vfs/tar.c

   1 /* Virtual File System: GNU Tar file system.
   2    Copyright (C) 1995, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005,
   3    2006, 2007 Free Software Foundation, Inc.
   4
   5    Written by: 1995 Jakub Jelinek
   6    Rewritten by: 1998 Pavel Machek
   7
   8    This program is free software; you can redistribute it and/or
   9    modify it under the terms of the GNU Library General Public License
  10    as published by the Free Software Foundation; either version 2 of
  11    the License, or (at your option) any later version.
  12
  13    This program is distributed in the hope that it will be useful,
  14    but WITHOUT ANY WARRANTY; without even the implied warranty of
  15    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16    GNU Library General Public License for more details.
  17
  18    You should have received a copy of the GNU Library General Public
  19    License along with this program; if not, write to the Free Software
  20    Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
  21
  22 /**
  23  * \file
  24  * \brief Source: Virtual File System: GNU Tar file system
  25  * \author Jakub Jelinek
  26  * \author Pavel Machek
  27  * \date 1995, 1998
  28  *
  29  * Namespace: init_tarfs
  30  */
  31
  32 #include <config.h>
  33 #include <sys/types.h>
  34 #include <errno.h>
  35 #include <ctype.h>
  36 #include <fcntl.h>
  37
  38 #ifdef hpux
  39 /* major() and minor() macros (among other things) defined here for hpux */
  40 #include <sys/mknod.h>
  41 #endif
  42
  43 #include "../src/global.h"
  44
  45 #include "../src/wtools.h"      /* message() */
  46 #include "../src/main.h"        /* print_vfs_message */
  47
  48 #include "utilvfs.h"
  49 #include "gc.h"         /* vfs_rmstamp */
  50 #include "xdirentry.h"
  51
  52 static struct vfs_class vfs_tarfs_ops;
  53
  54 enum {
  55     TAR_UNKNOWN = 0,
  56     TAR_V7,
  57     TAR_USTAR,
  58     TAR_POSIX,
  59     TAR_GNU
  60 };
  61
  62 /*
  63  * Header block on tape.
  64  *
  65  * I'm going to use traditional DP naming conventions here.
  66  * A "block" is a big chunk of stuff that we do I/O on.
  67  * A "record" is a piece of info that we care about.
  68  * Typically many "record"s fit into a "block".
  69  */
  70 #define RECORDSIZE      512
  71 #define NAMSIZ          100
  72 #define PREFIX_SIZE     155
  73 #define TUNMLEN         32
  74 #define TGNMLEN         32
  75 #define SPARSE_EXT_HDR  21
  76 #define SPARSE_IN_HDR   4
  77
  78 struct sparse {
  79     char offset[12];
  80     char numbytes[12];
  81 };
  82
  83 struct sp_array {
  84     int offset;
  85     int numbytes;
  86 };
  87
  88 union record {
  89     char charptr[RECORDSIZE];
  90     struct header {
  91         char arch_name[NAMSIZ];
  92         char mode[8];
  93         char uid[8];
  94         char gid[8];
  95         char size[12];
  96         char mtime[12];
  97         char chksum[8];
  98         char linkflag;
  99         char arch_linkname[NAMSIZ];
 100         char magic[8];
 101         char uname[TUNMLEN];
 102         char gname[TGNMLEN];
 103         char devmajor[8];
 104         char devminor[8];
 105         /* The following bytes of the tar header record were originally unused.
 106
 107            Archives following the ustar specification use almost all of those
 108            bytes to support pathnames of 256 characters in length.
