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ufs.h

/*
 * Copyright (c) 1982, 1986 Regents of the University of California.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms are permitted
 * provided that the above copyright notice and this paragraph are
 * duplicated in all such forms and that any documentation,
 * advertising materials, and other materials related to such
 * distribution and use acknowledge that the software was developed
 * by the University of California, Berkeley.  The name of the
 * University may not be used to endorse or promote products derived
 * from this software without specific prior written permission.
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 */
/* 
 * Mach Operating System
 * Copyright (c) 1993 Carnegie Mellon University
 * All Rights Reserved.
 * 
 * Permission to use, copy, modify and distribute this software and its
 * documentation is hereby granted, provided that both the copyright
 * notice and this permission notice appear in all copies of the
 * software, derivative works or modified versions, and any portions
 * thereof, and that both notices appear in supporting documentation.
 * 
 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
 * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
 * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
 * 
 * Carnegie Mellon requests users of this software to return to
 * 
 *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
 *  School of Computer Science
 *  Carnegie Mellon University
 *  Pittsburgh PA 15213-3890
 * 
 * any improvements or extensions that they make and grant Carnegie Mellon
 * the rights to redistribute these changes.
 */
/*
 * HISTORY
 * $Log: ufs.h,v $
 * Revision 1.1.1.1  2001/10/08 23:03:52  wgwoods
 * initial import of CVS source from alphalinux.org, plus a couple bugfixes
 *
 * Revision 1.1.1.1  2000/05/03 03:58:23  dhd
 * Initial import (from 0.7 release)
 *
 * Revision 2.3  93/03/09  10:49:48  danner
 *    Make damn sure we get sys/types.h from the right place.
 *    [93/03/05            af]
 * 
 * Revision 2.2  93/02/05  08:01:43  danner
 *    Adapted for alpha.
 *    [93/02/04            af]
 * 
 * Revision 2.2  90/08/27  21:45:05  dbg
 *    Created.
 *    [90/07/16            dbg]
 * 
 */

/*
 * Common definitions for Berkeley Fast File System.
 */
#include <linux/types.h>

#define DEV_BSIZE 512

#ifndef NBBY
#define     NBBY  8
#endif

/*
 * The file system is made out of blocks of at most MAXBSIZE units,
 * with smaller units (fragments) only in the last direct block.
 * MAXBSIZE primarily determines the size of buffers in the buffer
 * pool.  It may be made larger without any effect on existing
 * file systems; however, making it smaller may make some file
 * systems unmountable.
 *
 * Note that the disk devices are assumed to have DEV_BSIZE "sectors"
 * and that fragments must be some multiple of this size.
 */
#define     MAXBSIZE    8192
#define     MAXFRAG           8

/*
 * MAXPATHLEN defines the longest permissible path length
 * after expanding symbolic links.
 *
 * MAXSYMLINKS defines the maximum number of symbolic links
 * that may be expanded in a path name.  It should be set
 * high enough to allow all legitimate uses, but halt infinite
 * loops reasonably quickly.
 */

#define     MAXPATHLEN  1024
#define     MAXSYMLINKS 8


/*
 * Error codes for file system errors.
 */

#define     FS_NOT_DIRECTORY  5000        /* not a directory */
#define     FS_NO_ENTRY       5001        /* name not found */
#define     FS_NAME_TOO_LONG  5002        /* name too long */
#define     FS_SYMLINK_LOOP         5003        /* symbolic link loop */
#define     FS_INVALID_FS           5004        /* bad file system */
#define     FS_NOT_IN_FILE          5005        /* offset not in file */
#define     FS_INVALID_PARAMETER    5006        /* bad parameter to
                                       a routine */
/*
 * Each disk drive contains some number of file systems.
 * A file system consists of a number of cylinder groups.
 * Each cylinder group has inodes and data.
 *
 * A file system is described by its super-block, which in turn
 * describes the cylinder groups.  The super-block is critical
 * data and is replicated in each cylinder group to protect against
 * catastrophic loss.  This is done at `newfs' time and the critical
 * super-block data does not change, so the copies need not be
 * referenced further unless disaster strikes.
 *
 * For file system fs, the offsets of the various blocks of interest
 * are given in the super block as:
 *    [fs->fs_sblkno]         Super-block
 *    [fs->fs_cblkno]         Cylinder group block
 *    [fs->fs_iblkno]         Inode blocks
 *    [fs->fs_dblkno]         Data blocks
 * The beginning of cylinder group cg in fs, is given by
 * the ``cgbase(fs, cg)'' macro.
 *
 * The first boot and super blocks are given in absolute disk addresses.
 * The byte-offset forms are preferred, as they don't imply a sector size.
 */
#define BBSIZE          8192
#define SBSIZE          8192
#define     BBOFF       ((off_t)(0))
#define     SBOFF       ((off_t)(BBOFF + BBSIZE))
#define     BBLOCK            ((daddr_t)(0))
#define     SBLOCK            ((daddr_t)(BBLOCK + BBSIZE / DEV_BSIZE))

