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[chaz/tar] / src / create.c

/* Create a tar archive.
   Copyright (C) 1985, 1992 Free Software Foundation

This file is part of GNU Tar.

GNU Tar is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.

GNU Tar is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with GNU Tar; see the file COPYING.  If not, write to
the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.  */

/*
 * Create a tar archive.
 *
 * Written 25 Aug 1985 by John Gilmore, ihnp4!hoptoad!gnu.
 */

#ifdef _AIX
 #pragma alloca
#endif
#include <sys/types.h>
#include <stdio.h>
#include <errno.h>
#ifndef STDC_HEADERS
extern int      errno;
#endif

#ifdef BSD42
#include <sys/file.h>
#else
#ifndef V7
#include <fcntl.h>
#endif
#endif

#include "tar.h"
#include "port.h"

#ifndef __MSDOS__
#include <pwd.h>
#include <grp.h>
#endif

#if defined(_POSIX_VERSION) || defined(DIRENT)
#include <dirent.h>
#ifdef direct
#undef direct
#endif /* direct */
#define direct dirent
#define DP_NAMELEN(x) strlen((x)->d_name)
#endif /* _POSIX_VERSION or DIRENT */
#if !defined(_POSIX_VERSION) && !defined(DIRENT) && defined(BSD42)
#include <sys/dir.h>
#define DP_NAMELEN(x)   (x)->d_namlen
#endif /* not _POSIX_VERSION and BSD42 */
#ifdef __MSDOS__
#include "msd_dir.h"
#define DP_NAMELEN(x)   (x)->d_namlen
#define direct dirent
#endif
#if defined(USG) && !defined(_POSIX_VERSION) && !defined(DIRENT)
#include <ndir.h>
#define DP_NAMELEN(x) strlen((x)->d_name)
#endif /* USG and not _POSIX_VERSION and not DIRENT */

extern struct stat hstat;               /* Stat struct corresponding */

#ifndef __MSDOS__
extern dev_t ar_dev;
extern ino_t ar_ino;
#endif

/* JF */
extern struct name *gnu_list_name;

/*
 * If there are no symbolic links, there is no lstat().  Use stat().
 */
#ifndef S_ISLNK
#define lstat stat
#endif

extern void print_header();

union record *start_header();
void add_mangle();
void add_symlink_mangle();
void blank_name_list();
int check_exclude();
PTR ck_malloc();
PTR ck_realloc();
void clear_buffer();
void close_archive();
void collect_and_sort_names();
int confirm();
int deal_with_sparse();
void find_new_file_size();
void finish_header();
int finish_sparse_file();
void finduname();
void findgname();
int is_dot_or_dotdot();
void open_archive();
char *name_next();
void name_close();
void to_oct();
void dump_file();
void write_dir_file();
void write_eot();
void write_mangled();
int zero_record();

/* This code moved from tar.h since create.c is the only file that cares
   about 'struct link's.  This means that other files might not have to
   include sys/types.h any more. */

struct link {
        struct link     *next;
        dev_t           dev;
        ino_t           ino;
        short           linkcount;
        char            name[1];
};

struct link     *linklist;      /* Points to first link in list */

static nolinks;                 /* Gets set if we run out of RAM */

/*
 * "Scratch" space to store the information about a sparse file before
 * writing the info into the header or extended header
 */
/* struct sp_array       *sparsearray;*/

/* number of elts storable in the sparsearray */
/*int   sparse_array_size = 10;*/

void
create_archive()
{
        register char   *p;
        char *name_from_list();

        open_archive(0);                /* Open for writing */

        if(f_gnudump) {
                char *buf = ck_malloc(PATH_MAX);
                char *q,*bufp;

                collect_and_sort_names();

                while(p=name_from_list())
                        dump_file(p,-1, 1);
                /* if(!f_dironly) { */
                        blank_name_list();
                        while(p=name_from_list()) {
                                strcpy(buf,p);
                                if(p[strlen(p)-1]!='/')
                                        strcat(buf,"/");
                                bufp=buf+strlen(buf);
                                for(q=gnu_list_name->dir_contents;q && *q;q+=strlen(q)+1) {
                                        if(*q=='Y') {
                                                strcpy(bufp,q+1);
                                                dump_file(buf,-1, 1);
                                        }
                                }
                        }
                /* } */
                free(buf);
        } else {
                p = name_next(1);
                do 
                  dump_file(p, -1, 1);
                while (p = name_next(1));
        }

        write_mangled();
        write_eot();
        close_archive();
        if(f_gnudump)
                write_dir_file();
        name_close();
}

