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 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 <save-cwd.h>
  25 #include <xgetcwd.h>
  26 #include <unlinkdir.h>
  27 #include <utimens.h>
  28
  29 #if HAVE_STROPTS_H
  30 # include <stropts.h>
  31 #endif
  32 #if HAVE_SYS_FILIO_H
  33 # include <sys/filio.h>
  34 #endif
  35
  36 #ifndef DOUBLE_SLASH_IS_DISTINCT_ROOT
  37 # define DOUBLE_SLASH_IS_DISTINCT_ROOT 0
  38 #endif
  39
  40 \f
  41 /* Handling strings.  */
  42
  43 /* Assign STRING to a copy of VALUE if not zero, or to zero.  If
  44    STRING was nonzero, it is freed first.  */
  45 void
  46 assign_string (char **string, const char *value)
  47 {
  48   if (*string)
  49     free (*string);
  50   *string = value ? xstrdup (value) : 0;
  51 }
  52
  53 /* Allocate a copy of the string quoted as in C, and returns that.  If
  54    the string does not have to be quoted, it returns a null pointer.
  55    The allocated copy should normally be freed with free() after the
  56    caller is done with it.
  57
  58    This is used in one context only: generating the directory file in
  59    incremental dumps.  The quoted string is not intended for human
  60    consumption; it is intended only for unquote_string.  The quoting
  61    is locale-independent, so that users needn't worry about locale
  62    when reading directory files.  This means that we can't use
  63    quotearg, as quotearg is locale-dependent and is meant for human
  64    consumption.  */
  65 char *
  66 quote_copy_string (const char *string)
  67 {
  68   const char *source = string;
  69   char *destination = 0;
  70   char *buffer = 0;
  71   int copying = 0;
  72
  73   while (*source)
  74     {
  75       int character = *source++;
  76
  77       switch (character)
  78         {
  79         case '\n': case '\\':
  80           if (!copying)
  81             {
  82               size_t length = (source - string) - 1;
  83
  84               copying = 1;
  85               buffer = xmalloc (length + 2 + 2 * strlen (source) + 1);
  86               memcpy (buffer, string, length);
  87               destination = buffer + length;
  88             }
  89           *destination++ = '\\';
  90           *destination++ = character == '\\' ? '\\' : 'n';
  91           break;
  92
  93         default:
  94           if (copying)
  95             *destination++ = character;
  96           break;
  97         }
  98     }
  99   if (copying)
 100     {
 101       *destination = '\0';
 102       return buffer;
 103     }
 104   return 0;
 105 }
 106
 107 /* Takes a quoted C string (like those produced by quote_copy_string)
 108    and turns it back into the un-quoted original.  This is done in
 109    place.  Returns 0 only if the string was not properly quoted, but
 110    completes the unquoting anyway.
 111
 112    This is used for reading the saved directory file in incremental
 113    dumps.  It is used for decoding old `N' records (demangling names).
