caching the RPM package list

[Dave Peterson]

Hello,

I have an application that periodically makes RPM library
calls to find out what packages are installed on a machine.
To reduce overhead, I'd like the application to cache this
information.  To implement this, I'd like to identify
which file(s) contain the RPM database, and stat() these
files to determine whether my cache needs updating.  Does
anyone know which file(s) I should stat()?  Does the answer
depend on which version of RPM is in use, or any other
factors such as the manner in which RPM is configured?

Thanks,
Dave