Dogcows Code - chaz/tar/blob - src/misc.c

   1 /* Miscellaneous functions, not really specific to GNU tar.
   2
   3    Copyright (C) 1988, 1992, 1994, 1995, 1996, 1997, 1999, 2000, 2001,
   4    2003, 2004, 2005, 2006, 2007, 2009, 2010 Free Software Foundation, Inc.
   5
   6    This program is free software; you can redistribute it and/or modify it
   7    under the terms of the GNU General Public License as published by the
   8    Free Software Foundation; either version 3, or (at your option) any later
   9    version.
  10
  11    This program is distributed in the hope that it will be useful, but
  12    WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General
  14    Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License along
  17    with this program; if not, write to the Free Software Foundation, Inc.,
  18    51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
  19
  20 #include <system.h>
  21 #include <rmt.h>
  22 #include "common.h"
  23 #include <quotearg.h>
  24 #include <xgetcwd.h>
  25 #include <unlinkdir.h>
  26 #include <utimens.h>
  27
  28 #ifndef DOUBLE_SLASH_IS_DISTINCT_ROOT
  29 # define DOUBLE_SLASH_IS_DISTINCT_ROOT 0
  30 #endif
  31
  32 \f
  33 /* Handling strings.  */
  34
  35 /* Assign STRING to a copy of VALUE if not zero, or to zero.  If
  36    STRING was nonzero, it is freed first.  */
  37 void
  38 assign_string (char **string, const char *value)
  39 {
  40   if (*string)
  41     free (*string);
  42   *string = value ? xstrdup (value) : 0;
  43 }
  44
  45 #if 0
  46 /* This function is currently unused; perhaps it should be removed?  */
  47
  48 /* Allocate a copy of the string quoted as in C, and returns that.  If
  49    the string does not have to be quoted, it returns a null pointer.
  50    The allocated copy should normally be freed with free() after the
  51    caller is done with it.
  52
  53    This is used in one context only: generating the directory file in
  54    incremental dumps.  The quoted string is not intended for human
  55    consumption; it is intended only for unquote_string.  The quoting
  56    is locale-independent, so that users needn't worry about locale
  57    when reading directory files.  This means that we can't use
  58    quotearg, as quotearg is locale-dependent and is meant for human
  59    consumption.  */
  60 static char *
  61 quote_copy_string (const char *string)
  62 {
  63   const char *source = string;
  64   char *destination = 0;
  65   char *buffer = 0;
  66   int copying = 0;
  67
  68   while (*source)
  69     {
  70       int character = *source++;
  71
  72       switch (character)
  73         {
  74         case '\n': case '\\':
  75           if (!copying)
  76             {
  77               size_t length = (source - string) - 1;
  78
  79               copying = 1;
  80               buffer = xmalloc (length + 2 + 2 * strlen (source) + 1);
  81               memcpy (buffer, string, length);
  82               destination = buffer + length;
  83             }
  84           *destination++ = '\\';
  85           *destination++ = character == '\\' ? '\\' : 'n';
  86           break;
  87
  88         default:
  89           if (copying)
  90             *destination++ = character;
  91           break;
  92         }
  93     }
  94   if (copying)
  95     {
  96       *destination = '\0';
  97       return buffer;
  98     }
  99   return 0;
 100 }
 101 #endif
 102
 103 /* Takes a quoted C string (like those produced by quote_copy_string)
 104    and turns it back into the un-quoted original.  This is done in
 105    place.  Returns 0 only if the string was not properly quoted, but
 106    completes the unquoting anyway.
 107
 108    This is used for reading the saved directory file in incremental
 109    dumps.  It is used for decoding old `N' records (demangling names).
