tables.c

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/*-
 * Copyright (c) 1992 Keith Muller.
 * Copyright (c) 1992, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Keith Muller of the University of California, San Diego.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#ifndef lint
#if 0
static char sccsid[] = "@(#)tables.c    8.1 (Berkeley) 5/31/93";
#endif
#endif /* not lint */

#include <sys/types.h>
#include <sys/time.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include "pax.h"
#include "tables.h"
#include "extern.h"

/*
 * Routines for controlling the contents of all the different databases pax
 * keeps. Tables are dynamically created only when they are needed. The
 * goal was speed and the ability to work with HUGE archives. The databases
 * were kept simple, but do have complex rules for when the contents change.
 * As of this writing, the POSIX library functions were more complex than
 * needed for this application (pax databases have very short lifetimes and
 * do not survive after pax is finished). Pax is required to handle very
 * large archives. These database routines carefully combine memory usage and
 * temporary file storage in ways which will not significantly impact runtime
 * performance while allowing the largest possible archives to be handled.
 * Trying to force the fit to the POSIX databases routines was not considered
 * time well spent.
 */

static HRDLNK **ltab = NULL;    /* hard link table for detecting hard links */
static FTM **ftab = NULL;       /* file time table for updating arch */
static NAMT **ntab = NULL;      /* interactive rename storage table */
static DEVT **dtab = NULL;      /* device/inode mapping tables */
static ATDIR **atab = NULL;     /* file tree directory time reset table */
static int dirfd = -1;          /* storage for setting created dir time/mode */
static u_long dircnt;           /* entries in dir time/mode storage */
static int ffd = -1;            /* tmp file for file time table name storage */

static DEVT *chk_dev(dev_t, int);

/*
 * hard link table routines
 *
 * The hard link table tries to detect hard links to files using the device and
 * inode values. We do this when writing an archive, so we can tell the format
 * write routine that this file is a hard link to another file. The format
 * write routine then can store this file in whatever way it wants (as a hard
 * link if the format supports that like tar, or ignore this info like cpio).
 * (Actually a field in the format driver table tells us if the format wants
 * hard link info. if not, we do not waste time looking for them). We also use
 * the same table when reading an archive. In that situation, this table is
 * used by the format read routine to detect hard links from stored dev and
 * inode numbers (like cpio). This will allow pax to create a link when one
 * can be detected by the archive format.
 */

/*
 * lnk_start
 *      Creates the hard link table.
 * Return:
 *      0 if created, -1 if failure
 */

int
lnk_start(void)
{
        if (ltab != NULL)
                return(0);
        if ((ltab = (HRDLNK **)calloc(L_TAB_SZ, sizeof(HRDLNK *))) == NULL) {
                paxwarn(1, "Cannot allocate memory for hard link table");
                return(-1);
        }
        return(0);
}

/*
 * chk_lnk()
 *      Looks up entry in hard link hash table. If found, it copies the name
 *      of the file it is linked to (we already saw that file) into ln_name.
 *      lnkcnt is decremented and if goes to 1 the node is deleted from the
 *      database. (We have seen all the links to this file). If not found,
 *      we add the file to the database if it has the potential for having
 *      hard links to other files we may process (it has a link count > 1)
 * Return:
 *      if found returns 1; if not found returns 0; -1 on error
 */

int
chk_lnk(ARCHD *arcn)
{
        HRDLNK *pt;
        HRDLNK **ppt;
        u_int indx;

        if (ltab == NULL)
                return(-1);
        /*
         * ignore those nodes that cannot have hard links
         */
        if ((arcn->type == PAX_DIR) || (arcn->sb.st_nlink <= 1))
                return(0);

        /*
         * hash inode number and look for this file
         */
        indx = ((unsigned)arcn->sb.st_ino) % L_TAB_SZ;
        if ((pt = ltab[indx]) != NULL) {
                /*
                 * it's hash chain in not empty, walk down looking for it
                 */
                ppt = &(ltab[indx]);
                while (pt != NULL) {
                        if ((pt->ino == arcn->sb.st_ino) &&
                            (pt->dev == arcn->sb.st_dev))
                                break;
                        ppt = &(pt->fow);
                        pt = pt->fow;
                }

                if (pt != NULL) {
                        /*
                         * found a link. set the node type and copy in the
                         * name of the file it is to link to. we need to
                         * handle hardlinks to regular files differently than
                         * other links.
                         */
                        arcn->ln_nlen = l_strncpy(arcn->ln_name, pt->name,
                                sizeof(arcn->ln_name) - 1);
                        arcn->ln_name[arcn->ln_nlen] = '\0';
                        if (arcn->type == PAX_REG)
                                arcn->type = PAX_HRG;
                        else
                                arcn->type = PAX_HLK;