/*
 * Dump a single file.  If it's a directory, recurse.
 * Result is 1 for success, 0 for failure.
 * Sets global "hstat" to stat() output for this file.
 */
void
dump_file (p, curdev, toplevel)
        char    *p;                     /* File name to dump */
        int     curdev;                 /* Device our parent dir was on */
        int     toplevel;               /* Whether we are a toplevel call */
{
        union record    *header;
        char type;
        extern char *save_name;         /* JF for multi-volume support */
        extern long save_totsize;
        extern long save_sizeleft;
        union record    *exhdr;
        char save_linkflag;
        extern time_t new_time;
        int critical_error = 0;
        time_t restore_times[2];
/*      int sparse_ind = 0;*/


        if(f_confirm && !confirm("add",p))
                return;

        /*
         * Use stat if following (rather than dumping) 4.2BSD's
         * symbolic links.  Otherwise, use lstat (which, on non-4.2
         * systems, is #define'd to stat anyway.
         */
#ifdef STX_HIDDEN /* AIX */
        if (0 != f_follow_links ?
            statx (p, &hstat, STATSIZE, STX_HIDDEN):
            statx (p, &hstat, STATSIZE, STX_HIDDEN|STX_LINK))
#else
        if (0 != f_follow_links? stat(p, &hstat): lstat(p, &hstat))
#endif
        {
badperror:
                msg_perror("can't add file %s",p);
badfile:
                if (!f_ignore_failed_read || critical_error)
                  errors++;
                return;
        }
        
        restore_times[0] = hstat.st_atime;
        restore_times[1] = hstat.st_utime;

#ifdef S_ISHIDDEN
        if (S_ISHIDDEN (hstat.st_mode)) {
                char *new = (char *)alloca (strlen (p) + 2);
                if (new) {
                        strcpy (new, p);
                        strcat (new, "@");
                        p = new;
                }
        }
#endif

        /* See if we only want new files, and check if this one is too old to
           put in the archive. */
        if(   f_new_files
           && !f_gnudump
           && new_time>hstat.st_mtime
           && !S_ISDIR(hstat.st_mode)
           && (f_new_files>1 || new_time>hstat.st_ctime)) {
                if(curdev<0) {
                        msg("%s: is unchanged; not dumped",p);
                }
                return;
        }

#ifndef __MSDOS__
        /* See if we are trying to dump the archive */
        if(ar_dev && hstat.st_dev==ar_dev && hstat.st_ino==ar_ino) {
                msg("%s is the archive; not dumped",p);
                return;
        }
#endif
        /*
         * Check for multiple links.
         *
         * We maintain a list of all such files that we've written so
         * far.  Any time we see another, we check the list and
         * avoid dumping the data again if we've done it once already.
         */
        if (hstat.st_nlink > 1
            && (S_ISREG(hstat.st_mode)
#ifdef S_ISCTG
                || S_ISCTG(hstat.st_mode)
#endif
#ifdef S_ISCHR
                || S_ISCHR(hstat.st_mode)
#endif
#ifdef S_ISBLK
                || S_ISBLK(hstat.st_mode)
#endif
#ifdef S_ISFIFO
                || S_ISFIFO(hstat.st_mode)
#endif
                )) {
                register struct link    *lp;

                /* First quick and dirty.  Hashing, etc later FIXME */
                for (lp = linklist; lp; lp = lp->next) {
                        if (lp->ino == hstat.st_ino &&
                            lp->dev == hstat.st_dev) {
                                char *link_name = lp->name;

                                /* We found a link. */
                                hstat.st_size = 0;
                                header = start_header(p, &hstat);
                                if (header == NULL) 
                                  {
                                    critical_error = 1;
                                    goto badfile;
                                  }
                                while(!f_absolute_paths && *link_name == '/') {
                                        static int link_warn = 0;

                                        if (!link_warn) {
                                                msg("Removing leading / from absolute links");
                                                link_warn++;
                                        }
                                        link_name++;
                                }
                                strncpy(header->header.linkname,
                                        link_name,NAMSIZ);
                                if(header->header.linkname[NAMSIZ-1]) {
                                        char *mangled;
                                        extern char *find_mangled();

                                        mangled=find_mangled(link_name);
                                        msg("%s: link name too long: mangled to %s",link_name,mangled);
                                        strncpy(header->header.linkname,mangled,NAMSIZ);
                                }
                                header->header.linkflag = LF_LINK;
                                finish_header(header);
                /* FIXME: Maybe remove from list after all links found? */
                                if (f_remove_files)
                                  {
                                    if (unlink (p) == -1)
                                      msg_perror ("cannot remove %s", p);
                                  }
                                return;         /* We dumped it */
                        }
                }

                /* Not found.  Add it to the list of possible links. */
                lp = (struct link *)malloc((unsigned)(sizeof(struct link)+strlen(p)));
                if (!lp) {
                        if (!nolinks) {
                                msg(
        "no memory for links, they will be dumped as separate files");
                                nolinks++;
                        }
                }
                lp->ino = hstat.st_ino;
                lp->dev = hstat.st_dev;
                strcpy(lp->name, p);
                lp->next = linklist;
                linklist = lp;
        }

