lib/backupfile.c

   1 /* backupfile.c -- make Emacs style backup file names
   2    Copyright (C) 1990,1991,1992,1993,1995,1997 Free Software Foundation, Inc.
   3
   4    This program is free software; you can redistribute it and/or modify
   5    it under the terms of the GNU General Public License as published by
   6    the Free Software Foundation; either version 2, or (at your option)
   7    any later version.
   8
   9    This program is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12    GNU General Public License for more details.
  13
  14    You should have received a copy of the GNU General Public License
  15    along with this program; see the file COPYING.
  16    If not, write to the Free Software Foundation,
  17    59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
  18
  19 /* Written by David MacKenzie <djm@gnu.ai.mit.edu>.
  20    Some algorithms adapted from GNU Emacs. */
  21
  22 #if HAVE_CONFIG_H
  23 # include <config.h>
  24 #endif
  25
  26 #include <argmatch.h>
  27 #include <backupfile.h>
  28
  29 #include <stdio.h>
  30 #include <sys/types.h>
  31 #if HAVE_STRING_H
  32 # include <string.h>
  33 #else
  34 # include <strings.h>
  35 #endif
  36
  37 #if HAVE_DIRENT_H
  38 # include <dirent.h>
  39 # define NLENGTH(direct) strlen ((direct)->d_name)
  40 #else
  41 # define dirent direct
  42 # define NLENGTH(direct) ((size_t) (direct)->d_namlen)
  43 # if HAVE_SYS_NDIR_H
  44 #  include <sys/ndir.h>
  45 # endif
  46 # if HAVE_SYS_DIR_H
  47 #  include <sys/dir.h>
  48 # endif
  49 # if HAVE_NDIR_H
  50 #  include <ndir.h>
  51 # endif
  52 #endif
  53
  54 #if CLOSEDIR_VOID
  55 /* Fake a return value. */
  56 # define CLOSEDIR(d) (closedir (d), 0)
  57 #else
  58 # define CLOSEDIR(d) closedir (d)
  59 #endif
  60
  61 #if STDC_HEADERS
  62 # include <stdlib.h>
  63 #else
  64 char *malloc ();
  65 #endif
  66
  67 #if HAVE_DIRENT_H || HAVE_NDIR_H || HAVE_SYS_DIR_H || HAVE_SYS_NDIR_H
  68 # define HAVE_DIR 1
  69 #else
  70 # define HAVE_DIR 0
  71 #endif
  72
  73 #if HAVE_LIMITS_H
  74 # include <limits.h>
  75 #endif
  76 #ifndef CHAR_BIT
  77 #define CHAR_BIT 8
  78 #endif
  79 /* Upper bound on the string length of an integer converted to string.
  80    302 / 1000 is ceil (log10 (2.0)).  Subtract 1 for the sign bit;
  81    add 1 for integer division truncation; add 1 more for a minus sign.  */
  82 #define INT_STRLEN_BOUND(t) ((sizeof (t) * CHAR_BIT - 1) * 302 / 1000 + 2)
  83
  84 /* ISDIGIT differs from isdigit, as follows:
  85    - Its arg may be any int or unsigned int; it need not be an unsigned char.
  86    - It's guaranteed to evaluate its argument exactly once.
  87    - It's typically faster.
  88    Posix 1003.2-1992 section 2.5.2.1 page 50 lines 1556-1558 says that
  89    only '0' through '9' are digits.  Prefer ISDIGIT to isdigit unless
  90    it's important to use the locale's definition of `digit' even when the
  91    host does not conform to Posix.  */
  92 #define ISDIGIT(c) ((unsigned) (c) - '0' <= 9)
  93
  94 #if D_INO_IN_DIRENT
  95 # define REAL_DIR_ENTRY(dp) ((dp)->d_ino != 0)
  96 #else
  97 # define REAL_DIR_ENTRY(dp) 1
  98 #endif
  99
 100 /* Which type of backup file names are generated. */
 101 enum backup_type backup_type = none;
 102
 103 /* The extension added to file names to produce a simple (as opposed
 104    to numbered) backup file name. */
 105 const char *simple_backup_suffix = ".orig";
 106
 107 static int max_backup_version __BACKUPFILE_P ((const char *, const char *));
 108 static int version_number __BACKUPFILE_P ((const char *, const char *, size_t));
 109
 110 /* Return the name of the new backup file for file FILE,
 111    allocated with malloc.  Return 0 if out of memory.