                        /*
                         * if we have found all the links to this file, remove
                         * it from the database
                         */
                        if (--pt->nlink <= 1) {
                                *ppt = pt->fow;
                                (void)free((char *)pt->name);
                                (void)free((char *)pt);
                        }
                        return(1);
                }
        }

        /*
         * we never saw this file before. It has links so we add it to the
         * front of this hash chain
         */
        if ((pt = (HRDLNK *)malloc(sizeof(HRDLNK))) != NULL) {
                if ((pt->name = strdup(arcn->name)) != NULL) {
                        pt->dev = arcn->sb.st_dev;
                        pt->ino = arcn->sb.st_ino;
                        pt->nlink = arcn->sb.st_nlink;
                        pt->fow = ltab[indx];
                        ltab[indx] = pt;
                        return(0);
                }
                (void)free((char *)pt);
        }

        paxwarn(1, "Hard link table out of memory");
        return(-1);
}

/*
 * purg_lnk
 *      remove reference for a file that we may have added to the data base as
 *      a potential source for hard links. We ended up not using the file, so
 *      we do not want to accidently point another file at it later on.
 */

void
purg_lnk(ARCHD *arcn)
{
        HRDLNK *pt;
        HRDLNK **ppt;
        u_int indx;

        if (ltab == NULL)
                return;
        /*
         * do not bother to look if it could not be in the database
         */
        if ((arcn->sb.st_nlink <= 1) || (arcn->type == PAX_DIR) ||
            (arcn->type == PAX_HLK) || (arcn->type == PAX_HRG))
                return;

        /*
         * find the hash chain for this inode value, if empty return
         */
        indx = ((unsigned)arcn->sb.st_ino) % L_TAB_SZ;
        if ((pt = ltab[indx]) == NULL)
                return;

        /*
         * walk down the list looking for the inode/dev pair, unlink and
         * free if found
         */
        ppt = &(ltab[indx]);
        while (pt != NULL) {
                if ((pt->ino == arcn->sb.st_ino) &&
                    (pt->dev == arcn->sb.st_dev))
                        break;
                ppt = &(pt->fow);
                pt = pt->fow;
        }
        if (pt == NULL)
                return;

        /*
         * remove and free it
         */
        *ppt = pt->fow;
        (void)free((char *)pt->name);
        (void)free((char *)pt);
}

/*
 * lnk_end()
 *      Pull apart an existing link table so we can reuse it. We do this between
 *      read and write phases of append with update. (The format may have
 *      used the link table, and we need to start with a fresh table for the
 *      write phase).
 */

void
lnk_end(void)
{
        int i;
        HRDLNK *pt;
        HRDLNK *ppt;

        if (ltab == NULL)
                return;

        for (i = 0; i < L_TAB_SZ; ++i) {
                if (ltab[i] == NULL)
                        continue;
                pt = ltab[i];
                ltab[i] = NULL;

                /*
                 * free up each entry on this chain
                 */
                while (pt != NULL) {
                        ppt = pt;
                        pt = ppt->fow;
                        (void)free((char *)ppt->name);
                        (void)free((char *)ppt);
                }
        }
        return;
}

/*
 * modification time table routines
 *
 * The modification time table keeps track of last modification times for all
 * files stored in an archive during a write phase when -u is set. We only
 * add a file to the archive if it is newer than a file with the same name
 * already stored on the archive (if there is no other file with the same
 * name on the archive it is added). This applies to writes and appends.
 * An append with an -u must read the archive and store the modification time
 * for every file on that archive before starting the write phase. It is clear
 * that this is one HUGE database. To save memory space, the actual file names
 * are stored in a scatch file and indexed by an in memory hash table. The
 * hash table is indexed by hashing the file path. The nodes in the table store
 * the length of the filename and the lseek offset within the scratch file
 * where the actual name is stored. Since there are never any deletions to this
 * table, fragmentation of the scratch file is never an issue. Lookups seem to
 * not exhibit any locality at all (files in the database are rarely
 * looked up more than once...). So caching is just a waste of memory. The
 * only limitation is the amount of scatch file space available to store the
 * path names.
 */

/*
 * ftime_start()
 *      create the file time hash table and open for read/write the scratch
 *      file. (after created it is unlinked, so when we exit we leave
 *      no witnesses).
 * Return:
 *      0 if the table and file was created ok, -1 otherwise
 */

int
ftime_start(void)
{

        if (ftab != NULL)
                return(0);
        if ((ftab = (FTM **)calloc(F_TAB_SZ, sizeof(FTM *))) == NULL) {
                paxwarn(1, "Cannot allocate memory for file time table");
                return(-1);
        }

