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 <save-cwd.h>
  25 #include <xgetcwd.h>
  26 #include <unlinkdir.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 rmdir (file_name);
 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 (unlink (file_name) == 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 && unlink (file_name) == 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 (stat (file_name, &file_stat))
 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 (rename (before_backup_name, after_backup_name) == 0)
 568     {
 569       if (verbose_option)
 570         fprintf (stdlis, _("Renaming %s to %s\n"),
 571                  quote_n (0, before_backup_name),
 572                  quote_n (1, after_backup_name));
 573       return true;
 574     }
 575   else
 576     {
 577       /* The backup operation failed.  */
 578       int e = errno;
 579       ERROR ((0, e, _("%s: Cannot rename to %s"),
 580               quotearg_colon (before_backup_name),
 581               quote_n (1, after_backup_name)));
 582       assign_string (&after_backup_name, 0);
 583       return false;
 584     }
 585 }
 586
 587 /* Try to restore the recently backed up file to its original name.
 588    This is usually only needed after a failed extraction.  */
 589 void
 590 undo_last_backup (void)
 591 {
 592   if (after_backup_name)
 593     {
 594       if (rename (after_backup_name, before_backup_name) != 0)
 595         {
 596           int e = errno;
 597           ERROR ((0, e, _("%s: Cannot rename to %s"),
 598                   quotearg_colon (after_backup_name),
 599                   quote_n (1, before_backup_name)));
 600         }
 601       if (verbose_option)
 602         fprintf (stdlis, _("Renaming %s back to %s\n"),
 603                  quote_n (0, after_backup_name),
 604                  quote_n (1, before_backup_name));
 605       assign_string (&after_backup_name, 0);
 606     }
 607 }
 608
 609 /* Depending on DEREF, apply either stat or lstat to (NAME, BUF).  */
 610 int
 611 deref_stat (bool deref, char const *name, struct stat *buf)
 612 {
 613   return deref ? stat (name, buf) : lstat (name, buf);
 614 }
 615
 616 /* Use futimens if possible, utimensat otherwise.  */
 617 int
 618 fd_utimensat (int fd, int parentfd, char const *file,
 619               struct timespec const ts[2], int atflag)
 620 {
 621   if (0 <= fd)
 622     {
 623       int result = futimens (fd, ts);
 624       if (! (result < 0 && errno == ENOSYS))
 625         return result;
 626     }
 627
 628   return utimensat (parentfd, file, ts, atflag);
 629 }
 630
 631 /* Set FD's (i.e., assuming the working directory is PARENTFD, FILE's)
 632    access time to ATIME.  ATFLAG controls symbolic-link following, in
 633    the style of openat.  */
 634 int
 635 set_file_atime (int fd, int parentfd, char const *file, struct timespec atime,
 636                 int atflag)
 637 {
 638   struct timespec ts[2];
 639   ts[0] = atime;
 640   ts[1].tv_nsec = UTIME_OMIT;
 641   return fd_utimensat (fd, parentfd, file, ts, atflag);
 642 }
 643
 644 /* A description of a working directory.  */
 645 struct wd
 646 {
 647   /* The directory's name.  */
 648   char const *name;
 649
 650   /* A negative value if no attempt has been made to save the
 651      directory, 0 if it was saved successfully, and a positive errno
 652      value if it was not saved successfully.  */
 653   int err;
 654
 655   /* The saved version of the directory, if ERR == 0.  */
 656   struct saved_cwd saved_cwd;
 657 };
 658
 659 /* A vector of chdir targets.  wd[0] is the initial working directory.  */
 660 static struct wd *wd;
 661
 662 /* The number of working directories in the vector.  */
 663 static size_t wd_count;
 664
 665 /* The allocated size of the vector.  */
 666 static size_t wd_alloc;
 667
 668 int
 669 chdir_count ()
 670 {
 671   if (wd_count == 0)
 672     return wd_count;
 673   return wd_count - 1;
 674 }
 675
 676 /* DIR is the operand of a -C option; add it to vector of chdir targets,
 677    and return the index of its location.  */
 678 int
 679 chdir_arg (char const *dir)
 680 {
 681   if (wd_count == wd_alloc)
 682     {
 683       if (wd_alloc == 0)
 684         {
 685           wd_alloc = 2;
 686           wd = xmalloc (sizeof *wd * wd_alloc);
 687         }
 688       else
 689         wd = x2nrealloc (wd, &wd_alloc, sizeof *wd);
 690
 691       if (! wd_count)
 692         {
 693           wd[wd_count].name = ".";
 694           wd[wd_count].err = -1;
 695           wd_count++;
 696         }
 697     }
 698
 699   /* Optimize the common special case of the working directory,
 700      or the working directory as a prefix.  */
 701   if (dir[0])
 702     {
 703       while (dir[0] == '.' && ISSLASH (dir[1]))
 704         for (dir += 2;  ISSLASH (*dir);  dir++)
 705           continue;
 706       if (! dir[dir[0] == '.'])