 110    But also, it is used for decoding file arguments, would they come
 111    from the shell or a -T file, and for decoding the --exclude
 112    argument.  */
 113 int
 114 unquote_string (char *string)
 115 {
 116   int result = 1;
 117   char *source = string;
 118   char *destination = string;
 119
 120   /* Escape sequences other than \\ and \n are no longer generated by
 121      quote_copy_string, but accept them for backwards compatibility,
 122      and also because unquote_string is used for purposes other than
 123      parsing the output of quote_copy_string.  */
 124
 125   while (*source)
 126     if (*source == '\\')
 127       switch (*++source)
 128         {
 129         case '\\':
 130           *destination++ = '\\';
 131           source++;
 132           break;
 133
 134         case 'a':
 135           *destination++ = '\a';
 136           source++;
 137           break;
 138
 139         case 'b':
 140           *destination++ = '\b';
 141           source++;
 142           break;
 143
 144         case 'f':
 145           *destination++ = '\f';
 146           source++;
 147           break;
 148
 149         case 'n':
 150           *destination++ = '\n';
 151           source++;
 152           break;
 153
 154         case 'r':
 155           *destination++ = '\r';
 156           source++;
 157           break;
 158
 159         case 't':
 160           *destination++ = '\t';
 161           source++;
 162           break;
 163
 164         case 'v':
 165           *destination++ = '\v';
 166           source++;
 167           break;
 168
 169         case '?':
 170           *destination++ = 0177;
 171           source++;
 172           break;
 173
 174         case '0':
 175         case '1':
 176         case '2':
 177         case '3':
 178         case '4':
 179         case '5':
 180         case '6':
 181         case '7':
 182           {
 183             int value = *source++ - '0';
 184
 185             if (*source < '0' || *source > '7')
 186               {
 187                 *destination++ = value;
 188                 break;
 189               }
 190             value = value * 8 + *source++ - '0';
 191             if (*source < '0' || *source > '7')
 192               {
 193                 *destination++ = value;
 194                 break;
 195               }
 196             value = value * 8 + *source++ - '0';
 197             *destination++ = value;
 198             break;
 199           }
 200
 201         default:
 202           result = 0;
 203           *destination++ = '\\';
 204           if (*source)
 205             *destination++ = *source++;
 206           break;
 207         }
 208     else if (source != destination)
 209       *destination++ = *source++;
 210     else
 211       source++, destination++;
 212
 213   if (source != destination)
 214     *destination = '\0';
 215   return result;
 216 }
 217
 218 /* Zap trailing slashes.  */
 219 char *
 220 zap_slashes (char *name)
 221 {
 222   char *q;
 223
 224   if (!name || *name == 0)
 225     return name;
 226   q = name + strlen (name) - 1;
 227   while (q > name && ISSLASH (*q))
 228     *q-- = '\0';
 229   return name;
 230 }
 231
 232 /* Normalize FILE_NAME by removing redundant slashes and "."
 233    components, including redundant trailing slashes.  Leave ".."
 234    alone, as it may be significant in the presence of symlinks and on
 235    platforms where "/.." != "/".  Destructive version: modifies its
 236    argument. */
 237 static void
 238 normalize_filename_x (char *file_name)
 239 {
 240   char *name = file_name + FILE_SYSTEM_PREFIX_LEN (file_name);
 241   char *p;
 242   char const *q;
 243   char c;
 244
 245   /* Don't squeeze leading "//" to "/", on hosts where they're distinct.  */
 246   name += (DOUBLE_SLASH_IS_DISTINCT_ROOT
 247            && ISSLASH (*name) && ISSLASH (name[1]) && ! ISSLASH (name[2]));
 248
 249   /* Omit redundant leading "." components.  */
 250   for (q = p = name; (*p = *q) == '.' && ISSLASH (q[1]); p += !*q)
 251     for (q += 2; ISSLASH (*q); q++)
 252       continue;
 253
 254   /* Copy components from Q to P, omitting redundant slashes and
 255      internal "."  components.  */
 256   while ((*p++ = c = *q++) != '\0')
 257     if (ISSLASH (c))
 258       while (ISSLASH (q[*q == '.']))