        /*
         * get random name and create temporary scratch file, unlink name
         * so it will get removed on exit
         */
        memcpy(tempbase, _TFILE_BASE, sizeof(_TFILE_BASE));
        if ((ffd = mkstemp(tempfile)) < 0) {
                syswarn(1, errno, "Unable to create temporary file: %s",
                    tempfile);
                return(-1);
        }
        (void)unlink(tempfile);

        return(0);
}

/*
 * chk_ftime()
 *      looks up entry in file time hash table. If not found, the file is
 *      added to the hash table and the file named stored in the scratch file.
 *      If a file with the same name is found, the file times are compared and
 *      the most recent file time is retained. If the new file was younger (or
 *      was not in the database) the new file is selected for storage.
 * Return:
 *      0 if file should be added to the archive, 1 if it should be skipped,
 *      -1 on error
 */

int
chk_ftime(ARCHD *arcn)
{
        FTM *pt;
        int namelen;
        u_int indx;
        char ckname[PAXPATHLEN+1];

        /*
         * no info, go ahead and add to archive
         */
        if (ftab == NULL)
                return(0);

        /*
         * hash the pathname and look up in table
         */
        namelen = arcn->nlen;
        indx = st_hash(arcn->name, namelen, F_TAB_SZ);
        if ((pt = ftab[indx]) != NULL) {
                /*
                 * the hash chain is not empty, walk down looking for match
                 * only read up the path names if the lengths match, speeds
                 * up the search a lot
                 */
                while (pt != NULL) {
                        if (pt->namelen == namelen) {
                                /*
                                 * potential match, have to read the name
                                 * from the scratch file.
                                 */
                                if (lseek(ffd,pt->seek,SEEK_SET) != pt->seek) {
                                        syswarn(1, errno,
                                            "Failed ftime table seek");
                                        return(-1);
                                }
                                if (read(ffd, ckname, namelen) != namelen) {
                                        syswarn(1, errno,
                                            "Failed ftime table read");
                                        return(-1);
                                }

                                /*
                                 * if the names match, we are done
                                 */
                                if (!strncmp(ckname, arcn->name, namelen))
                                        break;
                        }

                        /*
                         * try the next entry on the chain
                         */
                        pt = pt->fow;
                }

                if (pt != NULL) {
                        /*
                         * found the file, compare the times, save the newer
                         */
                        if (arcn->sb.st_mtime > pt->mtime) {
                                /*
                                 * file is newer
                                 */
                                pt->mtime = arcn->sb.st_mtime;
                                return(0);
                        }
                        /*
                         * file is older
                         */
                        return(1);
                }
        }

        /*
         * not in table, add it
         */
        if ((pt = (FTM *)malloc(sizeof(FTM))) != NULL) {
                /*
                 * add the name at the end of the scratch file, saving the
                 * offset. add the file to the head of the hash chain
                 */
                if ((pt->seek = lseek(ffd, (off_t)0, SEEK_END)) >= 0) {
                        if (write(ffd, arcn->name, namelen) == namelen) {
                                pt->mtime = arcn->sb.st_mtime;
                                pt->namelen = namelen;
                                pt->fow = ftab[indx];
                                ftab[indx] = pt;
                                return(0);
                        }
                        syswarn(1, errno, "Failed write to file time table");
                } else
                        syswarn(1, errno, "Failed seek on file time table");
        } else
                paxwarn(1, "File time table ran out of memory");

        if (pt != NULL)
                (void)free((char *)pt);
        return(-1);
}

/*
 * Interactive rename table routines
 *
 * The interactive rename table keeps track of the new names that the user
 * assigns to files from tty input. Since this map is unique for each file
 * we must store it in case there is a reference to the file later in archive
 * (a link). Otherwise we will be unable to find the file we know was
 * extracted. The remapping of these files is stored in a memory based hash
 * table (it is assumed since input must come from /dev/tty, it is unlikely to
 * be a very large table).
 */

/*
 * name_start()
 *      create the interactive rename table
 * Return:
 *      0 if successful, -1 otherwise
 */

int
name_start(void)
{
        if (ntab != NULL)
                return(0);
        if ((ntab = (NAMT **)calloc(N_TAB_SZ, sizeof(NAMT *))) == NULL) {
                paxwarn(1, "Cannot allocate memory for interactive rename table");
                return(-1);
        }
        return(0);
}

