Cache operations

Referring to cache operations, it seems like PackageFS supports only the package managers based on a cache mechanism. This is not true, because the cache is meant to be the place where the package manager retrieves information about packages. Although Slackware, for example, does not maintain any plain nor binary cache, it stores somewhere in the system many filenames representing the installed packages. Furthermore, its available packages are those that are present in a specified directory at a given time. Currently Slackware has neither a cache, nor a repository where pkgtools retrieves these information, but it uses well-known ``places''. These latter represent the cache being for PkgManager implementation. Not all these methods are really needed to make PackageFS working: it depends from the specific package manager it deals with.

The virtual methods belonging to this category are :

• $\texttt{int getInitCache(string \&}$buffer $\texttt{)}$ : it retrieves the name of all the available packages and their installation status then it writes them into the buffer given as a parameter in a well-known format;
• $\texttt{int findPkg(string }$pkg_name, $\texttt{void**}$ pkgPtr $\texttt{)}$: given a package name, it searches for its entry in the cache. Then it sets the pkgPtr pointer to the found entry. As soon as pkgPtr is updated and returns to the caller, it becomes a ``black box'' due to its $\texttt{void*}$ nature. It will be used as argument for other PkgManager's methods that are aware of its essential being;
• $\texttt{bool readCache()}$ : it synchronizes PackageFS with the package manager cache. It is used at mount time and after the execution of the low-level package manager since each operation can actually modify some packages metadata.
• $\texttt{void closeCache()}$, $\texttt{string CachePath()}$: these methods are optional methods used mainly to interact with a packages database;
• $\texttt{string Sections(int}$ value $\texttt{)}$ and $\texttt{string Priorities(int }$value $\texttt{)}$ : they return a buffer filled with a list of section or priority types supported by the package manager. In addition, they set the respective private variables to the configuration values given as parameters.