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1/* $OpenBSD: backupfile.c,v 1.23 2024/03/22 19:22:23 jcs Exp $ */
2
3/*
4 * backupfile.c -- make Emacs style backup file names Copyright (C) 1990 Free
5 * Software Foundation, Inc.
6 *
7 * This program is free software; you can redistribute it and/or modify it
8 * without restriction.
9 *
10 * This program is distributed in the hope that it will be useful, but WITHOUT
11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
12 * FITNESS FOR A PARTICULAR PURPOSE.
13 */
14
15/*
16 * David MacKenzie <djm@ai.mit.edu>. Some algorithms adapted from GNU Emacs.
17 */
18
19#include <ctype.h>
20#include <dirent.h>
21#include <libgen.h>
22#include <stdio.h>
23#include <stdlib.h>
24#include <string.h>
25#include <unistd.h>
26
27#include "backupfile.h"
28
29
30#define ISDIGIT(c) (isascii (c) && isdigit (c))
31
32/* Which type of backup file names are generated. */
33enum backup_type backup_type = none;
34
35/*
36 * The extension added to file names to produce a simple (as opposed to
37 * numbered) backup file name.
38 */
39char *simple_backup_suffix = "~";
40
41static char *concat(const char *, const char *);
42static char *make_version_name(const char *, int);
43static int max_backup_version(const char *, const char *);
44static int version_number(const char *, const char *, size_t);
45static int argmatch(const char *, const char **);
46static void invalid_arg(const char *, const char *, int);
47
48/*
49 * Return the name of the new backup file for file FILE, allocated with
50 * malloc. Return 0 if out of memory. FILE must not end with a '/' unless it
51 * is the root directory. Do not call this function if backup_type == none.
52 */
53char *
54find_backup_file_name(const char *file)
55{
56 char *dir, *base_versions, *tmp_file;
57 int highest_backup;
58
59 if (backup_type == simple)
60 return concat(file, simple_backup_suffix);
61 tmp_file = strdup(file);
62 if (tmp_file == NULL)
63 return NULL;
64 base_versions = concat(basename(tmp_file), ".~");
65 free(tmp_file);
66 if (base_versions == NULL)
67 return NULL;
68 tmp_file = strdup(file);
69 if (tmp_file == NULL) {
70 free(base_versions);
71 return NULL;
72 }
73 dir = dirname(tmp_file);
74 if (dir == NULL) {
75 free(base_versions);
76 free(tmp_file);
77 return NULL;
78 }
79 highest_backup = max_backup_version(base_versions, dir);
80 free(base_versions);
81 free(tmp_file);
82 if (backup_type == numbered_existing && highest_backup == 0)
83 return concat(file, simple_backup_suffix);
84 return make_version_name(file, highest_backup + 1);
85}
86
87/*
88 * Return the number of the highest-numbered backup file for file FILE in
89 * directory DIR. If there are no numbered backups of FILE in DIR, or an
90 * error occurs reading DIR, return 0. FILE should already have ".~" appended
91 * to it.
92 */
93static int
94max_backup_version(const char *file, const char *dir)
95{
96 DIR *dirp;
97 struct dirent *dp;
98 int highest_version, this_version;
99 size_t file_name_length;
100
101 dirp = opendir(dir);
102 if (dirp == NULL)
103 return 0;
104
105 highest_version = 0;
106 file_name_length = strlen(file);
107
108 while ((dp = readdir(dirp)) != NULL) {
109 if (dp->d_namlen <= file_name_length)
110 continue;
111
112 this_version = version_number(file, dp->d_name, file_name_length);
113 if (this_version > highest_version)
114 highest_version = this_version;
115 }
116 closedir(dirp);
117 return highest_version;
118}
119
120/*
121 * Return a string, allocated with malloc, containing "FILE.~VERSION~".
122 * Return 0 if out of memory.
123 */
124static char *
125make_version_name(const char *file, int version)
126{
127 char *backup_name;
128
129 if (asprintf(&backup_name, "%s.~%d~", file, version) == -1)
130 return NULL;
131 return backup_name;
132}
133
134/*
135 * If BACKUP is a numbered backup of BASE, return its version number;
136 * otherwise return 0. BASE_LENGTH is the length of BASE. BASE should
137 * already have ".~" appended to it.
138 */
139static int
140version_number(const char *base, const char *backup, size_t base_length)
141{
142 int version;
143 const char *p;
144
145 version = 0;
146 if (!strncmp(base, backup, base_length) &&
147 ISDIGIT((unsigned char)backup[base_length])) {
148 for (p = &backup[base_length]; ISDIGIT((unsigned char)*p); ++p)
149 version = version * 10 + *p - '0';
150 if (p[0] != '~' || p[1])
151 version = 0;
152 }
153 return version;
154}
155
156/*
157 * Return the newly-allocated concatenation of STR1 and STR2. If out of
158 * memory, return 0.
159 */
160static char *
161concat(const char *str1, const char *str2)
162{
163 char *newstr;
164
165 if (asprintf(&newstr, "%s%s", str1, str2) == -1)
166 return NULL;
167 return newstr;
168}
169
170/*
171 * If ARG is an unambiguous match for an element of the null-terminated array
172 * OPTLIST, return the index in OPTLIST of the matched element, else -1 if it
173 * does not match any element or -2 if it is ambiguous (is a prefix of more
174 * than one element).
175 */
176static int
177argmatch(const char *arg, const char **optlist)
178{
179 int i; /* Temporary index in OPTLIST. */
180 size_t arglen; /* Length of ARG. */
181 int matchind = -1; /* Index of first nonexact match. */
182 int ambiguous = 0; /* If nonzero, multiple nonexact match(es). */
183
184 arglen = strlen(arg);
185
186 /* Test all elements for either exact match or abbreviated matches. */
187 for (i = 0; optlist[i]; i++) {
188 if (!strncmp(optlist[i], arg, arglen)) {
189 if (strlen(optlist[i]) == arglen)
190 /* Exact match found. */
191 return i;
192 else if (matchind == -1)
193 /* First nonexact match found. */
194 matchind = i;
195 else
196 /* Second nonexact match found. */
197 ambiguous = 1;
198 }
199 }
200 if (ambiguous)
201 return -2;
202 else
203 return matchind;
204}
205
206/*
207 * Error reporting for argmatch. KIND is a description of the type of entity
208 * that was being matched. VALUE is the invalid value that was given. PROBLEM
209 * is the return value from argmatch.
210 */
211static void
212invalid_arg(const char *kind, const char *value, int problem)
213{
214 fprintf(stderr, "patch: ");
215 if (problem == -1)
216 fprintf(stderr, "invalid");
217 else /* Assume -2. */
218 fprintf(stderr, "ambiguous");
219 fprintf(stderr, " %s `%s'\n", kind, value);
220}
221
222static const char *backup_args[] = {
223 "none", "never", "simple", "nil", "existing", "t", "numbered", 0
224};
225
226static enum backup_type backup_types[] = {
227 none, simple, simple, numbered_existing,
228 numbered_existing, numbered, numbered
229};
230
231/*
232 * Return the type of backup indicated by VERSION. Unique abbreviations are
233 * accepted.
234 */
235enum backup_type
236get_version(const char *version)
237{
238 int i;
239
240 if (version == NULL || *version == '\0')
241 return numbered_existing;
242 i = argmatch(version, backup_args);
243 if (i >= 0)
244 return backup_types[i];
245 invalid_arg("version control type", version, i);
246 exit(2);
247}