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 extension added to file names to produce a simple (as opposed
101 to numbered) backup file name. */
102 const char *simple_backup_suffix = "~";
104 static int max_backup_version PARAMS ((const char *, const char *));
105 static int version_number PARAMS ((const char *, const char *, size_t));
107 /* Return the name of the new backup file for file FILE,
108 allocated with malloc. Return 0 if out of memory.
109 FILE must not end with a '/' unless it is the root directory.
110 Do not call this function if backup_type == none. */
113 find_backup_file_name (const char *file, enum backup_type backup_type)
115 size_t backup_suffix_size_max;
116 size_t file_len = strlen (file);
117 size_t numbered_suffix_size_max = INT_STRLEN_BOUND (int) + 4;
119 const char *suffix = simple_backup_suffix;
121 /* Allow room for simple or `.~N~' backups. */
122 backup_suffix_size_max = strlen (simple_backup_suffix) + 1;
123 if (HAVE_DIR && backup_suffix_size_max < numbered_suffix_size_max)
124 backup_suffix_size_max = numbered_suffix_size_max;
126 s = malloc (file_len + backup_suffix_size_max + numbered_suffix_size_max);
132 if (backup_type != simple)
135 size_t dir_len = base_name (s) - s;
137 strcpy (s + dir_len, ".");
138 highest_backup = max_backup_version (file + dir_len, s);
139 if (! (backup_type == numbered_existing && highest_backup == 0))
141 char *numbered_suffix = s + (file_len + backup_suffix_size_max);
142 sprintf (numbered_suffix, ".~%d~", highest_backup + 1);
143 suffix = numbered_suffix;
147 #endif /* HAVE_DIR */
149 addext (s, suffix, '~');
156 /* Return the number of the highest-numbered backup file for file
157 FILE in directory DIR. If there are no numbered backups
158 of FILE in DIR, or an error occurs reading DIR, return 0.
162 max_backup_version (const char *file, const char *dir)
168 size_t file_name_length;
170 dirp = opendir (dir);
175 file_name_length = strlen (file);
177 while ((dp = readdir (dirp)) != 0)
179 if (!REAL_DIR_ENTRY (dp) || NLENGTH (dp) < file_name_length + 4)
182 this_version = version_number (file, dp->d_name, file_name_length);
183 if (this_version > highest_version)
184 highest_version = this_version;
188 return highest_version;
191 /* If BACKUP is a numbered backup of BASE, return its version number;
192 otherwise return 0. BASE_LENGTH is the length of BASE.
196 version_number (const char *base, const char *backup, size_t base_length)
202 if (strncmp (base, backup, base_length) == 0
203 && backup[base_length] == '.'
204 && backup[base_length + 1] == '~')
206 for (p = &backup[base_length + 2]; ISDIGIT (*p); ++p)
207 version = version * 10 + *p - '0';
208 if (p[0] != '~' || p[1])
213 #endif /* HAVE_DIR */
215 static const char * const backup_args[] =
217 "never", "simple", "nil", "existing", "t", "numbered", 0
220 static const enum backup_type backup_types[] =
222 simple, simple, numbered_existing, numbered_existing, numbered, numbered
225 /* Return the type of backup indicated by VERSION.
226 Unique abbreviations are accepted. */
229 get_version (const char *version)
233 if (version == 0 || *version == 0)
234 return numbered_existing;
235 i = argmatch (version, backup_args);
238 invalid_arg ("version control type", version, i);
241 return backup_types[i];