
 -- See [note Buffer Flushing], GHC.IO.Handle.Types
 _ <- writeCharBuf bufRaw 0 '\r'
 let buf' = buf{ bufL=0, bufR=1 }
 readTextDevice handle_ buf'
 else do
 return buf

 -- buffer has some chars in it already: just return it
 _otherwise ->
 return buf

-- ---------------------------------------------------------------------------
-- hPutChar

-- | Computation 'hPutChar' @hdl ch@ writes the character @ch@ to the
-- file or channel managed by @hdl@. Characters may be buffered if
-- buffering is enabled for @hdl@.
--
-- This operation may fail with:
--
-- * 'isFullError' if the device is full; or
--
-- * 'isPermissionError' if another system resource limit would be exceeded.

hPutChar :: Handle -> Char -> IO ()
hPutChar handle c = do
 c `seq` return ()
 wantWritableHandle "hPutChar" handle $ \ handle_ -> do
 hPutcBuffered handle_ c

hPutcBuffered :: Handle__ -> Char -> IO ()
hPutcBuffered handle_@Handle__{..} c = do
 buf <- readIORef haCharBuffer
 if c == '\n'
 then do buf1 <- if haOutputNL == CRLF
 then do
 buf1 <- putc buf '\r'
 putc buf1 '\n'
 else do
 putc buf '\n'
 writeCharBuffer handle_ buf1
 when is_line $ flushByteWriteBuffer handle_
 else do
 buf1 <- putc buf c
 writeCharBuffer handle_ buf1
 return ()
 where
 is_line = case haBufferMode of
 LineBuffering -> True
 _ -> False

 putc buf@Buffer{ bufRaw=raw, bufR=w } c = do
 debugIO ("putc: " ++ summaryBuffer buf)
 w' <- writeCharBuf raw w c
 return buf{ bufR = w' }

-- ---------------------------------------------------------------------------
-- hPutStr

-- We go to some trouble to avoid keeping the handle locked while we're
-- evaluating the string argument to hPutStr, in case doing so triggers another
-- I/O operation on the same handle which would lead to deadlock. The classic
-- case is
--
-- putStr (trace "hello" "world")
--
-- so the basic scheme is this:
--
-- * copy the string into a fresh buffer,
-- * "commit" the buffer to the handle.
--
-- Committing may involve simply copying the contents of the new
-- buffer into the handle's buffer, flushing one or both buffers, or
-- maybe just swapping the buffers over (if the handle's buffer was
-- empty). See commitBuffer below.

-- | Computation 'hPutStr' @hdl s@ writes the string
-- @s@ to the file or channel managed by @hdl@.
--
-- This operation may fail with:
--
-- * 'isFullError' if the device is full; or
--
-- * 'isPermissionError' if another system resource limit would be exceeded.

hPutStr :: Handle -> String -> IO ()
hPutStr handle str = hPutStr' handle str False

-- | The same as 'hPutStr', but adds a newline character.
hPutStrLn :: Handle -> String -> IO ()
hPutStrLn handle str = hPutStr' handle str True
 -- An optimisation: we treat hPutStrLn specially, to avoid the
 -- overhead of a single putChar '\n', which is quite high now that we
 -- have to encode eagerly.

hPutStr' :: Handle -> String -> Bool -> IO ()
hPutStr' handle str add_nl =
 do
 (buffer_mode, nl) <-
 wantWritableHandle "hPutStr" handle $ \h_ -> do
 bmode <- getSpareBuffer h_
 return (bmode, haOutputNL h_)

 case buffer_mode of
 (NoBuffering, _) -> do
 hPutChars handle str -- v. slow, but we don't care
 when add_nl $ hPutChar handle '\n'
 (LineBuffering, buf) -> do
 writeBlocks handle True add_nl nl buf str
 (BlockBuffering _, buf) -> do
 writeBlocks handle False add_nl nl buf str

hPutChars :: Handle -> [Char] -> IO ()
hPutChars _ [] = return ()
hPutChars handle (c:cs) = hPutChar handle c >> hPutChars handle cs

getSpareBuffer :: Handle__ -> IO (BufferMode, CharBuffer)
getSpareBuffer Handle__{haCharBuffer=ref, 
 haBuffers=spare_ref,
 haBufferMode=mode}
 = do
 case mode of
 NoBuffering -> return (mode, error "no buffer!")
 _ -> do
 bufs <- readIORef spare_ref
 buf <- readIORef ref
 case bufs of
 BufferListCons b rest -> do
 writeIORef spare_ref rest
 return ( mode, emptyBuffer b (bufSize buf) WriteBuffer)
 BufferListNil -> do
 new_buf <- newCharBuffer (bufSize buf) WriteBuffer
 return (mode, new_buf)