 114    But also, it is used for decoding file arguments, would they come
 115    from the shell or a -T file, and for decoding the --exclude
 116    argument.  */
 117 int
 118 unquote_string (char *string)
 119 {
 120   int result = 1;
 121   char *source = string;
 122   char *destination = string;
 123
 124   /* Escape sequences other than \\ and \n are no longer generated by
 125      quote_copy_string, but accept them for backwards compatibility,
 126      and also because unquote_string is used for purposes other than
 127      parsing the output of quote_copy_string.  */
 128
 129   while (*source)
 130     if (*source == '\\')
 131       switch (*++source)
 132         {
 133         case '\\':
 134           *destination++ = '\\';
 135           source++;
 136           break;
 137
 138         case 'a':
 139           *destination++ = '\a';
 140           source++;
 141           break;
 142
 143         case 'b':
 144           *destination++ = '\b';
 145           source++;
 146           break;
 147
 148         case 'f':
 149           *destination++ = '\f';
 150           source++;
 151           break;
 152
 153         case 'n':
 154           *destination++ = '\n';
 155           source++;
 156           break;
 157
 158         case 'r':
 159           *destination++ = '\r';
 160           source++;
 161           break;
 162
 163         case 't':
 164           *destination++ = '\t';
 165           source++;
 166           break;
 167
 168         case 'v':
 169           *destination++ = '\v';
 170           source++;
 171           break;
 172
 173         case '?':
 174           *destination++ = 0177;
 175           source++;
 176           break;
 177
 178         case '0':
 179         case '1':
 180         case '2':
 181         case '3':
 182         case '4':
 183         case '5':
 184         case '6':
 185         case '7':
 186           {
 187             int value = *source++ - '0';
 188
 189             if (*source < '0' || *source > '7')
 190               {
 191                 *destination++ = value;
 192                 break;
 193               }
 194             value = value * 8 + *source++ - '0';
 195             if (*source < '0' || *source > '7')
 196               {
 197                 *destination++ = value;
 198                 break;
 199               }
 200             value = value * 8 + *source++ - '0';
 201             *destination++ = value;
 202             break;
 203           }
 204
 205         default:
 206           result = 0;
 207           *destination++ = '\\';
 208           if (*source)
 209             *destination++ = *source++;
 210           break;
 211         }
 212     else if (source != destination)
 213       *destination++ = *source++;
 214     else
 215       source++, destination++;
 216
 217   if (source != destination)
 218     *destination = '\0';
 219   return result;
 220 }
 221
 222 /* Zap trailing slashes.  */
 223 char *
 224 zap_slashes (char *name)
 225 {
 226   char *q;
 227
 228   if (!name || *name == 0)
 229     return name;
 230   q = name + strlen (name) - 1;
 231   while (q > name && ISSLASH (*q))
 232     *q-- = '\0';
 233   return name;
 234 }
 235
 236 /* Normalize NAME by resolving any relative references and
 237    removing trailing slashes.  Destructive version: modifies its argument. */
 238 static int
 239 normalize_filename_x (char *name)
 240 {
 241   char *p, *q;
 242
 243   p = name;
 244   if (DOUBLE_SLASH_IS_DISTINCT_ROOT && ISSLASH (*p))
 245     p++;
 246
 247   /* Remove /./, resolve /../ and compress sequences of slashes */
 248   for (q = p; *q; )
 249     {
 250       if (ISSLASH (*q))
 251         {
 252           *p++ = *q++;
 253           while (ISSLASH (*q))
 254             q++;
 255           continue;
 256         }
 257       else if (p == name)
 258         {
 259           if (*q == '.')
 260             {
 261               if (ISSLASH (q[1]))
 262                 {
 263                   q += 2;
 264                   continue;
 265                 }
 266               if (q[1] == '.' && ISSLASH (q[2]))
 267                 return 1;
 268             }
 269         }
 270       else
 271         {
 272           if (*q == '.' && ISSLASH (p[-1]))
 273             {
 274               if (ISSLASH (q[1]))
 275                 {
 276                   q += 2;
 277                   while (ISSLASH (*q))
