1/* backupfile.c -- make Emacs style backup file names
2   Copyright (C) 1990,91,92,93,94,95,96,97,98,99,2000, 2001, 2002 Free Software
3   Foundation, Inc.
4
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 2, or (at your option)
8   any later version.
9
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.
14
15   You should have received a copy of the GNU General Public License
16   along with this program; see the file COPYING.
17   If not, write to the Free Software Foundation,
18   59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
19
20/* Written by David MacKenzie <djm@gnu.ai.mit.edu>.
21   Some algorithms adapted from GNU Emacs. */
22
23#if HAVE_CONFIG_H
24# include <config.h>
25#endif
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# define NLENGTH(direct) strlen ((direct)->d_name)
38#else
39# define dirent direct
40# define NLENGTH(direct) ((size_t) (direct)->d_namlen)
41# if HAVE_SYS_NDIR_H
42#  include <sys/ndir.h>
43# endif
44# if HAVE_SYS_DIR_H
45#  include <sys/dir.h>
46# endif
47# if HAVE_NDIR_H
48#  include <ndir.h>
49# endif
50#endif
51
52#if CLOSEDIR_VOID
53/* Fake a return value. */
54# define CLOSEDIR(d) (closedir (d), 0)
55#else
56# define CLOSEDIR(d) closedir (d)
57#endif
58
59#if HAVE_STDLIB_H
60# include <stdlib.h>
61#endif
62
63#ifndef HAVE_DECL_GETENV
64"this configure-time declaration test was not run"
65#endif
66#if !HAVE_DECL_GETENV
67char *getenv ();
68#endif
69
70#ifndef HAVE_DECL_MALLOC
71"this configure-time declaration test was not run"
72#endif
73#if !HAVE_DECL_MALLOC
74char *malloc ();
75#endif
76
77#if HAVE_DIRENT_H || HAVE_NDIR_H || HAVE_SYS_DIR_H || HAVE_SYS_NDIR_H
78# define HAVE_DIR 1
79#else
80# define HAVE_DIR 0
81#endif
82
83#if HAVE_LIMITS_H
84# include <limits.h>
85#endif
86#ifndef CHAR_BIT
87# define CHAR_BIT 8
88#endif
89/* Upper bound on the string length of an integer converted to string.
90   302 / 1000 is ceil (log10 (2.0)).  Subtract 1 for the sign bit;
91   add 1 for integer division truncation; add 1 more for a minus sign.  */
92#define INT_STRLEN_BOUND(t) ((sizeof (t) * CHAR_BIT - 1) * 302 / 1000 + 2)
93
94/* ISDIGIT differs from isdigit, as follows:
95   - Its arg may be any int or unsigned int; it need not be an unsigned char.
96   - It's guaranteed to evaluate its argument exactly once.
97   - It's typically faster.
98   POSIX says that only '0' through '9' are digits.  Prefer ISDIGIT to
99   ISDIGIT_LOCALE unless it's important to use the locale's definition
100   of `digit' even when the host does not conform to POSIX.  */
101#define ISDIGIT(c) ((unsigned) (c) - '0' <= 9)
102
103#if D_INO_IN_DIRENT
104# define REAL_DIR_ENTRY(dp) ((dp)->d_ino != 0)
105#else
106# define REAL_DIR_ENTRY(dp) 1
107#endif
108
109#include "argmatch.h"
110#include "backupfile.h"
111#include "dirname.h"
112
113/* The extension added to file names to produce a simple (as opposed
114   to numbered) backup file name. */
115const char *simple_backup_suffix = "~";
116
117static int max_backup_version PARAMS ((const char *, const char *));
118static int version_number PARAMS ((const char *, const char *, size_t));
119
120/* Return the name of the new backup file for file FILE,
121   allocated with malloc.  Return 0 if out of memory.
