persistent-map (empty) → 0.0.0
raw patch · 12 files changed
+1249/−0 lines, 12 filesdep +EdisonAPIdep +EdisonCoredep +LRUsetup-changed
Dependencies added: EdisonAPI, EdisonCore, LRU, base, mtl, stm-io-hooks
Files
- Data/CacheStructure.hs +56/−0
- Data/CacheStructure/LRU.hs +35/−0
- Data/TMap.hs +260/−0
- Data/TMap/Backend.hs +46/−0
- Data/TMap/Backend/NoBackend.hs +26/−0
- Data/TMap/Backend/StdoutBackend.hs +32/−0
- Data/TMap/Exception.hs +29/−0
- Data/TStorage.hs +95/−0
- LICENSE +508/−0
- Sample.hs +58/−0
- Setup.lhs +4/−0
- persistent-map.cabal +100/−0
+ Data/CacheStructure.hs view
@@ -0,0 +1,56 @@+-----------------------------------------------------------------------------+-- |+-- Module : Data.CacheStructure+-- Copyright : Peter Robinson 2009+-- License : LGPL+--+-- Maintainer : Peter Robinson <thaldyron@gmail.com>+-- Stability : experimental+-- Portability : non-portable (requires STM)+--+-- A type class for implementing different caching policies (e.g. LRU, LFU,... ).+-- Should be imported qualified.+-----------------------------------------------------------------------------++module Data.CacheStructure( CacheStructure(..), CacheException(..) )+where+import Control.Exception +import Data.Typeable++data CacheException = CacheException String+ deriving (Show,Eq,Typeable)++instance Exception CacheException++-- | A type class for implementing a caching policy (e.g. LRU)+class CacheStructure c a where+ -- | A new element is added to the cache or an already existing element+ -- was accessed.+ hit :: a -> c a -> c a+ -- | Returns the \"last\" element w.r.t. the caching policy.+ last :: c a -> a+ -- | Removes and returns the \"last\" element w.r.t. the caching policy.+ pop :: c a -> (c a,a)+ -- | Creates an empty cache structure.+ empty :: c a+ -- | Checks for emptyness. + null :: c a -> Bool+ -- | Transforms the cache structure to a list.+ toList :: c a -> [a]+ -- | An element is deleted.+ delete :: a -> c a -> c a+ -- | Checks if an element is in the cache structure.+ member :: a -> c a -> Bool+ -- | Returns the size. Should be /O(1)/.+ size :: c a -> Int+ -- | Runs 'pop' a number of times. Has a default implementation. + popMany :: Int -> c a -> (c a,[a])+ popMany = popMany' []+ where+ popMany' del 0 cs = (cs,del) + popMany' del i cs + | i < 0 = throw $ CacheException "Invalid size for cache structure!"+ | otherwise = let (cs',a) = pop cs+ in popMany' (a:del) (i-1) cs' + +
+ Data/CacheStructure/LRU.hs view
@@ -0,0 +1,35 @@+-----------------------------------------------------------------------------+-- |+-- Module : Data.Policy.LRU+-- Copyright : Peter Robinson 2009+-- License : LGPL+--+-- Maintainer : Peter Robinson <thaldyron@gmail.com>+-- Stability : experimental+-- Portability : non-portable (requires STM)+--+-- Provides a least recently used caching policy.+-- Note: This module is simply a wrapper around the LRU-package.+-----------------------------------------------------------------------------++module Data.CacheStructure.LRU( L.LRU )+where+import Control.Exception +import Data.CacheStructure+import qualified Data.LRU as L++instance Ord a => CacheStructure L.LRU a where+ hit = L.hit+ pop l = case L.last l of+ Nothing -> throw $ CacheException "Cache structure is empty!"+ Just a -> (L.pop l,a)+ last l = case L.last l of+ Nothing -> throw $ CacheException "Cache structure is empty!"+ Just a -> a+ empty = L.empty+ null = L.null+ toList = L.toList+ delete = L.delete+ member = L.member+ size = L.size+
+ Data/TMap.hs view