 109
 110            GNU tar archives use the "unused" space to support incremental
 111            archives and sparse files. */
 112         union unused {
 113             char prefix[PREFIX_SIZE];
 114             /* GNU extensions to the ustar (POSIX.1-1988) archive format. */
 115             struct oldgnu {
 116                 char atime[12];
 117                 char ctime[12];
 118                 char offset[12];
 119                 char longnames[4];
 120                 char pad;
 121                 struct sparse sp[SPARSE_IN_HDR];
 122                 char isextended;
 123                 char realsize[12];      /* true size of the sparse file */
 124             } oldgnu;
 125         } unused;
 126     } header;
 127     struct extended_header {
 128         struct sparse sp[21];
 129         char isextended;
 130     } ext_hdr;
 131 };
 132
 133 /* The checksum field is filled with this while the checksum is computed. */
 134 #define CHKBLANKS       "        "      /* 8 blanks, no null */
 135
 136 /* The magic field is filled with this if uname and gname are valid. */
 137 #define TMAGIC          "ustar"         /* ustar and a null */
 138 #define OLDGNU_MAGIC    "ustar  "       /* 7 chars and a null */
 139
 140 /* The linkflag defines the type of file */
 141 #define LF_OLDNORMAL    '\0'    /* Normal disk file, Unix compat */
 142 #define LF_NORMAL       '0'     /* Normal disk file */
 143 #define LF_LINK         '1'     /* Link to previously dumped file */
 144 #define LF_SYMLINK      '2'     /* Symbolic link */
 145 #define LF_CHR          '3'     /* Character special file */
 146 #define LF_BLK          '4'     /* Block special file */
 147 #define LF_DIR          '5'     /* Directory */
 148 #define LF_FIFO         '6'     /* FIFO special file */
 149 #define LF_CONTIG       '7'     /* Contiguous file */
 150 #define LF_EXTHDR       'x'     /* pax Extended Header */
 151 #define LF_GLOBAL_EXTHDR 'g'    /* pax Global Extended Header */
 152 /* Further link types may be defined later. */
 153
 154 /* Note that the standards committee allows only capital A through
 155    capital Z for user-defined expansion.  This means that defining something
 156    as, say '8' is a *bad* idea. */
 157 #define LF_DUMPDIR      'D'     /* This is a dir entry that contains
 158                                            the names of files that were in
 159                                            the dir at the time the dump
 160                                            was made */
 161 #define LF_LONGLINK     'K'     /* Identifies the NEXT file on the tape
 162                                            as having a long linkname */
 163 #define LF_LONGNAME     'L'     /* Identifies the NEXT file on the tape
 164                                            as having a long name. */
 165 #define LF_MULTIVOL     'M'     /* This is the continuation
 166                                            of a file that began on another
 167                                            volume */
 168 #define LF_NAMES        'N'     /* For storing filenames that didn't
 169                                            fit in 100 characters */
 170 #define LF_SPARSE       'S'     /* This is for sparse files */
 171 #define LF_VOLHDR       'V'     /* This file is a tape/volume header */
 172 /* Ignore it on extraction */
 173
 174 /*
 175  * Exit codes from the "tar" program
 176  */
 177 #define EX_SUCCESS      0       /* success! */
 178 #define EX_ARGSBAD      1       /* invalid args */
 179 #define EX_BADFILE      2       /* invalid filename */
 180 #define EX_BADARCH      3       /* bad archive */
 181 #define EX_SYSTEM       4       /* system gave unexpected error */
 182 #define EX_BADVOL       5       /* Special error code means
 183                                    Tape volume doesn't match the one
 184                                    specified on the command line */
 185
 186 #define isodigit(c)     ( ((c) >= '0') && ((c) <= '7') )
 187
 188 /*
 189  * Quick and dirty octal conversion.
 190  *
 191  * Result is -1 if the field is invalid (all blank, or nonoctal).