/*
 * Addresses stored in inodes are capable of addressing fragments
 * of `blocks'. File system blocks of at most size MAXBSIZE can 
 * be optionally broken into 2, 4, or 8 pieces, each of which is
 * addressable; these pieces may be DEV_BSIZE, or some multiple of
 * a DEV_BSIZE unit.
 *
 * Large files consist of exclusively large data blocks.  To avoid
 * undue wasted disk space, the last data block of a small file may be
 * allocated as only as many fragments of a large block as are
 * necessary.  The file system format retains only a single pointer
 * to such a fragment, which is a piece of a single large block that
 * has been divided.  The size of such a fragment is determinable from
 * information in the inode, using the ``blksize(fs, ip, lbn)'' macro.
 *
 * The file system records space availability at the fragment level;
 * to determine block availability, aligned fragments are examined.
 *
 * The root inode is the root of the file system.
 * Inode 0 can't be used for normal purposes and
 * historically bad blocks were linked to inode 1,
 * thus the root inode is 2. (inode 1 is no longer used for
 * this purpose, however numerous dump tapes make this
 * assumption, so we are stuck with it)
 */
#define     ROOTINO           ((ino_t)2)  /* i number of all roots */

/*
 * MINBSIZE is the smallest allowable block size.
 * In order to insure that it is possible to create files of size
 * 2^32 with only two levels of indirection, MINBSIZE is set to 4096.
 * MINBSIZE must be big enough to hold a cylinder group block,
 * thus changes to (struct cg) must keep its size within MINBSIZE.
 * Note that super blocks are always of size SBSIZE,
 * and that both SBSIZE and MAXBSIZE must be >= MINBSIZE.
 */
#define MINBSIZE  4096

/*
 * The path name on which the file system is mounted is maintained
 * in fs_fsmnt. MAXMNTLEN defines the amount of space allocated in 
 * the super block for this name.
 * The limit on the amount of summary information per file system
 * is defined by MAXCSBUFS. It is currently parameterized for a
 * maximum of two million cylinders.
 */
#define MAXMNTLEN 512
#define MAXCSBUFS 32

/*
 * Per cylinder group information; summarized in blocks allocated
 * from first cylinder group data blocks.  These blocks have to be
 * read in from fs_csaddr (size fs_cssize) in addition to the
 * super block.
 *
 * N.B. sizeof(struct csum) must be a power of two in order for
 * the ``fs_cs'' macro to work (see below).
 */
struct csum {
      int   cs_ndir;    /* number of directories */
      int   cs_nbfree;  /* number of free blocks */
      int   cs_nifree;  /* number of free inodes */
      int   cs_nffree;  /* number of free frags */
};

typedef int ext_time_t;
typedef struct {
      unsigned int val[2];
} quad;

