id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc	os	architecture	failure	difficulty	testcase	blockedby	blocking	related
2473	Data.Array.IO.Internals hidden in GHC6.8 for no good reason	ryani	igloo	"I had some fast array modification code in C to modify the contents of an IOUArray, because I couldn't get my Haskell performance up to snuff.  Now that module is hidden in the array package and it doesn't seem possible to unhide it.

The code compiled & worked quite well in GHC6.6.  I understand that by going into the internals I may have to update the code as the internals change, but it doesn't seem to be possible to do so at all at this point.  The only workaround I can think of is to figure out the internal type from the source, re-declare it locally, and use unsafeCoerce# shenanigans to extract the data.  That seems terrible, since future changes to the internals could cause the code to start crashing without any compile-time warning at all.

Bitmap.hs:
{{{
{-# OPTIONS_GHC -fffi -fglasgow-exts #-}
{-# INCLUDE ""bitmap_operations.h"" #-}
module Bitmap(clearBitmap) where

import Data.Array.Base
import Data.Array.IO.Internals
import GHC.Exts
import Data.Word

foreign import ccall unsafe clear_bitmap
  :: MutableByteArray# RealWorld -> Word32 -> Word32 -> IO ()

{-# INLINE unsafeGetMutableArray# #-}
unsafeGetMutableArray# :: IOUArray Int Word32 -> MutableByteArray# RealWorld
unsafeGetMutableArray# (IOUArray (STUArray _ _ array#)) = array#

clearBitmap :: IOUArray Int Word32 -> Word32 -> Word32 -> IO ()
clearBitmap a c sz = clear_bitmap (unsafeGetMutableArray# a) c sz
}}}

bitmap_operations.h:
{{{
#include ""HsFFI.h""

void clear_bitmap(void* p, HsWord32 color, HsWord32 size);
}}}"	bug	closed	normal		libraries (other)	6.8.3	fixed			Unknown/Multiple	Unknown/Multiple		Unknown