 278                     q++;
 279                   continue;
 280                 }
 281               else if (q[1] == '.' && ISSLASH (q[2]))
 282                 {
 283                   do
 284                     {
 285                       --p;
 286                     }
 287                   while (p > name && !ISSLASH (p[-1]));
 288                   q += 3;
 289                   continue;
 290                 }
 291             }
 292         }
 293       *p++ = *q++;
 294     }
 295
 296   /* Remove trailing slashes */
 297   while (p - 1 > name && ISSLASH (p[-1]))
 298     p--;
 299
 300   *p = 0;
 301   return 0;
 302 }
 303
 304 /* Normalize NAME by resolving any relative references, removing trailing
 305    slashes, and converting it to absolute file name.  Return the normalized
 306    name, or NULL in case of error. */
 307
 308 char *
 309 normalize_filename (const char *name)
 310 {
 311   char *copy;
 312
 313   if (name[0] != '/')
 314     {
 315       copy = xgetcwd ();
 316       copy = xrealloc (copy, strlen (copy) + strlen (name) + 2);
 317
 318       strcat (copy, "/");
 319       strcat (copy, name);
 320     }
 321   else
 322     copy = xstrdup (name);
 323   if (normalize_filename_x (copy))
 324     {
 325       free (copy);
 326       return NULL;
 327     }
 328   return xrealloc (copy, strlen (copy) + 1);
 329 }
 330
 331 \f
 332 void
 333 replace_prefix (char **pname, const char *samp, size_t slen,
 334                 const char *repl, size_t rlen)
 335 {
 336   char *name = *pname;
 337   size_t nlen = strlen (name);
 338   if (nlen > slen && memcmp (name, samp, slen) == 0 && ISSLASH (name[slen]))
 339     {
 340       if (rlen > slen)
 341         {
 342           name = xrealloc (name, nlen - slen + rlen + 1);
 343           *pname = name;
 344         }
 345       memmove (name + rlen, name + slen, nlen - slen + 1);
 346       memcpy (name, repl, rlen);
 347     }
 348 }
 349
 350 \f
 351 /* Handling numbers.  */
 352
 353 /* Output fraction and trailing digits appropriate for a nanoseconds
 354    count equal to NS, but don't output unnecessary '.' or trailing
 355    zeros.  */
 356
 357 void
 358 code_ns_fraction (int ns, char *p)
 359 {
 360   if (ns == 0)
 361     *p = '\0';
 362   else
 363     {
 364       int i = 9;
 365       *p++ = '.';
 366
 367       while (ns % 10 == 0)
 368         {
 369           ns /= 10;
 370           i--;
 371         }
 372
 373       p[i] = '\0';
 374
 375       for (;;)
 376         {
 377           p[--i] = '0' + ns % 10;
 378           if (i == 0)
 379             break;
 380           ns /= 10;
 381         }
 382     }
 383 }
 384
 385 char const *
 386 code_timespec (struct timespec t, char sbuf[TIMESPEC_STRSIZE_BOUND])
 387 {
 388   time_t s = t.tv_sec;
 389   int ns = t.tv_nsec;
 390   char *np;
 391   bool negative = s < 0;
 392
 393   /* ignore invalid values of ns */
 394   if (BILLION <= ns || ns < 0)
 395     ns = 0;
 396
 397   if (negative && ns != 0)
 398     {
 399       s++;
 400       ns = BILLION - ns;
 401     }
 402
 403   np = umaxtostr (negative ? - (uintmax_t) s : (uintmax_t) s, sbuf + 1);
 404   if (negative)
 405     *--np = '-';
 406   code_ns_fraction (ns, sbuf + UINTMAX_STRSIZE_BOUND);
 407   return np;
 408 }
 409 \f
 410 /* File handling.  */
 411
 412 /* Saved names in case backup needs to be undone.  */
 413 static char *before_backup_name;
 414 static char *after_backup_name;
 415
 416 /* Return 1 if FILE_NAME is obviously "." or "/".  */
 417 static bool
 418 must_be_dot_or_slash (char const *file_name)
 419 {
 420   file_name += FILE_SYSTEM_PREFIX_LEN (file_name);
 421
 422   if (ISSLASH (file_name[0]))
 423     {
 424       for (;;)
 425         if (ISSLASH (file_name[1]))
 426           file_name++;
 427         else if (file_name[1] == '.'
 428                  && ISSLASH (file_name[2 + (file_name[2] == '.')]))
 429           file_name += 2 + (file_name[2] == '.');
 430         else
 431           return ! file_name[1];
 432     }
 433   else
 434     {
 435       while (file_name[0] == '.' && ISSLASH (file_name[1]))
 436         {
 437           file_name += 2;
 438           while (ISSLASH (*file_name))
 439             file_name++;
 440         }
 441
 442       return ! file_name[0] || (file_name[0] == '.' && ! file_name[1]);
 443     }
 444 }
 445
 446 /* Some implementations of rmdir let you remove '.' or '/'.
