CopyUnicodeTo( const nsAReadableString& aSource, PRUint32 aSrcOffset, PRUnichar* aDest, PRUint32 aLength )
CopyUnicodeTo( const nsReadingIterator<PRUnichar>& aSrcStart, const nsReadingIterator<PRUnichar>& aSrcEnd, nsAString& aDest )
CopyUnicodeTo( const nsAReadableString& aSource, PRUint32 aSrcOffset, PRUnichar* aDest, PRUint32 aLength )  {    nsReadingIterator<PRUnichar> fromBegin, fromEnd;    PRUnichar* toBegin = aDest;        copy_string(aSource.BeginReading(fromBegin).advance( PRInt32(aSrcOffset) ), aSource.BeginReading(fromEnd).advance( PRInt32(aSrcOffset+aLength) ), toBegin);    return aDest;  }