contrib/tar/lib/backupfile.c

   1 /* backupfile.c -- make Emacs style backup file names
   2    Copyright 1990,91,92,93,94,95,96,97,98,99,2000, 2001 Free Software
   3    Foundation, Inc.
   4
   5    This program is free software; you can redistribute it and/or modify
   6    it under the terms of the GNU General Public License as published by
   7    the Free Software Foundation; either version 2, or (at your option)
   8    any later version.
   9
  10    This program is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13    GNU General Public License for more details.
  14
  15    You should have received a copy of the GNU General Public License
  16    along with this program; see the file COPYING.
  17    If not, write to the Free Software Foundation,
  18    59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
  19
  20 /* Written by David MacKenzie <djm@gnu.ai.mit.edu>.
  21    Some algorithms adapted from GNU Emacs. */
  22
  23 #if HAVE_CONFIG_H
  24 # include <config.h>
  25 #endif
  26
  27 #include <stdio.h>
  28 #include <sys/types.h>
  29 #if HAVE_STRING_H
  30 # include <string.h>
  31 #else
  32 # include <strings.h>
  33 #endif
  34
  35 #if HAVE_DIRENT_H
  36 # include <dirent.h>
  37 # define NLENGTH(direct) strlen ((direct)->d_name)
  38 #else
  39 # define dirent direct
  40 # define NLENGTH(direct) ((size_t) (direct)->d_namlen)
  41 # if HAVE_SYS_NDIR_H
  42 #  include <sys/ndir.h>
  43 # endif
  44 # if HAVE_SYS_DIR_H
  45 #  include <sys/dir.h>
  46 # endif
  47 # if HAVE_NDIR_H
  48 #  include <ndir.h>
  49 # endif
  50 #endif
  51
  52 #if CLOSEDIR_VOID
  53 /* Fake a return value. */
  54 # define CLOSEDIR(d) (closedir (d), 0)
  55 #else
  56 # define CLOSEDIR(d) closedir (d)
  57 #endif
  58
  59 #if HAVE_STDLIB_H
  60 # include <stdlib.h>
  61 #endif
  62
  63 #ifndef HAVE_DECL_GETENV
  64 "this configure-time declaration test was not run"
  65 #endif
  66 #if !HAVE_DECL_GETENV
  67 char *getenv ();
  68 #endif
  69
  70 #ifndef HAVE_DECL_MALLOC
  71 "this configure-time declaration test was not run"
  72 #endif
  73 #if !HAVE_DECL_MALLOC
  74 char *malloc ();
  75 #endif
  76
  77 #if HAVE_DIRENT_H || HAVE_NDIR_H || HAVE_SYS_DIR_H || HAVE_SYS_NDIR_H
  78 # define HAVE_DIR 1
  79 #else
  80 # define HAVE_DIR 0
  81 #endif
  82
  83 #if HAVE_LIMITS_H
  84 # include <limits.h>
  85 #endif
  86 #ifndef CHAR_BIT
  87 # define CHAR_BIT 8
  88 #endif
  89 /* Upper bound on the string length of an integer converted to string.
  90    302 / 1000 is ceil (log10 (2.0)).  Subtract 1 for the sign bit;
  91    add 1 for integer division truncation; add 1 more for a minus sign.  */
  92 #define INT_STRLEN_BOUND(t) ((sizeof (t) * CHAR_BIT - 1) * 302 / 1000 + 2)
  93
  94 /* ISDIGIT differs from isdigit, as follows:
  95    - Its arg may be any int or unsigned int; it need not be an unsigned char.
  96    - It's guaranteed to evaluate its argument exactly once.
  97    - It's typically faster.
  98    Posix 1003.2-1992 section 2.5.2.1 page 50 lines 1556-1558 says that
  99    only '0' through '9' are digits.  Prefer ISDIGIT to isdigit unless
 100    it's important to use the locale's definition of `digit' even when the
 101    host does not conform to Posix.  */
 102 #define ISDIGIT(c) ((unsigned) (c) - '0' <= 9)
 103
 104 #if D_INO_IN_DIRENT
 105 # define REAL_DIR_ENTRY(dp) ((dp)->d_ino != 0)
 106 #else
 107 # define REAL_DIR_ENTRY(dp) 1
 108 #endif
 109
 110 #include "argmatch.h"
 111 #include "backupfile.h"
 112 #include "dirname.h"
 113
 114 /* The extension added to file names to produce a simple (as opposed
 115    to numbered) backup file name. */
 116 const char *simple_backup_suffix = "~";
 117
 118 static int max_backup_version PARAMS ((const char *, const char *));
 119 static int version_number PARAMS ((const char *, const char *, size_t));
 120
 121 /* Return the name of the new backup file for file FILE,
 122    allocated with malloc.  Return 0 if out of memory.