 447    Report an error with errno set to zero for obvious cases of this;
 448    otherwise call rmdir.  */
 449 static int
 450 safer_rmdir (const char *file_name)
 451 {
 452   if (must_be_dot_or_slash (file_name))
 453     {
 454       errno = 0;
 455       return -1;
 456     }
 457
 458   return rmdir (file_name);
 459 }
 460
 461 /* Remove FILE_NAME, returning 1 on success.  If FILE_NAME is a directory,
 462    then if OPTION is RECURSIVE_REMOVE_OPTION is set remove FILE_NAME
 463    recursively; otherwise, remove it only if it is empty.  If FILE_NAME is
 464    a directory that cannot be removed (e.g., because it is nonempty)
 465    and if OPTION is WANT_DIRECTORY_REMOVE_OPTION, then return -1.
 466    Return 0 on error, with errno set; if FILE_NAME is obviously the working
 467    directory return zero with errno set to zero.  */
 468 int
 469 remove_any_file (const char *file_name, enum remove_option option)
 470 {
 471   /* Try unlink first if we cannot unlink directories, as this saves
 472      us a system call in the common case where we're removing a
 473      non-directory.  */
 474   bool try_unlink_first = cannot_unlink_dir ();
 475
 476   if (try_unlink_first)
 477     {
 478       if (unlink (file_name) == 0)
 479         return 1;
 480
 481       /* POSIX 1003.1-2001 requires EPERM when attempting to unlink a
 482          directory without appropriate privileges, but many Linux
 483          kernels return the more-sensible EISDIR.  */
 484       if (errno != EPERM && errno != EISDIR)
 485         return 0;
 486     }
 487
 488   if (safer_rmdir (file_name) == 0)
 489     return 1;
 490
 491   switch (errno)
 492     {
 493     case ENOTDIR:
 494       return !try_unlink_first && unlink (file_name) == 0;
 495
 496     case 0:
 497     case EEXIST:
 498 #if defined ENOTEMPTY && ENOTEMPTY != EEXIST
 499     case ENOTEMPTY:
 500 #endif
 501       switch (option)
 502         {
 503         case ORDINARY_REMOVE_OPTION:
 504           break;
 505
 506         case WANT_DIRECTORY_REMOVE_OPTION:
 507           return -1;
 508
 509         case RECURSIVE_REMOVE_OPTION:
 510           {
 511             char *directory = savedir (file_name);
 512             char const *entry;
 513             size_t entrylen;
 514
 515             if (! directory)
 516               return 0;
 517
 518             for (entry = directory;
 519                  (entrylen = strlen (entry)) != 0;
 520                  entry += entrylen + 1)
 521               {
 522                 char *file_name_buffer = new_name (file_name, entry);
 523                 int r = remove_any_file (file_name_buffer,
 524                                          RECURSIVE_REMOVE_OPTION);
 525                 int e = errno;
 526                 free (file_name_buffer);
 527
 528                 if (! r)
 529                   {
 530                     free (directory);
 531                     errno = e;
 532                     return 0;
 533                   }
 534               }
 535
 536             free (directory);
 537             return safer_rmdir (file_name) == 0;
 538           }
 539         }
 540       break;
 541     }
 542
 543   return 0;
 544 }
 545
 546 /* Check if FILE_NAME already exists and make a backup of it right now.
 547    Return success (nonzero) only if the backup is either unneeded, or
 548    successful.  For now, directories are considered to never need
 549    backup.  If THIS_IS_THE_ARCHIVE is nonzero, this is the archive and
 550    so, we do not have to backup block or character devices, nor remote
 551    entities.  */
 552 bool
 553 maybe_backup_file (const char *file_name, bool this_is_the_archive)
 554 {
 555   struct stat file_stat;
 556
 557   assign_string (&before_backup_name, file_name);
 558
 559   /* A run situation may exist between Emacs or other GNU programs trying to
 560      make a backup for the same file simultaneously.  If theoretically
 561      possible, real problems are unlikely.  Doing any better would require a
 562      convention, GNU-wide, for all programs doing backups.  */
 563
 564   assign_string (&after_backup_name, 0);
 565
 566   /* Check if we really need to backup the file.  */
 567
 568   if (this_is_the_archive && _remdev (file_name))
 569     return true;
 570
 571   if (stat (file_name, &file_stat))
 572     {
 573       if (errno == ENOENT)
 574         return true;
 575
 576       stat_error (file_name);
 577       return false;
 578     }
 579
 580   if (S_ISDIR (file_stat.st_mode))
 581     return true;
 582
 583   if (this_is_the_archive
 584       && (S_ISBLK (file_stat.st_mode) || S_ISCHR (file_stat.st_mode)))
 585     return true;
 586
 587   after_backup_name = find_backup_file_name (file_name, backup_type);
 588   if (! after_backup_name)
 589     xalloc_die ();
 590
 591   if (rename (before_backup_name, after_backup_name) == 0)
 592     {
 593       if (verbose_option)
 594         fprintf (stdlis, _("Renaming %s to %s\n"),
 595                  quote_n (0, before_backup_name),
 596                  quote_n (1, after_backup_name));
 597       return true;
 598     }
 599   else
 600     {
 601       /* The backup operation failed.  */
 602       int e = errno;
 603       ERROR ((0, e, _("%s: Cannot rename to %s"),
 604               quotearg_colon (before_backup_name),
 605               quote_n (1, after_backup_name)));
 606       assign_string (&after_backup_name, 0);
 607       return false;
 608     }
 609 }
 610
 611 /* Try to restore the recently backed up file to its original name.
