1 /* backupfile.c -- make Emacs style backup file names
2 Copyright (C) 1990-1997, 1998 Free Software Foundation, Inc.
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)
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.
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. */
19 /* Written by David MacKenzie <djm@gnu.ai.mit.edu>.
20 Some algorithms adapted from GNU Emacs. */
27 #include <backupfile.h>
30 #include <sys/types.h>
39 # define NLENGTH(direct) strlen ((direct)->d_name)
41 # define dirent direct
42 # define NLENGTH(direct) ((size_t) (direct)->d_namlen)
44 # include <sys/ndir.h>
55 /* Fake a return value. */
56 # define CLOSEDIR(d) (closedir (d), 0)
58 # define CLOSEDIR(d) closedir (d)
67 #if HAVE_DIRENT_H || HAVE_NDIR_H || HAVE_SYS_DIR_H || HAVE_SYS_NDIR_H
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)
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)
95 # define REAL_DIR_ENTRY(dp) ((dp)->d_ino != 0)
97 # define REAL_DIR_ENTRY(dp) 1
100 /* The following test is to work around the gross typo in
101 systems like Sony NEWS-OS Release 4.0C, whereby EXIT_FAILURE
102 is defined to 0, not 1. */
105 # define EXIT_FAILURE 1
108 /* The extension added to file names to produce a simple (as opposed
109 to numbered) backup file name. */
110 const char *simple_backup_suffix = "~";
112 static int max_backup_version PARAMS ((const char *, const char *));
113 static int version_number PARAMS ((const char *, const char *, size_t));
115 /* Return the name of the new backup file for file FILE,
116 allocated with malloc. Return 0 if out of memory.
117 FILE must not end with a '/' unless it is the root directory.
118 Do not call this function if backup_type == none. */
121 find_backup_file_name (const char *file, enum backup_type backup_type)
123 size_t backup_suffix_size_max;
124 size_t file_len = strlen (file);
125 size_t numbered_suffix_size_max = INT_STRLEN_BOUND (int) + 4;
127 const char *suffix = simple_backup_suffix;
129 /* Allow room for simple or `.~N~' backups. */
130 backup_suffix_size_max = strlen (simple_backup_suffix) + 1;
131 if (HAVE_DIR && backup_suffix_size_max < numbered_suffix_size_max)
132 backup_suffix_size_max = numbered_suffix_size_max;
134 s = malloc (file_len + backup_suffix_size_max + numbered_suffix_size_max);
140 if (backup_type != simple)
143 size_t dir_len = base_name (s) - s;
145 strcpy (s + dir_len, ".");
146 highest_backup = max_backup_version (file + dir_len, s);
147 if (! (backup_type == numbered_existing && highest_backup == 0))
149 char *numbered_suffix = s + (file_len + backup_suffix_size_max);
150 sprintf (numbered_suffix, ".~%d~", highest_backup + 1);
151 suffix = numbered_suffix;
155 #endif /* HAVE_DIR */
157 addext (s, suffix, '~');
164 /* Return the number of the highest-numbered backup file for file
165 FILE in directory DIR. If there are no numbered backups
166 of FILE in DIR, or an error occurs reading DIR, return 0.
170 max_backup_version (const char *file, const char *dir)
176 size_t file_name_length;
178 dirp = opendir (dir);
183 file_name_length = strlen (file);
185 while ((dp = readdir (dirp)) != 0)
187 if (!REAL_DIR_ENTRY (dp) || NLENGTH (dp) < file_name_length + 4)
190 this_version = version_number (file, dp->d_name, file_name_length);
191 if (this_version > highest_version)
192 highest_version = this_version;
196 return highest_version;
199 /* If BACKUP is a numbered backup of BASE, return its version number;
200 otherwise return 0. BASE_LENGTH is the length of BASE.
204 version_number (const char *base, const char *backup, size_t base_length)
210 if (strncmp (base, backup, base_length) == 0
211 && backup[base_length] == '.'
212 && backup[base_length + 1] == '~')
214 for (p = &backup[base_length + 2]; ISDIGIT (*p); ++p)
215 version = version * 10 + *p - '0';
216 if (p[0] != '~' || p[1])
221 #endif /* HAVE_DIR */
223 static const char *const backup_args[] =
225 "never", "simple", "nil", "existing", "t", "numbered", 0
228 static const enum backup_type backup_types[] =
230 simple, simple, numbered_existing, numbered_existing, numbered, numbered
233 /* Return the type of backup indicated by VERSION.
234 Unique abbreviations are accepted. */
237 get_version (const char *version)
241 if (version == 0 || *version == 0)
242 return numbered_existing;
243 i = argmatch (version, backup_args);
246 invalid_arg ("version control type", version, i);
249 return backup_types[i];