 259         q += (*q == '.') + 1;
 260
 261   /* Omit redundant trailing "." component and slash.  */
 262   if (2 < p - name)
 263     {
 264       p -= p[-2] == '.' && ISSLASH (p[-3]);
 265       p -= 2 < p - name && ISSLASH (p[-2]);
 266       p[-1] = '\0';
 267     }
 268 }
 269
 270 /* Normalize NAME by removing redundant slashes and "." components,
 271    including redundant trailing slashes.  Return a normalized
 272    newly-allocated copy.  */
 273
 274 char *
 275 normalize_filename (const char *name)
 276 {
 277   char *copy = NULL;
 278
 279   if (IS_RELATIVE_FILE_NAME (name))
 280     {
 281       /* Set COPY to the absolute file name if possible.
 282
 283          FIXME: There should be no need to get the absolute file name.
 284          getcwd is slow, it might fail, and it does not necessarily
 285          return a canonical name even when it succeeds.  Perhaps we
 286          can use dev+ino pairs instead of names?  */
 287       copy = xgetcwd ();
 288       if (copy)
 289         {
 290           size_t copylen = strlen (copy);
 291           bool need_separator = ! (DOUBLE_SLASH_IS_DISTINCT_ROOT
 292                                    && copylen == 2 && ISSLASH (copy[1]));
 293           copy = xrealloc (copy, copylen + need_separator + strlen (name) + 1);
 294           copy[copylen] = DIRECTORY_SEPARATOR;
 295           strcpy (copy + copylen + need_separator, name);
 296         }
 297       else
 298         WARN ((0, errno, _("Cannot get working directory")));
 299     }
 300
 301   if (! copy)
 302     copy = xstrdup (name);
 303   normalize_filename_x (copy);
 304   return copy;
 305 }
 306
 307 \f
 308 void
 309 replace_prefix (char **pname, const char *samp, size_t slen,
 310                 const char *repl, size_t rlen)
 311 {
 312   char *name = *pname;
 313   size_t nlen = strlen (name);
 314   if (nlen > slen && memcmp (name, samp, slen) == 0 && ISSLASH (name[slen]))
 315     {
 316       if (rlen > slen)
 317         {
 318           name = xrealloc (name, nlen - slen + rlen + 1);
 319           *pname = name;
 320         }
 321       memmove (name + rlen, name + slen, nlen - slen + 1);
 322       memcpy (name, repl, rlen);
 323     }
 324 }
 325
 326 \f
 327 /* Handling numbers.  */
 328
 329 /* Output fraction and trailing digits appropriate for a nanoseconds
 330    count equal to NS, but don't output unnecessary '.' or trailing
 331    zeros.  */
 332
 333 void
 334 code_ns_fraction (int ns, char *p)
 335 {
 336   if (ns == 0)
 337     *p = '\0';
 338   else
 339     {
 340       int i = 9;
 341       *p++ = '.';
 342
 343       while (ns % 10 == 0)
 344         {
 345           ns /= 10;
 346           i--;
 347         }
 348
 349       p[i] = '\0';
 350
 351       for (;;)
 352         {
 353           p[--i] = '0' + ns % 10;
 354           if (i == 0)
 355             break;
 356           ns /= 10;
 357         }
 358     }
 359 }
 360
 361 char const *
 362 code_timespec (struct timespec t, char sbuf[TIMESPEC_STRSIZE_BOUND])
 363 {
 364   time_t s = t.tv_sec;
 365   int ns = t.tv_nsec;
 366   char *np;
 367   bool negative = s < 0;
 368
 369   /* ignore invalid values of ns */
 370   if (BILLION <= ns || ns < 0)
 371     ns = 0;
 372
 373   if (negative && ns != 0)
 374     {
 375       s++;
 376       ns = BILLION - ns;
 377     }
 378
 379   np = umaxtostr (negative ? - (uintmax_t) s : (uintmax_t) s, sbuf + 1);
 380   if (negative)
 381     *--np = '-';
 382   code_ns_fraction (ns, sbuf + UINTMAX_STRSIZE_BOUND);
 383   return np;
 384 }
 385 \f
 386 /* File handling.  */
 387
 388 /* Saved names in case backup needs to be undone.  */
 389 static char *before_backup_name;
 390 static char *after_backup_name;
 391
 392 /* Return 1 if FILE_NAME is obviously "." or "/".  */
 393 bool
 394 must_be_dot_or_slash (char const *file_name)
 395 {
 396   file_name += FILE_SYSTEM_PREFIX_LEN (file_name);
 397
 398   if (ISSLASH (file_name[0]))
 399     {
 400       for (;;)
 401         if (ISSLASH (file_name[1]))
 402           file_name++;
 403         else if (file_name[1] == '.'
