Package Ganga :: Package Utility :: Module Caching :: Class Cache

Class Cache

object --+
         |
        Cache

Known Subclasses:

FunctionCache

An abstract, multi-threaded cache object.

Instance Methods

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__init__(self, dset, max_size=0)
Builds a cache with a limit of max_size entries.

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__setitem__(self, name, value)
Populates the cache with a given name and value.

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__getitem__(self, name)
Gets a value from the cache, builds it if required.

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__delitem__(self, name)

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_get_entry(self, key)

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_checkitem(self, name)
Gets a value from the cache, builds it if required.

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mru(self)
Returns the Most Recently Used key

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lru(self)
Returns the Least Recently Used key

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key(self, name)
Override this method to extract a key from the name passed to the [] operator

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commit(self)
Override this method if you want to do something each time the underlying dictionary is modified (e.g.

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clear(self)
Clears the cache

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check(self, key, name, entry)
Override this method to check whether the entry with the given name is stale.

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build(self, key, name, opened, entry)
Build the cached value with the given name from the given opened resource.

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_access(self, entry)
Internal use only, must be invoked within a cache lock.

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_checklru(self)
Internal use only, must be invoked within a cache lock.

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_pack(self, entry, value)
Store the value in the entry.

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_unpack(self, entry)
Recover the value from the entry, returns NOT_INITIALIZED if it is not OK.

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Inherited from object: __delattr__, __format__, __getattribute__, __hash__, __new__, __reduce__, __reduce_ex__, __repr__, __setattr__, __sizeof__, __str__, __subclasshook__

Class Variables

[hide private]

cacheDict = {}

Properties

[hide private]

Inherited from object: __class__

Method Details

[hide private]

init(self, dset, max_size=0)
(Constructor)

source code

Builds a cache with a limit of max_size entries. If this limit is exceeded, the Least Recently Used entry is discarded. if max_size==0, the cache is unbounded (no LRU rule is applied).

Overrides: object.__init__

_checkitem(self, name)

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Gets a value from the cache, builds it if required. Returns a tuple is_new, key, value, entry. If is_new is True, the result had to be rebuilt.

commit(self)

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Override this method if you want to do something each time the underlying dictionary is modified (e.g. make it persistent).

check(self, key, name, entry)

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Override this method to check whether the entry with the given name is stale. Return None if it is fresh or an opened resource if it is stale. The object returned will be passed to the 'build' method as the 'opened' parameter. Use the 'entry' parameter to store meta-data if required. Don't worry about multiple threads accessing the same name, as this method is properly isolated.

build(self, key, name, opened, entry)

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Build the cached value with the given name from the given opened resource. Use entry to obtain or store meta-data if needed. Don't worry about multiple threads accessing the same name, as this method is properly isolated.

_access(self, entry)

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Internal use only, must be invoked within a cache lock. Updates the access list.

_checklru(self)

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Internal use only, must be invoked within a cache lock. Removes the LRU entry if needed.

Class Cache

__init__(self, dset, max_size=0) (Constructor)

_checkitem(self, name)

commit(self)

check(self, key, name, entry)

build(self, key, name, opened, entry)

_access(self, entry)

_checklru(self)

init(self, dset, max_size=0)
(Constructor)