/*
 * Super block for a file system.
 */
#define     FS_MAGIC    0x011954
struct fs
{
      int   xxx1;             /* struct   fs *fs_link;*/
      int   xxx2;             /* struct   fs *fs_rlink;*/
      daddr_t     fs_sblkno;        /* addr of super-block in filesys */
      daddr_t     fs_cblkno;        /* offset of cyl-block in filesys */
      daddr_t     fs_iblkno;        /* offset of inode-blocks in filesys */
      daddr_t     fs_dblkno;        /* offset of first data after cg */
      int   fs_cgoffset;            /* cylinder group offset in cylinder */
      int   fs_cgmask;        /* used to calc mod fs_ntrak */
      ext_time_t fs_time;           /* last time written */
      int   fs_size;          /* number of blocks in fs */
      int   fs_dsize;         /* number of data blocks in fs */
      int   fs_ncg;                 /* number of cylinder groups */
      int   fs_bsize;         /* size of basic blocks in fs */
      int   fs_fsize;         /* size of frag blocks in fs */
      int   fs_frag;          /* number of frags in a block in fs */
/* these are configuration parameters */
      int   fs_minfree;       /* minimum percentage of free blocks */
      int   fs_rotdelay;            /* num of ms for optimal next block */
      int   fs_rps;                 /* disk revolutions per second */
/* these fields can be computed from the others */
      int   fs_bmask;         /* ``blkoff'' calc of blk offsets */
      int   fs_fmask;         /* ``fragoff'' calc of frag offsets */
      int   fs_bshift;        /* ``lblkno'' calc of logical blkno */
      int   fs_fshift;        /* ``numfrags'' calc number of frags */
/* these are configuration parameters */
      int   fs_maxcontig;           /* max number of contiguous blks */
      int   fs_maxbpg;        /* max number of blks per cyl group */
/* these fields can be computed from the others */
      int   fs_fragshift;           /* block to frag shift */
      int   fs_fsbtodb;       /* fsbtodb and dbtofsb shift constant */
      int   fs_sbsize;        /* actual size of super block */
      int   fs_csmask;        /* csum block offset */
      int   fs_csshift;       /* csum block number */
      int   fs_nindir;        /* value of NINDIR */
      int   fs_inopb;         /* value of INOPB */
      int   fs_nspf;          /* value of NSPF */
/* yet another configuration parameter */
      int   fs_optim;         /* optimization preference, see below */
/* these fields are derived from the hardware */
      int   fs_npsect;        /* # sectors/track including spares */
      int   fs_interleave;          /* hardware sector interleave */
      int   fs_trackskew;           /* sector 0 skew, per track */
      int   fs_headswitch;          /* head switch time, usec */
      int   fs_trkseek;       /* track-to-track seek, usec */
/* sizes determined by number of cylinder groups and their sizes */
      daddr_t fs_csaddr;            /* blk addr of cyl grp summary area */
      int   fs_cssize;        /* size of cyl grp summary area */
      int   fs_cgsize;        /* cylinder group size */
/* these fields are derived from the hardware */
      int   fs_ntrak;         /* tracks per cylinder */
      int   fs_nsect;         /* sectors per track */
      int   fs_spc;           /* sectors per cylinder */
/* this comes from the disk driver partitioning */
      int   fs_ncyl;          /* cylinders in file system */
/* these fields can be computed from the others */
      int   fs_cpg;                 /* cylinders per group */
      int   fs_ipg;                 /* inodes per group */
      int   fs_fpg;                 /* blocks per group * fs_frag */
/* this data must be re-computed after crashes */
      struct      csum fs_cstotal;  /* cylinder summary information */
/* these fields are cleared at mount time */
      char        fs_fmod;                /* super block modified flag */
      char        fs_clean;               /* file system is clean flag */
      char        fs_ronly;               /* mounted read-only flag */
      char        fs_flags;               /* currently unused flag */
      char  fs_fsmnt[MAXMNTLEN];    /* name mounted on */
/* these fields retain the current block allocation info */
      int   fs_cgrotor;       /* last cg searched */
#ifdef __alpha__
      int   was_fs_csp[MAXCSBUFS];  /* unused on Alpha */
#else
      struct      csum *fs_csp[MAXCSBUFS];/* list of fs_cs info buffers */
#endif
      int   fs_cpc;                 /* cyl per cycle in postbl */
      short fs_opostbl[16][8];      /* old rotation block list head */
      int   fs_sparecon[56];  /* reserved for future constants */
      quad  fs_qbmask;        /* ~fs_bmask - for use with quad size */
      quad  fs_qfmask;        /* ~fs_fmask - for use with quad size */
      int   fs_postblformat;  /* format of positional layout tables */
      int   fs_nrpos;         /* number of rotaional positions */
      int   fs_postbloff;           /* (short) rotation block list head */
      int   fs_rotbloff;            /* (u_char) blocks for each rotation */
      int   fs_magic;         /* magic number */
      u_char      fs_space[1];            /* list of blocks for each rotation */
/* actually longer */
};
/*
 * Preference for optimization.
 */
#define FS_OPTTIME      0     /* minimize allocation time */
#define FS_OPTSPACE     1     /* minimize disk fragmentation */

