Andrew Coppin wrote:
> ChrisK wrote:
>> For GHC 6.6 I created
>>
>>
>>> foreign import ccall unsafe "memcpy"
>>> memcpy :: MutableByteArray# RealWorld -> MutableByteArray#
>>> RealWorld -> Int# -> IO ()
>>>
>>
>>
>>> {-# INLINE copySTU #-}
>>> copySTU :: (Show i,Ix i,MArray (STUArray s) e (ST s)) => STUArray s i
>>> e -> STUArray s i e -> ST s ()
>>> copySTU (STUArray _ _ msource) (STUArray _ _ mdest) =
>>> -- do b1 <- getBounds s1
>>> -- b2 <- getBounds s2
>>> -- when (b1/=b2) (error ("\n\nWTF copySTU: "++show (b1,b2)))
>>> ST $ \s1# ->
>>> case sizeofMutableByteArray# msource of { n# ->
>>> case unsafeCoerce# memcpy mdest msource n# s1# of { (# s2#, () #) ->
>>> (# s2#, () #) }}
>>>
>>
>> To allow efficient copying of STUArrays.
>>
>
> So... that copies the entire array into another array of the same size?
> (I'm having a lot of trouble understanding the code...)
Yes, that is what it does. The "STUArray" data type has the STUArray
constructor which I import and pattern match against. The imports are:
> import Data.Array.Base(unsafeRead,unsafeWrite,STUArray(..))
> import
> GHC.Prim(MutableByteArray#,RealWorld,Int#,sizeofMutableByteArray#,unsafeCoerce#)
in 6.6.1 this is defined as
> data STUArray s i a = STUArray !i !i (MutableByteArray# s)
in 6.8.1 this is defined as
> data STUArray s i a = STUArray !i !i !Int (MutableByteArray# s)
I use sizeofMutableByteArray# to get the source size, n#.
I have lost track of how unsafeCoerce# and s1# are being used...oops.
It is similar to data-dependency tricks used inside Data.Array.Base, though.
--
Chris
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