cache_disabled Class Reference

Required as it is needed for cache_config_disabled which extends cache_config_writer. More...

Inheritance diagram for cache_disabled:

Public Member Functions
	__construct (cache_definition $definition, cache_store $store, $loader=null)
	Constructs the cache.
	acquire_lock ($key)
	Pretend that we got a lock to avoid errors.
	check_lock_state ($key)
	Pretend that we have a lock to avoid errors.
	delete ($key, $recurse=true)
	Deletes an item from the cache.
	delete_many (array $keys, $recurse=true)
	Deletes many items at once from the cache.
	get ($key, $strictness=IGNORE_MISSING)
	Retrieves the value for the given key from the cache.
	get_many (array $keys, $strictness=IGNORE_MISSING)
	Gets many keys at once from the cache.
	get_versioned ($key, int $requiredversion, int $strictness=IGNORE_MISSING, &$actualversion=null)
	Retrieves the value and actual version for the given key, with at least the required version.
	has ($key, $tryloadifpossible=false)
	Checks if the cache has the requested key.
	has ($key)
	Test is a cache has a key.
	has_all (array $keys)
	Checks if the cache has all of the requested keys.
	has_any (array $keys)
	Checks if the cache has any of the requested keys.
	purge ()
	Purges all items from the cache.
	purge_current_user ()
	Subclasses may support purging cache of all data belonging to the current user.
	release_lock ($key)
	Pretend that we released a lock to avoid errors.
	set ($key, $data)
	Sends a key => value pair to the cache.
	set_identifiers (array $identifiers)
	Alters the identifiers that have been provided to the definition.
	set_many (array $keyvaluearray)
	Sets many key value pairs in the cache at once.
	set_versioned ($key, int $version, $data)
	Sets the value for the given key with the given version.

Static Public Member Functions
static	compare_purge_tokens ($tokena, $tokenb)
	Compare a pair of purge tokens.
static	get_purge_token ($reset=false)
	Get a 'purge' token used for cache invalidation handling.
static	make ($component, $area, array $identifiers=array(), $unused=null)
	Creates a new cache instance for a pre-defined definition.
static	make_from_params ($mode, $component, $area, array $identifiers=array(), array $options=array())
	Creates a new cache instance based upon the given params.
static	now ($float=false)
	Returns the timestamp from the first request for the time from the cache API.

Public Attributes
int const	VERSION_NONE = -1
	Constant for cache entries that do not have a version number.

Protected Member Functions
	deep_clone ($value)
	Creates a reference free clone of the given value.
	delete_from_persist_cache ()
	get_datasource ()
	Returns the data source associated with this cache.
	get_definition ()
	Returns the cache definition.
	get_from_persist_cache ()
	get_implementation ($key, int $requiredversion, int $strictness, &$actualversion=null)
	Gets a key from the cache.
	get_loader ()
	Returns the loader associated with this instance.
	get_store ()
	Returns the cache store.
	handle_invalidation_events ()
	Process any outstanding invalidation events for the cache we are registering,.
	has_a_ttl ()
	Returns true if the cache is making use of a ttl.
	is_in_persist_cache ()
	is_using_persist_cache ()
	parse_key ($key)
	Parses the key turning it into a string (or array is required) suitable to be passed to the cache store.
	requires_serialisation ($value, $depth=1)
	Checks to see if a var requires serialisation.
	set_data_source (cache_data_source $datasource)
	Set the data source for this cache.
	set_implementation ($key, int $version, $data, bool $setparents=true)
	Sets a key value pair in the cache.
	set_in_persist_cache ()
	set_is_sub_loader ($setting=true)
	Used to inform the loader of its state as a sub loader, or as the top of the chain.
	set_loader (cache_loader $loader)
	Set the loader for this cache.
	static_acceleration_delete ($key)
	Deletes an item from the static acceleration array.
	static_acceleration_get ($key)
	Returns the item from the static acceleration array if it exists there.
	static_acceleration_has ($key)
	Returns true if the requested key exists within the static acceleration array.
	static_acceleration_purge ()
	Purge the static acceleration cache.
	static_acceleration_set ($key, $data)
	Sets a key value pair into the static acceleration array.
	store_supports_key_awareness ()
	Returns true if the store supports key awareness.
	store_supports_native_locking ()
	Returns true if the store natively supports locking.
	store_supports_native_ttl ()
	Returns true if the cache store supports native ttl.
	unref ($data)
	Removes references where required.
	use_static_acceleration ()
	Returns true if this cache is making use of the static acceleration array.

