A pure virtual class which must be subclassed for data storage. More...

#include <VFS_datastore.h>

Inheritance diagram for VFS_datastore_cache_entry:

Public Slots
virtual void	timerEvent (QTimerEvent *e)
	Either a flush or expire has happened. More...

Signals
void	expired (VFS_datastore_cache_entry *)
	Signal emitted when a cache entry has expired and is no longer in use. More...

void	touched ()
	Signal emitted when a cache entry has made a change and should climb the cache queue. More...

Public Member Functions
	VFS_datastore_cache_entry (bool debug, int flushInterval, int expireInterval, bool raw=false)
	Construct the cache entry. More...

virtual	~VFS_datastore_cache_entry ()
	Destroy the cache entry. More...

virtual QJsonDocument	getData ()
	Return the data from an entry. More...

virtual QByteArray	getRawData ()
	Return the data from an entry. More...

virtual void	setData (QByteArray data)
	Write raw data to the entry. More...

virtual void	setData (QJsonObject json)
	Write data to the entry. More...

quint64	size ()

virtual bool	valid (QString &reason)

Public Attributes
QString	_key
	The cache entry key. More...

Protected Member Functions
virtual void	flush ()=0
	A pure virtual function that must be overridden in subclasses. This is the function that actually commits data to a storage medium. More...

virtual void	touch ()
	Reset the expiration timer. More...

Protected Attributes
QJsonDocument	_data
	The actual cache data. More...

bool	_debug
	Debug flag, for verbose output. More...

bool	_dirty
	Changes have occurred but they are not commited to storage yet. More...

int	_expireID
	Timer ID for expire events. More...

int	_expireInterval
	Expire interval, in milliseconds. More...

QBasicTimer	_expireTimer
	The expiration timer. More...

int	_flushID
	Timer ID for flush events. More...

int	_flushInterval
	Flush interval, in milliseconds. More...

bool	_raw
	A convenience flag used in subclasses. Not used by this class. More...

QByteArray	_rawData
	Raw binary data. Used if _raw=true. More...

QString	_reason
	The reason this may be invalid. Set by a subclass. More...

quint64	_size
	The size of the data. Always initialized to zero. Must be set in a subclass. More...

bool	_valid
	Defaults to false. A subclass will determine if _valid is true, like for instance if an underlying file doesn't exist. More...

Detailed Description

A pure virtual class which must be subclassed for data storage.

This class will provide basic functionality for caching data before flushing to a storage medium. It is designed to act as an entry in a VFS_datastore_cache.

Cache entries will flush at some interval if _dirty, regardless of expire status. touch() will restart the expire timer, pushing expiration into the future.

Definition at line 12 of file VFS_datastore.h.

Constructor & Destructor Documentation

◆ VFS_datastore_cache_entry()

VFS_datastore_cache_entry::VFS_datastore_cache_entry	(	bool	debug,
		int	flushInterval,
		int	expireInterval,
		bool	raw = `false`
	)

explicit

Construct the cache entry.

Parameters

debug	Verbose debug output
flushInterval	Interval to flush to storage medium, provided by a storage VFS_node like VFS_HD, but could be set uniquely per cache entry. In milliseconds.
expireInterval	Interval to expire a cache entry, which will cause it to be removed from the cache. In milliseconds.
raw	Whether or not to treat this data as JSON or raw data. Useful for subclasses as a flag, but unused in this class.

On creation, the cache entry will start the flush timer and call touch().

Note: Creating a cache entry with flushInterval or expireInterval to 0 will cause it to never flush and never expire.

Definition at line 31 of file VFS_datastore.cpp.

◆ ~VFS_datastore_cache_entry()

VFS_datastore_cache_entry::~VFS_datastore_cache_entry ( )

virtual

Destroy the cache entry.

If it is _dirty or not _valid, a warning will be issued, but a flush() is not called. Subclasses may choose to flush().

Definition at line 57 of file VFS_datastore.cpp.

Member Function Documentation

◆ expired

void VFS_datastore_cache_entry::expired ( VFS_datastore_cache_entry * )

signal

Signal emitted when a cache entry has expired and is no longer in use.

◆ flush()

virtual void VFS_datastore_cache_entry::flush ( )

protectedpure virtual

A pure virtual function that must be overridden in subclasses. This is the function that actually commits data to a storage medium.

Implemented in VFS_mongo_cache_entry, and VFS_HD_cache_entry.

◆ getData()

QJsonDocument VFS_datastore_cache_entry::getData ( )

virtual

Return the data from an entry.

Returns: The data as a QJsonDocument

Also touch() the cache entry, because this means it is in use and can expire later.

Definition at line 156 of file VFS_datastore.cpp.

◆ getRawData()

QByteArray VFS_datastore_cache_entry::getRawData ( )

virtual

Return the data from an entry.

Returns: The data as a QJsonDocument

Also touch() the cache entry, because this means it is in use and can expire later.

Definition at line 187 of file VFS_datastore.cpp.

◆ setData() [1/2]

void VFS_datastore_cache_entry::setData ( QByteArray data )

virtual

Write raw data to the entry.

Parameters

data The data

The _dirty flag will be set, because the data has not been flush()ed yet.