 192  */
 193 static long tar_from_oct (int digs, char *where)
 194 {
 195     register long value;
 196
 197     while (isspace ((unsigned char) *where)) {  /* Skip spaces */
 198         where++;
 199         if (--digs <= 0)
 200             return -1;          /* All blank field */
 201     }
 202     value = 0;
 203     while (digs > 0 && isodigit (*where)) {     /* Scan till nonoctal */
 204         value = (value << 3) | (*where++ - '0');
 205         --digs;
 206     }
 207
 208     if (digs > 0 && *where && !isspace ((unsigned char) *where))
 209         return -1;              /* Ended on non-space/nul */
 210
 211     return value;
 212 }
 213
 214 static void tar_free_archive (struct vfs_class *me, struct vfs_s_super *archive)
 215 {
 216     (void) me;
 217
 218     if (archive->u.arch.fd != -1)
 219         mc_close(archive->u.arch.fd);
 220 }
 221
 222 /* As we open one archive at a time, it is safe to have this static */
 223 static int current_tar_position = 0;
 224
 225 /* Returns fd of the open tar file */
 226 static int
 227 tar_open_archive_int (struct vfs_class *me, const char *name,
 228                       struct vfs_s_super *archive)
 229 {
 230     int result, type;
 231     mode_t mode;
 232     struct vfs_s_inode *root;
 233
 234     result = mc_open (name, O_RDONLY);
 235     if (result == -1) {
 236         message (D_ERROR, MSG_ERROR, _("Cannot open tar archive\n%s"), name);
 237         ERRNOR (ENOENT, -1);
 238     }
 239
 240     archive->name = g_strdup (name);
 241     mc_stat (name, &(archive->u.arch.st));
 242     archive->u.arch.fd = -1;
 243     archive->u.arch.type = TAR_UNKNOWN;
 244
 245     /* Find out the method to handle this tar file */
 246     type = get_compression_type (result, name);
 247     mc_lseek (result, 0, SEEK_SET);
 248     if (type != COMPRESSION_NONE) {
 249         char *s;
 250         mc_close (result);
 251         s = g_strconcat (archive->name, decompress_extension (type), (char *) NULL);
 252         result = mc_open (s, O_RDONLY);
 253         if (result == -1)
 254             message (D_ERROR, MSG_ERROR, _("Cannot open tar archive\n%s"), s);
 255         g_free (s);
 256         if (result == -1)
 257             ERRNOR (ENOENT, -1);
 258     }
 259
 260     archive->u.arch.fd = result;
 261     mode = archive->u.arch.st.st_mode & 07777;
 262     if (mode & 0400)
 263         mode |= 0100;
 264     if (mode & 0040)
 265         mode |= 0010;
 266     if (mode & 0004)
 267         mode |= 0001;
 268     mode |= S_IFDIR;
 269
 270     root = vfs_s_new_inode (me, archive, &archive->u.arch.st);
 271     root->st.st_mode = mode;
 272     root->data_offset = -1;
 273     root->st.st_nlink++;
 274     root->st.st_dev = MEDATA->rdev++;
 275
 276     archive->root = root;
 277
 278     return result;
 279 }
 280
 281 static union record rec_buf;
 282
 283 static union record *
 284 tar_get_next_record (struct vfs_s_super *archive, int tard)
 285 {
 286     int n;
 287
 288     (void) archive;
 289
 290     n = mc_read (tard, rec_buf.charptr, RECORDSIZE);
 291     if (n != RECORDSIZE)
 292         return NULL;            /* An error has occurred */
 293     current_tar_position += RECORDSIZE;
 294     return &rec_buf;
 295 }
 296
 297 static void tar_skip_n_records (struct vfs_s_super *archive, int tard, int n)
 298 {
 299     (void) archive;
 300
 301     mc_lseek (tard, n * RECORDSIZE, SEEK_CUR);
 302     current_tar_position += n * RECORDSIZE;
 303 }
 304
 305 static void
 306 tar_fill_stat (struct vfs_s_super *archive, struct stat *st, union record *header,
 307                size_t h_size)
 308 {
 309     st->st_mode = tar_from_oct (8, header->header.mode);
 310
 311     /* Adjust st->st_mode because there are tar-files with
 312      * linkflag==LF_SYMLINK and S_ISLNK(mod)==0. I don't
 313      * know about the other modes but I think I cause no new
 314      * problem when I adjust them, too. -- Norbert.
 315      */
 316     if (header->header.linkflag == LF_DIR) {
 317         st->st_mode |= S_IFDIR;
 318     } else if (header->header.linkflag == LF_SYMLINK) {
 319         st->st_mode |= S_IFLNK;
 320     } else if (header->header.linkflag == LF_CHR) {
 321         st->st_mode |= S_IFCHR;
 322     } else if (header->header.linkflag == LF_BLK) {
 323         st->st_mode |= S_IFBLK;
 324     } else if (header->header.linkflag == LF_FIFO) {
 325         st->st_mode |= S_IFIFO;
 326     } else
 327         st->st_mode |= S_IFREG;
 328
 329     st->st_rdev = 0;
 330     switch (archive->u.arch.type) {
 331     case TAR_USTAR:
 332     case TAR_POSIX:
 333     case TAR_GNU:
 334         st->st_uid =
 335             *header->header.uname ? vfs_finduid (header->header.
 336                                                  uname) : tar_from_oct (8,
 337                                                                         header->
 338                                                                         header.