Static Protected Member Functions
static	check_version ($result, int $requiredversion)
	Checks returned data to see if it matches the specified version number.

Protected Attributes
cache_store null	$nativelocking = null
	Gets set to true if the cache's primary store natively supports locking.
bool	$perfdebug = false
	Gets set to true if we want to collect performance information about the cache API.
bool	$requirelockingbeforewrite = false
	Gets set to true if the cache writes (set|delete) must have a manual lock created first.
strubg	$storetype = 'unknown'
	Gets set to the class name of the store during initialisation.
bool	$subloader = false
	Determines if this loader is a sub loader, not the top of the chain.

Static Protected Attributes
static int	$now
	We need a timestamp to use within the cache API.
static string	$purgetoken
	A purge token used to distinguish between multiple cache purges in the same second.

Detailed Description

Required as it is needed for cache_config_disabled which extends cache_config_writer.

The cache loader class used when the Cache has been disabled.

Copyright

2012 Sam Hemelryk

License

http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later

Constructor & Destructor Documentation

__construct()

cache_disabled::__construct	(	cache_definition	$definition,
		cache_store	$store,
			$loader = null )

Constructs the cache.

Parameters

cache_definition	$definition
cache_store	$store
null	$loader	Unused.

Reimplemented from cache.

Member Function Documentation

acquire_lock()

cache_disabled::acquire_lock

(

$key

)

Pretend that we got a lock to avoid errors.

Parameters

int | string

$key

Return values

bool

Implements cache_loader_with_locking.

check_lock_state()

cache_disabled::check_lock_state

(

$key

)

Pretend that we have a lock to avoid errors.

Parameters

int | string

$key

Return values

bool

Implements cache_loader_with_locking.

check_version()

static cache::check_version ( $result, int $requiredversion )

staticprotectedinherited

Checks returned data to see if it matches the specified version number.

For versioned data, this returns the version_wrapper object (or false). For other data, it returns the actual data (or false).

Parameters

mixed	$result	Result data
int	$requiredversion	Required version number or VERSION_NONE if there must be no version

Return values

bool	True if version is current, false if not (or if result is false)

Exceptions

coding_exception

If unexpected type of data (versioned vs non-versioned) is found

compare_purge_tokens()

static cache::compare_purge_tokens ( $tokena, $tokenb )

staticinherited

Compare a pair of purge tokens.

If the two tokens are identical, then the return value is 0. If the time component of token A is newer than token B, then a positive value is returned. If the time component of token B is newer than token A, then a negative value is returned.

Note: This function is intended for use from within the Cache API only and not by plugins, or cache stores.

Parameters

string	$tokena
string	$tokenb

Return values

int

deep_clone()

cache::deep_clone ( $value )

protectedinherited

Creates a reference free clone of the given value.

Parameters

mixed

$value

Return values

mixed

delete()

cache_disabled::delete	(		$key,
			$recurse = true )

Deletes an item from the cache.

Parameters

int | string	$key	Unused.
bool	$recurse	Unused.

Return values

bool

Reimplemented from cache.

delete_from_persist_cache()

cache::delete_from_persist_cache ( )

protectedinherited

Deprecated

since 2.6

See also

cache\static_acceleration_delete()

delete_many()

cache_disabled::delete_many	(	array	$keys,
			$recurse = true )

Deletes many items at once from the cache.

Parameters

array	$keys	Unused.
bool	$recurse	Unused.

Return values

int

Reimplemented from cache.

get()

cache::get ( $key, $strictness = IGNORE_MISSING )

inherited

Retrieves the value for the given key from the cache.

Parameters

string | int	$key	The key for the data being requested. It can be any structure although using a scalar string or int is recommended in the interests of performance. In advanced cases an array may be useful such as in situations requiring the multi-key functionality.
int	$strictness	One of IGNORE_MISSING | MUST_EXIST

Return values

mixed|false

The data from the cache or false if the key did not exist within the cache.

Exceptions

coding_exception

Implements cache_loader.

get_datasource()

cache::get_datasource ( )

protectedinherited

Returns the data source associated with this cache.

Since

Moodle 2.4.4

Return values

cache_data_source|false

get_definition()

cache::get_definition ( )

protectedinherited

Returns the cache definition.

