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Simplify useAsCString #516

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May 18, 2022
Merged

Simplify useAsCString #516

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12 changes: 5 additions & 7 deletions Data/ByteString.hs
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Original file line number Diff line number Diff line change
Expand Up @@ -243,7 +243,7 @@ import Control.Monad (when, void)

import Foreign.C.String (CString, CStringLen)
import Foreign.C.Types (CSize (CSize), CInt (CInt))
import Foreign.ForeignPtr (ForeignPtr, withForeignPtr, touchForeignPtr)
import Foreign.ForeignPtr (ForeignPtr, touchForeignPtr)
import Foreign.ForeignPtr.Unsafe(unsafeForeignPtrToPtr)
import Foreign.Marshal.Alloc (allocaBytes)
import Foreign.Marshal.Array (allocaArray)
Expand Down Expand Up @@ -1734,12 +1734,10 @@ sort (BS input l)
-- subcomputation finishes.
useAsCString :: ByteString -> (CString -> IO a) -> IO a
useAsCString (BS fp l) action =
allocaBytes (l+1) $ \buf ->
-- Cannot use unsafeWithForeignPtr, because action can diverge
withForeignPtr fp $ \p -> do
memcpy buf p l
pokeByteOff buf l (0::Word8)
action (castPtr buf)
allocaBytes (l+1) $ \buf -> do
unsafeWithForeignPtr fp $ \p -> memcpy buf p l
pokeByteOff buf l (0::Word8)
action (castPtr buf)
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-- | /O(n) construction/ Use a @ByteString@ with a function requiring a @CStringLen@.
-- As for @useAsCString@ this function makes a copy of the original @ByteString@.
Expand Down