-- NB. performance-critical code: eyeball the Core.
writeBlocks :: Handle -> Bool -> Bool -> Newline -> Buffer CharBufElem -> String -> IO ()
writeBlocks hdl line_buffered add_nl nl
 buf@Buffer{ bufRaw=raw, bufSize=len } s =
 let
 shoveString :: Int -> [Char] -> [Char] -> IO ()
 shoveString !n [] [] = do
 commitBuffer hdl raw len n False{-no flush-} True{-release-}
 shoveString !n [] rest = do
 shoveString n rest []
 shoveString !n (c:cs) rest
 -- n+1 so we have enough room to write '\r\n' if necessary
 | n + 1 >= len = do
 commitBuffer hdl raw len n False{-flush-} False
 shoveString 0 (c:cs) rest
 | c == '\n' = do
 n' <- if nl == CRLF
 then do 
 n1 <- writeCharBuf raw n '\r'
 writeCharBuf raw n1 '\n'
 else do
 writeCharBuf raw n c
 if line_buffered
 then do
 -- end of line, so write and flush
 commitBuffer hdl raw len n' True{-flush-} False
 shoveString 0 cs rest
 else do
 shoveString n' cs rest
 | otherwise = do
 n' <- writeCharBuf raw n c
 shoveString n' cs rest
 in
 shoveString 0 s (if add_nl then "\n" else "")

-- -----------------------------------------------------------------------------
-- commitBuffer handle buf sz count flush release
-- 
-- Write the contents of the buffer 'buf' ('sz' bytes long, containing
-- 'count' bytes of data) to handle (handle must be block or line buffered).

commitBuffer
 :: Handle -- handle to commit to
 -> RawCharBuffer -> Int -- address and size (in bytes) of buffer
 -> Int -- number of bytes of data in buffer
 -> Bool -- True <=> flush the handle afterward
 -> Bool -- release the buffer?
 -> IO ()

commitBuffer hdl !raw !sz !count flush release = 
 wantWritableHandle "commitBuffer" hdl $ \h_@Handle__{..} -> do
 debugIO ("commitBuffer: sz=" ++ show sz ++ ", count=" ++ show count
 ++ ", flush=" ++ show flush ++ ", release=" ++ show release)

 writeCharBuffer h_ Buffer{ bufRaw=raw, bufState=WriteBuffer,
 bufL=0, bufR=count, bufSize=sz }

 when flush $ flushByteWriteBuffer h_

 -- release the buffer if necessary
 when release $ do
 -- find size of current buffer
 old_buf@Buffer{ bufSize=size } <- readIORef haCharBuffer
 when (sz == size) $ do
 spare_bufs <- readIORef haBuffers
 writeIORef haBuffers (BufferListCons raw spare_bufs)

 return ()

-- backwards compatibility; the text package uses this
commitBuffer' :: RawCharBuffer -> Int -> Int -> Bool -> Bool -> Handle__
 -> IO CharBuffer
commitBuffer' raw sz@(I# _) count@(I# _) flush release h_@Handle__{..}
 = do
 debugIO ("commitBuffer: sz=" ++ show sz ++ ", count=" ++ show count
 ++ ", flush=" ++ show flush ++ ", release=" ++ show release)

 let this_buf = Buffer{ bufRaw=raw, bufState=WriteBuffer,
 bufL=0, bufR=count, bufSize=sz }

 writeCharBuffer h_ this_buf

 when flush $ flushByteWriteBuffer h_

 -- release the buffer if necessary
 when release $ do
 -- find size of current buffer
 old_buf@Buffer{ bufSize=size } <- readIORef haCharBuffer
 when (sz == size) $ do
 spare_bufs <- readIORef haBuffers
 writeIORef haBuffers (BufferListCons raw spare_bufs)

 return this_buf

-- ---------------------------------------------------------------------------
-- Reading/writing sequences of bytes.

