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intercalate-related cleanup #468

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merged 4 commits into from
Jan 20, 2022
Merged

intercalate-related cleanup #468

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da6cdfc
Use overflow-checked arithmetic in intercalate
clyring Jan 14, 2022
50cd7a0
Clean up intercalate-related INLINE pragmas
clyring Jan 14, 2022
1870287
Revert subtle increase in intercalate's strictness
clyring Jan 19, 2022
eaa967a
Mark intercalate as inlinable
clyring Jan 19, 2022
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10 changes: 5 additions & 5 deletions Data/ByteString.hs
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Original file line number Diff line number Diff line change
Expand Up @@ -277,9 +277,7 @@ import GHC.Word hiding (Word8)
-- | /O(1)/ Convert a 'Word8' into a 'ByteString'
singleton :: Word8 -> ByteString
singleton c = unsafeCreate 1 $ \p -> poke p c
{-# INLINE [1] singleton #-}

-- Inline [1] for intercalate rule
{-# INLINE singleton #-}

--
-- XXX The use of unsafePerformIO in allocating functions (unsafeCreate) is critical!
Expand Down Expand Up @@ -1210,6 +1208,7 @@ groupBy k xs = case uncons xs of
-- argument between each element of the list.
intercalate :: ByteString -> [ByteString] -> ByteString
intercalate _ [] = mempty
intercalate _ [x] = x -- This branch exists for laziness, not speed
intercalate (BS fSepPtr sepLen) (BS fhPtr hLen : t) =
unsafeCreate totalLen $ \dstPtr0 ->
unsafeWithForeignPtr fSepPtr $ \sepPtr -> do
Expand All @@ -1224,8 +1223,9 @@ intercalate (BS fSepPtr sepLen) (BS fhPtr hLen : t) =
go (destPtr' `plusPtr` chunkLen) chunks
go (dstPtr0 `plusPtr` hLen) t
where
totalLen = List.foldl' (\acc (BS _ chunkLen) -> acc + chunkLen + sepLen) hLen t
{-# INLINE [1] intercalate #-}
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totalLen = List.foldl' (\acc chunk -> acc +! sepLen +! length chunk) hLen t
(+!) = checkedAdd "intercalate"
{-# INLINABLE intercalate #-}

-- ---------------------------------------------------------------------
-- Indexing ByteStrings
Expand Down