 707         return wd_count - 1;
 708     }
 709
 710   wd[wd_count].name = dir;
 711   wd[wd_count].err = -1;
 712   return wd_count++;
 713 }
 714
 715 /* Index of current directory.  */
 716 int chdir_current;
 717
 718 /* Change to directory I.  If I is 0, change to the initial working
 719    directory; otherwise, I must be a value returned by chdir_arg.  */
 720 void
 721 chdir_do (int i)
 722 {
 723   if (chdir_current != i)
 724     {
 725       struct wd *prev = &wd[chdir_current];
 726       struct wd *curr = &wd[i];
 727
 728       if (prev->err < 0)
 729         {
 730           prev->err = 0;
 731           if (save_cwd (&prev->saved_cwd) != 0)
 732             prev->err = errno;
 733           else if (0 <= prev->saved_cwd.desc)
 734             {
 735               /* Make sure we still have at least one descriptor available.  */
 736               int fd1 = prev->saved_cwd.desc;
 737               int fd2 = dup (fd1);
 738               if (0 <= fd2)
 739                 close (fd2);
 740               else if (errno == EMFILE)
 741                 {
 742                   /* Force restore_cwd to use chdir_long.  */
 743                   close (fd1);
 744                   prev->saved_cwd.desc = -1;
 745                   prev->saved_cwd.name = xgetcwd ();
 746                   if (! prev->saved_cwd.name)
 747                     prev->err = errno;
 748                 }
 749               else
 750                 prev->err = errno;
 751             }
 752         }
 753
 754       if (0 <= curr->err)
 755         {
 756           int err = curr->err;
 757           if (err == 0 && restore_cwd (&curr->saved_cwd) != 0)
 758             err = errno;
 759           if (err)
 760             FATAL_ERROR ((0, err, _("Cannot restore working directory")));
 761         }
 762       else
 763         {
 764           if (i && ! ISSLASH (curr->name[0]))
 765             chdir_do (i - 1);
 766           if (chdir (curr->name) != 0)
 767             chdir_fatal (curr->name);
 768         }
 769
 770       chdir_current = i;
 771     }
 772 }
 773 \f
 774 void
 775 close_diag (char const *name)
 776 {
 777   if (ignore_failed_read_option)
 778     close_warn (name);
 779   else
 780     close_error (name);
 781 }
 782
 783 void
 784 open_diag (char const *name)
 785 {
 786   if (ignore_failed_read_option)
 787     open_warn (name);
 788   else
 789     open_error (name);
 790 }
 791
 792 void
 793 read_diag_details (char const *name, off_t offset, size_t size)
 794 {
 795   if (ignore_failed_read_option)
 796     read_warn_details (name, offset, size);
 797   else
 798     read_error_details (name, offset, size);
 799 }
 800
 801 void
 802 readlink_diag (char const *name)
 803 {
 804   if (ignore_failed_read_option)
 805     readlink_warn (name);
 806   else
 807     readlink_error (name);
 808 }
 809
 810 void
 811 savedir_diag (char const *name)
 812 {
 813   if (ignore_failed_read_option)
 814     savedir_warn (name);
 815   else
 816     savedir_error (name);
 817 }
 818
 819 void
 820 seek_diag_details (char const *name, off_t offset)
 821 {
 822   if (ignore_failed_read_option)
 823     seek_warn_details (name, offset);
 824   else
 825     seek_error_details (name, offset);
 826 }
 827
 828 void
 829 stat_diag (char const *name)
 830 {
 831   if (ignore_failed_read_option)
 832     stat_warn (name);
 833   else
 834     stat_error (name);
 835 }
 836
 837 void