-- ---------------------------------------------------------------------------
-- hPutBuf

-- | 'hPutBuf' @hdl buf count@ writes @count@ 8-bit bytes from the
-- buffer @buf@ to the handle @hdl@. It returns ().
--
-- 'hPutBuf' ignores any text encoding that applies to the 'Handle',
-- writing the bytes directly to the underlying file or device.
--
-- 'hPutBuf' ignores the prevailing 'TextEncoding' and
-- 'NewlineMode' on the 'Handle', and writes bytes directly.
--
-- This operation may fail with:
--
-- * 'ResourceVanished' if the handle is a pipe or socket, and the
-- reading end is closed. (If this is a POSIX system, and the program
-- has not asked to ignore SIGPIPE, then a SIGPIPE may be delivered
-- instead, whose default action is to terminate the program).

hPutBuf :: Handle -- handle to write to
 -> Ptr a -- address of buffer
 -> Int -- number of bytes of data in buffer
 -> IO ()
hPutBuf h ptr count = do _ <- hPutBuf' h ptr count True
 return ()

hPutBufNonBlocking
 :: Handle -- handle to write to
 -> Ptr a -- address of buffer
 -> Int -- number of bytes of data in buffer
 -> IO Int -- returns: number of bytes written
hPutBufNonBlocking h ptr count = hPutBuf' h ptr count False

hPutBuf':: Handle -- handle to write to
 -> Ptr a -- address of buffer
 -> Int -- number of bytes of data in buffer
 -> Bool -- allow blocking?
 -> IO Int
hPutBuf' handle ptr count can_block
 | count == 0 = return 0
 | count < 0 = illegalBufferSize handle "hPutBuf" count
 | otherwise = 
 wantWritableHandle "hPutBuf" handle $ 
 \ h_@Handle__{..} -> do
 debugIO ("hPutBuf count=" ++ show count)

 r <- bufWrite h_ (castPtr ptr) count can_block

 -- we must flush if this Handle is set to NoBuffering. If
 -- it is set to LineBuffering, be conservative and flush
 -- anyway (we didn't check for newlines in the data).
 case haBufferMode of
 BlockBuffering _ -> do return ()
 _line_or_no_buffering -> do flushWriteBuffer h_
 return r

bufWrite :: Handle__-> Ptr Word8 -> Int -> Bool -> IO Int
bufWrite h_@Handle__{..} ptr count can_block =
 seq count $ do -- strictness hack
 old_buf@Buffer{ bufRaw=old_raw, bufR=w, bufSize=size }
 <- readIORef haByteBuffer

 -- enough room in handle buffer?
 if (size - w > count)
 -- There's enough room in the buffer:
 -- just copy the data in and update bufR.
 then do debugIO ("hPutBuf: copying to buffer, w=" ++ show w)
 copyToRawBuffer old_raw w ptr count
 writeIORef haByteBuffer old_buf{ bufR = w + count }
 return count

 -- else, we have to flush
 else do debugIO "hPutBuf: flushing first"
 old_buf' <- Buffered.flushWriteBuffer haDevice old_buf
 -- TODO: we should do a non-blocking flush here
 writeIORef haByteBuffer old_buf'
 -- if we can fit in the buffer, then just loop 
 if count < size
 then bufWrite h_ ptr count can_block
 else if can_block
 then do writeChunk h_ (castPtr ptr) count
 return count
 else writeChunkNonBlocking h_ (castPtr ptr) count

writeChunk :: Handle__ -> Ptr Word8 -> Int -> IO ()
writeChunk h_@Handle__{..} ptr bytes
 | Just fd <- cast haDevice = RawIO.write (fd::FD) ptr bytes
 | otherwise = error "Todo: hPutBuf"

writeChunkNonBlocking :: Handle__ -> Ptr Word8 -> Int -> IO Int
writeChunkNonBlocking h_@Handle__{..} ptr bytes 
 | Just fd <- cast haDevice = RawIO.writeNonBlocking (fd::FD) ptr bytes
 | otherwise = error "Todo: hPutBuf"

-- ---------------------------------------------------------------------------
-- hGetBuf

-- | 'hGetBuf' @hdl buf count@ reads data from the handle @hdl@
-- into the buffer @buf@ until either EOF is reached or
-- @count@ 8-bit bytes have been read.
-- It returns the number of bytes actually read. This may be zero if
-- EOF was reached before any data was read (or if @count@ is zero).
--
-- 'hGetBuf' never raises an EOF exception, instead it returns a value
-- smaller than @count@.
--
-- If the handle is a pipe or socket, and the writing end
-- is closed, 'hGetBuf' will behave as if EOF was reached.
--
-- 'hGetBuf' ignores the prevailing 'TextEncoding' and 'NewlineMode'
-- on the 'Handle', and reads bytes directly.