@@ -0,0 +1,260 @@+-----------------------------------------------------------------------------+-- |+-- Module : Data.TMap+-- Copyright : Peter Robinson 2009+-- License : LGPL+--+-- Maintainer : Peter Robinson <thaldyron@gmail.com>+-- Stability : experimental+-- Portability : non-portable (requires STM)+--+-- Provides a thread-safe STM interface for finite map types with optional persistent+-- storage.+--+-----------------------------------------------------------------------------++module Data.TMap( -- * TMap + TMap, + -- * Creating a new TMap+ newTMapIO, + -- * Finite Map Interace+ lookup, + insert, + delete, + member, + adjust, + -- * Handling the size of the TMap + purgeTMap, + purgeTMapIO, + getMaximumSize, + setMaximumSize, + getCurrentSize,+ -- * Flushing the backend+ flushBackend,+ -- * Exception Type+ TMapException(..),+ )+where++import Control.Concurrent.AdvSTM+import Control.Concurrent.AdvSTM.TVar+-- import Control.Monad.CatchIO+import Control.Monad( liftM, when )+import Control.Monad.Trans( MonadIO, liftIO )++import qualified Control.Exception as Exc+import Data.Maybe( isJust )+import Prelude hiding (lookup,catch)++import qualified Data.TMap.Backend as B+import qualified Data.CacheStructure as C+import Data.TMap.Exception( TMapException(..) )++import qualified Data.Edison.Assoc as M+++--------------------------------------------------------------------------------+++data Entry a = Entry a -- ^ Cache hit+ | NotInTMap -- ^ Cache miss+ | NotInBackend -- ^ Element exists neither in backend nor in cache+ deriving (Show,Eq)++instance Functor Entry where+ fmap _ NotInBackend = NotInBackend+ fmap _ NotInTMap = NotInTMap+ fmap f (Entry a) = Entry (f a)+++data TMap map k a b c = TMap + { backend :: B.Backend k a b => b k a+ , sizeTVar :: TVar (Maybe Int)+ , tmapTVar :: (M.FiniteMapX map k, C.CacheStructure c k) + => TVar (map (Entry a),c k)+ }+++--------------------------------------------------------------------------------++-- | Creates a new TMap. You will need to use an apropriate backend and specify+-- the caching policy, e.g.,+--+-- @+-- import Data.TMap.Backend.StdoutBackend( newStdoutBackend )+-- import Data.TMap.CacheStructure.LRU+-- @+--+-- will simply log all backend operations to Stdout and use a \"least recently+-- used\" cache algorithm.+--+-- Now, to create an unbounded map that uses the 'FM Int String' (see package EdisonCore) +-- as the map type, you can write+--+-- @+-- tmap = newTMapIO newStdoutBackend Nothing :: IO (TMap (FM Int) Int String StdoutBackend LRU)+-- @+newTMapIO :: (M.FiniteMapX map k, Ord k, B.Backend k a b,C.CacheStructure c k) + => b k a -- ^ the backend+ -> Maybe Int -- ^ maximum-size: Use 'Nothing' for unbounded size.+ -> IO (TMap map k a b c)+newTMapIO b maxsize = do + tvar <- newTVarIO (M.empty,C.empty)+ tvarSize <- newTVarIO maxsize+ B.initialize b+ return $ TMap b tvarSize tvar ++{-+ - Deactivated --- Can cause a non-terminating retry-loop when used with lookup k:+ - When key 'k' is not found lookup retries. (Cond 1)+ - But this causes the creation of the tmap to be rolled back too, and so + - (Cond 1) holds forever.+newTMap :: (M.FiniteMapX map k, Ord k, B.Backend k a b, MonadAdvSTM m) + => b -> m (TMap map k a b)+newTMap b = do + tvar <- newTVar M.empty + return $ TMap b tvar +-}+++-- | Looks for a given key in the map and (if necessary) in the persistent storage +-- and updates the map if necessary.+lookup :: (M.FiniteMapX map k, MonadAdvSTM m, Ord k, B.Backend k a b,C.CacheStructure c k)+ => k -> TMap map k a b c -> m (Maybe a) +lookup k tmap = do+ (themap,accSeq) <- readTVar (tmapTVar tmap)+ case M.lookupWithDefault NotInTMap k themap of+ Entry v -> do + writeTVar (tmapTVar tmap) (themap,C.hit k accSeq)+-- onCommit $ print ("OldAccess List: ",C.toList accSeq)+-- onCommit $ print ("NewAccess List: ",C.toList $ C.hit k accSeq)+ return $ Just v+ NotInBackend -> return Nothing+ NotInTMap -> retryWith $ do +-- print $ "Lookup: Didn't find " ++ show k ++ ", retrying lookup..."