usr.bin/patch/backupfile.c

   1 /*
   2  * $OpenBSD: backupfile.c,v 1.19 2006/03/11 19:41:30 otto Exp $
   3  * $DragonFly: src/usr.bin/patch/backupfile.c,v 1.5 2008/08/11 00:05:06 joerg Exp $
   4  */
   5
   6 /*
   7  * backupfile.c -- make Emacs style backup file names
   8  *
   9  * Copyright (C) 1990 Free Software Foundation, Inc.
  10  *
  11  * This program is free software; you can redistribute it and/or modify it
  12  * without restriction.
  13  *
  14  * This program is distributed in the hope that it will be useful, but WITHOUT
  15  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  16  * FITNESS FOR A PARTICULAR PURPOSE.
  17  */
  18
  19 /*
  20  * David MacKenzie <djm@ai.mit.edu>. Some algorithms adapted from GNU Emacs.
  21  */
  22
  23 #include <ctype.h>
  24 #include <dirent.h>
  25 #include <libgen.h>
  26 #include <stdio.h>
  27 #include <stdlib.h>
  28 #include <string.h>
  29 #include <unistd.h>
  30
  31 #include "backupfile.h"
  32
  33
  34 #define ISDIGIT(c) (isascii ((unsigned char)c) && isdigit ((unsigned char)c))
  35
  36 /* Which type of backup file names are generated. */
  37 enum backup_type backup_type = none;
  38
  39 /*
  40  * The extension added to file names to produce a simple (as opposed to
  41  * numbered) backup file name.
  42  */
  43 const char      *simple_backup_suffix = "~";
  44
  45 static char     *concat(const char *, const char *);
  46 static char     *make_version_name(const char *, int);
  47 static int      max_backup_version(const char *, const char *);
  48 static int      version_number(const char *, const char *, size_t);
  49 static int      argmatch(const char *, const char **);
  50 static void     invalid_arg(const char *, const char *, int);
  51
  52 /*
  53  * Return the name of the new backup file for file FILE, allocated with
  54  * malloc.  Return 0 if out of memory. FILE must not end with a '/' unless it
  55  * is the root directory. Do not call this function if backup_type == none.
  56  */
  57 char *
  58 find_backup_file_name(const char *file)
  59 {
  60         char    *dir, *base_versions, *tmp_file;
  61         int     highest_backup;
  62
  63         if (backup_type == simple)
  64                 return concat(file, simple_backup_suffix);
  65         tmp_file = strdup(file);
  66         if (tmp_file == NULL)
  67                 return NULL;
  68         base_versions = concat(basename(tmp_file), ".~");
  69         free(tmp_file);
  70         if (base_versions == NULL)
  71                 return NULL;
  72         tmp_file = strdup(file);
  73         if (tmp_file == NULL) {
  74                 free(base_versions);
  75                 return NULL;
  76         }
  77         dir = dirname(tmp_file);
  78         if (dir == NULL) {
  79                 free(base_versions);
  80                 free(tmp_file);
  81                 return NULL;
  82         }
  83         highest_backup = max_backup_version(base_versions, dir);
  84         free(base_versions);
  85         free(tmp_file);
  86         if (backup_type == numbered_existing && highest_backup == 0)
  87                 return concat(file, simple_backup_suffix);
  88         return make_version_name(file, highest_backup + 1);
  89 }
  90
  91 /*
  92  * Return the number of the highest-numbered backup file for file FILE in
  93  * directory DIR.  If there are no numbered backups of FILE in DIR, or an
  94  * error occurs reading DIR, return 0. FILE should already have ".~" appended
  95  * to it.
  96  */
  97 static int
  98 max_backup_version(const char *file, const char *dir)
  99 {
 100         DIR     *dirp;
 101         struct dirent   *dp;
 102         int     highest_version, this_version;
 103         size_t  file_name_length;
 104
 105         dirp = opendir(dir);
 106         if (dirp == NULL)
 107                 return 0;
 108
 109         highest_version = 0;
 110         file_name_length = strlen(file);
 111
 112         while ((dp = readdir(dirp)) != NULL) {
 113                 if (dp->d_namlen <= file_name_length)
 114                         continue;
 115
 116                 this_version = version_number(file, dp->d_name, file_name_length);
 117                 if (this_version > highest_version)
 118                         highest_version = this_version;
 119         }
 120         closedir(dirp);
 121         return highest_version;
 122 }
 123
 124 /*
 125  * Return a string, allocated with malloc, containing "FILE.~VERSION~".
