drwnPersistentStorage Class Reference

Provides indexed storage for multiple records using two files (a binary data file and a text index file). More...

Public Member Functions
	drwnPersistentStorage (bool bCompressed=false)
	drwnPersistentStorage (const drwnPersistentStorage &storage)
bool	open (const char *indexFile, const char *dataFile)
	open persistent storage index and data files
bool	open (const char *fileStem)
	open persistent storage using default extension for index and data files
bool	reopen ()
	re-open previously opened persistent storage files
bool	close ()
	close (and write) persistent storage files
bool	isOpen () const
	returns true if the persistent storage has been opened and not closed
bool	canReopen () const
	returns true if the persistent storage object has valid filenames but is currently closed
int	numRecords () const
	number of drwnPersistentRecord records stored on disk
size_t	numTotalBytes () const
	total number of bytes on disk used by the data file
size_t	numUsedBytes () const
	number of bytes on disk actually needed by the data file
size_t	numFreeBytes () const
	number of free bytes (due to fragmentation) in data file
bool	hasKey (const char *key) const
	returns true if a record with given key exists in the persistent storage
set< string >	getKeys () const
	returns all keys stored in the persistent storage object
bool	erase (const char *key)
	erases the record with given key
bool	read (const char *key, drwnPersistentRecord *record)
	reads the record with given key
bool	write (const char *key, const drwnPersistentRecord *record)
	writes the record with given key
size_t	bytes (const char *key) const
	number of bytes on disk used for record with given key
bool	clear ()
	clears all records from the persistent storage object (takes affect when closed)
bool	defragment ()
	defragments data file

Static Public Attributes
static int	MAX_OPEN = 16
	max. number of open files
static string	DEFAULT_INDEX_EXT = string(".index")
	default extension for index files
static string	DEFAULT_DATA_EXT = string(".data")
	default extension for data files

Protected Member Functions
void	suspend ()
	self-suspend (close)
void	resume ()
	reopen if suspended
bool	atomic_reopen (bool locked)
	perform an atomic reopen operation
bool	atomic_close (bool locked)
	perform an atomic close operation
void	atomic_suspend (bool locked)
	perform an atomic suspend operation

Protected Attributes
string	_indexFilename
	name of index file
string	_dataFilename
	name of data file
map< string, drwnPersistentBlock >	_recordMapping
	key, start, length
list< drwnPersistentBlock >	_freeSpace
	start, length
bool	_bCompressed
	data in storage is compressed
fstream *	_fsdata
	data file stream (if open)
bool	_bSuspended
	self-suspended vs. closed (will reopen on any operation)
bool	_bDirty
	data has been written to the storage since opened

Static Protected Attributes
static list < drwnPersistentStorage * >	_openList
	list of open storage

Detailed Description

Provides indexed storage for multiple records using two files (a binary data file and a text index file).

The class maintains an open stream to the data file. The index file is written on closing. A closed storage object can be reopened without having to re-parse the index file. The class also manages the maximum number of actively open storage objects. If more storage objects are opened, the oldest ones will be suspended (temporarily closes). Any operation to the storage object will automatically re-open (resume) the storage (possibly suspending other storage objects). To use this class, objects must implement the drwnPersistentRecord interface. Automatic compression of records can be set and is managed by through the drwnCompressionBuffer class.

The erase(), read() and write() methods are thread-safe allowing the same persistent storage object to be accessed from multiple threads.

See Also

Darwin Tutorial for an example.

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The documentation for this class was generated from the following files:

• drwnPersistentStorage.h
• drwnPersistentStorage.cpp