1 /* backupfile.c -- make Emacs style backup file names
2 Copyright (C) 1990-1999, 2000-2003, 2005-2006 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 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
18
19 /* Written by David MacKenzie <djm@gnu.ai.mit.edu>.
20 Some algorithms adapted from GNU Emacs. */
21
22 #include <config.h>
23
24 #include "argmatch.h"
25 #include "backupfile.h"
26
27 #include <stdio.h>
28 #include <sys/types.h>
29 #if HAVE_STRING_H
30 # include <string.h>
31 #else
32 # include <strings.h>
33 #endif
34
35 #if HAVE_DIRENT_H
36 # include <dirent.h>
37 #endif
38
39 #include <stdlib.h>
40
41 #include "basename.h"
42
43 #if HAVE_DIRENT_H
44 # define HAVE_DIR 1
45 #else
46 # define HAVE_DIR 0
47 #endif
48
49 #include <limits.h>
50
51 /* Upper bound on the string length of an integer converted to string.
52 302 / 1000 is ceil (log10 (2.0)). Subtract 1 for the sign bit;
53 add 1 for integer division truncation; add 1 more for a minus sign. */
54 #define INT_STRLEN_BOUND(t) ((sizeof (t) * CHAR_BIT - 1) * 302 / 1000 + 2)
55
56 /* ISDIGIT differs from isdigit, as follows:
57 - Its arg may be any int or unsigned int; it need not be an unsigned char.
58 - It's guaranteed to evaluate its argument exactly once.
59 - It's typically faster.
60 Posix 1003.2-1992 section 2.5.2.1 page 50 lines 1556-1558 says that
61 only '0' through '9' are digits. Prefer ISDIGIT to isdigit unless
62 it's important to use the locale's definition of `digit' even when the
63 host does not conform to Posix. */
64 #define ISDIGIT(c) ((unsigned) (c) - '0' <= 9)
65
66 #if D_INO_IN_DIRENT
67 # define REAL_DIR_ENTRY(dp) ((dp)->d_ino != 0)
68 #else
69 # define REAL_DIR_ENTRY(dp) 1
70 #endif
71
72 /* The extension added to file names to produce a simple (as opposed
73 to numbered) backup file name. */
74 const char *simple_backup_suffix = "~";
75
76 #if HAVE_DIR
77 static int max_backup_version (const char *, const char *);
78 static int version_number (const char *, const char *, size_t);
79 #endif
80
81 /* Return the name of the new backup file for file FILE,
82 allocated with malloc. Return 0 if out of memory.
83 FILE must not end with a '/' unless it is the root directory.
84 Do not call this function if backup_type == none. */
85
86 char *
find_backup_file_name(const char * file,enum backup_type backup_type)87 find_backup_file_name (const char *file, enum backup_type backup_type)
88 {
89 size_t backup_suffix_size_max;
90 size_t file_len = strlen (file);
91 size_t numbered_suffix_size_max = INT_STRLEN_BOUND (int) + 4;
92 char *s;
93 const char *suffix = simple_backup_suffix;
94
95 /* Allow room for simple or `.~N~' backups. */
96 backup_suffix_size_max = strlen (simple_backup_suffix) + 1;
97 if (HAVE_DIR && backup_suffix_size_max < numbered_suffix_size_max)
98 backup_suffix_size_max = numbered_suffix_size_max;
99
100 s = malloc (file_len + backup_suffix_size_max + numbered_suffix_size_max);
101 if (s)
102 {
103 strcpy (s, file);
104
105 #if HAVE_DIR
106 if (backup_type != simple)
107 {
108 int highest_backup;
109 size_t dir_len = basename (s) - s;
110
111 strcpy (s + dir_len, ".");
112 highest_backup = max_backup_version (file + dir_len, s);
113 if (! (backup_type == numbered_existing && highest_backup == 0))
114 {
115 char *numbered_suffix = s + (file_len + backup_suffix_size_max);
116 sprintf (numbered_suffix, ".~%d~", highest_backup + 1);
117 suffix = numbered_suffix;
118 }
119 strcpy (s, file);
120 }
121 #endif /* HAVE_DIR */
122
123 addext (s, suffix, '~');
124 }
125 return s;
126 }
127
128 #if HAVE_DIR
129
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.
133 */
134
135 static int
max_backup_version(const char * file,const char * dir)136 max_backup_version (const char *file, const char *dir)
137 {
138 DIR *dirp;
139 struct dirent *dp;
140 int highest_version;
141 int this_version;
142 size_t file_name_length;
143
144 dirp = opendir (dir);
145 if (!dirp)
146 return 0;
147
148 highest_version = 0;
149 file_name_length = strlen (file);
150
151 while ((dp = readdir (dirp)) != 0)
152 {
153 if (!REAL_DIR_ENTRY (dp) || strlen (dp->d_name) < file_name_length + 4)
154 continue;
155
156 this_version = version_number (file, dp->d_name, file_name_length);
157 if (this_version > highest_version)
158 highest_version = this_version;
159 }
160 if (closedir (dirp))
161 return 0;
162 return highest_version;
163 }
164
165 /* If BACKUP is a numbered backup of BASE, return its version number;
166 otherwise return 0. BASE_LENGTH is the length of BASE.
167 */
168
169 static int
version_number(const char * base,const char * backup,size_t base_length)170 version_number (const char *base, const char *backup, size_t base_length)
171 {
172 int version;
173 const char *p;
174
175 version = 0;
176 if (strncmp (base, backup, base_length) == 0
177 && backup[base_length] == '.'
178 && backup[base_length + 1] == '~')
179 {
180 for (p = &backup[base_length + 2]; ISDIGIT (*p); ++p)
181 version = version * 10 + *p - '0';
182 if (p[0] != '~' || p[1])
183 version = 0;
184 }
185 return version;
186 }
187 #endif /* HAVE_DIR */
188
189 static const char * const backup_args[] =
190 {
191 /* In a series of synonyms, present the most meaning full first, so
192 that argmatch_valid be more readable. */
193 "none", "off",
194 "simple", "never",
195 "existing", "nil",
196 "numbered", "t",
197 0
198 };
199
200 static const enum backup_type backup_types[] =
201 {
202 none, none,
203 simple, simple,
204 numbered_existing, numbered_existing,
205 numbered, numbered
206 };
207
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. */
212
213 enum backup_type
get_version(const char * context,const char * version)214 get_version (const char *context, const char *version)
215 {
216 if (version == 0 || *version == 0)
217 return numbered_existing;
218 else
219 return XARGMATCH (context, version, backup_args, backup_types);
220 }
221
222
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. */
228
229 enum backup_type
xget_version(const char * context,const char * version)230 xget_version (const char *context, const char *version)
231 {
232 if (version && *version)
233 return get_version (context, version);
234 else
235 return get_version ("$VERSION_CONTROL", getenv ("VERSION_CONTROL"));
236 }
237