Squid internals

The Storage Manager (src/store*.c)
SquidFS API - handling disk IO
A "generic" API is provided to allow flexibility in the storedir design
Every open file in the storedirs has a StoreIOState (sio) created to track state
Each StoreEntry has two parameters identifying the object on disk
swap_dirn - the storedir the object resides upon
swap_filen - an arbitrary number identifying where the object is on disk, storedir dependant