        /*
         * This is not a link to a previously dumped file, so dump it.
         */
        if (S_ISREG(hstat.st_mode)
#ifdef S_ISCTG
            || S_ISCTG(hstat.st_mode)
#endif
            )
        {
                int     f;              /* File descriptor */
                long    bufsize, count;
                long    sizeleft;
                register union record   *start;
                int     header_moved;
                char    isextended = 0;
                int     upperbound;
/*              int     end_nulls = 0; */
                
                header_moved = 0;

#ifdef BSD42
                if (f_sparse_files) {
                /*
                 * JK - This is the test for sparseness: whether the
                 * "size" of the file matches the number of blocks
                 * allocated for it.  If there is a smaller number
                 * of blocks that would be necessary to accommodate
                 * a file of this size, we have a sparse file, i.e.,
                 * at least one of those records in the file is just
                 * a useless hole.
                 */
#ifdef hpux     /* Nice of HPUX to gratuitiously change it, huh?  - mib */
                        if (hstat.st_size - (hstat.st_blocks * 1024) > 1024 )
#else
                        if (hstat.st_size - (hstat.st_blocks * RECORDSIZE) > RECORDSIZE)
#endif
                          {
                                int     filesize = hstat.st_size;
                                register int i;
                                
                                header = start_header(p, &hstat);
                                if (header == NULL)
                                  {
                                    critical_error = 1;
                                    goto badfile;
                                  }
                                header->header.linkflag = LF_SPARSE;
                                header_moved++;
                                
                        /*
                         * Call the routine that figures out the
                         * layout of the sparse file in question.
                         * UPPERBOUND is the index of the last
                         * element of the "sparsearray," i.e.,
                         * the number of elements it needed to
                         * describe the file.
                         */
                                 
                                upperbound = deal_with_sparse(p, header);
                                                
                        /* 
                         * See if we'll need an extended header
                         * later
                         */
                                if (upperbound > SPARSE_IN_HDR-1)
                                        header->header.isextended++;
                        /*
                         * We store the "real" file size so
                         * we can show that in case someone wants
                         * to list the archive, i.e., tar tvf <file>.
                         * It might be kind of disconcerting if the
                         * shrunken file size was the one that showed
                         * up.
                         */
                                 to_oct((long) hstat.st_size, 1+12, 
                                                header->header.realsize);
                                        
                        /*
                         * This will be the new "size" of the
                         * file, i.e., the size of the file
                         * minus the records of holes that we're
                         * skipping over. 
                         */
                                 
                                find_new_file_size(&filesize, upperbound);
                                hstat.st_size = filesize;
                                to_oct((long) filesize, 1+12,
                                                header->header.size);
/*                              to_oct((long) end_nulls, 1+12, 
                                                header->header.ending_blanks);*/
                                                
                                for (i = 0; i < SPARSE_IN_HDR; i++) {
                                        if (!sparsearray[i].numbytes)
                                                break;
                                        to_oct(sparsearray[i].offset, 1+12,
                                                header->header.sp[i].offset);
                                        to_oct(sparsearray[i].numbytes, 1+12,
                                                header->header.sp[i].numbytes);
                                }
                                        
                        }
                }
#else
                upperbound=SPARSE_IN_HDR-1;
#endif
                
                sizeleft = hstat.st_size;
                /* Don't bother opening empty, world readable files. */
                if (sizeleft > 0 || 0444 != (0444 & hstat.st_mode)) {
                        f = open(p, O_RDONLY|O_BINARY);
                        if (f < 0) goto badperror;
                } else {
                        f = -1;
                }
                
                /* If the file is sparse, we've already taken care of this */
                if (!header_moved) {
                        header = start_header(p, &hstat);
                        if (header == NULL) {
                                if(f>=0)
                                        (void)close(f);
                                critical_error = 1;
                                goto badfile;
                        }
                }
#ifdef S_ISCTG
                /* Mark contiguous files, if we support them */
                if (f_standard && S_ISCTG(hstat.st_mode)) {
                        header->header.linkflag = LF_CONTIG;
                }
#endif
                isextended = header->header.isextended;
                save_linkflag = header->header.linkflag;
                finish_header(header);
                if (isextended) {
/*                      int      sum = 0;*/
                        register int i;
/*                      register union record *exhdr;*/
/*                      int      arraybound = SPARSE_EXT_HDR;*/
                        /* static */ int index_offset = SPARSE_IN_HDR;
                        
        extend:         exhdr = findrec();
                        
