pkgCache::PkgIterator

This is the class of the package entry identifier set in the $\texttt{findPkg()}$ method. It is involved in the whole ``single package operation'' category. The
$\texttt{PkgIterator}$ class belongs to a set of iterators useful for navigation of the cache structure. They provide common visit operations and an $\texttt{end()}$ function. The last one can be used to check if the corresponding list has been fully traversed. Unlike Standard Template Library iterators, they contain helper functions to access data that is being iterated over. This is because the data structures cannot be formed in a manner that is intuitive to use and also memory mappable. For each variable in the target structure that would need a translation to be accessed correctly, a translating function of the same name is present in the iterator. If applicable this function will return an iterator. We show here the interesting part of the interface to all this type of iterators defined in $\texttt{<apt-pkg/cacheiterators.h>}$:

• $\texttt{const char *Name() const}$: it returns the package name;
• $\texttt{const char *Section() const}$: it returns the name of the section the package belongs to;
• $\texttt{VerIterator VersionList() const}$: in this way we access a
  $\texttt{VerIterator}$ instance, that iterates over available versions of a package. The methods of this new iterator, are used to retrieve the corresponding version number ( $\texttt{VerStr()}$), the priority type ( $\texttt{PriorityType()}$), its dependencies ( $\texttt{DependsList()}$), or the list of provided packages ( $\texttt{ProvidesList()}$). They are all involved in the $\texttt{getInfo()}$ method of the PkgDebian class;
• $\texttt{DepIterator RevDependsList() const}$: the $\texttt{DepIterator}$ iterator belongs to the same category of iterators. It can iterate over two lists, a list of version depends (we have just seen the $\texttt{DependsList()}$ method), or a list of package reverse depends. The type is determined by the structure passed to the constructor, which should be the structure that has the depends pointer as a member. This method, for example, returns the reverse dependencies iterator. Thus, in the PkgDebian implementation, the $\texttt{DepIterator}$ is central in developing the functions $\texttt{getDepends()}$ and $\texttt{getRDepends()}$.