/*
 * add_name()
 *      add the new name to old name mapping just created by the user.
 *      If an old name mapping is found (there may be duplicate names on an
 *      archive) only the most recent is kept.
 * Return:
 *      0 if added, -1 otherwise
 */

int
add_name(char *oname, int onamelen, char *nname)
{
        NAMT *pt;
        u_int indx;

        if (ntab == NULL) {
                /*
                 * should never happen
                 */
                paxwarn(0, "No interactive rename table, links may fail\n");
                return(0);
        }

        /*
         * look to see if we have already mapped this file, if so we
         * will update it
         */
        indx = st_hash(oname, onamelen, N_TAB_SZ);
        if ((pt = ntab[indx]) != NULL) {
                /*
                 * look down the has chain for the file
                 */
                while ((pt != NULL) && (strcmp(oname, pt->oname) != 0))
                        pt = pt->fow;

                if (pt != NULL) {
                        /*
                         * found an old mapping, replace it with the new one
                         * the user just input (if it is different)
                         */
                        if (strcmp(nname, pt->nname) == 0)
                                return(0);

                        (void)free((char *)pt->nname);
                        if ((pt->nname = strdup(nname)) == NULL) {
                                paxwarn(1, "Cannot update rename table");
                                return(-1);
                        }
                        return(0);
                }
        }

        /*
         * this is a new mapping, add it to the table
         */
        if ((pt = (NAMT *)malloc(sizeof(NAMT))) != NULL) {
                if ((pt->oname = strdup(oname)) != NULL) {
                        if ((pt->nname = strdup(nname)) != NULL) {
                                pt->fow = ntab[indx];
                                ntab[indx] = pt;
                                return(0);
                        }
                        (void)free((char *)pt->oname);
                }
                (void)free((char *)pt);
        }
        paxwarn(1, "Interactive rename table out of memory");
        return(-1);
}

/*
 * sub_name()
 *      look up a link name to see if it points at a file that has been
 *      remapped by the user. If found, the link is adjusted to contain the
 *      new name (oname is the link to name)
 */

void
sub_name(char *oname, int *onamelen, size_t onamesize)
{
        NAMT *pt;
        u_int indx;

        if (ntab == NULL)
                return;
        /*
         * look the name up in the hash table
         */
        indx = st_hash(oname, *onamelen, N_TAB_SZ);
        if ((pt = ntab[indx]) == NULL)
                return;

        while (pt != NULL) {
                /*
                 * walk down the hash chain looking for a match
                 */
                if (strcmp(oname, pt->oname) == 0) {
                        /*
                         * found it, replace it with the new name
                         * and return (we know that oname has enough space)
                         */
                        *onamelen = l_strncpy(oname, pt->nname, onamesize - 1);
                        oname[*onamelen] = '\0';
                        return;
                }
                pt = pt->fow;
        }

        /*
         * no match, just return
         */
        return;
}

/*
 * device/inode mapping table routines
 * (used with formats that store device and inodes fields)
 *
 * device/inode mapping tables remap the device field in an archive header. The
 * device/inode fields are used to determine when files are hard links to each
 * other. However these values have very little meaning outside of that. This
 * database is used to solve one of two different problems.
 *
 * 1) when files are appended to an archive, while the new files may have hard
 * links to each other, you cannot determine if they have hard links to any
 * file already stored on the archive from a prior run of pax. We must assume
 * that these inode/device pairs are unique only within a SINGLE run of pax
 * (which adds a set of files to an archive). So we have to make sure the
 * inode/dev pairs we add each time are always unique. We do this by observing
 * while the inode field is very dense, the use of the dev field is fairly
 * sparse. Within each run of pax, we remap any device number of a new archive
 * member that has a device number used in a prior run and already stored in a
 * file on the archive. During the read phase of the append, we store the
 * device numbers used and mark them to not be used by any file during the
 * write phase. If during write we go to use one of those old device numbers,
 * we remap it to a new value.
 *
 * 2) Often the fields in the archive header used to store these values are
 * too small to store the entire value. The result is an inode or device value
 * which can be truncated. This really can foul up an archive. With truncation
 * we end up creating links between files that are really not links (after
 * truncation the inodes are the same value). We address that by detecting
 * truncation and forcing a remap of the device field to split truncated
 * inodes away from each other. Each truncation creates a pattern of bits that
 * are removed. We use this pattern of truncated bits to partition the inodes
 * on a single device to many different devices (each one represented by the
 * truncated bit pattern). All inodes on the same device that have the same
 * truncation pattern are mapped to the same new device. Two inodes that
 * truncate to the same value clearly will always have different truncation
 * bit patterns, so they will be split from away each other. When we spot
 * device truncation we remap the device number to a non truncated value.
 * (for more info see table.h for the data structures involved).
 */