                        if (exhdr == NULL) 
                          {
                            critical_error = 1;
                            goto badfile;
                          }
                        bzero(exhdr->charptr, RECORDSIZE);
                        for (i = 0; i < SPARSE_EXT_HDR; i++) {
                                if (i+index_offset > upperbound)
                                        break;
                                to_oct((long) sparsearray[i+index_offset].numbytes,
                                        1+12,
                                        exhdr->ext_hdr.sp[i].numbytes);
                                to_oct((long) sparsearray[i+index_offset].offset,
                                        1+12,
                                        exhdr->ext_hdr.sp[i].offset);
                        }
                        userec(exhdr);
/*                      sum += i;
                        if (sum < upperbound)
                                goto extend;*/
                        if (index_offset+i < upperbound) {
                                index_offset += i;
                                exhdr->ext_hdr.isextended++;
                                goto extend;
                        }
                                
                }
                if (save_linkflag == LF_SPARSE) {
                        if (finish_sparse_file(f, &sizeleft, hstat.st_size, p))
                                goto padit;
                }
                else
                  while (sizeleft > 0) {
                        
                        if(f_multivol) {   
                                save_name = p;
                                save_sizeleft = sizeleft;
                                save_totsize = hstat.st_size;
                        }
                        start = findrec();

                        bufsize = endofrecs()->charptr - start->charptr;
                                
                        if (sizeleft < bufsize) {
                                /* Last read -- zero out area beyond */
                                bufsize = (int)sizeleft;
                                count = bufsize % RECORDSIZE;
                                if (count) 
                                        bzero(start->charptr + sizeleft,
                                                (int)(RECORDSIZE - count));
                        }
                        count = read(f, start->charptr, bufsize);
                        if (count < 0) {
                                msg_perror("read error at byte %ld, reading\
 %d bytes, in file %s",  hstat.st_size - sizeleft, bufsize,p);
                                goto padit;
                        }
                        sizeleft -= count;

                        /* This is nonportable (the type of userec's arg). */
                        userec(start+(count-1)/RECORDSIZE);

                        if (count == bufsize) continue;
                        msg( "file %s shrunk by %d bytes, padding with zeros.", p, sizeleft);
                        goto padit;             /* Short read */
                }

                if(f_multivol)
                        save_name = 0;

                if (f >= 0)
                        (void)close(f);

                if (f_remove_files)
                  {
                    if (unlink (p) == -1)
                      msg_perror ("cannot remove %s", p);
                  }
                if (f_atime_preserve)
                  utime (p, restore_times);
                return;

                /*
                 * File shrunk or gave error, pad out tape to match
                 * the size we specified in the header.
                 */
        padit:
                while(sizeleft>0) {
                        save_sizeleft=sizeleft;
                        start=findrec();
                        bzero(start->charptr,RECORDSIZE);
                        userec(start);
                        sizeleft-=RECORDSIZE;
                }
                if(f_multivol)
                        save_name=0;
                if(f>=0)
                        (void)close(f);
                if (f_atime_preserve)
                  utime (p, restore_times);
                return;
        }

#ifdef S_ISLNK
        else if(S_ISLNK(hstat.st_mode))
        {
                int size;

                hstat.st_size = 0;              /* Force 0 size on symlink */
                header = start_header(p, &hstat);
                if (header == NULL) 
                  {
                    critical_error = 1;
                    goto badfile;
                  }
                size = readlink(p, header->header.linkname, NAMSIZ);
                if (size < 0) goto badperror;
                if (size == NAMSIZ) {
                        char *buf = ck_malloc(PATH_MAX);

                        readlink(p,buf,PATH_MAX);
                        /* next_mangle(header->header.linkname); */
                        add_symlink_mangle(buf,p,header->header.linkname);
                        msg("symbolic link %s too long: mangling to %s",p, header->header.linkname);
                        /* size=strlen(header->header.linkname); */
                        free(buf);
                } else
                        header->header.linkname[size] = '\0';
                header->header.linkflag = LF_SYMLINK;
                finish_header(header);          /* Nothing more to do to it */
                if (f_remove_files)
                  {
                    if (unlink (p) == -1)
                      msg_perror ("cannot remove %s", p);
                  }
                return;
        }
#endif

        else if (S_ISDIR(hstat.st_mode))
        {
                register DIR *dirp;
                register struct direct *d;
                char *namebuf;
                int buflen;
                register int len;
                int our_device = hstat.st_dev;

                /* Build new prototype name */
                len = strlen(p);
                buflen=len+NAMSIZ;
                namebuf=ck_malloc(buflen+1);
                strncpy(namebuf, p, buflen);
                while (len >= 1 && '/' == namebuf[len-1]) 
                        len--;                  /* Delete trailing slashes */
                namebuf[len++] = '/';           /* Now add exactly one back */
                namebuf[len] = '\0';            /* Make sure null-terminated */

