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Write database to a temporary file, then rename, so that hitting Ctrl+C does not leave you with a corrupted database. #465

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Merged
Bodigrim merged 1 commit into from
Dec 16, 2025
Merged

Write database to a temporary file, then rename, so that hitting Ctrl+C does not leave you with a corrupted database. #465

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1 change: 1 addition & 0 deletions hoogle.cabal
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Original file line number Diff line number Diff line change
Expand Up @@ -80,6 +80,7 @@ library
storable-tuple,
tar,
template-haskell,
temporary,
text >= 2,
time >= 1.5,
transformers,
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9 changes: 7 additions & 2 deletions src/General/Store.hs
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Expand Up @@ -33,8 +33,11 @@ import General.Util
import Numeric.Extra
import Paths_hoogle
import Prelude
import System.IO.Extra
import System.Directory (renameFile)
import System.FilePath (takeDirectory, takeFileName)
import System.IO.Extra (Handle, hTell, hClose, hPutBuf)
import System.IO.MMap
import System.IO.Temp (withTempFile)
import System.IO.Unsafe

-- Ensure the string is always 25 chars long, so version numbers don't change its size
Expand Down Expand Up @@ -108,7 +111,7 @@ storeWriteFile :: FilePath -> (StoreWrite -> IO a) -> IO ([String], a)
storeWriteFile file act = do
atoms <- newIORef Map.empty
parts <- newIORef Nothing
withBinaryFile file WriteMode $ \h -> do
withTempFile (takeDirectory file) (takeFileName file) $ \tmpFile h -> do
-- put the version string at the start and end, so we can tell truncation vs wrong version
BS.hPut h verString
ref <- newIORef $ SW h (BS.length verString) []
Expand All @@ -130,6 +133,8 @@ storeWriteFile file act = do
let stats = prettyTable 0 "Bytes" $
("Overheads", intToDouble $ fromIntegral final - sum (map atomSize $ Map.elems atoms)) :
[(name ++ " :: " ++ atomType, intToDouble atomSize) | (name, Atom{..}) <- Map.toList atoms]
hClose h
renameFile tmpFile file
pure (stats, res)

storeWrite :: (Typeable (t a), Typeable a, Stored a) => StoreWrite -> t a -> a -> IO ()
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