 123    FILE must not end with a '/' unless it is the root directory.
 124    Do not call this function if backup_type == none. */
 125
 126 char *
 127 find_backup_file_name (const char *file, enum backup_type backup_type)
 128 {
 129   size_t backup_suffix_size_max;
 130   size_t file_len = strlen (file);
 131   size_t numbered_suffix_size_max = INT_STRLEN_BOUND (int) + 4;
 132   char *s;
 133   const char *suffix = simple_backup_suffix;
 134
 135   /* Allow room for simple or `.~N~' backups.  */
 136   backup_suffix_size_max = strlen (simple_backup_suffix) + 1;
 137   if (HAVE_DIR && backup_suffix_size_max < numbered_suffix_size_max)
 138     backup_suffix_size_max = numbered_suffix_size_max;
 139
 140   s = malloc (file_len + 1
 141               + backup_suffix_size_max + numbered_suffix_size_max);
 142   if (s)
 143     {
 144 #if HAVE_DIR
 145       if (backup_type != simple)
 146         {
 147           int highest_backup;
 148           size_t dirlen = dir_len (file);
 149
 150           memcpy (s, file, dirlen);
 151           if (dirlen == FILESYSTEM_PREFIX_LEN (file))
 152             s[dirlen++] = '.';
 153           s[dirlen] = '\0';
 154           highest_backup = max_backup_version (base_name (file), s);
 155           if (! (backup_type == numbered_existing && highest_backup == 0))
 156             {
 157               char *numbered_suffix = s + (file_len + backup_suffix_size_max);
 158               sprintf (numbered_suffix, ".~%d~", highest_backup + 1);
 159               suffix = numbered_suffix;
 160             }
 161         }
 162 #endif /* HAVE_DIR */
 163
 164       strcpy (s, file);
 165       addext (s, suffix, '~');
 166     }
 167   return s;
 168 }
 169
 170 #if HAVE_DIR
 171
 172 /* Return the number of the highest-numbered backup file for file
 173    FILE in directory DIR.  If there are no numbered backups
 174    of FILE in DIR, or an error occurs reading DIR, return 0.
 175    */
 176
 177 static int
 178 max_backup_version (const char *file, const char *dir)
 179 {
 180   DIR *dirp;
 181   struct dirent *dp;
 182   int highest_version;
 183   int this_version;
 184   size_t file_name_length;
 185
 186   dirp = opendir (dir);
 187   if (!dirp)
 188     return 0;
 189
 190   highest_version = 0;
 191   file_name_length = base_len (file);
 192
 193   while ((dp = readdir (dirp)) != 0)
 194     {
 195       if (!REAL_DIR_ENTRY (dp) || NLENGTH (dp) < file_name_length + 4)
 196         continue;
 197
 198       this_version = version_number (file, dp->d_name, file_name_length);
 199       if (this_version > highest_version)
 200         highest_version = this_version;
 201     }
 202   if (CLOSEDIR (dirp))
 203     return 0;
 204   return highest_version;
 205 }
 206
 207 /* If BACKUP is a numbered backup of BASE, return its version number;
 208    otherwise return 0.  BASE_LENGTH is the length of BASE.
 209    */
 210
 211 static int
 212 version_number (const char *base, const char *backup, size_t base_length)
 213 {
 214   int version;
 215   const char *p;
 216
 217   version = 0;
 218   if (strncmp (base, backup, base_length) == 0
 219       && backup[base_length] == '.'
 220       && backup[base_length + 1] == '~')
 221     {
 222       for (p = &backup[base_length + 2]; ISDIGIT (*p); ++p)
 223         version = version * 10 + *p - '0';
 224       if (p[0] != '~' || p[1])
 225         version = 0;
 226     }
 227   return version;
 228 }
 229 #endif /* HAVE_DIR */
 230
 231 static const char * const backup_args[] =
 232 {
 233   /* In a series of synonyms, present the most meaning full first, so
 234      that argmatch_valid be more readable. */
 235   "none", "off",
 236   "simple", "never",
 237   "existing", "nil",
 238   "numbered", "t",
 239   0
 240 };
 241
 242 static const enum backup_type backup_types[] =
 243 {
 244   none, none,
 245   simple, simple,
 246   numbered_existing, numbered_existing,
 247   numbered, numbered
 248 };
 249
 250 /* Return the type of backup specified by VERSION.
 251    If VERSION is NULL or the empty string, return numbered_existing.
 252    If VERSION is invalid or ambiguous, fail with a diagnostic appropriate
 253    for the specified CONTEXT.  Unambiguous abbreviations are accepted.  */
 254
 255 enum backup_type
 256 get_version (const char *context, const char *version)
 257 {
 258   if (version == 0 || *version == 0)
 259     return numbered_existing;
 260   else
 261     return XARGMATCH (context, version, backup_args, backup_types);
 262 }
 263
 264
 265 /* Return the type of backup specified by VERSION.
 266    If VERSION is NULL, use the value of the envvar VERSION_CONTROL.
 267    If the specified string is invalid or ambiguous, fail with a diagnostic
 268    appropriate for the specified CONTEXT.
 269    Unambiguous abbreviations are accepted.  */
 270
 271 enum backup_type
 272 xget_version (const char *context, const char *version)
 273 {
 274   if (version && *version)
 275     return get_version (context, version);
 276   else
 277     return get_version ("$VERSION_CONTROL", getenv ("VERSION_CONTROL"));
 278 }