 339                                                                         uid);
 340         st->st_gid =
 341             *header->header.gname ? vfs_findgid (header->header.
 342                                                  gname) : tar_from_oct (8,
 343                                                                         header->
 344                                                                         header.
 345                                                                         gid);
 346         switch (header->header.linkflag) {
 347         case LF_BLK:
 348         case LF_CHR:
 349             st->st_rdev =
 350                 (tar_from_oct (8, header->header.devmajor) << 8) |
 351                 tar_from_oct (8, header->header.devminor);
 352         }
 353     default:
 354         st->st_uid = tar_from_oct (8, header->header.uid);
 355         st->st_gid = tar_from_oct (8, header->header.gid);
 356     }
 357     st->st_size = h_size;
 358     st->st_mtime = tar_from_oct (1 + 12, header->header.mtime);
 359     st->st_atime = 0;
 360     st->st_ctime = 0;
 361     if (archive->u.arch.type == TAR_GNU) {
 362         st->st_atime = tar_from_oct (1 + 12,
 363                                      header->header.unused.oldgnu.atime);
 364         st->st_ctime = tar_from_oct (1 + 12,
 365                                      header->header.unused.oldgnu.ctime);
 366     }
 367 }
 368
 369
 370 typedef enum {
 371     STATUS_BADCHECKSUM,
 372     STATUS_SUCCESS,
 373     STATUS_EOFMARK,
 374     STATUS_EOF
 375 } ReadStatus;
 376 /*
 377  * Return 1 for success, 0 if the checksum is bad, EOF on eof,
 378  * 2 for a record full of zeros (EOF marker).
 379  *
 380  */
 381 static ReadStatus
 382 tar_read_header (struct vfs_class *me, struct vfs_s_super *archive,
 383                  int tard, size_t *h_size)
 384 {
 385     register int i;
 386     register long sum, signed_sum, recsum;
 387     register char *p;
 388     register union record *header;
 389     static char *next_long_name = NULL, *next_long_link = NULL;
 390
 391   recurse:
 392
 393     header = tar_get_next_record (archive, tard);
 394     if (NULL == header)
 395         return STATUS_EOF;
 396
 397     recsum = tar_from_oct (8, header->header.chksum);
 398
 399     sum = 0;
 400     signed_sum = 0;
 401     p = header->charptr;
 402     for (i = sizeof (*header); --i >= 0;) {
 403         /*
 404          * We can't use unsigned char here because of old compilers,
 405          * e.g. V7.
 406          */
 407         signed_sum += *p;
 408         sum += 0xFF & *p++;
 409     }
 410
 411     /* Adjust checksum to count the "chksum" field as blanks. */
 412     for (i = sizeof (header->header.chksum); --i >= 0;) {
 413         sum -= 0xFF & header->header.chksum[i];
 414         signed_sum -= (char) header->header.chksum[i];
 415     }
 416     sum += ' ' * sizeof header->header.chksum;
 417     signed_sum += ' ' * sizeof header->header.chksum;
 418
 419     /*
 420      * This is a zeroed record...whole record is 0's except
 421      * for the 8 blanks we faked for the checksum field.
 422      */
 423     if (sum == 8 * ' ')
 424         return STATUS_EOFMARK;
 425
 426     if (sum != recsum && signed_sum != recsum)
 427         return STATUS_BADCHECKSUM;
 428
 429     /*
 430      * Try to determine the archive format.
 431      */
 432     if (archive->u.arch.type == TAR_UNKNOWN) {
 433         if (!strcmp (header->header.magic, TMAGIC)) {
 434             if (header->header.linkflag == LF_GLOBAL_EXTHDR)
 435                 archive->u.arch.type = TAR_POSIX;
 436             else
 437                 archive->u.arch.type = TAR_USTAR;
 438         } else if (!strcmp (header->header.magic, OLDGNU_MAGIC)) {
 439             archive->u.arch.type = TAR_GNU;
 440         }
 441     }
 442
 443     /*
 444      * linkflag on BSDI tar (pax) always '\000'
 445      */
 446     if (header->header.linkflag == '\000') {
 447         if (header->header.arch_name[NAMSIZ - 1] != '\0')
 448             i = NAMSIZ;
 449         else
 450             i = strlen (header->header.arch_name);
 451
 452         if (i && header->header.arch_name[i - 1] == '/')
 453             header->header.linkflag = LF_DIR;
 454     }
 455
 456     /*
 457      * Good record.  Decode file size and return.