Return values

cache_definition

get_from_persist_cache()

cache::get_from_persist_cache ( )

protectedinherited

Deprecated

since 2.6

See also

cache\static_acceleration_get

get_implementation()

cache_disabled::get_implementation ( $key, int $requiredversion, int $strictness, & $actualversion = null )

protected

Gets a key from the cache.

Parameters

int | string	$key
int	$requiredversion	Minimum required version of the data or cache\VERSION_NONE
int	$strictness	Unused.
mixed	&$actualversion	If specified, will be set to the actual version number retrieved

Return values

bool

Reimplemented from cache.

get_loader()

cache::get_loader ( )

protectedinherited

Returns the loader associated with this instance.

Since

Moodle 2.4.4

Return values

cache|false

get_many()

cache_disabled::get_many	(	array	$keys,
			$strictness = IGNORE_MISSING )

Gets many keys at once from the cache.

Parameters

array	$keys
int	$strictness	Unused.

Return values

array

Reimplemented from cache.

get_purge_token()

static cache::get_purge_token ( $reset = false )

staticinherited

Get a 'purge' token used for cache invalidation handling.

Note: This function is intended for use from within the Cache API only and not by plugins, or cache stores.

Parameters

bool

$reset

Whether to reset the token and generate a new one.

Return values

string

get_store()

cache::get_store ( )

protectedinherited

Returns the cache store.

Return values

cache_store

get_versioned()

cache::get_versioned ( $key, int $requiredversion, int $strictness = IGNORE_MISSING, & $actualversion = null )

inherited

Retrieves the value and actual version for the given key, with at least the required version.

If there is no value for the key, or there is a value but it doesn't have the required version, then this function will return null (or throw an exception if you set strictness to MUST_EXIST).

This function can be used to make it easier to support localisable caches (where the cache could be stored on a local server as well as a shared cache). Specifying the version means that it will automatically retrieve the correct version if available, either from the local server or [if that has an older version] from the shared server.

If the cached version is newer than specified version, it will be returned regardless. For example, if you request version 4, but the locally cached version is 5, it will be returned. If you request version 6, and the locally cached version is 5, then the system will look in higher-level caches (if any); if there still isn't a version 6 or greater, it will return null.

You must use this function if you use set_versioned.

Parameters

string | int	$key	The key for the data being requested.
int	$requiredversion	Minimum required version of the data
int	$strictness	One of IGNORE_MISSING or MUST_EXIST.
mixed	$actualversion	If specified, will be set to the actual version number retrieved

Return values

mixed

Data from the cache, or false if the key did not exist or was too old

Exceptions

coding_exception

If you call get_versioned on a non-versioned cache key

Implements cache_loader.

handle_invalidation_events()

cache::handle_invalidation_events ( )

protectedinherited

Process any outstanding invalidation events for the cache we are registering,.

Identifiers and event invalidation are not compatible with each other at this time. As a result the cache does not need to consider identifiers when working out what to invalidate.

has() [1/2]

cache_disabled::has	(		$key,
			$tryloadifpossible = false )

Checks if the cache has the requested key.

Parameters

int | string	$key	Unused.
bool	$tryloadifpossible	Unused.

Return values

bool

Reimplemented from cache.

has() [2/2]

cache_loader::has ( $key )

inherited

Test is a cache has a key.

The use of the has methods is strongly discouraged. In a high load environment the cache may well change between the test and any subsequent action (get, set, delete etc). Instead it is recommended to write your code in such a way they it performs the following steps:

1. Attempt to retrieve the information.
2. Generate the information.
3. Attempt to set the information

Its also worth mentioning that not all stores support key tests. For stores that don't support key tests this functionality is mimicked by using the equivalent get method. Just one more reason you should not use these methods unless you have a very good reason to do so.

Parameters

string | int

$key

Return values

bool	True if the cache has the requested key, false otherwise.

has_a_ttl()

cache::has_a_ttl ( )

protectedinherited

Returns true if the cache is making use of a ttl.

Return values

bool

has_all()

cache_disabled::has_all

(

array

$keys

)

Checks if the cache has all of the requested keys.

Parameters

array

$keys

Unused.

Return values

bool

Reimplemented from cache.

has_any()

cache_disabled::has_any

(

array

$keys

)

Checks if the cache has any of the requested keys.

Parameters

array

$keys

Unused.

