krh@1: - pkg manifest is list of files
krh@1: 
krh@1: 	/usr/bin/bash 1321321372198798
krh@1: 
krh@1:   plus provides, requires and version?
krh@1: 
krh@1: - keep history of installed packages/journal of package transaction,
krh@1:   so we can roll back to yesterday, or see what got installed in the
krh@1:   latest yum update.
krh@1: 
krh@1: - we build a cache of the currently installed set to service
krh@1:   dependency inquiries fast:
krh@1: 
krh@1: 	map from property to pkg (as hash) providing it
krh@1: 	map from property to pkgs requiring it
krh@1: 	map from pkg name to manifest
krh@1: 	map from string to string pool index
krh@1: 
krh@1: 	no implicit provides? not even pkgname?
krh@1: 
krh@1: - properties are strings, stored in a string table
krh@1: 
krh@1: - on disk maps are binary files of (string table index, hash) pairs
krh@1: 
krh@1: - at run time, we mmap the map, and keep changes in memory in a splay
krh@1:   tree or similar.  if searching the splay tree fails we punt to the
krh@1:   mmap.  once the transaction is done, we merge the map and the splay
krh@1:   tree and write it back out.
krh@1: 
krh@1: - the on-disk string pool is sorted and we keep a list of indices into
krh@1:   the string pool in sorted order so we can bsearch the list with a
krh@1:   string to get its string pool index.  maybe a hash table is better,
krh@1:   less I/O as we will expect to find the string within the block we
krh@1:   look up with the hash function.
krh@1: 
krh@1: - signed pkgs
krh@1: - gzip pkg xml files somehow?