There is a separate check in the <code>calculate_checksum</code> function to make sure the iterator refers to a valid byte (Not negative and smaller than the total number of bytes in the file). If the iterator is outside the mapped region but still valid, the required region of the file will be mapped. | There is a separate check in the <code>calculate_checksum</code> function to make sure the iterator refers to a valid byte (Not negative and smaller than the total number of bytes in the file). If the iterator is outside the mapped region but still valid, the required region of the file will be mapped. |