/*
 * Rotational layout table format types
 */
#define FS_42POSTBLFMT        -1    /* 4.2BSD rotational table format */
#define FS_DYNAMICPOSTBLFMT   1     /* dynamic rotational table format */
/*
 * Macros for access to superblock array structures
 */
#define fs_postbl(fs, cylno) \
    (((fs)->fs_postblformat == FS_42POSTBLFMT) \
    ? ((fs)->fs_opostbl[cylno]) \
    : ((short *)((char *)(fs) + (fs)->fs_postbloff) + (cylno) * (fs)->fs_nrpos))
#define fs_rotbl(fs) \
    (((fs)->fs_postblformat == FS_42POSTBLFMT) \
    ? ((fs)->fs_space) \
    : ((u_char *)((char *)(fs) + (fs)->fs_rotbloff)))

/*
 * Convert cylinder group to base address of its global summary info.
 *
 * N.B. This macro assumes that sizeof(struct csum) is a power of two.
 */
#define fs_cs(fs, indx) \
      fs_csp[(indx) >> (fs)->fs_csshift][(indx) & ~(fs)->fs_csmask]

/*
 * Cylinder group block for a file system.
 */
#define     CG_MAGIC    0x090255
struct      cg {
      int   xxx1;             /* struct   cg *cg_link;*/
      int   cg_magic;         /* magic number */
      ext_time_t cg_time;           /* time last written */
      int   cg_cgx;                 /* we are the cgx'th cylinder group */
      short cg_ncyl;          /* number of cyl's this cg */
      short cg_niblk;         /* number of inode blocks this cg */
      int   cg_ndblk;         /* number of data blocks this cg */
      struct      csum cg_cs;       /* cylinder summary information */
      int   cg_rotor;         /* position of last used block */
      int   cg_frotor;        /* position of last used frag */
      int   cg_irotor;        /* position of last used inode */
      int   cg_frsum[MAXFRAG];      /* counts of available frags */
      int   cg_btotoff;       /* (long) block totals per cylinder */
      int   cg_boff;          /* (short) free block positions */
      int   cg_iusedoff;            /* (char) used inode map */
      int   cg_freeoff;       /* (u_char) free block map */
      int   cg_nextfreeoff;         /* (u_char) next available space */
      int   cg_sparecon[16];  /* reserved for future use */
      u_char      cg_space[1];            /* space for cylinder group maps */
/* actually longer */
};
/*
 * Macros for access to cylinder group array structures
 */
#define cg_blktot(cgp) \
    (((cgp)->cg_magic != CG_MAGIC) \
    ? (((struct ocg *)(cgp))->cg_btot) \
    : ((int *)((char *)(cgp) + (cgp)->cg_btotoff)))
#define cg_blks(fs, cgp, cylno) \
    (((cgp)->cg_magic != CG_MAGIC) \
    ? (((struct ocg *)(cgp))->cg_b[cylno]) \
    : ((short *)((char *)(cgp) + (cgp)->cg_boff) + (cylno) * (fs)->fs_nrpos))
#define cg_inosused(cgp) \
    (((cgp)->cg_magic != CG_MAGIC) \
    ? (((struct ocg *)(cgp))->cg_iused) \
    : ((char *)((char *)(cgp) + (cgp)->cg_iusedoff)))
#define cg_blksfree(cgp) \
    (((cgp)->cg_magic != CG_MAGIC) \
    ? (((struct ocg *)(cgp))->cg_free) \
    : ((u_char *)((char *)(cgp) + (cgp)->cg_freeoff)))
#define cg_chkmagic(cgp) \
    ((cgp)->cg_magic == CG_MAGIC || ((struct ocg *)(cgp))->cg_magic == CG_MAGIC)

/*
 * The following structure is defined
 * for compatibility with old file systems.
 */
struct      ocg {
      int   xxx1;             /* struct   ocg *cg_link;*/
      int   xxx2;             /* struct   ocg *cg_rlink;*/
      ext_time_t cg_time;           /* time last written */
      int   cg_cgx;                 /* we are the cgx'th cylinder group */
      short cg_ncyl;          /* number of cyl's this cg */
      short cg_niblk;         /* number of inode blocks this cg */
      int   cg_ndblk;         /* number of data blocks this cg */
      struct      csum cg_cs;       /* cylinder summary information */
      int   cg_rotor;         /* position of last used block */
      int   cg_frotor;        /* position of last used frag */
      int   cg_irotor;        /* position of last used inode */
      int   cg_frsum[8];            /* counts of available frags */
      int   cg_btot[32];            /* block totals per cylinder */
      short cg_b[32][8];            /* positions of free blocks */
      char  cg_iused[256];          /* used inode map */
      int   cg_magic;         /* magic number */
      u_char      cg_free[1];       /* free block map */
/* actually longer */
};