+ result <- B.lookup (backend tmap) k + case result of + Nothing -> do +-- print "Entry not in backend"+ atomically $ do + (themap',accSeq') <- readTVar (tmapTVar tmap)+ writeTVar (tmapTVar tmap) (M.insert k (NotInBackend) themap', accSeq')+ Just v -> do +-- print "Found entry in backend"+ atomically $ do + (themap',accSeq') <- readTVar (tmapTVar tmap)+ writeTVar (tmapTVar tmap) ( M.insert k (Entry v) themap'+ , C.hit k accSeq')+-- onCommit $ print ("Access List: ",C.toList $ C.hit k accSeq')++-- | Checks whether the given key is in the map.+member :: (M.FiniteMapX map k, MonadAdvSTM m, Ord k, B.Backend k a b,C.CacheStructure c k) + => k -> TMap map k a b c -> m Bool+member k tmap = liftM isJust (lookup k tmap)+++-- | Adds a key-value mapping to the map. Can throw a 'DuplicateEntry'+-- exception.+insert :: (M.FiniteMapX map k, MonadAdvSTM m, Ord k, B.Backend k a b, C.CacheStructure c k) + => k -> a -> TMap map k a b c -> m () +insert k a tmap = do+ res <- lookup k tmap + case res of+ Just _ -> Exc.throw $ DuplicateEntry -- (show (k,v))+ Nothing -> do+ (themap,accSeq) <- readTVar (tmapTVar tmap)+ writeTVar (tmapTVar tmap) ( M.insert k (Entry a) themap+ , C.hit k accSeq)+ onCommit $ B.insert (backend tmap) k a+++-- | Applies a function to the element identified by the key. Can throw an 'EntryNotFound' exception.+adjust :: (M.FiniteMapX map k, MonadAdvSTM m, Ord k, B.Backend k a b, C.CacheStructure c k) + => (a -> a) -> k -> TMap map k a b c -> m () +adjust f k tmap = do+ res <- lookup k tmap + case res of+ Nothing -> Exc.throw EntryNotFound + Just _ -> do+ (themap,accSeq) <- readTVar (tmapTVar tmap)+ writeTVar (tmapTVar tmap) (M.adjust (fmap f) k themap, C.hit k accSeq)+ onCommit $ B.adjust (backend tmap) f k +++-- | Removes a key from the map. Can throw an 'EntryNotFound' exception.+delete :: (M.FiniteMapX map k, MonadAdvSTM m, Ord k, B.Backend k a b,C.CacheStructure c k) + => k -> TMap map k a b c -> m () +delete k tmap = do+ res <- lookup k tmap + case res of+ Nothing -> Exc.throw EntryNotFound + Just _ -> do+ (themap,accSeq) <- readTVar (tmapTVar tmap)+ writeTVar (tmapTVar tmap) (M.insert k NotInBackend themap, accSeq)+ onCommit $ B.delete (backend tmap) k ++--------------------------------------------------------------------------------++-- | Reduces the map to the appropriate size if the maximum size was exceeded.+-- Calls /Data.TMap.Backend.flush/ if the map is purged.+-- Runs in /O(1)/ if the map size is within bounds, otherwise /O(n)/.+purgeTMapIO :: (M.FiniteMapX map k, MonadIO m, Ord k, B.Backend k a b, C.CacheStructure c k) + => TMap map k a b c -> m ()+purgeTMapIO tmap = liftIO . atomically $ purgeTMap tmap +++-- | Reduces the map to the appropriate size if the maximum size was exceeded.+-- Calls /Data.TMap.Backend.flush/ if the map is purged.+-- Runs in /O(1)/ if the map size is within bounds, otherwise /O(n)/. +-- /Warning:/ This function should always be called at the end of a transaction to+-- prevent nonterminating retry-loops!+purgeTMap :: (M.FiniteMapX map k, MonadAdvSTM m, Ord k, B.Backend k a b, C.CacheStructure c k) + => TMap map k a b c -> m () +purgeTMap tmap = do+ mSize <- readTVar (sizeTVar tmap)+ case mSize of+ Just maxSize -> do+ (themap,accSeq) <- readTVar (tmapTVar tmap)+-- onCommit $ print ("Old List: ",C.toList accSeq)+ when (C.size accSeq > maxSize) $ do+ let (restSeq,delSeq) = C.popMany (C.size accSeq - maxSize) accSeq+ writeTVar (tmapTVar tmap) (foldr M.delete themap delSeq, restSeq)+ onCommit $ B.flush (backend tmap)+-- onCommit $ print ("Purged List: ",C.toList restSeq)+ Nothing -> return ()++--------------------------------------------------------------------------------++-- | Sets the maximum size of the map. /O(1)/. Note that the size of the TMap needs+-- to be reduced manually to the maximum size by calling /purgeTMap/.