                /*
                 * Output directory header record with permissions
                 * FIXME, do this AFTER files, to avoid R/O dir problems?
                 * If old archive format, don't write record at all.
                 */
                if (!f_oldarch) {
                        hstat.st_size = 0;      /* Force 0 size on dir */
                        /*
                         * If people could really read standard archives,
                         * this should be:              (FIXME)
                        header = start_header(f_standard? p: namebuf, &hstat);
                         * but since they'd interpret LF_DIR records as
                         * regular files, we'd better put the / on the name.
                         */
                        header = start_header(namebuf, &hstat);
                        if (header == NULL)
                          {
                            critical_error = 1;
                            goto badfile;       /* eg name too long */
                          }

                        if (f_gnudump)
                                header->header.linkflag = LF_DUMPDIR;
                        else if (f_standard)
                                header->header.linkflag = LF_DIR;

                        /* If we're gnudumping, we aren't done yet so don't close it. */
                        if(!f_gnudump)
                                finish_header(header);  /* Done with directory header */
                }

                if(f_gnudump) {
                        int sizeleft;
                        int totsize;
                        int bufsize;
                        union record *start;
                        int count;
                        char *buf,*p_buf;

                        buf=gnu_list_name->dir_contents; /* FOO */
                        totsize=0;
                        for(p_buf=buf;p_buf && *p_buf;) {
                                int tmp;

                                tmp=strlen(p_buf)+1;
                                totsize+=tmp;
                                p_buf+=tmp;
                        }
                        totsize++;
                        to_oct((long)totsize,1+12,header->header.size);
                        finish_header(header);
                        p_buf=buf;
                        sizeleft=totsize;
                        while(sizeleft>0) {
                                if(f_multivol) {
                                        save_name=p;
                                        save_sizeleft=sizeleft;
                                        save_totsize=totsize;
                                }
                                start=findrec();
                                bufsize=endofrecs()->charptr - start->charptr;
                                if(sizeleft<bufsize) {
                                        bufsize=sizeleft;
                                        count=bufsize%RECORDSIZE;
                                        if(count)
                                                bzero(start->charptr+sizeleft,RECORDSIZE-count);
                                }
                                bcopy(p_buf,start->charptr,bufsize);
                                sizeleft-=bufsize;
                                p_buf+=bufsize;
                                userec(start+(bufsize-1)/RECORDSIZE);
                        }
                        if(f_multivol)
                                save_name = 0;
                        if (f_atime_preserve)
                          utime (p, restore_times);
                        return;
                }

                /* Now output all the files in the directory */
#if 0
                if (f_dironly)
                        return;         /* Unless the cmdline said not to */
#endif
                /*
                 * See if we are crossing from one file system to another,
                 * and avoid doing so if the user only wants to dump one file system.
                 */
                if (f_local_filesys && !toplevel && curdev != hstat.st_dev) {
                        if(f_verbose)
                                msg("%s: is on a different filesystem; not dumped",p);
                        return;
                }


                errno = 0;
                dirp = opendir(p);
                if (!dirp) {
                        if (errno) {
                                msg_perror ("can't open directory %s",p);
                        } else {
                                msg("error opening directory %s",
                                        p);
                        }
                        return;
                }

                /* Hack to remove "./" from the front of all the file names */
                if (len == 2 && namebuf[0] == '.' && namebuf[1]=='/')
                        len = 0;

                /* Should speed this up by cd-ing into the dir, FIXME */
                while (NULL != (d=readdir(dirp))) {
                        /* Skip . and .. */
                        if(is_dot_or_dotdot(d->d_name))
                                continue;

                        if (DP_NAMELEN(d) + len >= buflen) {
                                buflen=len+DP_NAMELEN(d);
                                namebuf=ck_realloc(namebuf,buflen+1);
                                /* namebuf[len]='\0';
                                msg("file name %s%s too long", 
                                        namebuf, d->d_name);
                                continue; */
                        }
                        strcpy(namebuf+len, d->d_name);
                        if(f_exclude && check_exclude(namebuf))
                                continue;
                        dump_file(namebuf, our_device, 0);
                }

                closedir(dirp);
                free(namebuf);
                if (f_atime_preserve)
                  utime (p, restore_times);
                return;
        }

#ifdef S_ISCHR
        else if (S_ISCHR(hstat.st_mode)) {
                type = LF_CHR;
              }
#endif

#ifdef S_ISBLK
        else if (S_ISBLK(hstat.st_mode)) {
                type = LF_BLK;
              }
#endif

/* Avoid screwy apollo lossage where S_IFIFO == S_IFSOCK */
#if (_ISP__M68K == 0) && (_ISP__A88K == 0) && defined(S_ISFIFO)
        else if (S_ISFIFO(hstat.st_mode)) {
                type = LF_FIFO;
              }
#endif