/*
 * dev_start()
 *      create the device mapping table
 * Return:
 *      0 if successful, -1 otherwise
 */

int
dev_start(void)
{
        if (dtab != NULL)
                return(0);
        if ((dtab = (DEVT **)calloc(D_TAB_SZ, sizeof(DEVT *))) == NULL) {
                paxwarn(1, "Cannot allocate memory for device mapping table");
                return(-1);
        }
        return(0);
}

/*
 * add_dev()
 *      add a device number to the table. this will force the device to be
 *      remapped to a new value if it be used during a write phase. This
 *      function is called during the read phase of an append to prohibit the
 *      use of any device number already in the archive.
 * Return:
 *      0 if added ok, -1 otherwise
 */

int
add_dev(ARCHD *arcn)
{
        if (chk_dev(arcn->sb.st_dev, 1) == NULL)
                return(-1);
        return(0);
}

/*
 * chk_dev()
 *      check for a device value in the device table. If not found and the add
 *      flag is set, it is added. This does NOT assign any mapping values, just
 *      adds the device number as one that need to be remapped. If this device
 *      is already mapped, just return with a pointer to that entry.
 * Return:
 *      pointer to the entry for this device in the device map table. Null
 *      if the add flag is not set and the device is not in the table (it is
 *      not been seen yet). If add is set and the device cannot be added, null
 *      is returned (indicates an error).
 */

static DEVT *
chk_dev(dev_t dev, int add)
{
        DEVT *pt;
        u_int indx;

        if (dtab == NULL)
                return(NULL);
        /*
         * look to see if this device is already in the table
         */
        indx = ((unsigned)dev) % D_TAB_SZ;
        if ((pt = dtab[indx]) != NULL) {
                while ((pt != NULL) && (pt->dev != dev))
                        pt = pt->fow;

                /*
                 * found it, return a pointer to it
                 */
                if (pt != NULL)
                        return(pt);
        }

        /*
         * not in table, we add it only if told to as this may just be a check
         * to see if a device number is being used.
         */
        if (add == 0)
                return(NULL);

        /*
         * allocate a node for this device and add it to the front of the hash
         * chain. Note we do not assign remaps values here, so the pt->list
         * list must be NULL.
         */
        if ((pt = (DEVT *)malloc(sizeof(DEVT))) == NULL) {
                paxwarn(1, "Device map table out of memory");
                return(NULL);
        }
        pt->dev = dev;
        pt->list = NULL;
        pt->fow = dtab[indx];
        dtab[indx] = pt;
        return(pt);
}
/*
 * map_dev()
 *      given an inode and device storage mask (the mask has a 1 for each bit
 *      the archive format is able to store in a header), we check for inode
 *      and device truncation and remap the device as required. Device mapping
 *      can also occur when during the read phase of append a device number was
 *      seen (and was marked as do not use during the write phase). WE ASSUME
 *      that unsigned longs are the same size or bigger than the fields used
 *      for ino_t and dev_t. If not the types will have to be changed.
 * Return:
 *      0 if all ok, -1 otherwise.
 */

int
map_dev(ARCHD *arcn, u_long dev_mask, u_long ino_mask)
{
        DEVT *pt;
        DLIST *dpt;
        static dev_t lastdev = 0;       /* next device number to try */
        int trc_ino = 0;
        int trc_dev = 0;
        ino_t trunc_bits = 0;
        ino_t nino;

        if (dtab == NULL)
                return(0);
        /*
         * check for device and inode truncation, and extract the truncated
         * bit pattern.
         */
        if ((arcn->sb.st_dev & (dev_t)dev_mask) != arcn->sb.st_dev)
                ++trc_dev;
        if ((nino = arcn->sb.st_ino & (ino_t)ino_mask) != arcn->sb.st_ino) {
                ++trc_ino;
                trunc_bits = arcn->sb.st_ino & (ino_t)(~ino_mask);
        }

        /*
         * see if this device is already being mapped, look up the device
         * then find the truncation bit pattern which applies
         */
        if ((pt = chk_dev(arcn->sb.st_dev, 0)) != NULL) {
                /*
                 * this device is already marked to be remapped
                 */
                for (dpt = pt->list; dpt != NULL; dpt = dpt->fow)
                        if (dpt->trunc_bits == trunc_bits)
                                break;

                if (dpt != NULL) {
                        /*
                         * we are being remapped for this device and pattern
                         * change the device number to be stored and return
                         */
                        arcn->sb.st_dev = dpt->dev;
                        arcn->sb.st_ino = nino;
                        return(0);
                }
        } else {
                /*
                 * this device is not being remapped YET. if we do not have any
                 * form of truncation, we do not need a remap
                 */
                if (!trc_ino && !trc_dev)
                        return(0);

