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