Data/Array/IO.hs

{-# LANGUAGE MagicHash, UnliftedFFITypes #-}

-----------------------------------------------------------------------------
-- |
-- Module : Data.Array.IO
-- Copyright : (c) The University of Glasgow 2001
-- License : BSD-style (see the file libraries/base/LICENSE)
--
-- Maintainer : libraries@haskell.org
-- Stability : experimental
-- Portability : non-portable (uses Data.Array.MArray)
--
-- Mutable boxed and unboxed arrays in the IO monad.
--
-----------------------------------------------------------------------------

module Data.Array.IO (
 -- * @IO@ arrays with boxed elements
 IOArray, -- instance of: Eq, Typeable

 -- * @IO@ arrays with unboxed elements
 IOUArray, -- instance of: Eq, Typeable

 -- * Overloaded mutable array interface
 module Data.Array.MArray,

 -- * Doing I\/O with @IOUArray@s
 hGetArray, -- :: Handle -> IOUArray Int Word8 -> Int -> IO Int
 hPutArray, -- :: Handle -> IOUArray Int Word8 -> Int -> IO ()
 ) where

import Data.Array.Base
import Data.Array.IO.Internals
import Data.Array.MArray
import System.IO.Error

import Foreign
import Foreign.C

import GHC.Exts (MutableByteArray#, RealWorld)
import GHC.IO.Handle
import GHC.IO.Exception

-- ---------------------------------------------------------------------------
-- hGetArray

-- | Reads a number of 'Word8's from the specified 'Handle' directly
-- into an array.
hGetArray
 :: Handle -- ^ Handle to read from
 -> IOUArray Int Word8 -- ^ Array in which to place the values
 -> Int -- ^ Number of 'Word8's to read
 -> IO Int
 -- ^ Returns: the number of 'Word8's actually
 -- read, which might be smaller than the number requested
 -- if the end of file was reached.

hGetArray handle (IOUArray (STUArray _l _u n ptr)) count
 | count == 0 = return 0
 | count < 0 || count > n = illegalBufferSize handle "hGetArray" count
 | otherwise = do
 -- we would like to read directly into the buffer, but we can't
 -- be sure that the MutableByteArray# is pinned, so we have to
 -- allocate a separate area of memory and copy.
 allocaBytes count $ \p -> do
 r <- hGetBuf handle p count
 _ <- memcpy_ba_ptr ptr p (fromIntegral r)
 return r

foreign import ccall unsafe "memcpy"
 memcpy_ba_ptr :: MutableByteArray# RealWorld -> Ptr a -> CSize -> IO (Ptr ())

-- ---------------------------------------------------------------------------
-- hPutArray

-- | Writes an array of 'Word8' to the specified 'Handle'.
hPutArray
 :: Handle -- ^ Handle to write to
 -> IOUArray Int Word8 -- ^ Array to write from
 -> Int -- ^ Number of 'Word8's to write
 -> IO ()

hPutArray handle (IOUArray (STUArray _l _u n raw)) count
 | count == 0 = return ()
 | count < 0 || count > n = illegalBufferSize handle "hPutArray" count
 | otherwise = do
 -- as in hGetArray, we would like to use the array directly, but
 -- we can't be sure that the MutableByteArray# is pinned.
 allocaBytes count $ \p -> do
 _ <- memcpy_ptr_ba p raw (fromIntegral count)
 hPutBuf handle p count

foreign import ccall unsafe "memcpy"
 memcpy_ptr_ba :: Ptr a -> MutableByteArray# RealWorld -> CSize -> IO (Ptr ())

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

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