1e00573 · streamly · git.iko.soy

git.iko.soy/streamly

Add bracket' combinator

It is a flavor of bracket that can take separate cleanup handlers for the cases when the stream is garbage collected, terminates on exception or terminates normally.

commit1e00573b344d73d84b7de59a3840fb8a5275b8b5 authorHarendra Kumar <harendra@composewell.com> dateWed 28 Jul 2021, 19:15 (5 years ago) parent3017898

2 files changed+45−20

compare with master

unifiedsplit

src/Streamly/Internal/Data/Stream/IsStream/Exception.hs+19−2 src/Streamly/Internal/Data/Stream/StreamD/Exception.hs+26−18

src/Streamly/Internal/Data/Stream/IsStream/Exception.hs+19−2

@@ -13,6 +13,7 @@ module Streamly.Internal.Data.Stream.IsStream.Exception

1313 , after

1414 , bracket_

1515 , bracket

16+ , bracket'

1617 , onException

1718 , finally_

1819 , finally

@@ -166,8 +167,24 @@ bracket_ bef aft bet = D.fromStreamD $

166167{-# INLINE bracket #-}

167168bracket :: (IsStream t, MonadAsync m, MonadCatch m)

168169 => m b -> (b -> m c) -> (b -> t m a) -> t m a

169−bracket bef aft bet = D.fromStreamD $

170− D.bracket bef aft (toStreamD . bet)

170+bracket bef aft = bracket' bef aft aft aft

171+

172+-- For a use case of this see the "streamly-process" package. It needs to kill

173+-- the process in case of exception or garbage collection, but waits for the

174+-- process to terminate in normal cases.

175+--

176+-- | Like 'bracket' but can use separate cleanup actions depending on the mode

177+-- of termination. @bracket' before onStop onGC onException action@ runs

178+-- @action@ using the result of @before@. If the stream stops, @onStop@ action

179+-- is executed, if the stream is abandoned @onGC@ is executed, if the stream

180+-- encounters an exception @onException@ is executed.

181+--

182+-- /Pre-release/

183+{-# INLINE bracket' #-}

184+bracket' :: (IsStream t, MonadAsync m, MonadCatch m)

185+ => m b -> (b -> m c) -> (b -> m d) -> (b -> m e) -> (b -> t m a) -> t m a

186+bracket' bef aft gc exc bet = D.fromStreamD $

187+ D.bracket' bef aft exc gc (toStreamD . bet)

171188

172189-- | Like 'handle' but the exception handler is also provided with the stream

173190-- that generated the exception as input. The exception handler can thus

src/Streamly/Internal/Data/Stream/StreamD/Exception.hs+26−18

@@ -14,7 +14,7 @@ module Streamly.Internal.Data.Stream.StreamD.Exception

1414 , after_

1515 , after

1616 , bracket_

17− , bracket

17+ , bracket'

1818 , onException

1919 , finally_

2020 , finally

@@ -101,7 +101,9 @@ data GbracketIOState s1 s2 v wref

101101-- output @c@ as input to @c -> Stream m b@ to generate an output stream. When

102102-- generating the stream use the supplied @try@ operation @forall s. m s -> m

103103-- (Either e s)@ to catch synchronous exceptions. If an exception occurs run

104−-- the exception handler @c -> e -> Stream m b -> m (Stream m b)@.

104+-- the exception handler @c -> e -> Stream m b -> m (Stream m b)@. Note that

105+-- 'gbracket' does not rethrow the exception, it has to be done by the

106+-- exception handler if desired.

105107--

106108-- The cleanup action @c -> m d@, runs whenever the stream ends normally, due

107109-- to a sync or async exception or if it gets garbage collected after a partial

@@ -115,13 +117,14 @@ data GbracketIOState s1 s2 v wref

115117{-# INLINE_NORMAL gbracket #-}

116118gbracket

117119 :: (MonadIO m, MonadBaseControl IO m)

118− => m c -- ^ before

119− -> (forall s. m s -> m (Either e s)) -- ^ try (exception handling)

120− -> (c -> m d) -- ^ after, on normal stop or GC

120+ => m c -- ^ before

121+ -> (forall s. m s -> m (Either e s)) -- ^ try (exception handling)

122+ -> (c -> m d1) -- ^ on normal stop

123+ -> (c -> m d2) -- ^ on GC without normal stop or exception

121124 -> (c -> e -> Stream m b -> m (Stream m b)) -- ^ on exception

122− -> (c -> Stream m b) -- ^ stream generator

125+ -> (c -> Stream m b) -- ^ stream generator

123126 -> Stream m b

124−gbracket bef exc aft fexc fnormal =

127+gbracket bef exc aft gc fexc fnormal =

125128 Stream step GBracketIOInit

126129

127130 where

@@ -137,7 +140,7 @@ gbracket bef exc aft fexc fnormal =

137140 -- Tutorial: https://markkarpov.com/tutorial/exceptions.html

138141 (r, ref) <- liftBaseOp_ mask_ $ do

139142 r <- bef

140− ref <- newIOFinalizer (aft r)

143+ ref <- newIOFinalizer (gc r)

141144 return (r, ref)

142145 return $ Skip $ GBracketIONormal (fnormal r) r ref

143146

@@ -149,9 +152,8 @@ gbracket bef exc aft fexc fnormal =

149152 return $ Yield x (GBracketIONormal (Stream step1 s) v ref)

150153 Skip s ->

151154 return $ Skip (GBracketIONormal (Stream step1 s) v ref)

152− Stop -> do

153− runIOFinalizer ref

154− return Stop

155+ Stop ->

156+ clearingIOFinalizer ref (aft v) >> return Stop

155157 -- XXX Do not handle async exceptions, just rethrow them.

156158 Left e -> do

157159 -- Clearing of finalizer and running of exception handler must

@@ -261,12 +263,17 @@ bracket_ bef aft bet =

261263

262264-- | See 'Streamly.Internal.Data.Stream.IsStream.bracket'.

263265--

264−{-# INLINE_NORMAL bracket #-}

265−bracket :: (MonadAsync m, MonadCatch m)

266− => m b -> (b -> m c) -> (b -> Stream m a) -> Stream m a

267−bracket bef aft bet =

268− gbracket bef (inline MC.try) aft

269− (\a (e :: SomeException) _ -> aft a >> return (nilM (MC.throwM e))) bet

266+{-# INLINE_NORMAL bracket' #-}

267+bracket' :: (MonadAsync m, MonadCatch m) =>

268+ m b

269+ -> (b -> m c)

270+ -> (b -> m d)

271+ -> (b -> m e)

272+ -> (b -> Stream m a)

273+ -> Stream m a

274+bracket' bef aft exc gc =

275+ gbracket bef (inline MC.try) aft gc

276+ (\a (e :: SomeException) _ -> exc a >> return (nilM (MC.throwM e)))

270277

271278data BracketState s v = BracketInit | BracketRun s v

272279

@@ -306,7 +313,8 @@ finally_ action xs = bracket_ (return ()) (\_ -> action) (const xs)

306313--

307314{-# INLINE finally #-}

308315finally :: (MonadAsync m, MonadCatch m) => m b -> Stream m a -> Stream m a

309−finally action xs = bracket (return ()) (\_ -> action) (const xs)

316+finally action xs = bracket' (return ()) act act act (const xs)

317+ where act _ = action

310318

311319-- | See 'Streamly.Internal.Data.Stream.IsStream.ghandle'.

312320--