 112    FILE must not end with a '/' unless it is the root directory.
 113    Do not call this function if backup_type == none. */
 114
 115 char *
 116 find_backup_file_name (file)
 117      const char *file;
 118 {
 119   size_t backup_suffix_size_max;
 120   size_t file_len = strlen (file);
 121   size_t numbered_suffix_size_max = INT_STRLEN_BOUND (int) + 4;
 122   char *s;
 123   const char *suffix = simple_backup_suffix;
 124
 125   /* Allow room for simple or `.~N~' backups.  */
 126   backup_suffix_size_max = strlen (simple_backup_suffix) + 1;
 127   if (HAVE_DIR && backup_suffix_size_max < numbered_suffix_size_max)
 128     backup_suffix_size_max = numbered_suffix_size_max;
 129
 130   s = malloc (file_len + backup_suffix_size_max + numbered_suffix_size_max);
 131   if (s)
 132     {
 133       strcpy (s, file);
 134
 135 #if HAVE_DIR
 136       if (backup_type != simple)
 137         {
 138           int highest_backup;
 139           size_t dir_len = base_name (s) - s;
 140
 141           strcpy (s + dir_len, ".");
 142           highest_backup = max_backup_version (file + dir_len, s);
 143           if (! (backup_type == numbered_existing && highest_backup == 0))
 144             {
 145               char *numbered_suffix = s + (file_len + backup_suffix_size_max);
 146               sprintf (numbered_suffix, ".~%d~", highest_backup + 1);
 147               suffix = numbered_suffix;
 148             }
 149           strcpy (s, file);
 150         }
 151 #endif /* HAVE_DIR */
 152
 153       addext (s, suffix, '~');
 154     }
 155   return s;
 156 }
 157
 158 #if HAVE_DIR
 159
 160 /* Return the number of the highest-numbered backup file for file
 161    FILE in directory DIR.  If there are no numbered backups
 162    of FILE in DIR, or an error occurs reading DIR, return 0.
 163    */
 164
 165 static int
 166 max_backup_version (file, dir)
 167      const char *file;
 168      const char *dir;
 169 {
 170   DIR *dirp;
 171   struct dirent *dp;
 172   int highest_version;
 173   int this_version;
 174   size_t file_name_length;
 175
 176   dirp = opendir (dir);
 177   if (!dirp)
 178     return 0;
 179
 180   highest_version = 0;
 181   file_name_length = strlen (file);
 182
 183   while ((dp = readdir (dirp)) != 0)
 184     {
 185       if (!REAL_DIR_ENTRY (dp) || NLENGTH (dp) < file_name_length + 4)
 186         continue;
 187
 188       this_version = version_number (file, dp->d_name, file_name_length);
 189       if (this_version > highest_version)
 190         highest_version = this_version;
 191     }
 192   if (CLOSEDIR (dirp))
 193     return 0;
 194   return highest_version;
 195 }
 196
 197 /* If BACKUP is a numbered backup of BASE, return its version number;
 198    otherwise return 0.  BASE_LENGTH is the length of BASE.
 199    */
 200
 201 static int
 202 version_number (base, backup, base_length)
 203      const char *base;
 204      const char *backup;
 205      size_t base_length;
 206 {
 207   int version;
 208   const char *p;
 209
 210   version = 0;
 211   if (strncmp (base, backup, base_length) == 0
 212       && backup[base_length] == '.'
 213       && backup[base_length + 1] == '~')
 214     {
 215       for (p = &backup[base_length + 2]; ISDIGIT (*p); ++p)
 216         version = version * 10 + *p - '0';
 217       if (p[0] != '~' || p[1])
 218         version = 0;
 219     }
 220   return version;
 221 }
 222 #endif /* HAVE_DIR */
 223
 224 static const char * const backup_args[] =
 225 {
 226   "never", "simple", "nil", "existing", "t", "numbered", 0
 227 };
 228
 229 static const enum backup_type backup_types[] =
 230 {
 231   simple, simple, numbered_existing, numbered_existing, numbered, numbered
 232 };
 233
 234 /* Return the type of backup indicated by VERSION.
 235    Unique abbreviations are accepted. */
 236
 237 enum backup_type
 238 get_version (version)
 239      const char *version;
 240 {
 241   int i;
 242
 243   if (version == 0 || *version == 0)
 244     return numbered_existing;
 245   i = argmatch (version, backup_args);
 246   if (i < 0)
 247     {
 248       invalid_arg ("version control type", version, i);
 249       exit (2);
 250     }
 251   return backup_types[i];
 252 }