+setMaximumSize :: (M.FiniteMapX map k, MonadAdvSTM m, Ord k, B.Backend k a b, C.CacheStructure c k) + => TMap map k a b c -> Int -> m () +setMaximumSize tmap maxSize+ | maxSize <= 0 = Exc.throw $ TMapDefaultExc "setMaximumSize: Invalid size specified."+ | otherwise = writeTVar (sizeTVar tmap) $ Just maxSize++-- | Gets the maximum size of the map. /O(1)/.+getMaximumSize :: (M.FiniteMapX map k, MonadAdvSTM m, Ord k, B.Backend k a b, C.CacheStructure c k) + => TMap map k a b c + -> m (Maybe Int)+getMaximumSize tmap + | otherwise = readTVar (sizeTVar tmap) +++-- | Gets the current size of the map. /O(1)/.+getCurrentSize :: (M.FiniteMapX map k, MonadAdvSTM m, Ord k, B.Backend k a b, C.CacheStructure c k) + => TMap map k a b c + -> m Int+getCurrentSize tmap = do+ (_,accSeq) <- readTVar (tmapTVar tmap) + return $ C.size accSeq+++--------------------------------------------------------------------------------++-- | Sends a /B.flush/ request to the backend. Useful for asynchronous backend+-- implementations.+flushBackend :: (M.FiniteMapX map k, MonadIO m, Ord k, B.Backend k a b, C.CacheStructure c k) + => TMap map k a b c -> m ()+flushBackend tmap = B.flush (backend tmap)+
+ Data/TMap/Backend.hs view
@@ -0,0 +1,46 @@+-----------------------------------------------------------------------------+-- |+-- Module : Data.TMap.Backend+-- Copyright : Peter Robinson 2009+-- License : LGPL+--+-- Maintainer : Peter Robinson <thaldyron@gmail.com>+-- Stability : experimental+-- Portability : non-portable (requires STM)+--+-- Provides a type class for backend instantiations. To avoid data+-- inconsistencies, these functions should not be used directly but only by +-- means of the TMap interface.+--+-----------------------------------------------------------------------------++module Data.TMap.Backend( Backend(..) )+where+import Control.Monad.Trans( MonadIO )++-- | This class needs to be instantiated when developing a new+-- backend. The backend is expected to be able to handle concurrent+-- (non-conflicting) requests.+class Backend k a b | a -> k where++ -- | Called when a new element was inserted.+ insert :: MonadIO m => b k a -> k -> a -> m ()++ -- | Called when an element was updated.+ adjust :: MonadIO m => b k a-> (a -> a) -> k -> m ()+ + -- | Called when an element was deleted from the map.+ delete :: MonadIO m => b k a-> k -> m ()+ + -- | Called when an element is not found in the map. + lookup :: MonadIO m => b k a -> k -> m (Maybe a)++ -- | Called by /flushBackend/ and /purgeTMap/.+ flush :: MonadIO m => b k a -> m ()++ -- | Called in 'newTMapIO' + initialize :: MonadIO m => b k a -> m ()++ flush _ = return ()+ initialize _ = return ()+
+ Data/TMap/Backend/NoBackend.hs view
@@ -0,0 +1,26 @@+-----------------------------------------------------------------------------+-- |+-- Module : Data.TMap.Backend.NoBackend+-- Copyright : Peter Robinson 2009+-- License : LGPL+--+-- Maintainer : Peter Robinson <thaldyron@gmail.com>+-- Stability : experimental+-- Portability : non-portable (requires STM)+--+-- A backend instantiation that ignores all requests.+-- +--+-----------------------------------------------------------------------------+module Data.TMap.Backend.NoBackend( NoBackend(..) )+where+import Data.TMap.Backend( Backend(..) )++data NoBackend k a = NoBackend++instance Backend k a NoBackend where+ insert _ _ _ = return ()+ adjust _ _ _ = return ()+ lookup _ _ = return Nothing+ delete _ _ = return ()+