 404                  && ISSLASH (file_name[2 + (file_name[2] == '.')]))
 405           file_name += 2 + (file_name[2] == '.');
 406         else
 407           return ! file_name[1];
 408     }
 409   else
 410     {
 411       while (file_name[0] == '.' && ISSLASH (file_name[1]))
 412         {
 413           file_name += 2;
 414           while (ISSLASH (*file_name))
 415             file_name++;
 416         }
 417
 418       return ! file_name[0] || (file_name[0] == '.' && ! file_name[1]);
 419     }
 420 }
 421
 422 /* Some implementations of rmdir let you remove '.' or '/'.
 423    Report an error with errno set to zero for obvious cases of this;
 424    otherwise call rmdir.  */
 425 static int
 426 safer_rmdir (const char *file_name)
 427 {
 428   if (must_be_dot_or_slash (file_name))
 429     {
 430       errno = 0;
 431       return -1;
 432     }
 433
 434   return unlinkat (chdir_fd, file_name, AT_REMOVEDIR);
 435 }
 436
 437 /* Remove FILE_NAME, returning 1 on success.  If FILE_NAME is a directory,
 438    then if OPTION is RECURSIVE_REMOVE_OPTION is set remove FILE_NAME
 439    recursively; otherwise, remove it only if it is empty.  If FILE_NAME is
 440    a directory that cannot be removed (e.g., because it is nonempty)
 441    and if OPTION is WANT_DIRECTORY_REMOVE_OPTION, then return -1.
 442    Return 0 on error, with errno set; if FILE_NAME is obviously the working
 443    directory return zero with errno set to zero.  */
 444 int
 445 remove_any_file (const char *file_name, enum remove_option option)
 446 {
 447   /* Try unlink first if we cannot unlink directories, as this saves
 448      us a system call in the common case where we're removing a
 449      non-directory.  */
 450   bool try_unlink_first = cannot_unlink_dir ();
 451
 452   if (try_unlink_first)
 453     {
 454       if (unlinkat (chdir_fd, file_name, 0) == 0)
 455         return 1;
 456
 457       /* POSIX 1003.1-2001 requires EPERM when attempting to unlink a
 458          directory without appropriate privileges, but many Linux
 459          kernels return the more-sensible EISDIR.  */
 460       if (errno != EPERM && errno != EISDIR)
 461         return 0;
 462     }
 463
 464   if (safer_rmdir (file_name) == 0)
 465     return 1;
 466
 467   switch (errno)
 468     {
 469     case ENOTDIR:
 470       return !try_unlink_first && unlinkat (chdir_fd, file_name, 0) == 0;
 471
 472     case 0:
 473     case EEXIST:
 474 #if defined ENOTEMPTY && ENOTEMPTY != EEXIST
 475     case ENOTEMPTY:
 476 #endif
 477       switch (option)
 478         {
 479         case ORDINARY_REMOVE_OPTION:
 480           break;
 481
 482         case WANT_DIRECTORY_REMOVE_OPTION:
 483           return -1;
 484
 485         case RECURSIVE_REMOVE_OPTION:
 486           {
 487             char *directory = savedir (file_name);
 488             char const *entry;
 489             size_t entrylen;
 490
 491             if (! directory)
 492               return 0;
 493
 494             for (entry = directory;
 495                  (entrylen = strlen (entry)) != 0;
 496                  entry += entrylen + 1)
 497               {
 498                 char *file_name_buffer = new_name (file_name, entry);
 499                 int r = remove_any_file (file_name_buffer,
 500                                          RECURSIVE_REMOVE_OPTION);
 501                 int e = errno;
 502                 free (file_name_buffer);
 503
 504                 if (! r)
 505                   {
 506                     free (directory);
 507                     errno = e;
 508                     return 0;
 509                   }
 510               }
 511
 512             free (directory);
 513             return safer_rmdir (file_name) == 0;
 514           }
 515         }
 516       break;
 517     }
 518
 519   return 0;
 520 }
 521
 522 /* Check if FILE_NAME already exists and make a backup of it right now.
