Squid internals

The Storage Manager (src/store*.c)
StoreEntry - the centre of squid's universe
Each object in squid has an associated StoreEntry
A StoreEntry is identified by a cache key
Squid supports multiple types of cache keys, but the currently used one is an MD5 hash
Each StoreEntry contains a MemObject, refcount, flags,replacement / expiry information and on-disk information

MemObject - in-memory cache objects
Each object with active clients or servers and/or object memory attached has a MemObject attached
Not all StoreEntry's require a MemObject when inactive