 612    This is usually only needed after a failed extraction.  */
 613 void
 614 undo_last_backup (void)
 615 {
 616   if (after_backup_name)
 617     {
 618       if (rename (after_backup_name, before_backup_name) != 0)
 619         {
 620           int e = errno;
 621           ERROR ((0, e, _("%s: Cannot rename to %s"),
 622                   quotearg_colon (after_backup_name),
 623                   quote_n (1, before_backup_name)));
 624         }
 625       if (verbose_option)
 626         fprintf (stdlis, _("Renaming %s back to %s\n"),
 627                  quote_n (0, after_backup_name),
 628                  quote_n (1, before_backup_name));
 629       assign_string (&after_backup_name, 0);
 630     }
 631 }
 632
 633 /* Depending on DEREF, apply either stat or lstat to (NAME, BUF).  */
 634 int
 635 deref_stat (bool deref, char const *name, struct stat *buf)
 636 {
 637   return deref ? stat (name, buf) : lstat (name, buf);
 638 }
 639
 640 /* Set FD's (i.e., FILE's) access time to TIMESPEC[0].  If that's not
 641    possible to do by itself, set its access and data modification
 642    times to TIMESPEC[0] and TIMESPEC[1], respectively.  */
 643 int
 644 set_file_atime (int fd, char const *file, struct timespec const timespec[2])
 645 {
 646 #ifdef _FIOSATIME
 647   if (0 <= fd)
 648     {
 649       struct timeval timeval;
 650       timeval.tv_sec = timespec[0].tv_sec;
 651       timeval.tv_usec = timespec[0].tv_nsec / 1000;
 652       if (ioctl (fd, _FIOSATIME, &timeval) == 0)
 653         return 0;
 654     }
 655 #endif
 656
 657   return gl_futimens (fd, file, timespec);
 658 }
 659
 660 /* A description of a working directory.  */
 661 struct wd
 662 {
 663   char const *name;
 664   int saved;
 665   struct saved_cwd saved_cwd;
 666 };
 667
 668 /* A vector of chdir targets.  wd[0] is the initial working directory.  */
 669 static struct wd *wd;
 670
 671 /* The number of working directories in the vector.  */
 672 static size_t wd_count;
 673
 674 /* The allocated size of the vector.  */
 675 static size_t wd_alloc;
 676
 677 int
 678 chdir_count ()
 679 {
 680   if (wd_count == 0)
 681     return wd_count;
 682   return wd_count - 1;
 683 }
 684
 685 /* DIR is the operand of a -C option; add it to vector of chdir targets,
 686    and return the index of its location.  */
 687 int
 688 chdir_arg (char const *dir)
 689 {
 690   if (wd_count == wd_alloc)
 691     {
 692       if (wd_alloc == 0)
 693         {
 694           wd_alloc = 2;
 695           wd = xmalloc (sizeof *wd * wd_alloc);
 696         }
 697       else
 698         wd = x2nrealloc (wd, &wd_alloc, sizeof *wd);
 699
 700       if (! wd_count)
 701         {
 702           wd[wd_count].name = ".";
 703           wd[wd_count].saved = 0;
 704           wd_count++;
 705         }
 706     }
 707
 708   /* Optimize the common special case of the working directory,
 709      or the working directory as a prefix.  */
 710   if (dir[0])
 711     {
 712       while (dir[0] == '.' && ISSLASH (dir[1]))
 713         for (dir += 2;  ISSLASH (*dir);  dir++)
 714           continue;
 715       if (! dir[dir[0] == '.'])
