lib/backupfile.c

   1 /* backupfile.c -- make Emacs style backup file names
   2    Copyright (C) 1990 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; if not, write to the Free Software
  16    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.  */
  17
  18 /* David MacKenzie <djm@gnu.ai.mit.edu>.
  19    Some algorithms adapted from GNU Emacs. */
  20
  21 #ifdef HAVE_CONFIG_H
  22 #if defined (CONFIG_BROKETS)
  23 /* We use <config.h> instead of "config.h" so that a compilation
  24    using -I. -I will use ./config.h rather than /config.h
  25    (which it would do because it found this file in ).  */
  26 #include <config.h>
  27 #else
  28 #include "config.h"
  29 #endif
  30 #endif
  31
  32 #include <stdio.h>
  33 #include <ctype.h>
  34 #include <sys/types.h>
  35 #include "backupfile.h"
  36 #if defined(STDC_HEADERS) || defined(HAVE_STRING_H)
  37 #include <string.h>
  38 #ifndef index
  39 #define index strchr
  40 #endif
  41 #ifndef rindex
  42 #define rindex strrchr
  43 #endif
  44 #else
  45 #include <strings.h>
  46 #endif
  47
  48 #if defined(DIRENT) || defined(_POSIX_VERSION)
  49 #include <dirent.h>
  50 #define NLENGTH(direct) (strlen((direct)->d_name))
  51 #else /* not (DIRENT or _POSIX_VERSION) */
  52 #define dirent direct
  53 #define NLENGTH(direct) ((direct)->d_namlen)
  54 #ifdef SYSNDIR
  55 #include <sys/ndir.h>
  56 #endif /* SYSNDIR */
  57 #ifdef SYSDIR
  58 #include <sys/dir.h>
  59 #endif /* SYSDIR */
  60 #ifdef NDIR
  61 #include <ndir.h>
  62 #endif /* NDIR */
  63 #endif /* DIRENT or _POSIX_VERSION */
  64
  65 #ifdef VOID_CLOSEDIR
  66 /* Fake a return value. */
  67 #define CLOSEDIR(d) (closedir (d), 0)
  68 #else
  69 #define CLOSEDIR(d) closedir (d)
  70 #endif
  71
  72 #ifdef STDC_HEADERS
  73 #include <stdlib.h>
  74 #else
  75 char *malloc ();
  76 #endif
  77
  78 #if !defined (isascii) || defined (STDC_HEADERS)
  79 #undef isascii
  80 #define isascii(c) 1
  81 #endif
  82
  83 #define ISDIGIT(c) (isascii ((unsigned char ) c) \
  84                     && isdigit ((unsigned char) (c)))
  85
  86 #if defined (HAVE_UNISTD_H)
  87 #include <unistd.h>
  88 #endif
  89
  90 #if defined (_POSIX_VERSION)
  91 /* POSIX does not require that the d_ino field be present, and some
  92    systems do not provide it. */
  93 #define REAL_DIR_ENTRY(dp) 1
  94 #else
  95 #define REAL_DIR_ENTRY(dp) ((dp)->d_ino != 0)
  96 #endif
  97
  98 /* Which type of backup file names are generated. */
  99 enum backup_type backup_type = none;
 100
 101 /* The extension added to file names to produce a simple (as opposed
 102    to numbered) backup file name. */
 103 char *simple_backup_suffix = "~";
 104
 105 char *basename ();
 106 char *dirname ();
 107 static char *concat ();
 108 char *find_backup_file_name ();
 109 static char *make_version_name ();
 110 static int max_backup_version ();
 111 static int version_number ();
 112
 113 /* Return the name of the new backup file for file FILE,
 114    allocated with malloc.  Return 0 if out of memory.
 115    FILE must not end with a '/' unless it is the root directory.
 116    Do not call this function if backup_type == none. */
 117
 118 char *
 119 find_backup_file_name (file)
 120      char *file;
 121 {
 122   char *dir;
 123   char *base_versions;
 124   int highest_backup;
 125
 126   if (backup_type == simple)
 127     return concat (file, simple_backup_suffix);
 128   base_versions = concat (basename (file), ".~");
 129   if (base_versions == 0)
 130     return 0;
 131   dir = dirname (file);
 132   if (dir == 0)
 133     {
 134       free (base_versions);
 135       return 0;
 136     }
 137   highest_backup = max_backup_version (base_versions, dir);
 138   free (base_versions);
 139   free (dir);
 140   if (backup_type == numbered_existing && highest_backup == 0)
 141     return concat (file, simple_backup_suffix);
 142   return make_version_name (file, highest_backup + 1);
 143 }
 144
 145 /* Return the number of the highest-numbered backup file for file
 146    FILE in directory DIR.  If there are no numbered backups
 147    of FILE in DIR, or an error occurs reading DIR, return 0.
 148    FILE should already have ".~" appended to it. */
 149
 150 static int
 151 max_backup_version (file, dir)
 152      char *file, *dir;
 153 {
 154   DIR *dirp;
 155   struct dirent *dp;
 156   int highest_version;
 157   int this_version;
 158   int file_name_length;
 159
 160   dirp = opendir (dir);
 161   if (!dirp)
 162     return 0;
 163
 164   highest_version = 0;
 165   file_name_length = strlen (file);
 166
 167   while ((dp = readdir (dirp)) != 0)
 168     {
 169       if (!REAL_DIR_ENTRY (dp) || NLENGTH (dp) <= file_name_length)
 170         continue;
 171
 172       this_version = version_number (file, dp->d_name, file_name_length);
 173       if (this_version > highest_version)
 174         highest_version = this_version;
 175     }
 176   if (CLOSEDIR (dirp))
 177     return 0;
 178   return highest_version;
 179 }
 180
 181 /* Return a string, allocated with malloc, containing
 182    "FILE.~VERSION~".  Return 0 if out of memory. */
 183
 184 static char *
 185 make_version_name (file, version)
 186      char *file;
 187      int version;
 188 {
 189   char *backup_name;
 190
 191   backup_name = malloc (strlen (file) + 16);
 192   if (backup_name == 0)
 193     return 0;
 194   sprintf (backup_name, "%s.~%d~", file, version);
 195   return backup_name;
 196 }
 197
 198 /* If BACKUP is a numbered backup of BASE, return its version number;
 199    otherwise return 0.  BASE_LENGTH is the length of BASE.
 200    BASE should already have ".~" appended to it. */
 201
 202 static int
 203 version_number (base, backup, base_length)
 204      char *base;
 205      char *backup;
 206      int base_length;
 207 {
 208   int version;
 209   char *p;
 210
 211   version = 0;
 212   if (!strncmp (base, backup, base_length) && ISDIGIT (backup[base_length]))
 213     {
 214       for (p = &backup[base_length]; ISDIGIT (*p); ++p)
 215         version = version * 10 + *p - '0';
 216       if (p[0] != '~' || p[1])
 217         version = 0;
 218     }
 219   return version;
 220 }
 221
 222 /* Return the newly-allocated concatenation of STR1 and STR2.
 223    If out of memory, return 0. */
 224
 225 static char *
 226 concat (str1, str2)
 227      char *str1, *str2;
 228 {
 229   char *newstr;
 230   int str1_length = strlen (str1);
 231
 232   newstr = malloc (str1_length + strlen (str2) + 1);
 233   if (newstr == 0)
 234     return 0;
 235   strcpy (newstr, str1);
 236   strcpy (newstr + str1_length, str2);
 237   return newstr;
 238 }