                /*
                 * we have truncation, have to add this as a device to remap
                 */
                if ((pt = chk_dev(arcn->sb.st_dev, 1)) == NULL)
                        goto bad;

                /*
                 * if we just have a truncated inode, we have to make sure that
                 * all future inodes that do not truncate (they have the
                 * truncation pattern of all 0's) continue to map to the same
                 * device number. We probably have already written inodes with
                 * this device number to the archive with the truncation
                 * pattern of all 0's. So we add the mapping for all 0's to the
                 * same device number.
                 */
                if (!trc_dev && (trunc_bits != 0)) {
                        if ((dpt = (DLIST *)malloc(sizeof(DLIST))) == NULL)
                                goto bad;
                        dpt->trunc_bits = 0;
                        dpt->dev = arcn->sb.st_dev;
                        dpt->fow = pt->list;
                        pt->list = dpt;
                }
        }

        /*
         * look for a device number not being used. We must watch for wrap
         * around on lastdev (so we do not get stuck looking forever!)
         */
        while (++lastdev > 0) {
                if (chk_dev(lastdev, 0) != NULL)
                        continue;
                /*
                 * found an unused value. If we have reached truncation point
                 * for this format we are hosed, so we give up. Otherwise we
                 * mark it as being used.
                 */
                if (((lastdev & ((dev_t)dev_mask)) != lastdev) ||
                    (chk_dev(lastdev, 1) == NULL))
                        goto bad;
                break;
        }

        if ((lastdev <= 0) || ((dpt = (DLIST *)malloc(sizeof(DLIST))) == NULL))
                goto bad;

        /*
         * got a new device number, store it under this truncation pattern.
         * change the device number this file is being stored with.
         */
        dpt->trunc_bits = trunc_bits;
        dpt->dev = lastdev;
        dpt->fow = pt->list;
        pt->list = dpt;
        arcn->sb.st_dev = lastdev;
        arcn->sb.st_ino = nino;
        return(0);

    bad:
        paxwarn(1, "Unable to fix truncated inode/device field when storing %s",
            arcn->name);
        paxwarn(0, "Archive may create improper hard links when extracted");
        return(0);
}

/*
 * directory access/mod time reset table routines (for directories READ by pax)
 *
 * The pax -t flag requires that access times of archive files to be the same
 * before being read by pax. For regular files, access time is restored after
 * the file has been copied. This database provides the same functionality for
 * directories read during file tree traversal. Restoring directory access time
 * is more complex than files since directories may be read several times until
 * all the descendants in their subtree are visited by fts. Directory access
 * and modification times are stored during the fts pre-order visit (done
 * before any descendants in the subtree is visited) and restored after the
 * fts post-order visit (after all the descendants have been visited). In the
 * case of premature exit from a subtree (like from the effects of -n), any
 * directory entries left in this database are reset during final cleanup
 * operations of pax. Entries are hashed by inode number for fast lookup.
 */

/*
 * atdir_start()
 *      create the directory access time database for directories READ by pax.
 * Return:
 *      0 is created ok, -1 otherwise.
 */

int
atdir_start(void)
{
        if (atab != NULL)
                return(0);
        if ((atab = (ATDIR **)calloc(A_TAB_SZ, sizeof(ATDIR *))) == NULL) {
                paxwarn(1,"Cannot allocate space for directory access time table");
                return(-1);
        }
        return(0);
}


/*
 * atdir_end()
 *      walk through the directory access time table and reset the access time
 *      of any directory who still has an entry left in the database. These
 *      entries are for directories READ by pax
 */

void
atdir_end(void)
{
        ATDIR *pt;
        int i;

        if (atab == NULL)
                return;
        /*
         * for each non-empty hash table entry reset all the directories
         * chained there.
         */
        for (i = 0; i < A_TAB_SZ; ++i) {
                if ((pt = atab[i]) == NULL)
                        continue;
                /*
                 * remember to force the times, set_ftime() looks at pmtime
                 * and patime, which only applies to things CREATED by pax,
                 * not read by pax. Read time reset is controlled by -t.
                 */
                for (; pt != NULL; pt = pt->fow)
                        set_ftime(pt->name, pt->mtime, pt->atime, 1);
        }
}

/*
 * add_atdir()
 *      add a directory to the directory access time table. Table is hashed
 *      and chained by inode number. This is for directories READ by pax
 */

void
add_atdir(char *fname, dev_t dev, ino_t ino, time_t mtime, time_t atime)
{
        ATDIR *pt;
        u_int indx;

        if (atab == NULL)
                return;

