Source code of Windows XP (NT5)
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//
// mbr.h - minimum stuff to allow diskpart to work on MBRs.
//
//
// MBR:
// There are 3 kinds of MBRs.
// 1. GPT Shadow MBR - an MBR filled in with particular values
// to keep legacy software from puking on GPT disks.
// 2. MBR base - an MBR that allows for up to 4 paritions.
// 3. Extended MBR - nested inside other MBRs to allow more than
// 4 partitions on a non-GPT disk.
//
// This program, and therefore this header file, is only concerned
// with case 1, and a limited subset of case 2.
//
//
// MBR contains code, with a table of 4 Partition entries and
// a signature at the end.
//
#pragma pack (1)
typedef struct _MBR_ENTRY {
CHAR8 ActiveFlag; // Bootable or not
CHAR8 StartingTrack; // Not used
CHAR8 StartingCylinderLsb; // Not used
CHAR8 StartingCylinderMsb; // Not used
CHAR8 PartitionType; // 12 bit FAT, 16 bit FAT etc.
CHAR8 EndingTrack; // Not used
CHAR8 EndingCylinderLsb; // Not used
CHAR8 EndingCylinderMsb; // Not used
UINT32 StartingSector; // Hidden sectors
UINT32 PartitionLength; // Sectors in this partition
} MBR_ENTRY;
//
// Number of partition table entries
//
#define NUM_PARTITION_TABLE_ENTRIES 4
//
// Partition table record and boot signature offsets in bytes
//
#define MBR_TABLE_OFFSET (0x1be)
#define MBR_SIGNATURE_OFFSET (0x200 - 2)
//
// Boot record signature value.
//
#define BOOT_RECORD_SIGNATURE (0xaa55)
//
// Special Partition type used only on GPT disks
//
#define PARTITION_TYPE_GPT_SHADOW (0xEE)
#pragma pack ()