 523    Return success (nonzero) only if the backup is either unneeded, or
 524    successful.  For now, directories are considered to never need
 525    backup.  If THIS_IS_THE_ARCHIVE is nonzero, this is the archive and
 526    so, we do not have to backup block or character devices, nor remote
 527    entities.  */
 528 bool
 529 maybe_backup_file (const char *file_name, bool this_is_the_archive)
 530 {
 531   struct stat file_stat;
 532
 533   assign_string (&before_backup_name, file_name);
 534
 535   /* A run situation may exist between Emacs or other GNU programs trying to
 536      make a backup for the same file simultaneously.  If theoretically
 537      possible, real problems are unlikely.  Doing any better would require a
 538      convention, GNU-wide, for all programs doing backups.  */
 539
 540   assign_string (&after_backup_name, 0);
 541
 542   /* Check if we really need to backup the file.  */
 543
 544   if (this_is_the_archive && _remdev (file_name))
 545     return true;
 546
 547   if (deref_stat (file_name, &file_stat) != 0)
 548     {
 549       if (errno == ENOENT)
 550         return true;
 551
 552       stat_error (file_name);
 553       return false;
 554     }
 555
 556   if (S_ISDIR (file_stat.st_mode))
 557     return true;
 558
 559   if (this_is_the_archive
 560       && (S_ISBLK (file_stat.st_mode) || S_ISCHR (file_stat.st_mode)))
 561     return true;
 562
 563   after_backup_name = find_backup_file_name (file_name, backup_type);
 564   if (! after_backup_name)
 565     xalloc_die ();
 566
 567   if (renameat (chdir_fd, before_backup_name, chdir_fd, after_backup_name)
 568       == 0)
 569     {
 570       if (verbose_option)
 571         fprintf (stdlis, _("Renaming %s to %s\n"),
 572                  quote_n (0, before_backup_name),
 573                  quote_n (1, after_backup_name));
 574       return true;
 575     }
 576   else
 577     {
 578       /* The backup operation failed.  */
 579       int e = errno;
 580       ERROR ((0, e, _("%s: Cannot rename to %s"),
 581               quotearg_colon (before_backup_name),
 582               quote_n (1, after_backup_name)));
 583       assign_string (&after_backup_name, 0);
 584       return false;
 585     }
 586 }
 587
 588 /* Try to restore the recently backed up file to its original name.