 838 file_removed_diag (const char *name, bool top_level,
 839                    void (*diagfn) (char const *name))
 840 {
 841   if (!top_level && errno == ENOENT)
 842     {
 843       WARNOPT (WARN_FILE_REMOVED,
 844                (0, 0, _("%s: File removed before we read it"),
 845                 quotearg_colon (name)));
 846       set_exit_status (TAREXIT_DIFFERS);
 847     }
 848   else
 849     diagfn (name);
 850 }
 851
 852 void
 853 dir_removed_diag (const char *name, bool top_level,
 854                    void (*diagfn) (char const *name))
 855 {
 856   if (!top_level && errno == ENOENT)
 857     {
 858       WARNOPT (WARN_FILE_REMOVED,
 859                (0, 0, _("%s: Directory removed before we read it"),
 860                 quotearg_colon (name)));
 861       set_exit_status (TAREXIT_DIFFERS);
 862     }
 863   else
 864     diagfn (name);
 865 }
 866
 867 void
 868 write_fatal_details (char const *name, ssize_t status, size_t size)
 869 {
 870   write_error_details (name, status, size);
 871   fatal_exit ();
 872 }
 873
 874 /* Fork, aborting if unsuccessful.  */
 875 pid_t
 876 xfork (void)
 877 {
 878   pid_t p = fork ();
 879   if (p == (pid_t) -1)
 880     call_arg_fatal ("fork", _("child process"));
 881   return p;
 882 }
 883
 884 /* Create a pipe, aborting if unsuccessful.  */
 885 void
 886 xpipe (int fd[2])
 887 {
 888   if (pipe (fd) < 0)
 889     call_arg_fatal ("pipe", _("interprocess channel"));
 890 }
 891
 892 /* Return PTR, aligned upward to the next multiple of ALIGNMENT.
 893    ALIGNMENT must be nonzero.  The caller must arrange for ((char *)
 894    PTR) through ((char *) PTR + ALIGNMENT - 1) to be addressable
 895    locations.  */
 896
 897 static inline void *
 898 ptr_align (void *ptr, size_t alignment)
 899 {
 900   char *p0 = ptr;
 901   char *p1 = p0 + alignment - 1;
 902   return p1 - (size_t) p1 % alignment;
 903 }
 904
 905 /* Return the address of a page-aligned buffer of at least SIZE bytes.
 906    The caller should free *PTR when done with the buffer.  */
 907
 908 void *
 909 page_aligned_alloc (void **ptr, size_t size)
 910 {
 911   size_t alignment = getpagesize ();
 912   size_t size1 = size + alignment;
 913   if (size1 < size)
 914     xalloc_die ();
 915   *ptr = xmalloc (size1);
 916   return ptr_align (*ptr, alignment);
 917 }
 918
 919 \f
 920
 921 struct namebuf
 922 {
 923   char *buffer;         /* directory, `/', and directory member */
 924   size_t buffer_size;   /* allocated size of name_buffer */
 925   size_t dir_length;    /* length of directory part in buffer */
 926 };
 927
 928 namebuf_t
 929 namebuf_create (const char *dir)
 930 {
 931   namebuf_t buf = xmalloc (sizeof (*buf));
 932   buf->buffer_size = strlen (dir) + 2;
 933   buf->buffer = xmalloc (buf->buffer_size);
 934   strcpy (buf->buffer, dir);
 935   buf->dir_length = strlen (buf->buffer);
 936   if (!ISSLASH (buf->buffer[buf->dir_length - 1]))
 937     buf->buffer[buf->dir_length++] = DIRECTORY_SEPARATOR;
 938   return buf;
 939 }
 940
 941 void
 942 namebuf_free (namebuf_t buf)
 943 {
 944   free (buf->buffer);
 945   free (buf);
 946 }
 947
 948 char *
 949 namebuf_name (namebuf_t buf, const char *name)
 950 {
 951   size_t len = strlen (name);
 952   while (buf->dir_length + len + 1 >= buf->buffer_size)
 953     buf->buffer = x2realloc (buf->buffer, &buf->buffer_size);
 954   strcpy (buf->buffer + buf->dir_length, name);
 955   return buf->buffer;
 956 }