 716         return wd_count - 1;
 717     }
 718
 719   wd[wd_count].name = dir;
 720   wd[wd_count].saved = 0;
 721   return wd_count++;
 722 }
 723
 724 /* Change to directory I.  If I is 0, change to the initial working
 725    directory; otherwise, I must be a value returned by chdir_arg.  */
 726 void
 727 chdir_do (int i)
 728 {
 729   static int previous;
 730
 731   if (previous != i)
 732     {
 733       struct wd *prev = &wd[previous];
 734       struct wd *curr = &wd[i];
 735
 736       if (! prev->saved)
 737         {
 738           int err = 0;
 739           prev->saved = 1;
 740           if (save_cwd (&prev->saved_cwd) != 0)
 741             err = errno;
 742           else if (0 <= prev->saved_cwd.desc)
 743             {
 744               /* Make sure we still have at least one descriptor available.  */
 745               int fd1 = prev->saved_cwd.desc;
 746               int fd2 = dup (fd1);
 747               if (0 <= fd2)
 748                 close (fd2);
 749               else if (errno == EMFILE)
 750                 {
 751                   /* Force restore_cwd to use chdir_long.  */
 752                   close (fd1);
 753                   prev->saved_cwd.desc = -1;
 754                   prev->saved_cwd.name = xgetcwd ();
 755                 }
 756               else
 757                 err = errno;
 758             }
 759
 760           if (err)
 761             FATAL_ERROR ((0, err, _("Cannot save working directory")));
 762         }
 763
 764       if (curr->saved)
 765         {
 766           if (restore_cwd (&curr->saved_cwd))
 767             FATAL_ERROR ((0, 0, _("Cannot change working directory")));
 768         }
 769       else
 770         {
 771           if (i && ! ISSLASH (curr->name[0]))
 772             chdir_do (i - 1);
 773           if (chdir (curr->name) != 0)
 774             chdir_fatal (curr->name);
 775         }
 776
 777       previous = i;
 778     }
 779 }
 780 \f
 781 void
 782 close_diag (char const *name)
 783 {
 784   if (ignore_failed_read_option)
 785     close_warn (name);
 786   else
 787     close_error (name);
 788 }
 789
 790 void
 791 open_diag (char const *name)
 792 {
 793   if (ignore_failed_read_option)
 794     open_warn (name);
 795   else
 796     open_error (name);
 797 }
 798
 799 void
 800 read_diag_details (char const *name, off_t offset, size_t size)
 801 {
 802   if (ignore_failed_read_option)
 803     read_warn_details (name, offset, size);
 804   else
 805     read_error_details (name, offset, size);
 806 }
 807
 808 void
 809 readlink_diag (char const *name)
 810 {
 811   if (ignore_failed_read_option)
 812     readlink_warn (name);
 813   else
 814     readlink_error (name);
 815 }
 816
 817 void
 818 savedir_diag (char const *name)
 819 {
 820   if (ignore_failed_read_option)
 821     savedir_warn (name);
 822   else
 823     savedir_error (name);
 824 }
 825
 826 void
 827 seek_diag_details (char const *name, off_t offset)
 828 {
 829   if (ignore_failed_read_option)
 830     seek_warn_details (name, offset);
 831   else
 832     seek_error_details (name, offset);
 833 }
 834
 835 void
 836 stat_diag (char const *name)
 837 {
 838   if (ignore_failed_read_option)
 839     stat_warn (name);
 840   else
 841     stat_error (name);
 842 }
 843
 844 void
 845 file_removed_diag (const char *name, bool top_level,