+ Data/TMap/Backend/StdoutBackend.hs view
@@ -0,0 +1,32 @@+-----------------------------------------------------------------------------+-- |+-- Module : Data.TMap.Backend.StdoutBackend+-- Copyright : Peter Robinson 2009+-- License : LGPL+--+-- Maintainer : Peter Robinson <thaldyron@gmail.com>+-- Stability : experimental+-- Portability : non-portable (requires STM)+--+-- Simply prints out all backend requests to stdout.+--+-----------------------------------------------------------------------------++module Data.TMap.Backend.StdoutBackend( StdoutBackend+ , newStdoutBackend )+where+import Data.TMap.Backend+import Control.Monad.Trans( MonadIO, liftIO )++data StdoutBackend k a = StdoutBackend++instance (Show a,Show k) => Backend k a StdoutBackend where+ insert _ _ a = liftIO (print ("inserting: ",a)) >> return ()+ adjust _ _ k = liftIO (print ("adjusting: ",k)) >> return ()+ lookup _ k = liftIO (print ("looking up: ",k)) >> return Nothing+ delete _ k = liftIO (print ("deleting: ",k)) >> return ()++-- | Creates a new 'StdoutBackend'.+newStdoutBackend :: StdoutBackend k a+newStdoutBackend = StdoutBackend+
+ Data/TMap/Exception.hs view
@@ -0,0 +1,29 @@+-----------------------------------------------------------------------------+-- |+-- Module : Data.TMap.Exception+-- Copyright : Peter Robinson 2009+-- License : LGPL+--+-- Maintainer : Peter Robinson <thaldyron@gmail.com>+-- Stability : experimental+-- Portability : non-portable (requires STM)+--+-- +--+-----------------------------------------------------------------------------++module Data.TMap.Exception( TMapException(..) )+where+import Control.Exception+import Data.Typeable++data TMapException = DuplicateEntry + | EntryNotFound + | TMapNotFound + | TMapDefaultExc String+ | BackendException String+ deriving (Show,Eq,Typeable)+ +instance Exception TMapException ++
+ Data/TStorage.hs view
@@ -0,0 +1,95 @@+-----------------------------------------------------------------------------+-- |+-- Module : Data.TStorage+-- Copyright : Peter Robinson 2009+-- License : LGPL+--+-- Maintainer : Peter Robinson <thaldyron@gmail.com>+-- Stability : experimental+-- Portability : non-portable (requires STM)+--+-- Provides a high level interface to 'Data.TMap'. This module was inspired+-- by the TCache package, (C) Alberto Gomez Corona.+--+-- The essential difference to the low level functions in 'Data.TMap' is +-- that this interface assumes that the stored type is an instance of +-- 'HasKey', allowing partially filled (i.e. complete enough for deducing +-- the key) values to be passed to the interface functions. +-----------------------------------------------------------------------------++module Data.TStorage( TMap,+ HasKey(..),+ newTMapIO,+ add,+ tryComplete,+ complete,+ remove,+ removeKey,+ apply,+ purgeTMap,+ purgeTMapIO,+ )+ +where+import Control.Concurrent.AdvSTM+import Control.Exception +import Prelude hiding (lookup,catch)++import qualified Data.TMap.Backend as B+import qualified Data.CacheStructure as C++import qualified Data.Edison.Assoc as M++import Data.TMap++-- | Instantiated by types where values have a unique key. +class HasKey a k | a -> k where+ key :: a -> k++-- | Adds a new element to the map. The key is automatically deduced by the+-- 'HasKey' instantiation.