1 /* backupfile.c -- make Emacs style backup file names
2 Copyright (C) 1990-2003, 2005-2006, 2012, 2015 Free Software
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 3 of the License, or
8 (at your option) any later version.
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.
15 You should have received a copy of the GNU General Public License
16 along with this program. If not, see <http://www.gnu.org/licenses/>. */
18 /* Written by David MacKenzie <djm@gnu.ai.mit.edu>.
19 Some algorithms adapted from GNU Emacs. */
24 #include "backupfile.h"
27 #include <sys/types.h>
50 /* Upper bound on the string length of an integer converted to string.
51 302 / 1000 is ceil (log10 (2.0)). Subtract 1 for the sign bit;
52 add 1 for integer division truncation; add 1 more for a minus sign. */
53 #define INT_STRLEN_BOUND(t) ((sizeof (t) * CHAR_BIT - 1) * 302 / 1000 + 2)
55 /* ISDIGIT differs from isdigit, as follows:
56 - Its arg may be any int or unsigned int; it need not be an unsigned char.
57 - It's guaranteed to evaluate its argument exactly once.
58 - It's typically faster.
59 Posix 1003.2-1992 section 2.5.2.1 page 50 lines 1556-1558 says that
60 only '0' through '9' are digits. Prefer ISDIGIT to isdigit unless
61 it's important to use the locale's definition of 'digit' even when the
62 host does not conform to Posix. */
63 #define ISDIGIT(c) ((unsigned) (c) - '0' <= 9)
66 # define REAL_DIR_ENTRY(dp) ((dp)->d_ino != 0)
68 # define REAL_DIR_ENTRY(dp) 1
71 /* The extension added to file names to produce a simple (as opposed
72 to numbered) backup file name. */
73 const char *simple_backup_suffix = "~";
76 static int max_backup_version (const char *, const char *);
77 static int version_number (const char *, const char *, size_t);
80 /* Return the name of the new backup file for file FILE,
81 allocated with malloc. Return 0 if out of memory.
82 FILE must not end with a '/' unless it is the root directory.
83 Do not call this function if backup_type == none. */
86 find_backup_file_name (const char *file, enum backup_type backup_type)
88 size_t backup_suffix_size_max;
89 size_t file_len = strlen (file);
90 size_t numbered_suffix_size_max = INT_STRLEN_BOUND (int) + 4;
92 const char *suffix = simple_backup_suffix;
94 /* Allow room for simple or '.~N~' backups. */
95 backup_suffix_size_max = strlen (simple_backup_suffix) + 1;
96 if (HAVE_DIR && backup_suffix_size_max < numbered_suffix_size_max)
97 backup_suffix_size_max = numbered_suffix_size_max;
99 s = (char *) malloc (file_len + backup_suffix_size_max
100 + numbered_suffix_size_max);
106 if (backup_type != simple)
109 size_t dir_len = basename (s) - s;
111 strcpy (s + dir_len, ".");
112 highest_backup = max_backup_version (file + dir_len, s);
113 if (! (backup_type == numbered_existing && highest_backup == 0))
115 char *numbered_suffix = s + (file_len + backup_suffix_size_max);
116 sprintf (numbered_suffix, ".~%d~", highest_backup + 1);
117 suffix = numbered_suffix;
121 #endif /* HAVE_DIR */
123 addext (s, suffix, '~');
130 /* Return the number of the highest-numbered backup file for file
131 FILE in directory DIR. If there are no numbered backups
132 of FILE in DIR, or an error occurs reading DIR, return 0.
136 max_backup_version (const char *file, const char *dir)
142 size_t file_name_length;
144 dirp = opendir (dir);
149 file_name_length = strlen (file);
151 while ((dp = readdir (dirp)) != 0)
153 if (!REAL_DIR_ENTRY (dp) || strlen (dp->d_name) < file_name_length + 4)
156 this_version = version_number (file, dp->d_name, file_name_length);
157 if (this_version > highest_version)
158 highest_version = this_version;
162 return highest_version;
165 /* If BACKUP is a numbered backup of BASE, return its version number;
166 otherwise return 0. BASE_LENGTH is the length of BASE.
170 version_number (const char *base, const char *backup, size_t base_length)
176 if (strncmp (base, backup, base_length) == 0
177 && backup[base_length] == '.'
178 && backup[base_length + 1] == '~')
180 for (p = &backup[base_length + 2]; ISDIGIT (*p); ++p)
181 version = version * 10 + *p - '0';
182 if (p[0] != '~' || p[1])
187 #endif /* HAVE_DIR */
189 static const char * const backup_args[] =
191 /* In a series of synonyms, present the most meaning full first, so
192 that argmatch_valid be more readable. */
200 static const enum backup_type backup_types[] =
204 numbered_existing, numbered_existing,
208 /* Return the type of backup specified by VERSION.
209 If VERSION is NULL or the empty string, return numbered_existing.
210 If VERSION is invalid or ambiguous, fail with a diagnostic appropriate
211 for the specified CONTEXT. Unambiguous abbreviations are accepted. */
214 get_version (const char *context, const char *version)
216 if (version == 0 || *version == 0)
217 return numbered_existing;
219 return XARGMATCH (context, version, backup_args, backup_types);
223 /* Return the type of backup specified by VERSION.
224 If VERSION is NULL, use the value of the envvar VERSION_CONTROL.
225 If the specified string is invalid or ambiguous, fail with a diagnostic
226 appropriate for the specified CONTEXT.
227 Unambiguous abbreviations are accepted. */
230 xget_version (const char *context, const char *version)
232 if (version && *version)
233 return get_version (context, version);
235 return get_version ("$VERSION_CONTROL", getenv ("VERSION_CONTROL"));