hGetBuf :: Handle -> Ptr a -> Int -> IO Int
hGetBuf h ptr count
 | count == 0 = return 0
 | count < 0 = illegalBufferSize h "hGetBuf" count
 | otherwise = 
 wantReadableHandle_ "hGetBuf" h $ \ h_@Handle__{..} -> do
 flushCharReadBuffer h_
 buf@Buffer{ bufRaw=raw, bufR=w, bufL=r, bufSize=sz }
 <- readIORef haByteBuffer
 if isEmptyBuffer buf
 then bufReadEmpty h_ buf (castPtr ptr) 0 count
 else bufReadNonEmpty h_ buf (castPtr ptr) 0 count

-- small reads go through the buffer, large reads are satisfied by
-- taking data first from the buffer and then direct from the file
-- descriptor.

bufReadNonEmpty :: Handle__ -> Buffer Word8 -> Ptr Word8 -> Int -> Int -> IO Int
bufReadNonEmpty h_@Handle__{..}
 buf@Buffer{ bufRaw=raw, bufR=w, bufL=r, bufSize=sz }
 ptr !so_far !count 
 = do
 let avail = w - r
 if (count < avail)
 then do 
 copyFromRawBuffer ptr raw r count
 writeIORef haByteBuffer buf{ bufL = r + count }
 return (so_far + count)
 else do
 
 copyFromRawBuffer ptr raw r avail
 let buf' = buf{ bufR=0, bufL=0 }
 writeIORef haByteBuffer buf'
 let remaining = count - avail
 so_far' = so_far + avail
 ptr' = ptr `plusPtr` avail

 if remaining == 0 
 then return so_far'
 else bufReadEmpty h_ buf' ptr' so_far' remaining


bufReadEmpty :: Handle__ -> Buffer Word8 -> Ptr Word8 -> Int -> Int -> IO Int
bufReadEmpty h_@Handle__{..}
 buf@Buffer{ bufRaw=raw, bufR=w, bufL=r, bufSize=sz }
 ptr so_far count
 | count > sz, Just fd <- cast haDevice = loop fd 0 count
 | otherwise = do
 (r,buf') <- Buffered.fillReadBuffer haDevice buf
 if r == 0 
 then return so_far
 else do writeIORef haByteBuffer buf'
 bufReadNonEmpty h_ buf' ptr so_far count
 where
 loop :: FD -> Int -> Int -> IO Int
 loop fd off bytes | bytes <= 0 = return (so_far + off)
 loop fd off bytes = do
 r <- RawIO.read (fd::FD) (ptr `plusPtr` off) bytes
 if r == 0
 then return (so_far + off)
 else loop fd (off + r) (bytes - r)

-- ---------------------------------------------------------------------------
-- hGetBufSome

-- | 'hGetBufSome' @hdl buf count@ reads data from the handle @hdl@
-- into the buffer @buf@. If there is any data available to read,
-- then 'hGetBufSome' returns it immediately; it only blocks if there
-- is no data to be read.
--
-- It returns the number of bytes actually read. This may be zero if
-- EOF was reached before any data was read (or if @count@ is zero).
--
-- 'hGetBufSome' never raises an EOF exception, instead it returns a value
-- smaller than @count@.
--
-- If the handle is a pipe or socket, and the writing end
-- is closed, 'hGetBufSome' will behave as if EOF was reached.
--
-- 'hGetBufSome' ignores the prevailing 'TextEncoding' and 'NewlineMode'
-- on the 'Handle', and reads bytes directly.

hGetBufSome :: Handle -> Ptr a -> Int -> IO Int
hGetBufSome h ptr count
 | count == 0 = return 0
 | count < 0 = illegalBufferSize h "hGetBufSome" count
 | otherwise =
 wantReadableHandle_ "hGetBufSome" h $ \ h_@Handle__{..} -> do
 flushCharReadBuffer h_
 buf@Buffer{ bufSize=sz } <- readIORef haByteBuffer
 if isEmptyBuffer buf
 then if count > sz -- large read?
 then do RawIO.read (haFD h_) (castPtr ptr) count
 else do (r,buf') <- Buffered.fillReadBuffer haDevice buf
 if r == 0
 then return 0
 else do writeIORef haByteBuffer buf'
 bufReadNBNonEmpty h_ buf' (castPtr ptr) 0 (min r count)
 -- new count is (min r count), so
 -- that bufReadNBNonEmpty will not
 -- issue another read.
 else
 let count' = min count (bufferElems buf)
 in bufReadNBNonEmpty h_ buf (castPtr ptr) 0 count'

haFD :: Handle__ -> FD
haFD h_@Handle__{..} =
 case cast haDevice of
 Nothing -> error "not an FD"
 Just fd -> fd