+add :: (M.FiniteMapX map k, MonadAdvSTM m, Ord k, B.Backend k a b, C.CacheStructure c k+ , HasKey a k) + => a -> TMap map k a b c -> m () +add a = insert (key a) a+++-- | Tries to fill a partially initialized value with data from the TMap. Returns+-- 'Nothing' if the TMap does not contain a corresponding entry. +tryComplete :: (M.FiniteMapX map k, MonadAdvSTM m, Ord k, B.Backend k a b, C.CacheStructure c k+ , HasKey a k) + => a -> TMap map k a b c -> m (Maybe a)+tryComplete a = lookup (key a)++-- | Fills a partially initialized value with data from the TMap. Throws+-- a 'TMapNotFound' exception if there is no corresponding entry.+complete :: (M.FiniteMapX map k, MonadAdvSTM m, Ord k, B.Backend k a b, C.CacheStructure c k+ , HasKey a k) + => a -> TMap map k a b c -> m a+complete a tmap = do+ mval <- tryComplete a tmap+ case mval of+ Just val -> return val+ Nothing -> throw TMapNotFound++-- | Removes the element from the map.+remove :: (M.FiniteMapX map k, MonadAdvSTM m, Ord k, B.Backend k a b, C.CacheStructure c k+ , HasKey a k) + => a -> TMap map k a b c -> m ()+remove a = delete (key a) ++-- | Removes the entry that has the supplied key.+removeKey :: (M.FiniteMapX map k, MonadAdvSTM m, Ord k, B.Backend k a b, C.CacheStructure c k+ , HasKey a k) + => k -> TMap map k a b c -> m ()+removeKey = delete ++-- | Applies a function to an element that might be only partially initialized.+apply :: (M.FiniteMapX map k, MonadAdvSTM m, Ord k, B.Backend k a b, C.CacheStructure c k+ , HasKey a k) + => (a -> a) -> a -> TMap map k a b c -> m a+apply f a tmap = do+ adjust f (key a) tmap+ complete a tmap++
+ LICENSE view
@@ -0,0 +1,508 @@+Copyright 2008-2009, Peter Robinson <thaldyron@gmail.com>. All rights reserved.++ GNU LESSER GENERAL PUBLIC LICENSE+ Version 2.1, February 1999++ Copyright (C) 1991, 1999 Free Software Foundation, Inc.+ 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA+ Everyone is permitted to copy and distribute verbatim copies+ of this license document, but changing it is not allowed.++[This is the first released version of the Lesser GPL. It also counts+ as the successor of the GNU Library Public License, version 2, hence+ the version number 2.1.]++ Preamble++ The licenses for most software are designed to take away your+freedom to share and change it. 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+ Sample.hs view
@@ -0,0 +1,58 @@+module Sample+where+import Control.Monad( when )+import Data.TStorage+import Data.TMap+import Data.TMap.Backend.StdoutBackend+import qualified Data.CacheStructure.LRU as C+import Control.Concurrent.AdvSTM +import qualified Control.Exception as Exc+import qualified Data.Edison.Assoc.StandardMap as M+import Prelude hiding( lookup )++data Sometype = Sometype { theid :: Int, name :: String }+ deriving (Show,Eq,Ord)++instance HasKey Sometype Int where+ key = theid++sample :: IO ()+sample = Exc.handle (\(e::Exc.SomeException) -> print e) $ do+ tmap <- newTMapIO newStdoutBackend (Just 4) + :: IO (TMap (M.FM Int) Int Sometype StdoutBackend C.LRU)+ -- First the low level TMap interface:+ res <- atomically $ do+ insert 1 (Sometype 1 "somename") tmap+ insert 2 (Sometype 2 "somename2") tmap+ insert 3 (Sometype 3 "somename3") tmap+ insert 4 (Sometype 4 "somename4") tmap+ insert 5 (Sometype 5 "somename5") tmap+ insert 6 (Sometype 6 "somename6") tmap+ lookup 2 tmap+ delete 2 tmap+ lookup 2 tmap+ atomically $ purgeTMap tmap+ print ("Result1: ",res) ++ -- Let's try the high-level TStorage interface:+ res2 <- atomically $ do+ add (Sometype 7 "somename7") tmap+ v1 <- apply (\s -> s{name="_"}) (Sometype {theid = 4}) tmap+ v2 <- complete (Sometype {theid = 5}) tmap+ return (v1,v2)+ print ("Result2: ",res2)++test :: IO ()+test = do+ tmap <- newTMapIO newStdoutBackend (Just 4) + :: IO (TMap (M.FM Int) Int String StdoutBackend C.LRU)+ atomically $ do+ isMemb <- member 1 tmap+ when (not isMemb) $ + insert 1 "john doe" tmap+ + atomically $ do+ v <- lookup 1 tmap+ -- ... doing something here with 'v'+ adjust (\_ -> "jd") 1 tmap+