Definition at line 170 of file VFS_datastore.cpp.

◆ setData() [2/2]

void VFS_datastore_cache_entry::setData ( QJsonObject json )

virtual

Write data to the entry.

Parameters

json The data

If a subclass chooses to use the raw flag, it will want to use setData(QByteArray).

The _dirty flag will be set, because the data has not been flush()ed yet.

Definition at line 135 of file VFS_datastore.cpp.

◆ size()

quint64 VFS_datastore_cache_entry::size ( )

Returns: The cache entry size

Definition at line 121 of file VFS_datastore.cpp.

◆ timerEvent

void VFS_datastore_cache_entry::timerEvent ( QTimerEvent * event )

virtualslot

Either a flush or expire has happened.

Parameters

event The timer event

In either case, call flush() to commit data to a storage medium, or report an error if flush() was not possible.

If expired and flush was not possible, the expired() signal will not be emitted. This is a tricky case to deal with, because it implies that some other problem, like a full disk, is the culprit. At least the data here is not lost yet.

Definition at line 75 of file VFS_datastore.cpp.

◆ touch()

void VFS_datastore_cache_entry::touch ( )

protectedvirtual

Reset the expiration timer.

This will cause expiration to happen in the future. Another touch() will extend this.

Definition at line 215 of file VFS_datastore.cpp.

◆ touched

void VFS_datastore_cache_entry::touched ( )

signal

Signal emitted when a cache entry has made a change and should climb the cache queue.

◆ valid()

bool VFS_datastore_cache_entry::valid ( QString & reason )

virtual

Parameters

reason If invalid, the reason will be written to this string.

Returns: The _valid flag value

A subclass must set an entry as _valid, based on whatever criteria it wants. By default all entries are _valid==false.

Reimplemented in VFS_mongo_cache_entry, and VFS_HD_cache_entry.

Definition at line 201 of file VFS_datastore.cpp.

Member Data Documentation

◆ _data

QJsonDocument VFS_datastore_cache_entry::_data

protected

The actual cache data.

Definition at line 32 of file VFS_datastore.h.

◆ _debug

bool VFS_datastore_cache_entry::_debug

protected

Debug flag, for verbose output.

Definition at line 39 of file VFS_datastore.h.

◆ _dirty

bool VFS_datastore_cache_entry::_dirty

protected

Changes have occurred but they are not commited to storage yet.

Definition at line 36 of file VFS_datastore.h.

◆ _expireID

int VFS_datastore_cache_entry::_expireID

protected

Timer ID for expire events.

Definition at line 43 of file VFS_datastore.h.

◆ _expireInterval

int VFS_datastore_cache_entry::_expireInterval

protected

Expire interval, in milliseconds.

Definition at line 44 of file VFS_datastore.h.

◆ _expireTimer

QBasicTimer VFS_datastore_cache_entry::_expireTimer

protected

The expiration timer.

Definition at line 45 of file VFS_datastore.h.

◆ _flushID

int VFS_datastore_cache_entry::_flushID

protected

Timer ID for flush events.

Definition at line 41 of file VFS_datastore.h.

◆ _flushInterval

int VFS_datastore_cache_entry::_flushInterval

protected

Flush interval, in milliseconds.

Definition at line 42 of file VFS_datastore.h.

◆ _key

QString VFS_datastore_cache_entry::_key

The cache entry key.

Definition at line 26 of file VFS_datastore.h.

◆ _raw

bool VFS_datastore_cache_entry::_raw

protected

A convenience flag used in subclasses. Not used by this class.

Definition at line 35 of file VFS_datastore.h.

◆ _rawData

QByteArray VFS_datastore_cache_entry::_rawData

protected

Raw binary data. Used if _raw=true.

Definition at line 33 of file VFS_datastore.h.

◆ _reason

QString VFS_datastore_cache_entry::_reason

protected

The reason this may be invalid. Set by a subclass.

Definition at line 38 of file VFS_datastore.h.

◆ _size

quint64 VFS_datastore_cache_entry::_size

protected

The size of the data. Always initialized to zero. Must be set in a subclass.

Definition at line 34 of file VFS_datastore.h.

◆ _valid

bool VFS_datastore_cache_entry::_valid

protected

Defaults to false. A subclass will determine if _valid is true, like for instance if an underlying file doesn't exist.

Definition at line 37 of file VFS_datastore.h.

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

Public Slots

Signals

Public Member Functions

Public Attributes

Protected Member Functions

Protected Attributes

Detailed Description

Constructor & Destructor Documentation

◆ VFS_datastore_cache_entry()

◆ ~VFS_datastore_cache_entry()

Member Function Documentation

◆ expired

◆ flush()

◆ getData()

◆ getRawData()

◆ setData() [1/2]

◆ setData() [2/2]

◆ size()

◆ timerEvent

◆ touch()

◆ touched

◆ valid()

Member Data Documentation

◆ _data

◆ _debug

◆ _dirty

◆ _expireID

◆ _expireInterval

◆ _expireTimer

◆ _flushID

◆ _flushInterval

◆ _key

◆ _raw

◆ _rawData

◆ _reason

◆ _size

◆ _valid