lifetimes-0.2.0.0: Flexible manual resource management
Safe HaskellSafe-Inferred
LanguageHaskell2010

Lifetimes

Description

This package is centered around a couple types:

  • Acquire is a monadic context in which resources can be acquired. These can be executed using acquire, or for simpler cases withAcquire or acquireValue.
  • Resource is a handle to a resource. The value for the resource can be read from this, and the Resource can also be used to manipulate the resource's lifetime.
  • Liftime is the type of first-class liftimes; resources are attached to these and can be moved between them.
Synopsis

Lifetimes

data Lifetime Source #

A Lifetime is a represents the scope in which a Resource is valid; resources are attached to a lifetime when they are acquired, and will be released when the lifetime ends.

newLifetime :: Acquire Lifetime Source #

Acquire a new lifetime, as its own resource. This allows creating sub-groups of resources, which can be later moved as a unit.

withLifetime :: (Lifetime -> IO a) -> IO a Source #

Execute an IO action within the scope of a newly allocated lifetime, which ends when the IO action completes.

Acquiring resources

data Acquire a Source #

An Acquire is a monadic action that acquires some number of resources, and registers cleanup handlers to be executed when their lifetime expires.

Instances

Instances details
MonadIO Acquire Source # 
Instance details

Defined in Lifetimes

Methods

liftIO :: IO a -> Acquire a #

Applicative Acquire Source # 
Instance details

Defined in Lifetimes

Methods

pure :: a -> Acquire a #

(<*>) :: Acquire (a -> b) -> Acquire a -> Acquire b #

liftA2 :: (a -> b -> c) -> Acquire a -> Acquire b -> Acquire c #

(*>) :: Acquire a -> Acquire b -> Acquire b #

(<*) :: Acquire a -> Acquire b -> Acquire a #

Functor Acquire Source # 
Instance details

Defined in Lifetimes

Methods

fmap :: (a -> b) -> Acquire a -> Acquire b #

(<$) :: a -> Acquire b -> Acquire a #

Monad Acquire Source # 
Instance details

Defined in Lifetimes

Methods

(>>=) :: Acquire a -> (a -> Acquire b) -> Acquire b #

(>>) :: Acquire a -> Acquire b -> Acquire b #

return :: a -> Acquire a #

mkAcquire :: IO a -> (a -> IO ()) -> Acquire a Source #

mkAcquire get cleanup acquires a resource with get, which will be released by calling cleanup when its lifetime ends.

withAcquire :: Acquire a -> (a -> IO b) -> IO b Source #

withAcquire acuires a resource, uses it, and then releases it. withAcquire (mkAcquire get cleanup) is equivalent to bracket get cleanup.

acquire :: Lifetime -> Acquire a -> IO (Resource a) Source #

Acquire a resource, attaching it to the supplied lifetime.

acquireValue :: Lifetime -> Acquire a -> IO a Source #

Like acquire, but returns the value, rather than a Resource wrapper. conveinent when you don't need to move the resource or release it before the lifetime expires.

currentLifetime :: Acquire Lifetime Source #

Get the lifetime for the resources being acquired.

Using resources

data Resource a Source #

Represents a resource with type a, which has a lifetime and an associated cleanup handler.

getResource :: MonadSTM m => Resource a -> m (Maybe a) Source #

Get the value associated with a resource, returning Nothing if the resource's lifetime is expired.

mustGetResource :: MonadSTM m => Resource a -> m a Source #

Like getResource, but throws a ResourceExpired exception instead of returning a Maybe.

Releasing resources

releaseEarly :: Resource a -> IO () Source #

Release a resource early, before its lifetime would otherwise end.

detach :: MonadSTM m => Resource a -> m (IO ()) Source #

Detach the resource from its lifetime, returning the cleanup handler. NOTE: if the caller does not otherwise arrange to run the cleanup handler, it will *not* be executed.

Move semantics

moveTo :: MonadSTM m => Resource a -> Lifetime -> m () Source #

Move a resource to another lifetime. The resource will be detached from its existing lifetime, and so may live past it, but will be released when the new lifetime expires.

Errors