Private data

The PKGFS class holds also some private variables which reference each PackageFS object, and keep configuration values:

• $\texttt{baselevel}$. During the presentation of the class we met this variable many times. How is it computed? At the very beginning its value is 1. While the PKGFS constructor is executing, it evaluates $\texttt{sectionValue}$ and $\texttt{priorityValue}$ settings: for each of those which are bigger than 0, it adds one to the $\texttt{baselevel}$ value. It is straightforward. In this way, PackageFS achieves hierarchy configuration goal, which is one of its most interesting features;
• $\texttt{PkgManager *pkgmgr}$ represents the current package management layer;
• $\texttt{void *pkgPtr}$. This pointer has been introduced to decrease the amount of researches in the package manager cache: it is a ``black box'' storing the package identifier within the cache itself, no matter what data type it is. Processing a package often involves several PkgManager's methods. We do not want passing them the package name and searching for its identifier every time. PKGFS calls the $\texttt{PkgManager::findPkg()}$ method once to get this pointer that will be given as input to other PkgManager's methods;
• $\texttt{Vtree *pkgVtree}$ points to an instance of the virtual tree;
• $\texttt{PKGFSCache *fsCache}$ implements the virtual tree caching mechanism.

Figura 5.8: Vtree and Ventry public methods and private data.