hide NoteData::InsertHoldTails away in NoteDataUtils

stepmania/src/NoteDataUtil.cpp

@@ -227,13 +227,41 @@ void NoteDataUtil::LoadFromSMNoteDataString( NoteData &out, CString sSMNoteData
 	}
 }
 
+namespace
+{
+	void InsertHoldTails( NoteData &inout )
+	{
+		for( int t=0; t < inout.GetNumTracks(); t++ )
+		{
+			NoteData::iterator begin = inout.begin(t), end = inout.end(t);
+
+			for( ; begin != end; ++begin )
+			{
+				int iRow = begin->first;
+				const TapNote &tn = begin->second;
+				if( tn.type != TapNote::hold_head )
+					continue;
+
+				TapNote tail = tn;
+				tail.type = TapNote::hold_tail;
+
+				/* If iDuration is 0, we'd end up overwriting the head with the tail
+				* (and invalidating our iterator).  Empty hold notes aren't valid. */
+				ASSERT( tn.iDuration != 0 );
+
+				inout.SetTapNote( t, iRow + tn.iDuration, tail );
+			}
+		}
+	}
+};
+
 void NoteDataUtil::GetSMNoteDataString( const NoteData &in_, CString &notes_out )
 {
 	//
 	// Get note data
 	//
 	NoteData in( in_ );
-	in.InsertHoldTails();
+	InsertHoldTails( in );
 
 	float fLastBeat = in.GetLastBeat();
 	int iLastMeasure = int( fLastBeat/BEATS_PER_MEASURE );