 589    This is usually only needed after a failed extraction.  */
 590 void
 591 undo_last_backup (void)
 592 {
 593   if (after_backup_name)
 594     {
 595       if (renameat (chdir_fd, after_backup_name, chdir_fd, before_backup_name)
 596           != 0)
 597         {
 598           int e = errno;
 599           ERROR ((0, e, _("%s: Cannot rename to %s"),
 600                   quotearg_colon (after_backup_name),
 601                   quote_n (1, before_backup_name)));
 602         }
 603       if (verbose_option)
 604         fprintf (stdlis, _("Renaming %s back to %s\n"),
 605                  quote_n (0, after_backup_name),
 606                  quote_n (1, before_backup_name));
 607       assign_string (&after_backup_name, 0);
 608     }
 609 }
 610
 611 /* Apply either stat or lstat to (NAME, BUF), depending on the
 612    presence of the --dereference option.  NAME is relative to the
 613    most-recent argument to chdir_do.  */
 614 int
 615 deref_stat (char const *name, struct stat *buf)
 616 {
 617   return fstatat (chdir_fd, name, buf, fstatat_flags);
 618 }
 619
 620 /* Set FD's (i.e., assuming the working directory is PARENTFD, FILE's)
 621    access time to ATIME.  */
 622 int
 623 set_file_atime (int fd, int parentfd, char const *file, struct timespec atime)
 624 {
 625   struct timespec ts[2];
 626   ts[0] = atime;
 627   ts[1].tv_nsec = UTIME_OMIT;
 628   return fdutimensat (fd, parentfd, file, ts, fstatat_flags);
 629 }
 630
 631 /* A description of a working directory.  */
 632 struct wd
 633 {
 634   /* The directory's name.  */
 635   char const *name;
 636
 637   /* If nonzero, the file descriptor of the directory, or AT_FDCWD if
 638      the working directory.  If zero, the directory needs to be opened
 639      to be used.  */
 640   int fd;
 641 };
 642
 643 /* A vector of chdir targets.  wd[0] is the initial working directory.  */
 644 static struct wd *wd;
 645
 646 /* The number of working directories in the vector.  */
 647 static size_t wd_count;
 648
 649 /* The allocated size of the vector.  */
 650 static size_t wd_alloc;
 651
 652 /* The maximum number of chdir targets with open directories.
 653    Don't make it too large, as many operating systems have a small
 654    limit on the number of open file descriptors.  Also, the current
 655    implementation does not scale well.  */
 656 enum { CHDIR_CACHE_SIZE = 16 };
 657
 658 /* Indexes into WD of chdir targets with open file descriptors, sorted
 659    most-recently used first.  Zero indexes are unused.  */
 660 static int wdcache[CHDIR_CACHE_SIZE];
 661
 662 /* Number of nonzero entries in WDCACHE.  */
 663 static size_t wdcache_count;
 664
 665 int
 666 chdir_count ()
 667 {
 668   if (wd_count == 0)
 669     return wd_count;
 670   return wd_count - 1;
 671 }
 672
 673 /* DIR is the operand of a -C option; add it to vector of chdir targets,
 674    and return the index of its location.  */
 675 int
 676 chdir_arg (char const *dir)
 677 {
 678   if (wd_count == wd_alloc)
 679     {
 680       if (wd_alloc == 0)
 681         {
 682           wd_alloc = 2;
 683           wd = xmalloc (sizeof *wd * wd_alloc);
 684         }
 685       else
 686         wd = x2nrealloc (wd, &wd_alloc, sizeof *wd);
 687
 688       if (! wd_count)
 689         {
 690           wd[wd_count].name = ".";
 691           wd[wd_count].fd = AT_FDCWD;
 692           wd_count++;
 693         }
 694     }
 695
 696   /* Optimize the common special case of the working directory,
 697      or the working directory as a prefix.  */
 698   if (dir[0])
 699     {
 700       while (dir[0] == '.' && ISSLASH (dir[1]))
 701         for (dir += 2;  ISSLASH (*dir);  dir++)
 702           continue;
 703       if (! dir[dir[0] == '.'])