Return values

bool

Reimplemented from cache.

is_in_persist_cache()

cache::is_in_persist_cache ( )

protectedinherited

See also

cache\static_acceleration_has

Deprecated

since 2.6

is_using_persist_cache()

cache::is_using_persist_cache ( )

protectedinherited

Deprecated

since 2.6

See also

cache\use_static_acceleration()

make()

static cache::make ( $component, $area, array $identifiers = array(), $unused = null )

staticinherited

Creates a new cache instance for a pre-defined definition.

Parameters

string	$component	The component for the definition
string	$area	The area for the definition
array	$identifiers	Any additional identifiers that should be provided to the definition.
string	$unused	Used to be datasourceaggregate but that was removed and this is now unused.

Return values

cache_application|cache_session|cache_store

make_from_params()

static cache::make_from_params ( $mode, $component, $area, array $identifiers = array(), array $options = array() )

staticinherited

Creates a new cache instance based upon the given params.

Parameters

int	$mode	One of cache_store\MODE_*
string	$component	The component this cache relates to.
string	$area	The area this cache relates to.
array	$identifiers	Any additional identifiers that should be provided to the definition.
array	$options	An array of options, available options are: simplekeys : Set to true if the keys you will use are a-zA-Z0-9_ simpledata : Set to true if the type of the data you are going to store is scalar, or an array of scalar vars staticacceleration : If set to true the cache will hold onto data passing through it. staticaccelerationsize : The max size for the static acceleration array.

Return values

cache_application|cache_session|cache_request

now()

static cache::now ( $float = false )

staticinherited

Returns the timestamp from the first request for the time from the cache API.

This stamp needs to be used for all ttl and time based operations to ensure that we don't end up with timing issues.

Parameters

bool

$float

Whether to use floating precision accuracy.

Return values

int|float

parse_key()

cache::parse_key ( $key )

protectedinherited

Parses the key turning it into a string (or array is required) suitable to be passed to the cache store.

Parameters

string | int

$key

As passed to get|set|delete etc.

Return values

string|array

String unless the store supports multi-identifiers in which case an array if returned.

Reimplemented in cache_session.

purge()

cache_disabled::purge

(

)

Purges all items from the cache.

Return values

bool

Reimplemented from cache.

purge_current_user()

cache::purge_current_user ( )

inherited

Subclasses may support purging cache of all data belonging to the current user.

Reimplemented in cache_session.

release_lock()

cache_disabled::release_lock

(

$key

)

Pretend that we released a lock to avoid errors.

Parameters

int | string

$key

Return values

bool

Implements cache_loader_with_locking.

requires_serialisation()

cache::requires_serialisation ( $value, $depth = 1 )

protectedinherited

Checks to see if a var requires serialisation.

Parameters

mixed	$value	The value to check.
int	$depth	Used to ensure we don't enter an endless loop (think recursion).

Return values

bool	Returns true if the value is going to require serialisation in order to ensure a reference free copy or false if its safe to clone.

set()

cache::set ( $key, $data )

inherited

Sends a key => value pair to the cache.

// This code will add four entries to the cache, one for each url. $cache->set('main', 'http://moodle.org'); $cache->set('docs', 'http://docs.moodle.org'); $cache->set('tracker', 'http://tracker.moodle.org'); $cache->set('qa', 'http://qa.moodle.net');

Parameters

string | int	$key	The key for the data being requested. It can be any structure although using a scalar string or int is recommended in the interests of performance. In advanced cases an array may be useful such as in situations requiring the multi-key functionality.
mixed	$data	The data to set against the key.

Return values

bool	True on success, false otherwise.

Implements cache_loader.

Reimplemented in cache_session.

set_data_source()

cache::set_data_source ( cache_data_source $datasource )

protectedinherited

Set the data source for this cache.

Parameters

cache_data_source

$datasource

set_identifiers()

cache::set_identifiers ( array $identifiers )

inherited

Alters the identifiers that have been provided to the definition.

This is an advanced method and should not be used unless really needed. It allows the developer to slightly alter the definition without having to re-establish the cache. It will cause more processing as the definition will need to clear and reprepare some of its properties.

Parameters

array

$identifiers

set_implementation()

cache_disabled::set_implementation ( $key, int $version, $data, bool $setparents = true )

protected

Sets a key value pair in the cache.

Parameters

int | string	$key	Unused.
int	$version	Unused.
mixed	$data	Unused.
bool	$setparents	Unused.

