swift::misc::CDataCacheRevision Class Reference

Encapsulates metastate about how the version of the cache in memory compares to the one on disk. More...

Public Member Functions
	CDataCacheRevision (const QString &basename)
	Construct the single instance of the revision metastate.
	~CDataCacheRevision ()
	Destructor.
LockGuard	beginUpdate (const QMap< QString, qint64 > &timestamps, bool updateUuid=true, bool pinsOnly=false)
	Get the state of the disk cache, and prepare to update any values which are out of date. Return value can be converted to bool, false means update is not started (error, or already up-to-date). More...
void	writeNewRevision (const QMap< QString, qint64 > &timestamps, const QSet< QString > &excludeKeys={})
	During update, writes a new revision file with new timestamps.
void	regenerate (const CValueCachePacket &keys)
	Write a new revision file with keys deduced from the available JSON files.
void	finishUpdate (bool keepPromises=false)
	Release the revision file lock and mark everything up-to-date (called by LockGuard destructor). More...
bool	isFound () const
	Existing revision file was found.
bool	isPendingRead () const
	True if beginUpdate found some values with timestamps newer than in memory.
void	notifyPendingWrite ()
	Call before beginUpdate if there is a write pending, so update will start even if there is nothing to read.
QSet< QString >	keysWithNewerTimestamps () const
	During update, returns keys which have on-disk timestamps newer than in-memory. Guaranteed not empty.
const QMap< QString, qint64 > &	newerTimestamps () const
	During update, returns timestamps which have on-disk timestamps newer than in-memory. Guaranteed not empty.
bool	isNewerValueAvailable (const QString &key, qint64 timestamp)
	During update, returns true if the on-disk timestamp of this key is newer than in-memory.
std::future< void >	promiseLoadedValue (const QString &key, qint64 currentTimestamp)
	Return a future which will be made ready when the value is loaded. Future is invalid if value is not loading.
std::vector< std::promise< void > >	loadedValuePromises ()
	Returns (by move) the container of promises to load values.
void	breakPromises ()
	Abandon all promises.
QString	timestampsAsString () const
	Keys with timestamps.
void	setTimeToLive (const QString &key, int ttl)
	Set TTL value that will be written to the revision file.
void	overrideTimestamp (const QString &key, qint64 timestamp)
	Causes the new timestamp to be written to the revision file.
qint64	getTimestampOnDisk (const QString &key)
	Read the revision file to get a timestamp.
void	pinValue (const QString &key)
	Set the flag which will cause the value to be pre-loaded.
void	deferValue (const QString &key)
	Set the flag which will cause the value to be deferred-loaded.
void	admitValue (const QString &key)
	Set the flag which will cause a deferred-load value to be loaded.
void	sessionValue (const QString &key)
	Set the flag which will cause a value to be reset when starting a new session.
	CDataCacheRevision (const CDataCacheRevision &)=delete
	Non-copyable.
CDataCacheRevision &	operator= (const CDataCacheRevision &)=delete
	Non-copyable.

Detailed Description

Encapsulates metastate about how the version of the cache in memory compares to the one on disk.

Remarks

This function is thread safe.

Definition at line 79 of file datacache.h.

Member Function Documentation

beginUpdate()

LockGuard swift::misc::CDataCacheRevision::beginUpdate	(	const QMap< QString, qint64 > &	timestamps,
		bool	updateUuid = true,
		bool	pinsOnly = false
	)

Get the state of the disk cache, and prepare to update any values which are out of date. Return value can be converted to bool, false means update is not started (error, or already up-to-date).

Parameters

timestamps	Current in-memory timestamps, to be compared with the on-disk ones.
updateUuid	Whether to prepare for an actual update, or just interrograte whether one is needed.
pinsOnly	Only load pinned values.

finishUpdate()

void swift::misc::CDataCacheRevision::finishUpdate

(

bool

keepPromises = false

)

Release the revision file lock and mark everything up-to-date (called by LockGuard destructor).

Parameters

keepPromises

Don't break pending promises.

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

• src/misc/datacache.h