        /*
         * make sure this directory is not already in the table, if so just
         * return (the older entry always has the correct time). The only
         * way this will happen is when the same subtree can be traversed by
         * different args to pax and the -n option is aborting fts out of a
         * subtree before all the post-order visits have been made).
         */
        indx = ((unsigned)ino) % A_TAB_SZ;
        if ((pt = atab[indx]) != NULL) {
                while (pt != NULL) {
                        if ((pt->ino == ino) && (pt->dev == dev))
                                break;
                        pt = pt->fow;
                }

                /*
                 * oops, already there. Leave it alone.
                 */
                if (pt != NULL)
                        return;
        }

        /*
         * add it to the front of the hash chain
         */
        if ((pt = (ATDIR *)malloc(sizeof(ATDIR))) != NULL) {
                if ((pt->name = strdup(fname)) != NULL) {
                        pt->dev = dev;
                        pt->ino = ino;
                        pt->mtime = mtime;
                        pt->atime = atime;
                        pt->fow = atab[indx];
                        atab[indx] = pt;
                        return;
                }
                (void)free((char *)pt);
        }

        paxwarn(1, "Directory access time reset table ran out of memory");
        return;
}

/*
 * get_atdir()
 *      look up a directory by inode and device number to obtain the access
 *      and modification time you want to set to. If found, the modification
 *      and access time parameters are set and the entry is removed from the
 *      table (as it is no longer needed). These are for directories READ by
 *      pax
 * Return:
 *      0 if found, -1 if not found.
 */

int
get_atdir(dev_t dev, ino_t ino, time_t *mtime, time_t *atime)
{
        ATDIR *pt;
        ATDIR **ppt;
        u_int indx;

        if (atab == NULL)
                return(-1);
        /*
         * hash by inode and search the chain for an inode and device match
         */
        indx = ((unsigned)ino) % A_TAB_SZ;
        if ((pt = atab[indx]) == NULL)
                return(-1);

        ppt = &(atab[indx]);
        while (pt != NULL) {
                if ((pt->ino == ino) && (pt->dev == dev))
                        break;
                /*
                 * no match, go to next one
                 */
                ppt = &(pt->fow);
                pt = pt->fow;
        }

        /*
         * return if we did not find it.
         */
        if (pt == NULL)
                return(-1);

        /*
         * found it. return the times and remove the entry from the table.
         */
        *ppt = pt->fow;
        *mtime = pt->mtime;
        *atime = pt->atime;
        (void)free((char *)pt->name);
        (void)free((char *)pt);
        return(0);
}

/*
 * directory access mode and time storage routines (for directories CREATED
 * by pax).
 *
 * Pax requires that extracted directories, by default, have their access/mod
 * times and permissions set to the values specified in the archive. During the
 * actions of extracting (and creating the destination subtree during -rw copy)
 * directories extracted may be modified after being created. Even worse is
 * that these directories may have been created with file permissions which
 * prohibits any descendants of these directories from being extracted. When
 * directories are created by pax, access rights may be added to permit the
 * creation of files in their subtree. Every time pax creates a directory, the
 * times and file permissions specified by the archive are stored. After all
 * files have been extracted (or copied), these directories have their times
 * and file modes reset to the stored values. The directory info is restored in
 * reverse order as entries were added to the data file from root to leaf. To
 * restore atime properly, we must go backwards. The data file consists of
 * records with two parts, the file name followed by a DIRDATA trailer. The
 * fixed sized trailer contains the size of the name plus the off_t location in
 * the file. To restore we work backwards through the file reading the trailer
 * then the file name.
 */

/*
 * dir_start()
 *      set up the directory time and file mode storage for directories CREATED
 *      by pax.
 * Return:
 *      0 if ok, -1 otherwise
 */

int
dir_start(void)
{

        if (dirfd != -1)
                return(0);

        /*
         * unlink the file so it goes away at termination by itself
         */
        memcpy(tempbase, _TFILE_BASE, sizeof(_TFILE_BASE));
        if ((dirfd = mkstemp(tempfile)) >= 0) {
                (void)unlink(tempfile);
                return(0);
        }
        paxwarn(1, "Unable to create temporary file for directory times: %s",
            tempfile);
        return(-1);
}

/*
 * add_dir()
 *      add the mode and times for a newly CREATED directory
 *      name is name of the directory, psb the stat buffer with the data in it,
 *      frc_mode is a flag that says whether to force the setting of the mode
 *      (ignoring the user set values for preserving file mode). Frc_mode is
 *      for the case where we created a file and found that the resulting
 *      directory was not writeable and the user asked for file modes to NOT
 *      be preserved. (we have to preserve what was created by default, so we
 *      have to force the setting at the end. this is stated explicitly in the
 *      pax spec)
 */

void
add_dir(char *name, int nlen, struct stat *psb, int frc_mode)
{
        DIRDATA dblk;

        if (dirfd < 0)
                return;

