Squid internals

The Storage Manager (src/store*.c)
Store Clients - typical flow
There are two types of store clients
Disk clients (STORE_DISK_CLIENT)
If the beginning of the object isn't avaliable in memory, the client must be a disk client
Memory clients (STORE_MEM_CLIENT)
If the beginning of the object is in memory or the object is an internal object, the client must be a mem client
StoreClientCopy() will return when data is avaliable, or an error occurs
The "magic" inside StoreClientCopy*() chooses whether to read from disk (STORE_DISK_CLIENT) or to wait for data (STORE_MEM_CLIENT)