Base class for state storage which accesses State values. More...

#include <creativity/state/StorageBackend.hpp>

Public Member Functions
	StorageBackend (CreativitySettings &settings)
	Constructor: takes a CreativitySettings reference. More...

virtual size_t	size ()=0
	Returns the number of states stored in the storage object, not including queued but not-yet-added states. More...

bool	empty ()
	Returns true if the container is empty; exactly equivalent to `size() == 0`

virtual void	reserve (size_t T)
	Optional method that subclasses can override if knowing the number of states that will be stored in advance is useful. More...

virtual void	writeSettings ()=0
	Writes the settings in settings_ to the storage medium (if appropriate). More...

void	flush (bool flush_buffers=true)
	Flushes changes. More...

bool	flush_for (long milliseconds, bool flush_buffers=true)
	Attempts to flush changes, waiting at most the given number of milliseconds for the flush to complete. More...

virtual void	enqueue (std::shared_ptr< const State > &&s)
	Adds a state to this storage container. More...

virtual size_t	pending () const
	Returns the number of states still pending in the queue. More...

virtual std::shared_ptr< const State >	load (eris::eris_time_t t)=0
	Gets the requested state from the backend. More...

virtual	~StorageBackend ()
	Virtual destructor that tells the thread (if created) to quit and waits for it.

Protected Member Functions
virtual void	thread_insert (std::shared_ptr< const State > &&s)
	Called from the queue thread to write the given State to the underlying storage. More...

virtual void	storage_flush ()
	Flush any buffered data to the underlying storage system. More...

Protected Attributes
CreativitySettings &	settings_
	CreativitySettings reference. More...

Detailed Description

Base class for state storage which accesses State values.

Subclasses must set size_ when initialized; after initialization, this class will take care of updating it as new states are added.

Subclasses must implement the subscript [] operator, size() method, and push_back(&&) method.

See also: creativity::state::MemoryStorage; creativity::state::FileStorage

Constructor & Destructor Documentation

§ StorageBackend()

creativity::state::StorageBackend::StorageBackend ( CreativitySettings & settings )

inline

Constructor: takes a CreativitySettings reference.

The reference must stay valid for the duration of the StorageBackend.

Member Function Documentation

§ enqueue()

virtual void creativity::state::StorageBackend::enqueue ( std::shared_ptr< const State > && s )

virtual

Adds a state to this storage container.

The default implementation spawns a thread then adds it to queue_. Subclasses not using threaded storage MUST override this method to perform the storage immediately.

§ flush()

void creativity::state::StorageBackend::flush ( bool flush_buffers = true )

Flushes changes.

This method blocks until the current thread has finished writing all queued states and the device has been flushed to storage (if applicable and the given argument is true).

If a subclass supports additional flushing capabilities (e.g. syncing a file to disk), it should override storage_flush(), which this method calls.

§ flush_for()

bool creativity::state::StorageBackend::flush_for	(	long	milliseconds,
		bool	flush_buffers = `true`
	)

Attempts to flush changes, waiting at most the given number of milliseconds for the flush to complete.

Returns true if the flush completed, false if the duration expired before the flush completed.

Returns: true if the flush completed, false if the duration expired without the flush finishing.

§ load()

virtual std::shared_ptr<const State> creativity::state::StorageBackend::load ( eris::eris_time_t t )

pure virtual

Gets the requested state from the backend.

This is not required to check for objects in the queue: the caller is responsible for caching queued objects.

If the state does not exist in the storage medium, a subclass should return a void shared_ptr.

Implemented in creativity::state::FileStorage.

§ pending()

virtual size_t creativity::state::StorageBackend::pending ( ) const

virtual

Returns the number of states still pending in the queue.

§ reserve()

virtual void creativity::state::StorageBackend::reserve ( size_t T )

virtual

Optional method that subclasses can override if knowing the number of states that will be stored in advance is useful.

The default implementation does nothing.

§ size()

virtual size_t creativity::state::StorageBackend::size ( )

pure virtual

Returns the number of states stored in the storage object, not including queued but not-yet-added states.

This is typically called just once by Storage immediately after constructing the object to determine the number of initial storage states; Storage internally tracks (by the number of enqueue calls) the number of states after that.

Implemented in creativity::state::FileStorage.