 458      */
 459     if (header->header.linkflag == LF_LINK
 460         || header->header.linkflag == LF_DIR)
 461         *h_size = 0;            /* Links 0 size on tape */
 462     else
 463         *h_size = tar_from_oct (1 + 12, header->header.size);
 464
 465     /*
 466      * Skip over directory snapshot info records that
 467      * are stored in incremental tar archives.
 468      */
 469     if (header->header.linkflag == LF_DUMPDIR) {
 470         if (archive->u.arch.type == TAR_UNKNOWN)
 471             archive->u.arch.type = TAR_GNU;
 472         return STATUS_SUCCESS;
 473     }
 474
 475     /*
 476      * Skip over pax extended header and global extended
 477      * header records.
 478      */
 479     if (header->header.linkflag == LF_EXTHDR ||
 480         header->header.linkflag == LF_GLOBAL_EXTHDR) {
 481         if (archive->u.arch.type == TAR_UNKNOWN)
 482             archive->u.arch.type = TAR_POSIX;
 483         return STATUS_SUCCESS;
 484     }
 485
 486     if (header->header.linkflag == LF_LONGNAME
 487         || header->header.linkflag == LF_LONGLINK) {
 488         char **longp;
 489         char *bp, *data;
 490         int size, written;
 491
 492         if (archive->u.arch.type == TAR_UNKNOWN)
 493             archive->u.arch.type = TAR_GNU;
 494
 495         if (*h_size > MC_MAXPATHLEN) {
 496             message (D_ERROR, MSG_ERROR, _("Inconsistent tar archive"));
 497             return STATUS_BADCHECKSUM;
 498         }
 499
 500         longp = ((header->header.linkflag == LF_LONGNAME)
 501                  ? &next_long_name : &next_long_link);
 502
 503         g_free (*longp);
 504         bp = *longp = g_malloc (*h_size + 1);
 505
 506         for (size = *h_size; size > 0; size -= written) {
 507             data = tar_get_next_record (archive, tard)->charptr;
 508             if (data == NULL) {
 509                 g_free (*longp);
 510                 *longp = NULL;
 511                 message (D_ERROR, MSG_ERROR,
 512                          _("Unexpected EOF on archive file"));
 513                 return STATUS_BADCHECKSUM;
 514             }
 515             written = RECORDSIZE;
 516             if (written > size)
 517                 written = size;
 518
 519             memcpy (bp, data, written);
 520             bp += written;
 521         }
 522
 523         if (bp - *longp == MC_MAXPATHLEN && bp[-1] != '\0') {
 524             g_free (*longp);
 525             *longp = NULL;
 526             message (D_ERROR, MSG_ERROR, _("Inconsistent tar archive"));
 527             return STATUS_BADCHECKSUM;
 528         }
 529         *bp = 0;
 530         goto recurse;
 531     } else {
 532         struct stat st;
 533         struct vfs_s_entry *entry;
 534         struct vfs_s_inode *inode = NULL, *parent;
 535         long data_position;
 536         char *q;
 537         int len;
 538         char *current_file_name, *current_link_name;
 539
 540         current_link_name =
 541             (next_long_link ? next_long_link :
 542              g_strndup (header->header.arch_linkname, NAMSIZ));
 543         len = strlen (current_link_name);
 544         if (len > 1 && current_link_name[len - 1] == '/')
 545             current_link_name[len - 1] = 0;
 546
 547         current_file_name = NULL;
 548         switch (archive->u.arch.type) {
 549         case TAR_USTAR:
 550         case TAR_POSIX:
 551             /* The ustar archive format supports pathnames of upto 256
 552              * characters in length. This is achieved by concatenating
 553              * the contents of the `prefix' and `arch_name' fields like
 554              * this:
 555              *
 556              *   prefix + path_separator + arch_name
 557              *
 558              * If the `prefix' field contains an empty string i.e. its
 559              * first characters is '\0' the prefix field is ignored.