122   FILE must not end with a '/' unless it is the root directory.
123   Do not call this function if backup_type == none. */
124
125char *
126find_backup_file_name (const char *file, enum backup_type backup_type)
127{
128  size_t backup_suffix_size_max;
129  size_t file_len = strlen (file);
130  size_t numbered_suffix_size_max = INT_STRLEN_BOUND (int) + 4;
131  char *s;
132  const char *suffix = simple_backup_suffix;
133
134  /* Allow room for simple or `.~N~' backups.  */
135  backup_suffix_size_max = strlen (simple_backup_suffix) + 1;
136  if (HAVE_DIR && backup_suffix_size_max < numbered_suffix_size_max)
137    backup_suffix_size_max = numbered_suffix_size_max;
138
139  s = malloc (file_len + 1
140	      + backup_suffix_size_max + numbered_suffix_size_max);
141  if (s)
142    {
143#if HAVE_DIR
144      if (backup_type != simple)
145	{
146	  int highest_backup;
147	  size_t dirlen = dir_len (file);
148
149	  memcpy (s, file, dirlen);
150	  if (dirlen == FILESYSTEM_PREFIX_LEN (file))
151	    s[dirlen++] = '.';
152	  s[dirlen] = '\0';
153	  highest_backup = max_backup_version (base_name (file), s);
154	  if (! (backup_type == numbered_existing && highest_backup == 0))
155	    {
156	      char *numbered_suffix = s + (file_len + backup_suffix_size_max);
157	      sprintf (numbered_suffix, ".~%d~", highest_backup + 1);
158	      suffix = numbered_suffix;
159	    }
160	}
161#endif /* HAVE_DIR */
162
163      strcpy (s, file);
164      addext (s, suffix, '~');
165    }
166  return s;
167}
168
169#if HAVE_DIR
170
171/* Return the number of the highest-numbered backup file for file
172   FILE in directory DIR.  If there are no numbered backups
173   of FILE in DIR, or an error occurs reading DIR, return 0.
174   */
175
176static int
177max_backup_version (const char *file, const char *dir)
178{
179  DIR *dirp;
180  struct dirent *dp;
181  int highest_version;
182  int this_version;
183  size_t file_name_length;
184
185  dirp = opendir (dir);
186  if (!dirp)
187    return 0;
188
189  highest_version = 0;
190  file_name_length = base_len (file);
191
192  while ((dp = readdir (dirp)) != 0)
193    {
194      if (!REAL_DIR_ENTRY (dp) || NLENGTH (dp) < file_name_length + 4)
195	continue;
196
197      this_version = version_number (file, dp->d_name, file_name_length);
198      if (this_version > highest_version)
199	highest_version = this_version;
200    }
201  if (CLOSEDIR (dirp))
202    return 0;
203  return highest_version;
204}
205
206/* If BACKUP is a numbered backup of BASE, return its version number;
207   otherwise return 0.  BASE_LENGTH is the length of BASE.
208   */
209
210static int
211version_number (const char *base, const char *backup, size_t base_length)
212{
213  int version;
214  const char *p;
215
216  version = 0;
217  if (strncmp (base, backup, base_length) == 0
218      && backup[base_length] == '.'
219      && backup[base_length + 1] == '~')
220    {
221      for (p = &backup[base_length + 2]; ISDIGIT (*p); ++p)
222	version = version * 10 + *p - '0';
223      if (p[0] != '~' || p[1])
224	version = 0;
225    }
226  return version;
227}
228#endif /* HAVE_DIR */
229
230static const char * const backup_args[] =
231{
232  /* In a series of synonyms, present the most meaning full first, so
233     that argmatch_valid be more readable. */
234  "none", "off",
235  "simple", "never",
236  "existing", "nil",
237  "numbered", "t",
238  0
239};
240
241static const enum backup_type backup_types[] =
242{
243  none, none,
244  simple, simple,
245  numbered_existing, numbered_existing,
246  numbered, numbered
247};
248
249/* Return the type of backup specified by VERSION.
250   If VERSION is NULL or the empty string, return numbered_existing.
251   If VERSION is invalid or ambiguous, fail with a diagnostic appropriate
252   for the specified CONTEXT.  Unambiguous abbreviations are accepted.  */
253
254enum backup_type
255get_version (const char *context, const char *version)
256{
257  if (version == 0 || *version == 0)
258    return numbered_existing;
259  else
260    return XARGMATCH (context, version, backup_args, backup_types);
261}
262
263
264/* Return the type of backup specified by VERSION.
265   If VERSION is NULL, use the value of the envvar VERSION_CONTROL.
266   If the specified string is invalid or ambiguous, fail with a diagnostic
267   appropriate for the specified CONTEXT.
268   Unambiguous abbreviations are accepted.  */
269
270enum backup_type
271xget_version (const char *context, const char *version)
272{
273  if (version && *version)
274    return get_version (context, version);
275  else
276    return get_version ("$VERSION_CONTROL", getenv ("VERSION_CONTROL"));
277}
278