Initialize the iterator to point to the first metadata block in the
given chain.
\param iterator A pointer to an existing iterator.
\param chain A pointer to an existing and initialized (read) chain.
\assert
\code iterator != NULL \endcode
\code chain != NULL \endcode
Initialize the iterator to point to the first metadata block in the given chain.
\param iterator A pointer to an existing iterator. \param chain A pointer to an existing and initialized (read) chain. \assert \code iterator != NULL \endcode \code chain != NULL \endcode