 560              */
 561             if (header->header.unused.prefix[0] != '\0') {
 562                 char *temp_name, *temp_prefix;
 563
 564                 temp_name = g_strndup (header->header.arch_name, NAMSIZ);
 565                 temp_prefix  = g_strndup (header->header.unused.prefix,
 566                                           PREFIX_SIZE);
 567                 current_file_name = g_strconcat (temp_prefix, PATH_SEP_STR,
 568                                                  temp_name, (char *) NULL);
 569                 g_free (temp_name);
 570                 g_free (temp_prefix);
 571             }
 572             break;
 573         case TAR_GNU:
 574             if (next_long_name != NULL)
 575                 current_file_name = next_long_name;
 576             break;
 577         default:
 578             break;
 579         }
 580
 581         if (current_file_name == NULL)
 582             current_file_name = g_strndup (header->header.arch_name, NAMSIZ);
 583
 584         canonicalize_pathname (current_file_name);
 585         len = strlen (current_file_name);
 586
 587         data_position = current_tar_position;
 588
 589         p = strrchr (current_file_name, '/');
 590         if (p == NULL) {
 591             p = current_file_name;
 592             q = current_file_name + len;        /* "" */
 593         } else {
 594             *(p++) = 0;
 595             q = current_file_name;
 596         }
 597
 598         parent =
 599             vfs_s_find_inode (me, archive, q, LINK_NO_FOLLOW, FL_MKDIR);
 600         if (parent == NULL) {
 601             message (D_ERROR, MSG_ERROR, _("Inconsistent tar archive"));
 602             return STATUS_BADCHECKSUM;
 603         }
 604
 605         if (header->header.linkflag == LF_LINK) {
 606             inode =
 607                 vfs_s_find_inode (me, archive, current_link_name,
 608                                   LINK_NO_FOLLOW, 0);
 609             if (inode == NULL) {
 610                 message (D_ERROR, MSG_ERROR, _("Inconsistent tar archive"));
 611             } else {
 612                 entry = vfs_s_new_entry (me, p, inode);
 613                 vfs_s_insert_entry (me, parent, entry);
 614                 g_free (current_link_name);
 615                 goto done;
 616             }
 617         }
 618
 619         tar_fill_stat (archive, &st, header, *h_size);
 620         if (S_ISDIR(st.st_mode)) {
 621             entry = MEDATA->find_entry (me, parent, p, LINK_NO_FOLLOW, FL_NONE);
 622             if (entry)
 623                 goto done;
 624         }
 625         inode = vfs_s_new_inode (me, archive, &st);
 626
 627         inode->data_offset = data_position;
 628         if (*current_link_name) {
 629             inode->linkname = current_link_name;
 630         } else if (current_link_name != next_long_link) {
 631             g_free (current_link_name);
 632         }
 633         entry = vfs_s_new_entry (me, p, inode);
 634
 635         vfs_s_insert_entry (me, parent, entry);
 636         g_free (current_file_name);
 637
 638       done:
 639         next_long_link = next_long_name = NULL;
 640
 641         if (archive->u.arch.type == TAR_GNU &&
 642             header->header.unused.oldgnu.isextended) {
 643             while (tar_get_next_record (archive, tard)->ext_hdr.
 644                    isextended);
 645             inode->data_offset = current_tar_position;
 646         }
 647         return STATUS_SUCCESS;
 648     }
 649 }
 650
 651 /*
 652  * Main loop for reading an archive.
 653  * Returns 0 on success, -1 on error.
 654  */
 655 static int
 656 tar_open_archive (struct vfs_class *me, struct vfs_s_super *archive,
 657                   const char *name, char *op)
 658 {
 659     /* Initial status at start of archive */
 660     ReadStatus status = STATUS_EOFMARK;
 661     ReadStatus prev_status;
 662     int tard;
 663
 664     (void) op;
 665
 666     current_tar_position = 0;
 667     /* Open for reading */
 668     if ((tard = tar_open_archive_int (me, name, archive)) == -1)
 669         return -1;
 670
 671     for (;;) {
 672         size_t h_size;
 673
 674         prev_status = status;
 675         status = tar_read_header (me, archive, tard, &h_size);
 676
 677         switch (status) {
 678
 679         case STATUS_SUCCESS:
 680             tar_skip_n_records (archive, tard,
 681                                 (h_size + RECORDSIZE -
 682                                  1) / RECORDSIZE);
 683             continue;
 684
 685             /*
 686              * Invalid header:
 687              *
 688              * If the previous header was good, tell them
 689              * that we are skipping bad ones.