 704         return wd_count - 1;
 705     }
 706
 707   wd[wd_count].name = dir;
 708   wd[wd_count].fd = 0;
 709   return wd_count++;
 710 }
 711
 712 /* Index of current directory.  */
 713 int chdir_current;
 714
 715 /* Value suitable for use as the first argument to openat, and in
 716    similar locations for fstatat, etc.  This is an open file
 717    descriptor, or AT_FDCWD if the working directory is current.  It is
 718    valid until the next invocation of chdir_do.  */
 719 int chdir_fd = AT_FDCWD;
 720
 721 /* Change to directory I, in a virtual way.  This does not actually
 722    invoke chdir; it merely sets chdir_fd to an int suitable as the
 723    first argument for openat, etc.  If I is 0, change to the initial
 724    working directory; otherwise, I must be a value returned by
 725    chdir_arg.  */
 726 void
 727 chdir_do (int i)
 728 {
 729   if (chdir_current != i)
 730     {
 731       static size_t counter;
 732       struct wd *curr = &wd[i];
 733       int fd = curr->fd;
 734
 735       if (! fd)
 736         {
 737           if (! IS_ABSOLUTE_FILE_NAME (curr->name))
 738             chdir_do (i - 1);
 739           fd = openat (chdir_fd, curr->name,
 740                        open_searchdir_flags & ~ O_NOFOLLOW);
 741           if (fd < 0)
 742             open_fatal (curr->name);
 743
 744           curr->fd = fd;
 745
 746           /* Add I to the cache, tossing out the lowest-ranking entry if the
 747              cache is full.  */
 748           if (wdcache_count < CHDIR_CACHE_SIZE)
 749             wdcache[wdcache_count++] = i;
 750           else
 751             {
 752               struct wd *stale = &wd[wdcache[CHDIR_CACHE_SIZE - 1]];
 753               if (close (stale->fd) != 0)
 754                 close_diag (stale->name);
 755               stale->fd = 0;
 756               wdcache[CHDIR_CACHE_SIZE - 1] = i;
 757             }
 758         }
 759
 760       if (0 < fd)
 761         {
 762           /* Move the i value to the front of the cache.  This is
 763              O(CHDIR_CACHE_SIZE), but the cache is small.  */
 764           size_t ci;
 765           int prev = wdcache[0];
 766           for (ci = 1; prev != i; ci++)
 767             {
 768               int curr = wdcache[ci];
 769               wdcache[ci] = prev;
 770               if (curr == i)
 771                 break;
 772               prev = curr;
 773             }
 774           wdcache[0] = i;
 775         }
 776
 777       chdir_current = i;
 778       chdir_fd = fd;
 779     }
 780 }
 781 \f
 782 void
 783 close_diag (char const *name)
 784 {
 785   if (ignore_failed_read_option)
 786     close_warn (name);
 787   else
 788     close_error (name);
 789 }
 790
 791 void
 792 open_diag (char const *name)
 793 {
 794   if (ignore_failed_read_option)
 795     open_warn (name);
 796   else
 797     open_error (name);
 798 }
 799
 800 void
 801 read_diag_details (char const *name, off_t offset, size_t size)
 802 {
 803   if (ignore_failed_read_option)
 804     read_warn_details (name, offset, size);
 805   else
 806     read_error_details (name, offset, size);
 807 }
 808
 809 void
 810 readlink_diag (char const *name)
 811 {
 812   if (ignore_failed_read_option)
 813     readlink_warn (name);
 814   else
 815     readlink_error (name);
 816 }
 817
 818 void
 819 savedir_diag (char const *name)
 820 {
 821   if (ignore_failed_read_option)
 822     savedir_warn (name);
 823   else
 824     savedir_error (name);
 825 }
 826
 827 void
 828 seek_diag_details (char const *name, off_t offset)
 829 {
 830   if (ignore_failed_read_option)
 831     seek_warn_details (name, offset);
 832   else