 126  * Return 0 if out of memory.
 127  */
 128 static char *
 129 make_version_name(const char *file, int version)
 130 {
 131         char    *backup_name;
 132
 133         if (asprintf(&backup_name, "%s.~%d~", file, version) == -1)
 134                 return NULL;
 135         return backup_name;
 136 }
 137
 138 /*
 139  * If BACKUP is a numbered backup of BASE, return its version number;
 140  * otherwise return 0.  BASE_LENGTH is the length of BASE. BASE should
 141  * already have ".~" appended to it.
 142  */
 143 static int
 144 version_number(const char *base, const char *backup, size_t base_length)
 145 {
 146         int             version;
 147         const char      *p;
 148
 149         version = 0;
 150         if (!strncmp(base, backup, base_length) && ISDIGIT(backup[base_length])) {
 151                 for (p = &backup[base_length]; ISDIGIT(*p); ++p)
 152                         version = version * 10 + *p - '0';
 153                 if (p[0] != '~' || p[1])
 154                         version = 0;
 155         }
 156         return version;
 157 }
 158
 159 /*
 160  * Return the newly-allocated concatenation of STR1 and STR2. If out of
 161  * memory, return 0.
 162  */
 163 static char  *
 164 concat(const char *str1, const char *str2)
 165 {
 166         char    *newstr;
 167
 168         if (asprintf(&newstr, "%s%s", str1, str2) == -1)
 169                 return NULL;
 170         return newstr;
 171 }
 172
 173 /*
 174  * If ARG is an unambiguous match for an element of the null-terminated array
 175  * OPTLIST, return the index in OPTLIST of the matched element, else -1 if it
 176  * does not match any element or -2 if it is ambiguous (is a prefix of more
 177  * than one element).
 178  */
 179 static int
 180 argmatch(const char *arg, const char **optlist)
 181 {
 182         int     i;      /* Temporary index in OPTLIST. */
 183         size_t  arglen; /* Length of ARG. */
 184         int     matchind = -1;  /* Index of first nonexact match. */
 185         int     ambiguous = 0;  /* If nonzero, multiple nonexact match(es). */
 186
 187         arglen = strlen(arg);
 188
 189         /* Test all elements for either exact match or abbreviated matches.  */
 190         for (i = 0; optlist[i]; i++) {
 191                 if (!strncmp(optlist[i], arg, arglen)) {
 192                         if (strlen(optlist[i]) == arglen)
 193                                 /* Exact match found.  */
 194                                 return i;
 195                         else if (matchind == -1)
 196                                 /* First nonexact match found.  */
 197                                 matchind = i;
 198                         else
 199                                 /* Second nonexact match found.  */
 200                                 ambiguous = 1;
 201                 }
 202         }
 203         if (ambiguous)
 204                 return -2;
 205         else
 206                 return matchind;
 207 }
 208
 209 /*
 210  * Error reporting for argmatch. KIND is a description of the type of entity
 211  * that was being matched. VALUE is the invalid value that was given. PROBLEM
 212  * is the return value from argmatch.
 213  */
 214 static void
 215 invalid_arg(const char *kind, const char *value, int problem)
 216 {
 217         fprintf(stderr, "patch: ");
 218         if (problem == -1)
 219                 fprintf(stderr, "invalid");
 220         else                    /* Assume -2. */
 221                 fprintf(stderr, "ambiguous");
 222         fprintf(stderr, " %s `%s'\n", kind, value);
 223 }
 224
 225 static const char *backup_args[] = {
 226         "never", "simple", "nil", "existing", "t", "numbered", 0
 227 };
 228
 229 static enum backup_type backup_types[] = {
 230         simple, simple, numbered_existing,
 231         numbered_existing, numbered, numbered
 232 };
 233
 234 /*
 235  * Return the type of backup indicated by VERSION. Unique abbreviations are
 236  * accepted.
 237  */
 238 enum backup_type
 239 get_version(const char *version)
 240 {
 241         int     i;
 242
 243         if (version == NULL || *version == '\0')
 244                 return numbered_existing;
 245         i = argmatch(version, backup_args);
 246         if (i >= 0)
 247                 return backup_types[i];
 248         invalid_arg("version control type", version, i);
 249         exit(2);
 250 }