 690              */
 691         case STATUS_BADCHECKSUM:
 692             switch (prev_status) {
 693
 694                 /* Error on first record */
 695             case STATUS_EOFMARK:
 696                 message (D_ERROR, MSG_ERROR,
 697                          _
 698                          ("Hmm,...\n%s\ndoesn't look like a tar archive."),
 699                          name);
 700                 /* FALL THRU */
 701
 702                 /* Error after header rec */
 703             case STATUS_SUCCESS:
 704                 /* Error after error */
 705
 706             case STATUS_BADCHECKSUM:
 707                 return -1;
 708
 709             case STATUS_EOF:
 710                 return 0;
 711             }
 712
 713             /* Record of zeroes */
 714         case STATUS_EOFMARK:
 715             status = prev_status;       /* If error after 0's */
 716             /* FALL THRU */
 717
 718         case STATUS_EOF:        /* End of archive */
 719             break;
 720         }
 721         break;
 722     };
 723     return 0;
 724 }
 725
 726 static void *
 727 tar_super_check (struct vfs_class *me, const char *archive_name, char *op)
 728 {
 729     static struct stat stat_buf;
 730
 731     (void) me;
 732     (void) op;
 733
 734     if (mc_stat (archive_name, &stat_buf))
 735         return NULL;
 736     return &stat_buf;
 737 }
 738
 739 static int
 740 tar_super_same (struct vfs_class *me, struct vfs_s_super *parc,
 741                 const char *archive_name, char *op, void *cookie)
 742 {
 743     struct stat *archive_stat = cookie; /* stat of main archive */
 744
 745     (void) me;
 746     (void) op;
 747
 748     if (strcmp (parc->name, archive_name))
 749         return 0;
 750
 751     /* Has the cached archive been changed on the disk? */
 752     if (parc->u.arch.st.st_mtime < archive_stat->st_mtime) {
 753         /* Yes, reload! */
 754         (*vfs_tarfs_ops.free) ((vfsid) parc);
 755         vfs_rmstamp (&vfs_tarfs_ops, (vfsid) parc);
 756         return 2;
 757     }
 758     /* Hasn't been modified, give it a new timeout */
 759     vfs_stamp (&vfs_tarfs_ops, (vfsid) parc);
 760     return 1;
 761 }
 762
 763 static ssize_t tar_read (void *fh, char *buffer, int count)
 764 {
 765     off_t begin = FH->ino->data_offset;
 766     int fd = FH_SUPER->u.arch.fd;
 767     struct vfs_class *me = FH_SUPER->me;
 768
 769     if (mc_lseek (fd, begin + FH->pos, SEEK_SET) !=
 770         begin + FH->pos) ERRNOR (EIO, -1);
 771
 772     count = MIN(count, FH->ino->st.st_size - FH->pos);
 773
 774     if ((count = mc_read (fd, buffer, count)) == -1) ERRNOR (errno, -1);
 775
 776     FH->pos += count;
 777     return count;
 778 }
 779
 780 static int tar_fh_open (struct vfs_class *me, struct vfs_s_fh *fh, int flags, int mode)
 781 {
 782     (void) fh;
 783     (void) mode;
 784
 785     if ((flags & O_ACCMODE) != O_RDONLY) ERRNOR (EROFS, -1);
 786     return 0;
 787 }
 788
 789 void
 790 init_tarfs (void)
 791 {
 792     static struct vfs_s_subclass tarfs_subclass;
 793
 794     tarfs_subclass.flags = VFS_S_READONLY;
 795     tarfs_subclass.archive_check = tar_super_check;
 796     tarfs_subclass.archive_same = tar_super_same;
 797     tarfs_subclass.open_archive = tar_open_archive;
 798     tarfs_subclass.free_archive = tar_free_archive;
 799     tarfs_subclass.fh_open = tar_fh_open;
 800
 801     vfs_s_init_class (&vfs_tarfs_ops, &tarfs_subclass);
 802     vfs_tarfs_ops.name = "tarfs";
 803     vfs_tarfs_ops.prefix = "utar";
 804     vfs_tarfs_ops.read = tar_read;
 805     vfs_tarfs_ops.setctl = NULL;
 806     vfs_register_class (&vfs_tarfs_ops);
 807 }