 846                    void (*diagfn) (char const *name))
 847 {
 848   if (!top_level && errno == ENOENT)
 849     {
 850       WARNOPT (WARN_FILE_REMOVED,
 851                (0, 0, _("%s: File removed before we read it"),
 852                 quotearg_colon (name)));
 853       set_exit_status (TAREXIT_DIFFERS);
 854     }
 855   else
 856     diagfn (name);
 857 }
 858
 859 void
 860 dir_removed_diag (const char *name, bool top_level,
 861                    void (*diagfn) (char const *name))
 862 {
 863   if (!top_level && errno == ENOENT)
 864     {
 865       WARNOPT (WARN_FILE_REMOVED,
 866                (0, 0, _("%s: Directory removed before we read it"),
 867                 quotearg_colon (name)));
 868       set_exit_status (TAREXIT_DIFFERS);
 869     }
 870   else
 871     diagfn (name);
 872 }
 873
 874 void
 875 write_fatal_details (char const *name, ssize_t status, size_t size)
 876 {
 877   write_error_details (name, status, size);
 878   fatal_exit ();
 879 }
 880
 881 /* Fork, aborting if unsuccessful.  */
 882 pid_t
 883 xfork (void)
 884 {
 885   pid_t p = fork ();
 886   if (p == (pid_t) -1)
 887     call_arg_fatal ("fork", _("child process"));
 888   return p;
 889 }
 890
 891 /* Create a pipe, aborting if unsuccessful.  */
 892 void
 893 xpipe (int fd[2])
 894 {
 895   if (pipe (fd) < 0)
 896     call_arg_fatal ("pipe", _("interprocess channel"));
 897 }
 898
 899 /* Return PTR, aligned upward to the next multiple of ALIGNMENT.
 900    ALIGNMENT must be nonzero.  The caller must arrange for ((char *)
 901    PTR) through ((char *) PTR + ALIGNMENT - 1) to be addressable
 902    locations.  */
 903
 904 static inline void *
 905 ptr_align (void *ptr, size_t alignment)
 906 {
 907   char *p0 = ptr;
 908   char *p1 = p0 + alignment - 1;
 909   return p1 - (size_t) p1 % alignment;
 910 }
 911
 912 /* Return the address of a page-aligned buffer of at least SIZE bytes.
 913    The caller should free *PTR when done with the buffer.  */
 914
 915 void *
 916 page_aligned_alloc (void **ptr, size_t size)
 917 {
 918   size_t alignment = getpagesize ();
 919   size_t size1 = size + alignment;
 920   if (size1 < size)
 921     xalloc_die ();
 922   *ptr = xmalloc (size1);
 923   return ptr_align (*ptr, alignment);
 924 }
 925
 926 \f
 927
 928 struct namebuf
 929 {
 930   char *buffer;         /* directory, `/', and directory member */
 931   size_t buffer_size;   /* allocated size of name_buffer */
 932   size_t dir_length;    /* length of directory part in buffer */
 933 };
 934
 935 namebuf_t
 936 namebuf_create (const char *dir)
 937 {
 938   namebuf_t buf = xmalloc (sizeof (*buf));
 939   buf->buffer_size = strlen (dir) + 2;
 940   buf->buffer = xmalloc (buf->buffer_size);
 941   strcpy (buf->buffer, dir);
 942   buf->dir_length = strlen (buf->buffer);
 943   if (!ISSLASH (buf->buffer[buf->dir_length - 1]))
 944     buf->buffer[buf->dir_length++] = DIRECTORY_SEPARATOR;
 945   return buf;
 946 }
 947
 948 void
 949 namebuf_free (namebuf_t buf)
 950 {
 951   free (buf->buffer);
 952   free (buf);
 953 }
 954
 955 char *
 956 namebuf_name (namebuf_t buf, const char *name)
 957 {
 958   size_t len = strlen (name);
 959   while (buf->dir_length + len + 1 >= buf->buffer_size)
 960     buf->buffer = x2realloc (buf->buffer, &buf->buffer_size);
 961   strcpy (buf->buffer + buf->dir_length, name);
 962   return buf->buffer;
 963 }