
/* When one GPT structure points to another, it does so via a block number (in the terms used by the specification, this is a logical block address, or LBA). To correlate this to a byte offset (for example, if you're seeking within a device node), you must multiply it by the block size. You can get the block size of a device node by calling ioctl with the DKIOCGETBLOCKSIZE selector (defined in <sys/disk.h>). Do not assume that the block size is always going to be 512 bytes.*/
#define DKIOCGETBLOCKSIZE 512 

