lrucache-0.1: a simple pure LRU cache

Data.Cache.LRU.Internal

Description

This module provides access to all the internals use by the LRU type. This can be used to create data structures that violate the invariants the public interface maintains. Be careful when using this module. The valid function can be used to check if an LRU structure satisfies the invariants the public interface maintains.

If this degree of control isn't needed, consider using Data.Cache.LRU instead.

Synopsis

Documentation

data LRU key val Source

Stores the information that makes up an LRU cache

Constructors

LRU 

Fields

first :: Maybe key

the key of the most recently accessed entry

last :: Maybe key

the key of the least recently accessed entry

maxSize :: Int

the maximum size of the LRU cache

content :: Map key (LinkedVal key val)

the backing Map

data LinkedVal key val Source

The values stored in the Map of the LRU cache. They embed a doubly-linked list through the values of the Map.

Constructors

Link 

Fields

value :: val

The actual value

prev :: Maybe key

the key of the value before this one

next :: Maybe key

the key of the value after this one

newLRUSource

Arguments

:: Ord key 
=> Int

the maximum size of the LRU

-> LRU key val 

Make an LRU. The LRU is guaranteed to not grow above the specified number of entries.

fromListSource

Arguments

:: Ord key 
=> Int

the maximum size of the LRU

-> [(key, val)] 
-> LRU key val 

Build a new LRU from the given maximum size and list of contents, in order from most recently accessed to least recently accessed.

toList :: Ord key => LRU key val -> [(key, val)]Source

Retrieve a list view of an LRU. The items are returned in order from most recently accessed to least recently accessed.

insert :: Ord key => key -> val -> LRU key val -> LRU key valSource

Add an item to an LRU. If the key was already present in the LRU, the value is changed to the new value passed in. The item added is marked as the most recently accessed item in the LRU returned.

If this would cause the LRU to exceed its maximum size, the least recently used item is dropped from the cache.

lookup :: Ord key => key -> LRU key val -> (LRU key val, Maybe val)Source

Look up an item in an LRU. If it was present, it is marked as the most recently accesed in the returned LRU.

delete :: Ord key => key -> LRU key val -> (LRU key val, Bool)Source

Remove an item from an LRU. Returns the new LRU, and if the item was present to be removed.

size :: LRU key val -> IntSource

Returns the number of elements the LRU currently contains.

hit' :: Ord key => key -> LRU key val -> LRU key valSource

Internal function. The key passed in must be present in the LRU. Moves the item associated with that key to the most recently accessed position.

valid :: Ord key => LRU key val -> BoolSource

Internal function. This checks the three structural invariants of the LRU cache structure:

  1. The cache's size does not exceed the specified max size.
  2. The linked list through the nodes is consistent in both directions.
  3. The linked list contains the same number of nodes as the cache.