Revert "Delete dead code"

This reverts commit 1d6bac6.

include/exiv2/datasets.hpp

@@ -238,6 +238,21 @@ namespace Exiv2 {
          */
         static const char* recordDesc(uint16_t recordId);
 
+        /*!
+           @brief Return the Id number of a record
+           @param recordName Name of a record type
+           @return the Id number of a Record
+           @throw Error if the record is not known;
+         */
+        static uint16_t recordId(const std::string& recordName);
+
+        //! Return read-only list of built-in Envelope Record datasets
+        static const DataSet* envelopeRecordList();
+
+        //! Return read-only list of built-in Application2 Record datasets
+        static const DataSet* application2RecordList();
+
+        //! Print a list of all dataSets to output stream
         static void dataSetList(std::ostream& os);
 
     private:

src/datasets.cpp

@@ -421,6 +421,16 @@ namespace Exiv2 {
         0xffffffff, Exiv2::string,     IptcDataSets::invalidRecord, N_("Unknown dataset"),
     };
 
+    const DataSet* IptcDataSets::envelopeRecordList()
+    {
+        return envelopeRecord;
+    }
+
+    const DataSet* IptcDataSets::application2RecordList()
+    {
+        return application2Record;
+    }
+
     // Dataset lookup lists.This is an array with pointers to one list per IIM4 Record.
     // The record id is used as the index into the array.
     constexpr const DataSet* IptcDataSets::records_[] = {