+ Setup.lhs view
@@ -0,0 +1,4 @@+#! /usr/bin/env runhaskell++> import Distribution.Simple+> main = defaultMain
+ persistent-map.cabal view
@@ -0,0 +1,100 @@+Name: persistent-map+Synopsis: A thread-safe interface for finite map types with optional persistency support.+Description:+ This library provides a thread-safe (STM) frontend for finite map types together with a+ backend interface for persistent storage. The /TMap/ data type+ is thread-safe, since all access functions run inside an STM monad . Any type + instantiating 'Data.Edison.Assoc.FiniteMapX' + (see EdisonAPI) can be used as a map type. + .+ When a TMap is modified within an STM transaction, a corresponding+ backend IO-request is added using the onCommit hook (cf. stm-io-hooks+ package). To ensure consistency,+ the (Adv)STM monad runs these requests iff the transaction commits. + Additional backends (e.g. HDBC) can be added by instantiating the class + 'Backend'.+ .+ /Example:/+ .+ Thread 1:+ .+ > atomically $ do+ > isMemb <- member 1 tmap+ > when (not isMemb) $ + > insert 1 "john doe" tmap+ .+ Thread 2:+ .+ > atomically $ do+ > v <- lookup 1 tmap+ > -- ... do something with 'v'+ > adjust (\_ -> "jd") 1 tmap+ .+ The function 'member' will first check whether the key value '1' is in the map;+ if not, it sends a lookup-request to the persistent backend + and then retries the transaction. Note that \"sending a lookup-request\"+ essentially means adding a call to the corresponding IO-function of the backend + to the list of retry-IO actions. (This is done using the 'retryWith' + IO hook of the stm-io-package.)+ .+ If the value does not exist yet, function 'insert' adds the key-value mapping to the+ TMap and sends an insert-request to the backend using the+ 'onCommit' hook of the stm-io-package. Note that 'onCommit' guarantees that+ the backend IO action is only executed iff the transaction commits. Any + changes that were made to the TMap are invisible to other threads until + the onCommit actions are run. Therefore, the threads will always observe a+ consistent state.+ .+ The module 'Data.TStorage' provides a high level interface to TMap inspired+ by the TCache package ((C) Alberto Gomez Corona). It+ can store any type that has a key (i.e. is an instance of type class 'HasKey').+ See file Sample.hs for an example on how to use it.+ .+ /Warning:/ This package is very experimental and the interface will+ probably change.++Author: Peter Robinson+Maintainer: thaldyron@gmail.com+License: LGPL+License-file: LICENSE+Version: 0.0.0+Category: Data, Concurrency+Stability: experimental+Homepage: http://darcs.monoid.at/persistent-map++build-type: Simple +cabal-version: >= 1.2.3+library+ ghc-options: -Wall -fno-ignore-asserts++ exposed-modules: Data.TMap+ Data.TStorage+-- Data.TMap.Exception+ Data.TMap.Backend+ Data.TMap.Backend.NoBackend+ Data.TMap.Backend.StdoutBackend+ Data.CacheStructure+ Data.CacheStructure.LRU++ other-modules: Sample+ Data.TMap.Exception++ build-depends: base >= 4 && < 5, + EdisonAPI >= 1.2.1 && < 1.3,+ LRU >= 0.1.1 && < 0.2,+ EdisonCore >= 1.2.1.3 && < 1.3,+-- binary,+ stm-io-hooks >= 0.2.0 && < 0.3, +-- HDBC >= 2.0 && < 2.1, + mtl >= 1.1.0.2 && < 1.2+-- MonadCatchIO-mtl++ extensions: MultiParamTypeClasses,+ RankNTypes, + FunctionalDependencies, + FlexibleContexts,+ FlexibleInstances,+ UndecidableInstances,+ DeriveDataTypeable,+ ScopedTypeVariables+