-- | 'hGetBufNonBlocking' @hdl buf count@ reads data from the handle @hdl@
-- into the buffer @buf@ until either EOF is reached, or
-- @count@ 8-bit bytes have been read, or there is no more data available
-- to read immediately.
--
-- 'hGetBufNonBlocking' is identical to 'hGetBuf', except that it will
-- never block waiting for data to become available, instead it returns
-- only whatever data is available. To wait for data to arrive before
-- calling 'hGetBufNonBlocking', use 'hWaitForInput'.
--
-- If the handle is a pipe or socket, and the writing end
-- is closed, 'hGetBufNonBlocking' will behave as if EOF was reached.
--
-- 'hGetBufNonBlocking' ignores the prevailing 'TextEncoding' and
-- 'NewlineMode' on the 'Handle', and reads bytes directly.
--
-- NOTE: on Windows, this function does not work correctly; it
-- behaves identically to 'hGetBuf'.

hGetBufNonBlocking :: Handle -> Ptr a -> Int -> IO Int
hGetBufNonBlocking h ptr count
 | count == 0 = return 0
 | count < 0 = illegalBufferSize h "hGetBufNonBlocking" count
 | otherwise = 
 wantReadableHandle_ "hGetBufNonBlocking" h $ \ h_@Handle__{..} -> do
 flushCharReadBuffer h_
 buf@Buffer{ bufRaw=raw, bufR=w, bufL=r, bufSize=sz }
 <- readIORef haByteBuffer
 if isEmptyBuffer buf
 then bufReadNBEmpty h_ buf (castPtr ptr) 0 count
 else bufReadNBNonEmpty h_ buf (castPtr ptr) 0 count

bufReadNBEmpty :: Handle__ -> Buffer Word8 -> Ptr Word8 -> Int -> Int -> IO Int
bufReadNBEmpty h_@Handle__{..}
 buf@Buffer{ bufRaw=raw, bufR=w, bufL=r, bufSize=sz }
 ptr so_far count
 | count > sz,
 Just fd <- cast haDevice = do
 m <- RawIO.readNonBlocking (fd::FD) ptr count
 case m of
 Nothing -> return so_far
 Just n -> return (so_far + n)

 | otherwise = do
 buf <- readIORef haByteBuffer
 (r,buf') <- Buffered.fillReadBuffer0 haDevice buf
 case r of
 Nothing -> return so_far
 Just 0 -> return so_far
 Just r -> do
 writeIORef haByteBuffer buf'
 bufReadNBNonEmpty h_ buf' ptr so_far (min count r)
 -- NOTE: new count is min count r
 -- so we will just copy the contents of the
 -- buffer in the recursive call, and not
 -- loop again.


bufReadNBNonEmpty :: Handle__ -> Buffer Word8 -> Ptr Word8 -> Int -> Int -> IO Int
bufReadNBNonEmpty h_@Handle__{..}
 buf@Buffer{ bufRaw=raw, bufR=w, bufL=r, bufSize=sz }
 ptr so_far count
 = do
 let avail = w - r
 if (count < avail)
 then do 
 copyFromRawBuffer ptr raw r count
 writeIORef haByteBuffer buf{ bufL = r + count }
 return (so_far + count)
 else do

 copyFromRawBuffer ptr raw r avail
 let buf' = buf{ bufR=0, bufL=0 }
 writeIORef haByteBuffer buf'
 let remaining = count - avail
 so_far' = so_far + avail
 ptr' = ptr `plusPtr` avail

 if remaining == 0
 then return so_far'
 else bufReadNBEmpty h_ buf' ptr' so_far' remaining

-- ---------------------------------------------------------------------------
-- memcpy wrappers

copyToRawBuffer :: RawBuffer e -> Int -> Ptr e -> Int -> IO ()
copyToRawBuffer raw off ptr bytes =
 withRawBuffer raw $ \praw ->
 do _ <- memcpy (praw `plusPtr` off) ptr (fromIntegral bytes)
 return ()

copyFromRawBuffer :: Ptr e -> RawBuffer e -> Int -> Int -> IO ()
copyFromRawBuffer ptr raw off bytes =
 withRawBuffer raw $ \praw ->
 do _ <- memcpy ptr (praw `plusPtr` off) (fromIntegral bytes)
 return ()

foreign import ccall unsafe "memcpy"
 memcpy :: Ptr a -> Ptr a -> CSize -> IO (Ptr ())

-----------------------------------------------------------------------------
-- Internal Utils

illegalBufferSize :: Handle -> String -> Int -> IO a
illegalBufferSize handle fn sz =
 ioException (IOError (Just handle)
 InvalidArgument fn
 ("illegal buffer size " ++ showsPrec 9 sz [])
 Nothing Nothing)