+/**
+ * \brief Build a \ref TagDocEntryHT (i.e. a std::map<>) from the current
+ * gdcmDocument.
+ *
+ * The structure used by a gdcmDocument (through \ref gdcmElementSet),
+ * in order to old the parsed entries of a Dicom header, is a recursive
+ * one. This is due to the fact that the sequences (when present)
+ * can be nested. Additionaly, the sequence items (represented in
+ * gdcm as \ref gdcmSQItem) add an extra complexity to the data
+ * structure. Hence, a gdcm user whishing to visit all the entries of
+ * a Dicom header will need to dig in the gdcm internals (which
+ * implies exposing all the internal data structures to the API).
+ * In order to avoid this burden to the user, \ref BuildFlatHashTable
+ * recursively builds a temporary hash table, which holds all the
+ * Dicom entries in a flat structure (a \ref TagDocEntryHT i.e. a
+ * std::map<>).
+ * \warning Of course there is NO integrity constrain between the
+ * returned \ref TagDocEntryHT and the \ref gdcmElementSet used
+ * to build it. Hence if the underlying \ref gdcmElementSet is
+ * altered, then it is the caller responsability to invoke
+ * \ref BuildFlatHashTable again...
+ * @return The flat std::map<> we juste build.
+ */
+TagDocEntryHT* gdcmDocument::BuildFlatHashTable()
+{
+ TagDocEntryHT* FlatHT = new TagDocEntryHT;
+ BuildFlatHashTableRecurse( *FlatHT, this );
+ return FlatHT;
+}
+