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Cache Class Design

1.0 Design Considerations

1.1 Assumptions
Store is a javascript object(Hash Map). 
When dealing with multiple cache layers, will use a fully inclusive approach where data from L2 wll be copied to L1.
The last level cache is a superset of all higher level caches.
Cache will use keys to store and find data.
Javascript does not have public and private methods but intention is stated in comments

1.2 General Purpose
The purpose of this cache is to store recently requested or written data for quicker access

2.0 System Archeticture

2.1 Overall Flow
l1 Cache -> l2 Cache -> Store

2.2 Cache Design
jsCache uses Direct Mapped Cache and Associative Cache Design

Direct Mapped
Cache is composed of an array of Queues [Queue, Queue, Queue, ...]
A hashing algorithim returns the index of where our Data resides

Associative Cache
Represented by a Queue. Data can be in any index of the Queue
Data is found by looping through the items in the Queue and comparing the keys

3.0 Cache Behaviors

3.1 Cache Hit

	Read
	If requested data is found in l1 cache, it is returned

	Write
	If cache has room, data is written in the cache but not in the store
3.2 Cache Miss

	Read-Allocate
	On cache miss, check lower level caches and finally store
	Allocate data to caches

	Write-Back
	If cache has room, write data to the cache
	when data is evicted write to the store

	Eviction
	If Queue is full, dequeue first item in Queue to make room for new data

4.0 User Interface

Instantiate a Cache and Store
var store = new Store()
var cache = new jsCache(cacheSetSize, setBlockSize, store, parentCache)

Methods Available
writeToCache(key, value)
fetchData(key)