#ifdef S_ISSOCK
        else if (S_ISSOCK(hstat.st_mode)) {
                type = LF_FIFO;
              }
#endif
        else
                goto unknown;

        if (!f_standard) goto unknown;

        hstat.st_size = 0;              /* Force 0 size */
        header = start_header(p, &hstat);
        if (header == NULL) 
          {
            critical_error = 1;
            goto badfile;       /* eg name too long */
          }

        header->header.linkflag = type;
#if defined(S_IFBLK) || defined(S_IFCHR)
        if (type != LF_FIFO) {
                to_oct((long) major(hstat.st_rdev), 8,
                        header->header.devmajor);
                to_oct((long) minor(hstat.st_rdev), 8,
                        header->header.devminor);
        }
#endif

        finish_header(header);
        if (f_remove_files)
          {
            if (unlink (p) == -1)
              msg_perror ("cannot remove %s", p);
          }
        return;

        unknown:
        msg("%s: Unknown file type; file ignored.", p);
}

int
finish_sparse_file(fd, sizeleft, fullsize, name)
        int     fd;
        long    *sizeleft,
                fullsize;
        char    *name;
{
        union record    *start;
        char            tempbuf[RECORDSIZE];
        int             bufsize,
                        sparse_ind = 0,
                        count;
        long            pos;
        long            nwritten = 0;


        while (*sizeleft > 0) {
                start = findrec();
                bzero(start->charptr, RECORDSIZE);
                bufsize = sparsearray[sparse_ind].numbytes;
                if (!bufsize) {  /* we blew it, maybe */
                        msg("Wrote %ld of %ld bytes to file %s",
                                   fullsize - *sizeleft, fullsize, name);
                        break;
                }
                pos = lseek(fd, sparsearray[sparse_ind++].offset, 0);
                /* 
                 * If the number of bytes to be written here exceeds
                 * the size of the temporary buffer, do it in steps.
                 */
                while (bufsize > RECORDSIZE) {
/*                      if (amt_read) {
                                count = read(fd, start->charptr+amt_read, RECORDSIZE-amt_read);
                                bufsize -= RECORDSIZE - amt_read;
                                amt_read = 0;
                                userec(start);
                                start = findrec();
                                bzero(start->charptr, RECORDSIZE);
                        }*/
                        /* store the data */
                        count = read(fd, start->charptr, RECORDSIZE);
                        if (count < 0)  {
                                msg_perror("read error at byte %ld, reading %d bytes, in file %s", 
                                                fullsize - *sizeleft, bufsize, name);
                                return 1;
                        }                       
                        bufsize -= count;
                        *sizeleft -= count;
                        userec(start);
                        nwritten += RECORDSIZE; /* XXX */
                        start = findrec();
                        bzero(start->charptr, RECORDSIZE);
                }


                clear_buffer(tempbuf);
                count = read(fd, tempbuf, bufsize);
                bcopy(tempbuf, start->charptr, RECORDSIZE);
                if (count < 0)  {
                        msg_perror("read error at byte %ld, reading %d bytes, in file %s", 
                                        fullsize - *sizeleft, bufsize, name);
                        return 1;
                }
/*              if (amt_read >= RECORDSIZE) {
                        amt_read = 0;
                        userec(start+(count-1)/RECORDSIZE);
                        if (count != bufsize) {
                                msg("file %s shrunk by %d bytes, padding with zeros.", name, sizeleft);
                                return 1;
                        }
                        start = findrec();
                } else 
                        amt_read += bufsize;*/
                nwritten += count; /* XXX */
                *sizeleft -= count;
                userec(start);

        }
        free(sparsearray);
/*      printf ("Amount actually written is (I hope) %d.\n", nwritten); */
/*      userec(start+(count-1)/RECORDSIZE);*/
        return 0;

}

void
init_sparsearray()
{
        register int i;

        sp_array_size = 10;
        /* 
         * Make room for our scratch space -- initially is 10 elts long
         */
        sparsearray = (struct sp_array *) malloc(sp_array_size * sizeof(struct sp_array));
        for (i = 0; i < sp_array_size; i++) {
                sparsearray[i].offset = 0;
                sparsearray[i].numbytes = 0;
        }
}



/*
 * Okay, we've got a sparse file on our hands -- now, what we need to do is
 * make a pass through the file and carefully note where any data is, i.e.,
 * we want to find how far into the file each instance of data is, and how
 * many bytes are there.  We store this information in the sparsearray,
 * which will later be translated into header information.  For now, we use
 * the sparsearray as convenient storage.
 *
 * As a side note, this routine is a mess.  If I could have found a cleaner
 * way to do it, I would have.  If anyone wants to find a nicer way to do
 * this, feel free.
 */