/*
 * Turn file system block numbers into disk block addresses.
 * This maps file system blocks to device size blocks.
 */
#define fsbtodb(fs, b)  ((b) << (fs)->fs_fsbtodb)
#define     dbtofsb(fs, b)    ((b) >> (fs)->fs_fsbtodb)

/*
 * Cylinder group macros to locate things in cylinder groups.
 * They calc file system addresses of cylinder group data structures.
 */
#define     cgbase(fs, c)     ((daddr_t)((fs)->fs_fpg * (c)))
#define cgstart(fs, c) \
      (cgbase(fs, c) + (fs)->fs_cgoffset * ((c) & ~((fs)->fs_cgmask)))
#define     cgsblock(fs, c)   (cgstart(fs, c) + (fs)->fs_sblkno)  /* super blk */
#define     cgtod(fs, c)      (cgstart(fs, c) + (fs)->fs_cblkno)  /* cg block */
#define     cgimin(fs, c)     (cgstart(fs, c) + (fs)->fs_iblkno)  /* inode blk */
#define     cgdmin(fs, c)     (cgstart(fs, c) + (fs)->fs_dblkno)  /* 1st data */

/*
 * Macros for handling inode numbers:
 *     inode number to file system block offset.
 *     inode number to cylinder group number.
 *     inode number to file system block address.
 */
#define     itoo(fs, x) ((x) % INOPB(fs))
#define     itog(fs, x) ((x) / (fs)->fs_ipg)
#define     itod(fs, x) \
      ((daddr_t)(cgimin(fs, itog(fs, x)) + \
      (blkstofrags((fs), (((x) % (fs)->fs_ipg) / INOPB(fs))))))

/*
 * Give cylinder group number for a file system block.
 * Give cylinder group block number for a file system block.
 */
#define     dtog(fs, d) ((d) / (fs)->fs_fpg)
#define     dtogd(fs, d)      ((d) % (fs)->fs_fpg)

/*
 * Extract the bits for a block from a map.
 * Compute the cylinder and rotational position of a cyl block addr.
 */
#define blkmap(fs, map, loc) \
    (((map)[(loc) / NBBY] >> ((loc) % NBBY)) & (0xff >> (NBBY - (fs)->fs_frag)))
#define cbtocylno(fs, bno) \
    ((bno) * NSPF(fs) / (fs)->fs_spc)
#define cbtorpos(fs, bno) \
    (((bno) * NSPF(fs) % (fs)->fs_spc / (fs)->fs_nsect * (fs)->fs_trackskew + \
     (bno) * NSPF(fs) % (fs)->fs_spc % (fs)->fs_nsect * (fs)->fs_interleave) % \
     (fs)->fs_nsect * (fs)->fs_nrpos / (fs)->fs_npsect)

/*
 * The following macros optimize certain frequently calculated
 * quantities by using shifts and masks in place of divisions
 * modulos and multiplications.
 */
#define blkoff(fs, loc)       /* calculates (loc % fs->fs_bsize) */ \
      ((loc) & ~(fs)->fs_bmask)
#define fragoff(fs, loc)      /* calculates (loc % fs->fs_fsize) */ \
      ((loc) & ~(fs)->fs_fmask)
#define lblkno(fs, loc)       /* calculates (loc / fs->fs_bsize) */ \
      ((loc) >> (fs)->fs_bshift)
#define numfrags(fs, loc)     /* calculates (loc / fs->fs_fsize) */ \
      ((loc) >> (fs)->fs_fshift)
#define blkroundup(fs, size)  /* calculates roundup(size, fs->fs_bsize) */ \
      (((size) + (fs)->fs_bsize - 1) & (fs)->fs_bmask)
#define fragroundup(fs, size) /* calculates roundup(size, fs->fs_fsize) */ \
      (((size) + (fs)->fs_fsize - 1) & (fs)->fs_fmask)
#define fragstoblks(fs, frags)      /* calculates (frags / fs->fs_frag) */ \
      ((frags) >> (fs)->fs_fragshift)
#define blkstofrags(fs, blks) /* calculates (blks * fs->fs_frag) */ \
      ((blks) << (fs)->fs_fragshift)
#define fragnum(fs, fsb)      /* calculates (fsb % fs->fs_frag) */ \
      ((fsb) & ((fs)->fs_frag - 1))
#define blknum(fs, fsb)       /* calculates rounddown(fsb, fs->fs_frag) */ \
      ((fsb) &~ ((fs)->fs_frag - 1))