        /*
         * get current position (where file name will start) so we can store it
         * in the trailer
         */
        if ((dblk.npos = lseek(dirfd, 0L, SEEK_CUR)) < 0) {
                paxwarn(1,"Unable to store mode and times for directory: %s",name);
                return;
        }

        /*
         * write the file name followed by the trailer
         */
        dblk.nlen = nlen + 1;
        dblk.mode = psb->st_mode & 0xffff;
        dblk.mtime = psb->st_mtime;
        dblk.atime = psb->st_atime;
        dblk.frc_mode = frc_mode;
        if ((write(dirfd, name, dblk.nlen) == dblk.nlen) &&
            (write(dirfd, (char *)&dblk, sizeof(dblk)) == sizeof(dblk))) {
                ++dircnt;
                return;
        }

        paxwarn(1,"Unable to store mode and times for created directory: %s",name);
        return;
}

/*
 * proc_dir()
 *      process all file modes and times stored for directories CREATED
 *      by pax
 */

void
proc_dir(void)
{
        char name[PAXPATHLEN+1];
        DIRDATA dblk;
        u_long cnt;

        if (dirfd < 0)
                return;
        /*
         * read backwards through the file and process each directory
         */
        for (cnt = 0; cnt < dircnt; ++cnt) {
                /*
                 * read the trailer, then the file name, if this fails
                 * just give up.
                 */
                if (lseek(dirfd, -((off_t)sizeof(dblk)), SEEK_CUR) < 0)
                        break;
                if (read(dirfd,(char *)&dblk, sizeof(dblk)) != sizeof(dblk))
                        break;
                if (lseek(dirfd, dblk.npos, SEEK_SET) < 0)
                        break;
                if (read(dirfd, name, dblk.nlen) != dblk.nlen)
                        break;
                if (lseek(dirfd, dblk.npos, SEEK_SET) < 0)
                        break;

                /*
                 * frc_mode set, make sure we set the file modes even if
                 * the user didn't ask for it (see file_subs.c for more info)
                 */
                if (pmode || dblk.frc_mode)
                        set_pmode(name, dblk.mode);
                if (patime || pmtime)
                        set_ftime(name, dblk.mtime, dblk.atime, 0);
        }

        (void)close(dirfd);
        dirfd = -1;
        if (cnt != dircnt)
                paxwarn(1,"Unable to set mode and times for created directories");
        return;
}

/*
 * database independent routines
 */

/*
 * st_hash()
 *      hashes filenames to a u_int for hashing into a table. Looks at the tail
 *      end of file, as this provides far better distribution than any other
 *      part of the name. For performance reasons we only care about the last
 *      MAXKEYLEN chars (should be at LEAST large enough to pick off the file
 *      name). Was tested on 500,000 name file tree traversal from the root
 *      and gave almost a perfectly uniform distribution of keys when used with
 *      prime sized tables (MAXKEYLEN was 128 in test). Hashes (sizeof int)
 *      chars at a time and pads with 0 for last addition.
 * Return:
 *      the hash value of the string MOD (%) the table size.
 */

u_int
st_hash(char *name, int len, int tabsz)
{
        char *pt;
        char *dest;
        char *end;
        int i;
        u_int key = 0;
        int steps;
        int res;
        u_int val;

        /*
         * only look at the tail up to MAXKEYLEN, we do not need to waste
         * time here (remember these are pathnames, the tail is what will
         * spread out the keys)
         */
        if (len > MAXKEYLEN) {
                pt = &(name[len - MAXKEYLEN]);
                len = MAXKEYLEN;
        } else
                pt = name;

        /*
         * calculate the number of u_int size steps in the string and if
         * there is a runt to deal with
         */
        steps = len/sizeof(u_int);
        res = len % sizeof(u_int);

        /*
         * add up the value of the string in unsigned integer sized pieces
         * too bad we cannot have unsigned int aligned strings, then we
         * could avoid the expensive copy.
         */
        for (i = 0; i < steps; ++i) {
                end = pt + sizeof(u_int);
                dest = (char *)&val;
                while (pt < end)
                        *dest++ = *pt++;
                key += val;
        }

        /*
         * add in the runt padded with zero to the right
         */
        if (res) {
                val = 0;
                end = pt + res;
                dest = (char *)&val;
                while (pt < end)
                        *dest++ = *pt++;
                key += val;
        }

        /*
         * return the result mod the table size
         */
        return(key % tabsz);
}

---