 833     seek_error_details (name, offset);
 834 }
 835
 836 void
 837 stat_diag (char const *name)
 838 {
 839   if (ignore_failed_read_option)
 840     stat_warn (name);
 841   else
 842     stat_error (name);
 843 }
 844
 845 void
 846 file_removed_diag (const char *name, bool top_level,
 847                    void (*diagfn) (char const *name))
 848 {
 849   if (!top_level && errno == ENOENT)
 850     {
 851       WARNOPT (WARN_FILE_REMOVED,
 852                (0, 0, _("%s: File removed before we read it"),
 853                 quotearg_colon (name)));
 854       set_exit_status (TAREXIT_DIFFERS);
 855     }
 856   else
 857     diagfn (name);
 858 }
 859
 860 void
 861 dir_removed_diag (const char *name, bool top_level,
 862                    void (*diagfn) (char const *name))
 863 {
 864   if (!top_level && errno == ENOENT)
 865     {
 866       WARNOPT (WARN_FILE_REMOVED,
 867                (0, 0, _("%s: Directory removed before we read it"),
 868                 quotearg_colon (name)));
 869       set_exit_status (TAREXIT_DIFFERS);
 870     }
 871   else
 872     diagfn (name);
 873 }
 874
 875 void
 876 write_fatal_details (char const *name, ssize_t status, size_t size)
 877 {
 878   write_error_details (name, status, size);
 879   fatal_exit ();
 880 }
 881
 882 /* Fork, aborting if unsuccessful.  */
 883 pid_t
 884 xfork (void)
 885 {
 886   pid_t p = fork ();
 887   if (p == (pid_t) -1)
 888     call_arg_fatal ("fork", _("child process"));
 889   return p;
 890 }
 891
 892 /* Create a pipe, aborting if unsuccessful.  */
 893 void
 894 xpipe (int fd[2])
 895 {
 896   if (pipe (fd) < 0)
 897     call_arg_fatal ("pipe", _("interprocess channel"));
 898 }
 899
 900 /* Return PTR, aligned upward to the next multiple of ALIGNMENT.
 901    ALIGNMENT must be nonzero.  The caller must arrange for ((char *)
 902    PTR) through ((char *) PTR + ALIGNMENT - 1) to be addressable
 903    locations.  */
 904
 905 static inline void *
 906 ptr_align (void *ptr, size_t alignment)
 907 {
 908   char *p0 = ptr;
 909   char *p1 = p0 + alignment - 1;
 910   return p1 - (size_t) p1 % alignment;
 911 }
 912
 913 /* Return the address of a page-aligned buffer of at least SIZE bytes.
 914    The caller should free *PTR when done with the buffer.  */
 915
 916 void *
 917 page_aligned_alloc (void **ptr, size_t size)
 918 {
 919   size_t alignment = getpagesize ();
 920   size_t size1 = size + alignment;
 921   if (size1 < size)
 922     xalloc_die ();
 923   *ptr = xmalloc (size1);
 924   return ptr_align (*ptr, alignment);
 925 }
 926
 927 \f
 928
 929 struct namebuf
 930 {
 931   char *buffer;         /* directory, `/', and directory member */
 932   size_t buffer_size;   /* allocated size of name_buffer */
 933   size_t dir_length;    /* length of directory part in buffer */
 934 };
 935
 936 namebuf_t
 937 namebuf_create (const char *dir)
 938 {
 939   namebuf_t buf = xmalloc (sizeof (*buf));
 940   buf->buffer_size = strlen (dir) + 2;
 941   buf->buffer = xmalloc (buf->buffer_size);
 942   strcpy (buf->buffer, dir);
 943   buf->dir_length = strlen (buf->buffer);
 944   if (!ISSLASH (buf->buffer[buf->dir_length - 1]))
 945     buf->buffer[buf->dir_length++] = DIRECTORY_SEPARATOR;
 946   return buf;
 947 }
 948
 949 void
 950 namebuf_free (namebuf_t buf)
 951 {
 952   free (buf->buffer);
 953   free (buf);
 954 }
 955
 956 char *
 957 namebuf_name (namebuf_t buf, const char *name)
 958 {
 959   size_t len = strlen (name);
 960   while (buf->dir_length + len + 1 >= buf->buffer_size)
 961     buf->buffer = x2realloc (buf->buffer, &buf->buffer_size);
 962   strcpy (buf->buffer + buf->dir_length, name);
 963   return buf->buffer;
 964 }