FreeBSD/Linux Kernel Cross Reference
sys/fs/msdosfs/bpb.h

     /* $FreeBSD: releng/6.0/sys/fs/msdosfs/bpb.h 139776 2005-01-06 18:10:42Z imp $ */
     /*      $NetBSD: bpb.h,v 1.7 1997/11/17 15:36:24 ws Exp $       */
     
     /*-
      * Written by Paul Popelka (paulp@uts.amdahl.com)
      *
      * You can do anything you want with this software, just don't say you wrote
      * it, and don't remove this notice.
      *
     * This software is provided "as is".
     *
     * The author supplies this software to be publicly redistributed on the
     * understanding that the author is not responsible for the correct
     * functioning of this software in any circumstances and is not liable for
     * any damages caused by this software.
     *
     * October 1992
     */
    
    /*
     * BIOS Parameter Block (BPB) for DOS 3.3
     */
    struct bpb33 {
            u_int16_t       bpbBytesPerSec; /* bytes per sector */
            u_int8_t        bpbSecPerClust; /* sectors per cluster */
            u_int16_t       bpbResSectors;  /* number of reserved sectors */
            u_int8_t        bpbFATs;        /* number of FATs */
            u_int16_t       bpbRootDirEnts; /* number of root directory entries */
            u_int16_t       bpbSectors;     /* total number of sectors */
            u_int8_t        bpbMedia;       /* media descriptor */
            u_int16_t       bpbFATsecs;     /* number of sectors per FAT */
            u_int16_t       bpbSecPerTrack; /* sectors per track */
            u_int16_t       bpbHeads;       /* number of heads */
            u_int16_t       bpbHiddenSecs;  /* number of hidden sectors */
    };
    
    /*
     * BPB for DOS 5.0 The difference is bpbHiddenSecs is a short for DOS 3.3,
     * and bpbHugeSectors is not in the 3.3 bpb.
     */
    struct bpb50 {
            u_int16_t       bpbBytesPerSec; /* bytes per sector */
            u_int8_t        bpbSecPerClust; /* sectors per cluster */
            u_int16_t       bpbResSectors;  /* number of reserved sectors */
            u_int8_t        bpbFATs;        /* number of FATs */
            u_int16_t       bpbRootDirEnts; /* number of root directory entries */
            u_int16_t       bpbSectors;     /* total number of sectors */
            u_int8_t        bpbMedia;       /* media descriptor */
            u_int16_t       bpbFATsecs;     /* number of sectors per FAT */
            u_int16_t       bpbSecPerTrack; /* sectors per track */
            u_int16_t       bpbHeads;       /* number of heads */
            u_int32_t       bpbHiddenSecs;  /* # of hidden sectors */
            u_int32_t       bpbHugeSectors; /* # of sectors if bpbSectors == 0 */
    };
    
    /*
     * BPB for DOS 7.10 (FAT32).  This one has a few extensions to bpb50.
     */
    struct bpb710 {
            u_int16_t       bpbBytesPerSec; /* bytes per sector */
            u_int8_t        bpbSecPerClust; /* sectors per cluster */
            u_int16_t       bpbResSectors;  /* number of reserved sectors */
            u_int8_t        bpbFATs;        /* number of FATs */
            u_int16_t       bpbRootDirEnts; /* number of root directory entries */
            u_int16_t       bpbSectors;     /* total number of sectors */
            u_int8_t        bpbMedia;       /* media descriptor */
            u_int16_t       bpbFATsecs;     /* number of sectors per FAT */
            u_int16_t       bpbSecPerTrack; /* sectors per track */
            u_int16_t       bpbHeads;       /* number of heads */
            u_int32_t       bpbHiddenSecs;  /* # of hidden sectors */
            u_int32_t       bpbHugeSectors; /* # of sectors if bpbSectors == 0 */
            u_int32_t       bpbBigFATsecs;  /* like bpbFATsecs for FAT32 */
            u_int16_t       bpbExtFlags;    /* extended flags: */
    #define FATNUM          0xf             /* mask for numbering active FAT */
    #define FATMIRROR       0x80            /* FAT is mirrored (like it always was) */
            u_int16_t       bpbFSVers;      /* filesystem version */
    #define FSVERS          0               /* currently only 0 is understood */
            u_int32_t       bpbRootClust;   /* start cluster for root directory */
            u_int16_t       bpbFSInfo;      /* filesystem info structure sector */
            u_int16_t       bpbBackup;      /* backup boot sector */
            /* There is a 12 byte filler here, but we ignore it */
    };
    
    /*
     * The following structures represent how the bpb's look on disk.  shorts
     * and longs are just character arrays of the appropriate length.  This is
     * because the compiler forces shorts and longs to align on word or
     * halfword boundaries.
     *
     * XXX The little-endian code here assumes that the processor can access
     * 16-bit and 32-bit quantities on byte boundaries.  If this is not true,
     * use the macros for the big-endian case.
     */
    