Return values

bool

Reimplemented from cache.

set_in_persist_cache()

cache::set_in_persist_cache ( )

protectedinherited

Deprecated

since 2.6

See also

cache\static_acceleration_set

set_is_sub_loader()

cache::set_is_sub_loader ( $setting = true )

protectedinherited

Used to inform the loader of its state as a sub loader, or as the top of the chain.

This is important as it ensures that we do not have more than one loader keeping static acceleration data. Subloaders need to be "pure" loaders in the sense that they are used to store and retrieve information from stores or the next loader/data source in the chain. Nothing fancy, nothing flash.

Parameters

bool

$setting

set_loader()

cache::set_loader ( cache_loader $loader )

protectedinherited

Set the loader for this cache.

Parameters

cache_loader

$loader

set_many()

cache_disabled::set_many

(

array

$keyvaluearray

)

Sets many key value pairs in the cache at once.

Parameters

array

$keyvaluearray

Unused.

Return values

int

Reimplemented from cache.

set_versioned()

cache::set_versioned ( $key, int $version, $data )

inherited

Sets the value for the given key with the given version.

The cache does not store multiple versions - any existing version will be overwritten with this one. This function should only be used if there is a known 'current version' (e.g. stored in a database table). It only ensures that the cache does not return outdated data.

This function can be used to help implement localisable caches (where the cache could be stored on a local server as well as a shared cache). The version will be recorded alongside the item and get_versioned will always return the correct version.

The version number must be an integer that always increases. This could be based on the current time, or a stored value that increases by 1 each time it changes, etc.

If you use this function you must use get_versioned to retrieve the data.

Parameters

string | int	$key	The key for the data being set.
int	$version	Integer for the version of the data
mixed	$data	The data to set against the key.

Return values

bool	True on success, false otherwise.

Implements cache_loader.

static_acceleration_delete()

cache::static_acceleration_delete ( $key )

protectedinherited

Deletes an item from the static acceleration array.

Parameters

string | int

$key

As given to get|set|delete

Return values

bool	True on success, false otherwise.

static_acceleration_get()

cache::static_acceleration_get ( $key )

protectedinherited

Returns the item from the static acceleration array if it exists there.

Parameters

string

$key

The parsed key

Return values

mixed|false

Dereferenced data from the static acceleration array or false if it wasn't there.

static_acceleration_has()

cache::static_acceleration_has ( $key )

protectedinherited

Returns true if the requested key exists within the static acceleration array.

Parameters

string

$key

The parsed key

Return values

bool

static_acceleration_set()

cache::static_acceleration_set ( $key, $data )

protectedinherited

Sets a key value pair into the static acceleration array.

Parameters

string	$key	The parsed key
mixed	$data

Return values

bool

store_supports_key_awareness()

cache::store_supports_key_awareness ( )

protectedinherited

Returns true if the store supports key awareness.

Return values

bool

store_supports_native_locking()

cache::store_supports_native_locking ( )

protectedinherited

Returns true if the store natively supports locking.

Return values

bool

store_supports_native_ttl()

cache::store_supports_native_ttl ( )

protectedinherited

Returns true if the cache store supports native ttl.

Return values

bool

unref()

cache::unref ( $data )

protectedinherited

Removes references where required.

Parameters

stdClass | array

$data

Return values

mixed

What ever was put in but without any references.

use_static_acceleration()

cache::use_static_acceleration ( )

protectedinherited

Returns true if this cache is making use of the static acceleration array.

Return values

bool

Reimplemented in cache_session.

Member Data Documentation

$nativelocking

cache_store null cache::$nativelocking = null

protectedinherited

Gets set to true if the cache's primary store natively supports locking.

If it does then we use that, otherwise we need to instantiate a second store to use for locking.

$now

int cache::$now

staticprotectedinherited

We need a timestamp to use within the cache API.

This stamp needs to be used for all ttl and time based operations to ensure that we don't end up with timing issues.

$purgetoken

string cache::$purgetoken

staticprotectedinherited

A purge token used to distinguish between multiple cache purges in the same second.

This is in the format <microtime>-<random string>.

$storetype

strubg cache::$storetype = 'unknown'

protectedinherited

Gets set to the class name of the store during initialisation.

This is used several times in the cache class internally and having it here helps speed up processing.

---

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

• cache/disabledlib.php