/* There is little point in trimming small amounts of null data at the */
 /* head and tail of blocks -- it's ok if we only avoid dumping blocks */
 /* of complete null data */
int
deal_with_sparse(name, header, nulls_at_end)
        char            *name;
        union record    *header;
        int             nulls_at_end;
{
        long    numbytes = 0;
        long    offset = 0;
/*      long    save_offset;*/
        int     fd;
/*      int     current_size = hstat.st_size;*/
        int     sparse_ind = 0,
                cc;
        char    buf[RECORDSIZE];
#if 0
        int     read_last_data = 0; /* did we just read the last record? */
#endif
        int     amidst_data = 0;
        
        header->header.isextended = 0;
        /* 
         * Can't open the file -- this problem will be caught later on,
         * so just return.
         */
        if ((fd = open(name, O_RDONLY)) < 0)
                return 0;
                
        init_sparsearray();
        clear_buffer(buf);

        while ((cc = read(fd, buf, sizeof buf)) != 0) {
                        
                if (sparse_ind > sp_array_size-1) {
                
                /*
                 * realloc the scratch area, since we've run out of room --
                 */
                        sparsearray = (struct sp_array *) 
                                        realloc(sparsearray,
                                                2 * sp_array_size * (sizeof(struct sp_array)));
                        sp_array_size *= 2;
                }
                if (cc == sizeof buf) {
                        if (zero_record(buf)) {
                                if (amidst_data) {
                                        sparsearray[sparse_ind++].numbytes
                                                = numbytes;
                                        amidst_data = 0;
                                }
                        } else {  /* !zero_record(buf) */
                                if (amidst_data)
                                        numbytes += cc;
                                else {
                                        amidst_data = 1;
                                        numbytes = cc;
                                        sparsearray[sparse_ind].offset
                                          = offset;
                                } 
                        }
                } else if (cc < sizeof buf) {
                  /* This has to be the last bit of the file, so this */
                  /* is somewhat shorter than the above. */
                        if (!zero_record(buf)) {
                                if (!amidst_data) {
                                        amidst_data = 1;
                                        numbytes = cc;
                                        sparsearray[sparse_ind].offset
                                          = offset;
                                } else
                                        numbytes += cc;
                        } 
                }
                offset += cc;
                clear_buffer(buf);
        }
        if (amidst_data)
                sparsearray[sparse_ind++].numbytes = numbytes;
        close(fd);

        return sparse_ind - 1;
}

/* 
 * Just zeroes out the buffer so we don't confuse ourselves with leftover
 * data.
 */
void
clear_buffer(buf)
        char    *buf;
{
        register int    i;

        for (i = 0; i < RECORDSIZE; i++)
                buf[i] = '\0';
}

#if 0  /* I'm leaving this as a monument to Joy Kendall, who wrote it -mib */
/* 
 * JK - 
 * This routine takes a character array, and tells where within that array
 * the data can be found.  It skips over any zeros, and sets the first
 * non-zero point in the array to be the "start", and continues until it
 * finds non-data again, which is marked as the "end."  This routine is 
 * mainly for 1) seeing how far into a file we must lseek to data, given
 * that we have a sparse file, and 2) determining the "real size" of the
 * file, i.e., the number of bytes in the sparse file that are data, as
 * opposed to the zeros we are trying to skip.
 */
where_is_data(from, to, buffer)
        int     *from,
                *to;
        char    *buffer;
{
        register int    i = 0;
        register int    save_to = *to;
        int     amidst_data = 0;

        
        while (!buffer[i])
                i++;
        *from = i;

        if (*from < 16) /* don't bother */
                *from = 0;
        /* keep going to make sure there isn't more real
           data in this record */
        while (i < RECORDSIZE) {
                if (!buffer[i]) {
                        if (amidst_data) {
                                save_to = i;
                                amidst_data = 0;
                        }
                        i++;
                }
                else if (buffer[i]) {
                        if (!amidst_data)
                                amidst_data = 1;
                        i++;
                }
        }
        if (i == RECORDSIZE)
                *to = i;
        else
                *to = save_to;
                
}
#endif

/* Note that this routine is only called if zero_record returned true */
#if 0 /* But we actually don't need it at all. */
where_is_data (from, to, buffer)
     int *from, *to;
     char *buffer;
{
  char *fp, *tp;

  for (fp = buffer; ! *fp; fp++)
    ;
  for (tp = buffer + RECORDSIZE - 1; ! *tp; tp--)
    ;
  *from = fp - buffer;
  *to = tp - buffer + 1;
}
#endif



/*
 * Takes a recordful of data and basically cruises through it to see if
 * it's made *entirely* of zeros, returning a 0 the instant it finds
 * something that is a non-zero, i.e., useful data.
 */
int
zero_record(buffer)
        char    *buffer;
{
        register int    i;

        for (i = 0; i < RECORDSIZE; i++)
                if (buffer[i] != '\000')
                        return 0;
        return 1;
}

void
find_new_file_size(filesize, highest_index)
        int     *filesize;
        int     highest_index;
{
        register int    i;

        *filesize = 0;
        for (i = 0; sparsearray[i].numbytes && i <= highest_index; i++)
                *filesize += sparsearray[i].numbytes;
}
        
