Reinier Lamers 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.
>>
>>
> How does this guarantee that it doesn't overflow the buffer of the
> destination array?
As is, the above is a very unsafe operation. The check is commented out.
You can uncomment the code above that says:
> do b1 <- getBounds s1
> b2 <- getBounds s2
> when (b1/=b2) (error ("\n\nWTF copySTU: "++show (b1,b2)))
Which checks the high-level boundary matches, not just the actual length.
I only have a single size of STUArray haning around, so I use the unsafe and
fast version.
--
Chris
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