1/*-
2 * Copyright (C) 1990 Free Software Foundation, Inc.
3 *
4 * This program is free software; you can redistribute it and/or modify it
5 * without restriction.
6 *
7 * This program is distributed in the hope that it will be useful, but WITHOUT
8 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
9 * FITNESS FOR A PARTICULAR PURPOSE.
10 *
11 * backupfile.c -- make Emacs style backup file names
12 *
13 * David MacKenzie <djm@ai.mit.edu>. Some algorithms adapted from GNU Emacs.
14 *
15 * $OpenBSD: backupfile.c,v 1.20 2009/10/27 23:59:41 deraadt Exp $
16 */
17
18#include <ctype.h>
19#include <dirent.h>
20#include <libgen.h>
21#include <stdio.h>
22#include <stdlib.h>
23#include <string.h>
24
25#include "backupfile.h"
26
27
28#define ISDIGIT(c) (isascii ((unsigned char)c) && isdigit ((unsigned char)c))
29
30/* Which type of backup file names are generated. */
31enum backup_type backup_type = none;
32
33/*
34 * The extension added to file names to produce a simple (as opposed to
35 * numbered) backup file name.
36 */
37const char	*simple_backup_suffix = "~";
38
39static char	*concat(const char *, const char *);
40static char	*make_version_name(const char *, int);
41static int	max_backup_version(const char *, const char *);
42static int	version_number(const char *, const char *, size_t);
43static int	argmatch(const char *, const char **);
44static void	invalid_arg(const char *, const char *, int);
45
46/*
47 * Return the name of the new backup file for file FILE, allocated with
48 * malloc.  Return 0 if out of memory. FILE must not end with a '/' unless it
49 * is the root directory. Do not call this function if backup_type == none.
50 */
51char *
52find_backup_file_name(const char *file)
53{
54	char	*dir, *base_versions, *tmp_file;
55	int	highest_backup;
56
57	if (backup_type == simple)
58		return concat(file, simple_backup_suffix);
59	tmp_file = strdup(file);
60	if (tmp_file == NULL)
61		return NULL;
62	base_versions = concat(basename(tmp_file), ".~");
63	free(tmp_file);
64	if (base_versions == NULL)
65		return NULL;
66	tmp_file = strdup(file);
67	if (tmp_file == NULL) {
68		free(base_versions);
69		return NULL;
70	}
71	dir = dirname(tmp_file);
72	if (dir == NULL) {
73		free(base_versions);
74		free(tmp_file);
75		return NULL;
76	}
77	highest_backup = max_backup_version(base_versions, dir);
78	free(base_versions);
79	free(tmp_file);
80	if (backup_type == numbered_existing && highest_backup == 0)
81		return concat(file, simple_backup_suffix);
82	return make_version_name(file, highest_backup + 1);
83}
84
85/*
86 * Return the number of the highest-numbered backup file for file FILE in
87 * directory DIR.  If there are no numbered backups of FILE in DIR, or an
88 * error occurs reading DIR, return 0. FILE should already have ".~" appended
89 * to it.
90 */
91static int
92max_backup_version(const char *file, const char *dir)
93{
94	DIR	*dirp;
95	struct dirent	*dp;
96	int	highest_version, this_version;
97	size_t	file_name_length;
98
99	dirp = opendir(dir);
100	if (dirp == NULL)
101		return 0;
102
103	highest_version = 0;
104	file_name_length = strlen(file);
105
106	while ((dp = readdir(dirp)) != NULL) {
107		if (dp->d_namlen <= file_name_length)
108			continue;
109
110		this_version = version_number(file, dp->d_name, file_name_length);
111		if (this_version > highest_version)
112			highest_version = this_version;
113	}
114	closedir(dirp);
115	return highest_version;
116}
117
118/*
119 * Return a string, allocated with malloc, containing "FILE.~VERSION~".
120 * Return 0 if out of memory.
121 */
122static char *
123make_version_name(const char *file, int version)
124{
125	char	*backup_name;
126
127	if (asprintf(&backup_name, "%s.~%d~", file, version) == -1)
128		return NULL;
129	return backup_name;
130}
131
132/*
133 * If BACKUP is a numbered backup of BASE, return its version number;
134 * otherwise return 0.  BASE_LENGTH is the length of BASE. BASE should
135 * already have ".~" appended to it.
136 */
137static int
138version_number(const char *base, const char *backup, size_t base_length)
139{
140	int		version;
141	const char	*p;
142
143	version = 0;
144	if (!strncmp(base, backup, base_length) && ISDIGIT(backup[base_length])) {
145		for (p = &backup[base_length]; ISDIGIT(*p); ++p)
146			version = version * 10 + *p - '0';
147		if (p[0] != '~' || p[1])
148			version = 0;
149	}
150	return version;
151}
152
153/*
154 * Return the newly-allocated concatenation of STR1 and STR2. If out of
155 * memory, return 0.
156 */
157static char  *
158concat(const char *str1, const char *str2)
159{
160	char	*newstr;
161
162	if (asprintf(&newstr, "%s%s", str1, str2) == -1)
163		return NULL;
164	return newstr;
165}
166
167/*
168 * If ARG is an unambiguous match for an element of the null-terminated array
169 * OPTLIST, return the index in OPTLIST of the matched element, else -1 if it
170 * does not match any element or -2 if it is ambiguous (is a prefix of more
171 * than one element).
172 */
173static int
174argmatch(const char *arg, const char **optlist)
175{
176	int	i;	/* Temporary index in OPTLIST. */
177	size_t	arglen;	/* Length of ARG. */
178	int	matchind = -1;	/* Index of first nonexact match. */
179	int	ambiguous = 0;	/* If nonzero, multiple nonexact match(es). */
180
181	arglen = strlen(arg);
182
183	/* Test all elements for either exact match or abbreviated matches.  */
184	for (i = 0; optlist[i]; i++) {
185		if (!strncmp(optlist[i], arg, arglen)) {
186			if (strlen(optlist[i]) == arglen)
187				/* Exact match found.  */
188				return i;
189			else if (matchind == -1)
190				/* First nonexact match found.  */
191				matchind = i;
192			else
193				/* Second nonexact match found.  */
194				ambiguous = 1;
195		}
196	}
197	if (ambiguous)
198		return -2;
199	else
200		return matchind;
201}
202
203/*
204 * Error reporting for argmatch. KIND is a description of the type of entity
205 * that was being matched. VALUE is the invalid value that was given. PROBLEM
206 * is the return value from argmatch.
207 */
208static void
209invalid_arg(const char *kind, const char *value, int problem)
210{
211	fprintf(stderr, "patch: ");
212	if (problem == -1)
213		fprintf(stderr, "invalid");
214	else			/* Assume -2. */
215		fprintf(stderr, "ambiguous");
216	fprintf(stderr, " %s `%s'\n", kind, value);
217}
218
219static const char *backup_args[] = {
220	"none", "never", "simple", "nil", "existing", "t", "numbered", 0
221};
222
223static enum backup_type backup_types[] = {
224	none, simple, simple, numbered_existing,
225	numbered_existing, numbered, numbered
226};
227
228/*
229 * Return the type of backup indicated by VERSION. Unique abbreviations are
230 * accepted.
231 */
232enum backup_type
233get_version(const char *version)
234{
235	int	i;
236
237	if (version == NULL || *version == '\0')
238		return numbered_existing;
239	i = argmatch(version, backup_args);
240	if (i >= 0)
241		return backup_types[i];
242	invalid_arg("version control type", version, i);
243	exit(2);
244}
245