/*
 * Make a header block for the file  name  whose stat info is  st .
 * Return header pointer for success, NULL if the name is too long.
 */
union record *
start_header(name, st)
        char    *name;
        register struct stat *st;
{
        register union record *header;

        header = (union record *) findrec();
        bzero(header->charptr, sizeof(*header)); /* XXX speed up */

        /*
         * Check the file name and put it in the record.
         */
        if(!f_absolute_paths) {
                static int warned_once = 0;
#ifdef __MSDOS__
                if(name[1]==':') {
                        name+=2;
                        if(!warned_once++)
                                msg("Removing drive spec from names in the archive");
                }
#endif
                while ('/' == *name) {
                        name++;                         /* Force relative path */
                        if (!warned_once++)
                                msg("Removing leading / from absolute path names in the archive.");
                }
        }
        strncpy(header->header.name, name, NAMSIZ);
        if (header->header.name[NAMSIZ-1]) {
/*              char *mangled;*/

                /* next_mangle(header->header.name); */
                add_mangle(name,header->header.name);
                msg("%s: is too long: mangling to %s", name, header->header.name);
        }

        to_oct((long) (st->st_mode & 07777),
                                        8,  header->header.mode);
        to_oct((long) st->st_uid,       8,  header->header.uid);
        to_oct((long) st->st_gid,       8,  header->header.gid);
        to_oct((long) st->st_size,      1+12, header->header.size);
        to_oct((long) st->st_mtime,     1+12, header->header.mtime);
        /* header->header.linkflag is left as null */
        if(f_gnudump) {
                to_oct((long) st->st_atime, 1+12, header->header.atime);
                to_oct((long) st->st_ctime, 1+12, header->header.ctime);
        }

#ifndef NONAMES
        /* Fill in new Unix Standard fields if desired. */
        if (f_standard) {
                header->header.linkflag = LF_NORMAL;    /* New default */
                strcpy(header->header.magic, TMAGIC);   /* Mark as Unix Std */
                finduname(header->header.uname, st->st_uid);
                findgname(header->header.gname, st->st_gid);
        }
#endif
        return header;
}

/* 
 * Finish off a filled-in header block and write it out.
 * We also print the file name and/or full info if verbose is on.
 */
void
finish_header(header)
        register union record *header;
{
        register int    i, sum;
        register char   *p;

        bcopy(CHKBLANKS, header->header.chksum, sizeof(header->header.chksum));

        sum = 0;
        p = header->charptr;
        for (i = sizeof(*header); --i >= 0; ) {
                /*
                 * We can't use unsigned char here because of old compilers,
                 * e.g. V7.
                 */
                sum += 0xFF & *p++;
        }

        /*
         * Fill in the checksum field.  It's formatted differently
         * from the other fields:  it has [6] digits, a null, then a
         * space -- rather than digits, a space, then a null.
         * We use to_oct then write the null in over to_oct's space.
         * The final space is already there, from checksumming, and
         * to_oct doesn't modify it.
         *
         * This is a fast way to do:
         * (void) sprintf(header->header.chksum, "%6o", sum);
         */
        to_oct((long) sum,      8,  header->header.chksum);
        header->header.chksum[6] = '\0';        /* Zap the space */

        userec(header);

        if (f_verbose) {
                extern union record *head;              /* Points to current tape header */
                extern int head_standard;               /* Tape header is in ANSI format */

                /* These globals are parameters to print_header, sigh */
                head = header;
                /* hstat is already set up */
                head_standard = f_standard;
                print_header();
        }

        return;
}


/*
 * Quick and dirty octal conversion.
 * Converts long "value" into a "digs"-digit field at "where",
 * including a trailing space and room for a null.  "digs"==3 means
 * 1 digit, a space, and room for a null.
 *
 * We assume the trailing null is already there and don't fill it in.
 * This fact is used by start_header and finish_header, so don't change it!
 *
 * This should be equivalent to:
 *      (void) sprintf(where, "%*lo ", digs-2, value);
 * except that sprintf fills in the trailing null and we don't.
 */
void
to_oct(value, digs, where)
        register long   value;
        register int    digs;
        register char   *where;
{
        
        --digs;                         /* Trailing null slot is left alone */
        where[--digs] = ' ';            /* Put in the space, though */

        /* Produce the digits -- at least one */
        do {
                where[--digs] = '0' + (char)(value & 7); /* one octal digit */
                value >>= 3;
        } while (digs > 0 && value != 0);

        /* Leading spaces, if necessary */
        while (digs > 0)
                where[--digs] = ' ';

}


/*
 * Write the EOT record(s).
 * We actually zero at least one record, through the end of the block.
 * Old tar writes garbage after two zeroed records -- and PDtar used to.
 */
void
write_eot()
{
        union record *p;
        int bufsize;

        p = findrec();
        if (p)
          {
            bufsize = endofrecs()->charptr - p->charptr;
            bzero(p->charptr, bufsize);
            userec(p);
          }
}