lib/backupfile.c

   1 /* backupfile.c -- make Emacs style backup file names
   2    Copyright (C) 1990-1997, 1998, 1999 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 #ifndef HAVE_DECL_GETENV
  68 char *getenv ();
  69 #endif
  70
  71 char *base_name PARAMS ((char const *));
  72
  73 #if HAVE_DIRENT_H || HAVE_NDIR_H || HAVE_SYS_DIR_H || HAVE_SYS_NDIR_H
  74 # define HAVE_DIR 1
  75 #else
  76 # define HAVE_DIR 0
  77 #endif
  78
  79 #if HAVE_LIMITS_H
  80 # include <limits.h>
  81 #endif
  82 #ifndef CHAR_BIT
  83 # define CHAR_BIT 8
  84 #endif
  85 /* Upper bound on the string length of an integer converted to string.
  86    302 / 1000 is ceil (log10 (2.0)).  Subtract 1 for the sign bit;
  87    add 1 for integer division truncation; add 1 more for a minus sign.  */
  88 #define INT_STRLEN_BOUND(t) ((sizeof (t) * CHAR_BIT - 1) * 302 / 1000 + 2)
  89
  90 /* ISDIGIT differs from isdigit, as follows:
  91    - Its arg may be any int or unsigned int; it need not be an unsigned char.
  92    - It's guaranteed to evaluate its argument exactly once.
  93    - It's typically faster.
  94    Posix 1003.2-1992 section 2.5.2.1 page 50 lines 1556-1558 says that
  95    only '0' through '9' are digits.  Prefer ISDIGIT to isdigit unless
  96    it's important to use the locale's definition of `digit' even when the
  97    host does not conform to Posix.  */
  98 #define ISDIGIT(c) ((unsigned) (c) - '0' <= 9)
  99
 100 #if D_INO_IN_DIRENT
 101 # define REAL_DIR_ENTRY(dp) ((dp)->d_ino != 0)
 102 #else
 103 # define REAL_DIR_ENTRY(dp) 1
 104 #endif
 105
 106 /* The extension added to file names to produce a simple (as opposed
 107    to numbered) backup file name. */
 108 const char *simple_backup_suffix = "~";
 109
 110 static int max_backup_version PARAMS ((const char *, const char *));
 111 static int version_number PARAMS ((const char *, const char *, size_t));
 112
 113 /* Return the name of the new backup file for file FILE,
 114    allocated with malloc.  Return 0 if out of memory.
 115    FILE must not end with a '/' unless it is the root directory.
 116    Do not call this function if backup_type == none. */
 117
 118 char *
 119 find_backup_file_name (const char *file, enum backup_type backup_type)
 120 {
 121   size_t backup_suffix_size_max;
 122   size_t file_len = strlen (file);
 123   size_t numbered_suffix_size_max = INT_STRLEN_BOUND (int) + 4;
 124   char *s;
 125   const char *suffix = simple_backup_suffix;
 126
 127   /* Allow room for simple or `.~N~' backups.  */
 128   backup_suffix_size_max = strlen (simple_backup_suffix) + 1;
 129   if (HAVE_DIR && backup_suffix_size_max < numbered_suffix_size_max)
 130     backup_suffix_size_max = numbered_suffix_size_max;
 131
 132   s = malloc (file_len + backup_suffix_size_max + numbered_suffix_size_max);
 133   if (s)
 134     {
 135       strcpy (s, file);
 136
 137 #if HAVE_DIR
 138       if (backup_type != simple)
 139         {
 140           int highest_backup;
 141           size_t dir_len = base_name (s) - s;
 142
 143           strcpy (s + dir_len, ".");
 144           highest_backup = max_backup_version (file + dir_len, s);
 145           if (! (backup_type == numbered_existing && highest_backup == 0))
 146             {
 147               char *numbered_suffix = s + (file_len + backup_suffix_size_max);
 148               sprintf (numbered_suffix, ".~%d~", highest_backup + 1);
 149               suffix = numbered_suffix;
 150             }
 151           strcpy (s, file);
 152         }
 153 #endif /* HAVE_DIR */
 154
 155       addext (s, suffix, '~');
 156     }
 157   return s;
 158 }
 159
 160 #if HAVE_DIR
 161
 162 /* Return the number of the highest-numbered backup file for file
 163    FILE in directory DIR.  If there are no numbered backups
 164    of FILE in DIR, or an error occurs reading DIR, return 0.
 165    */
 166
 167 static int
 168 max_backup_version (const char *file, 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 (const char *base, const char *backup, size_t base_length)
 203 {
 204   int version;
 205   const char *p;
 206
 207   version = 0;
 208   if (strncmp (base, backup, base_length) == 0
 209       && backup[base_length] == '.'
 210       && backup[base_length + 1] == '~')
 211     {
 212       for (p = &backup[base_length + 2]; ISDIGIT (*p); ++p)
 213         version = version * 10 + *p - '0';
 214       if (p[0] != '~' || p[1])
 215         version = 0;
 216     }
 217   return version;
 218 }
 219 #endif /* HAVE_DIR */
 220
 221 static const char * const backup_args[] =
 222 {
 223   /* In a series of synonyms, present the most meaning full first, so
 224      that argmatch_valid be more readable. */
 225   "none", "off",
 226   "simple", "never",
 227   "existing", "nil",
 228   "numbered", "t",
 229   0
 230 };
 231
 232 static const enum backup_type backup_types[] =
 233 {
 234   none, none,
 235   simple, simple,
 236   numbered_existing, numbered_existing,
 237   numbered, numbered
 238 };
 239
 240 /* Return the type of backup specified by VERSION.
 241    If VERSION is NULL or the empty string, return numbered_existing.
 242    If VERSION is invalid or ambiguous, fail with a diagnostic appropriate
 243    for the specified CONTEXT.  Unambiguous abbreviations are accepted.  */
 244
 245 enum backup_type
 246 get_version (const char *context, const char *version)
 247 {
 248   if (version == 0 || *version == 0)
 249     return numbered_existing;
 250   else
 251     return XARGMATCH (context, version, backup_args, backup_types);
 252 }
 253
 254
 255 /* Return the type of backup specified by VERSION.
 256    If VERSION is NULL, use the value of the envvar VERSION_CONTROL.
 257    If the specified string is invalid or ambiguous, fail with a diagnostic
 258    appropriate for the specified CONTEXT.
 259    Unambiguous abbreviations are accepted.  */
 260
 261 enum backup_type
 262 xget_version (const char *context, const char *version)
 263 {
 264   if (version && *version)
 265     return get_version (context, version);
 266   else
 267     return get_version ("$VERSION_CONTROL", getenv ("VERSION_CONTROL"));
 268 }