/*
 * Determine the number of available frags given a
 * percentage to hold in reserve
 */
#define freespace(fs, percentreserved) \
      (blkstofrags((fs), (fs)->fs_cstotal.cs_nbfree) + \
      (fs)->fs_cstotal.cs_nffree - ((fs)->fs_dsize * (percentreserved) / 100))

/*
 * Determining the size of a file block in the file system.
 */
#define blksize(fs, ip, lbn) \
      (((lbn) >= NDADDR || (ip)->i_size >= ((lbn) + 1) << (fs)->fs_bshift) \
          ? (fs)->fs_bsize \
          : (fragroundup(fs, blkoff(fs, (ip)->i_size))))
#define dblksize(fs, dip, lbn) \
      (((lbn) >= NDADDR || (dip)->di_size >= ((lbn) + 1) << (fs)->fs_bshift) \
          ? (fs)->fs_bsize \
          : (fragroundup(fs, blkoff(fs, (dip)->di_size))))

/*
 * Number of disk sectors per block; assumes DEV_BSIZE byte sector size.
 */
#define     NSPB(fs)    ((fs)->fs_nspf << (fs)->fs_fragshift)
#define     NSPF(fs)    ((fs)->fs_nspf)

/*
 * INOPB is the number of inodes in a secondary storage block.
 */
#define     INOPB(fs)   ((fs)->fs_inopb)
#define     INOPF(fs)   ((fs)->fs_inopb >> (fs)->fs_fragshift)

/*
 * NINDIR is the number of indirects in a file system block.
 */
#define     NINDIR(fs)  ((fs)->fs_nindir)

/*
 * Copyright (c) 1982, 1986, 1989 The Regents of the University of California.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms are permitted
 * provided that the above copyright notice and this paragraph are
 * duplicated in all such forms and that any documentation,
 * advertising materials, and other materials related to such
 * distribution and use acknowledge that the software was developed
 * by the University of California, Berkeley.  The name of the
 * University may not be used to endorse or promote products derived
 * from this software without specific prior written permission.
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 *
 *    @(#)dir.h   7.6 (Berkeley) 5/9/89
 */

/*
 * A directory consists of some number of blocks of DIRBLKSIZ
 * bytes, where DIRBLKSIZ is chosen such that it can be transferred
 * to disk in a single atomic operation (e.g. 512 bytes on most machines).
 *
 * Each DIRBLKSIZ byte block contains some number of directory entry
 * structures, which are of variable length.  Each directory entry has
 * a struct direct at the front of it, containing its inode number,
 * the length of the entry, and the length of the name contained in
 * the entry.  These are followed by the name padded to a 4 byte boundary
 * with null bytes.  All names are guaranteed null terminated.
 * The maximum length of a name in a directory is MAXNAMLEN.
 *
 * The macro DIRSIZ(dp) gives the amount of space required to represent
 * a directory entry.  Free space in a directory is represented by
 * entries which have dp->d_reclen > DIRSIZ(dp).  All DIRBLKSIZ bytes
 * in a directory block are claimed by the directory entries.  This
 * usually results in the last entry in a directory having a large
 * dp->d_reclen.  When entries are deleted from a directory, the
 * space is returned to the previous entry in the same directory
 * block by increasing its dp->d_reclen.  If the first entry of
 * a directory block is free, then its dp->d_ino is set to 0.
 * Entries other than the first in a directory do not normally have
 * dp->d_ino set to 0.
 */
#define DIRBLKSIZ DEV_BSIZE
#define     MAXNAMLEN   255

struct      direct {
      u_int d_ino;                  /* inode number of entry */
      u_short     d_reclen;         /* length of this record */
      u_short     d_namlen;         /* length of string in d_name */
      char  d_name[MAXNAMLEN + 1];  /* name with length <= MAXNAMLEN */
};