    #include <machine/endian.h>
    
    #ifdef __i386__
    #define UNLALIGNED_ACCESS
    #endif
   
   #if (BYTE_ORDER == LITTLE_ENDIAN) && defined(UNALIGNED_ACCESS)
   #define getushort(x)    *((u_int16_t *)(x))
   #define getulong(x)     *((u_int32_t *)(x))
   #define putushort(p, v) (*((u_int16_t *)(p)) = (v))
   #define putulong(p, v)  (*((u_int32_t *)(p)) = (v))
   #else
   #define getushort(x)    (((u_int8_t *)(x))[0] + (((u_int8_t *)(x))[1] << 8))
   #define getulong(x)     (((u_int8_t *)(x))[0] + (((u_int8_t *)(x))[1] << 8) \
                            + (((u_int8_t *)(x))[2] << 16) \
                            + (((u_int8_t *)(x))[3] << 24))
   #define putushort(p, v) (((u_int8_t *)(p))[0] = (v),    \
                            ((u_int8_t *)(p))[1] = (v) >> 8)
   #define putulong(p, v)  (((u_int8_t *)(p))[0] = (v),    \
                            ((u_int8_t *)(p))[1] = (v) >> 8, \
                            ((u_int8_t *)(p))[2] = (v) >> 16,\
                            ((u_int8_t *)(p))[3] = (v) >> 24)
   #endif
   
   /*
    * BIOS Parameter Block (BPB) for DOS 3.3
    */
   struct byte_bpb33 {
           int8_t bpbBytesPerSec[2];       /* bytes per sector */
           int8_t bpbSecPerClust;          /* sectors per cluster */
           int8_t bpbResSectors[2];        /* number of reserved sectors */
           int8_t bpbFATs;                 /* number of FATs */
           int8_t bpbRootDirEnts[2];       /* number of root directory entries */
           int8_t bpbSectors[2];           /* total number of sectors */
           int8_t bpbMedia;                /* media descriptor */
           int8_t bpbFATsecs[2];           /* number of sectors per FAT */
           int8_t bpbSecPerTrack[2];       /* sectors per track */
           int8_t bpbHeads[2];             /* number of heads */
           int8_t bpbHiddenSecs[2];        /* number of hidden sectors */
   };
   
   /*
    * BPB for DOS 5.0 The difference is bpbHiddenSecs is a short for DOS 3.3,
    * and bpbHugeSectors is not in the 3.3 bpb.
    */
   struct byte_bpb50 {
           int8_t bpbBytesPerSec[2];       /* bytes per sector */
           int8_t bpbSecPerClust;          /* sectors per cluster */
           int8_t bpbResSectors[2];        /* number of reserved sectors */
           int8_t bpbFATs;                 /* number of FATs */
           int8_t bpbRootDirEnts[2];       /* number of root directory entries */
           int8_t bpbSectors[2];           /* total number of sectors */
           int8_t bpbMedia;                /* media descriptor */
           int8_t bpbFATsecs[2];           /* number of sectors per FAT */
           int8_t bpbSecPerTrack[2];       /* sectors per track */
           int8_t bpbHeads[2];             /* number of heads */
           int8_t bpbHiddenSecs[4];        /* number of hidden sectors */
           int8_t bpbHugeSectors[4];       /* # of sectors if bpbSectors == 0 */
   };
   
   /*
    * BPB for DOS 7.10 (FAT32).  This one has a few extensions to bpb50.
    */
   struct byte_bpb710 {
           u_int8_t bpbBytesPerSec[2];     /* bytes per sector */
           u_int8_t bpbSecPerClust;        /* sectors per cluster */
           u_int8_t bpbResSectors[2];      /* number of reserved sectors */
           u_int8_t bpbFATs;               /* number of FATs */
           u_int8_t bpbRootDirEnts[2];     /* number of root directory entries */
           u_int8_t bpbSectors[2];         /* total number of sectors */
           u_int8_t bpbMedia;              /* media descriptor */
           u_int8_t bpbFATsecs[2];         /* number of sectors per FAT */
           u_int8_t bpbSecPerTrack[2];     /* sectors per track */
           u_int8_t bpbHeads[2];           /* number of heads */
           u_int8_t bpbHiddenSecs[4];      /* # of hidden sectors */
           u_int8_t bpbHugeSectors[4];     /* # of sectors if bpbSectors == 0 */
           u_int8_t bpbBigFATsecs[4];      /* like bpbFATsecs for FAT32 */
           u_int8_t bpbExtFlags[2];        /* extended flags: */
           u_int8_t bpbFSVers[2];          /* filesystem version */
           u_int8_t bpbRootClust[4];       /* start cluster for root directory */
           u_int8_t bpbFSInfo[2];          /* filesystem info structure sector */
           u_int8_t bpbBackup[2];          /* backup boot sector */
           /* There is a 12 byte filler here, but we ignore it */
   };
   
   /*
    * FAT32 FSInfo block.
    */
   struct fsinfo {
           u_int8_t fsisig1[4];
           u_int8_t fsifill1[480];
           u_int8_t fsisig2[4];
           u_int8_t fsinfree[4];
           u_int8_t fsinxtfree[4];
           u_int8_t fsifill2[12];
           u_int8_t fsisig3[4];
           u_int8_t fsifill3[508];
           u_int8_t fsisig4[4];
   };

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