/*
 * The DIRSIZ macro gives the minimum record length which will hold
 * the directory entry.  This requires the amount of space in struct direct
 * without the d_name field, plus enough space for the name with a terminating
 * null byte (dp->d_namlen+1), rounded up to a 4 byte boundary.
 */
#undef DIRSIZ
#define DIRSIZ(dp) \
    ((sizeof (struct direct) - (MAXNAMLEN+1)) + (((dp)->d_namlen+1 + 3) &~ 3))

/*
 * The I node is the focus of all file activity in the BSD Fast File System.
 * There is a unique inode allocated for each active file,
 * each current directory, each mounted-on file, text file, and the root.
 * An inode is 'named' by its dev/inumber pair. (iget/iget.c)
 * Data in icommon is read in from permanent inode on volume.
 */

#define     NDADDR      12          /* direct addresses in inode */
#define     NIADDR      3           /* indirect addresses in inode */

#define     MAX_FASTLINK_SIZE ((NDADDR + NIADDR) * sizeof(daddr_t))

struct      icommon {
      u_short     ic_mode;    /*  0: mode and type of file */
      short ic_nlink;   /*  2: number of links to file */
      u_short     ic_uid;           /*  4: owner's user id */
      u_short     ic_gid;           /*  6: owner's group id */
      long  ic_size;    /*  8: number of bytes in file */
      ext_time_t ic_atime;    /* 16: time last accessed */
      int   ic_atspare;
      ext_time_t ic_mtime;    /* 24: time last modified */
      int   ic_mtspare;
      ext_time_t ic_ctime;    /* 32: last time inode changed */
      int   ic_ctspare;
      union {
          struct {
            daddr_t     Mb_db[NDADDR];    /* 40: disk block addresses */
            daddr_t     Mb_ib[NIADDR];    /* 88: indirect blocks */
          } ic_Mb;
          char    ic_Msymlink[MAX_FASTLINK_SIZE];
                              /* 40: symbolic link name */
      } ic_Mun;
#define     ic_db       ic_Mun.ic_Mb.Mb_db
#define     ic_ib       ic_Mun.ic_Mb.Mb_ib
#define     ic_symlink  ic_Mun.ic_Msymlink
      int   ic_flags;   /* 100: status, currently unused */
#define     IC_FASTLINK 0x0001            /* Symbolic link in inode */
      int   ic_blocks;  /* 104: blocks actually held */
      int   ic_gen;           /* 108: generation number */
      int   ic_spare[4];      /* 112: reserved, currently unused */
};

#define     i_mode            i_ic.ic_mode
#define     i_nlink           i_ic.ic_nlink
#define     i_uid       i_ic.ic_uid
#define     i_gid       i_ic.ic_gid
#if   BYTE_MSF
#define     i_size            i_ic.ic_size
#else /* BYTE_LSF */
#define     i_size            i_ic.ic_size
#endif
#define     i_db        i_ic.ic_db
#define     i_ib        i_ic.ic_ib
#define     i_atime           i_ic.ic_atime
#define     i_mtime           i_ic.ic_mtime
#define     i_ctime           i_ic.ic_ctime
#define i_blocks  i_ic.ic_blocks
#define     i_rdev            i_ic.ic_db[0]
#define     i_symlink   i_ic.ic_symlink
#define i_flags         i_ic.ic_flags
#define i_gen           i_ic.ic_gen

/* modes */
#define     IFMT        0170000           /* type of file */
#define     IFCHR       0020000           /* character special */
#define     IFDIR       0040000           /* directory */
#define     IFBLK       0060000           /* block special */
#define     IFREG       0100000           /* regular */
#define     IFLNK       0120000           /* symbolic link */
#define     IFSOCK            0140000           /* socket */

#define     ISUID       04000       /* set user id on execution */
#define     ISGID       02000       /* set group id on execution */
#define     ISVTX       01000       /* save swapped text even after use */
#define     IREAD       0400        /* read, write, execute permissions */
#define     IWRITE            0200
#define     IEXEC       0100

/*
 *    Same structure, but on disk.
 */
struct dinode {
      union {
          struct icommon      di_com;
          char          di_char[128];
      } di_un;
};
#define     di_ic di_un.di_com

struct dev_t {
      int         handle;
      unsigned int      first_block;
      unsigned int      last_block;
};

typedef unsigned int recnum_t;


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