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 * $FreeBSD$
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 ((unsigned char)c) && isdigit ((unsigned char)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 */
39const char	*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) && ISDIGIT(backup[base_length])) {
147		for (p = &backup[base_length]; ISDIGIT(*p); ++p)
148			version = version * 10 + *p - '0';
149		if (p[0] != '~' || p[1])
150			version = 0;
151	}
152	return version;
153}
154
155/*
156 * Return the newly-allocated concatenation of STR1 and STR2. If out of
157 * memory, return 0.
158 */
159static char  *
160concat(const char *str1, const char *str2)
161{
162	char	*newstr;
163
164	if (asprintf(&newstr, "%s%s", str1, str2) == -1)
165		return NULL;
166	return newstr;
167}
168
169/*
170 * If ARG is an unambiguous match for an element of the null-terminated array
171 * OPTLIST, return the index in OPTLIST of the matched element, else -1 if it
172 * does not match any element or -2 if it is ambiguous (is a prefix of more
173 * than one element).
174 */
175static int
176argmatch(const char *arg, const char **optlist)
177{
178	int	i;	/* Temporary index in OPTLIST. */
179	size_t	arglen;	/* Length of ARG. */
180	int	matchind = -1;	/* Index of first nonexact match. */
181	int	ambiguous = 0;	/* If nonzero, multiple nonexact match(es). */
182
183	arglen = strlen(arg);
184
185	/* Test all elements for either exact match or abbreviated matches.  */
186	for (i = 0; optlist[i]; i++) {
187		if (!strncmp(optlist[i], arg, arglen)) {
188			if (strlen(optlist[i]) == arglen)
189				/* Exact match found.  */
190				return i;
191			else if (matchind == -1)
192				/* First nonexact match found.  */
193				matchind = i;
194			else
195				/* Second nonexact match found.  */
196				ambiguous = 1;
197		}
198	}
199	if (ambiguous)
200		return -2;
201	else
202		return matchind;
203}
204
205/*
206 * Error reporting for argmatch. KIND is a description of the type of entity
207 * that was being matched. VALUE is the invalid value that was given. PROBLEM
208 * is the return value from argmatch.
209 */
210static void
211invalid_arg(const char *kind, const char *value, int problem)
212{
213	fprintf(stderr, "patch: ");
214	if (problem == -1)
215		fprintf(stderr, "invalid");
216	else			/* Assume -2. */
217		fprintf(stderr, "ambiguous");
218	fprintf(stderr, " %s `%s'\n", kind, value);
219}
220
221static const char *backup_args[] = {
222	"never", "simple", "nil", "existing", "t", "numbered", 0
223};
224
225static enum backup_type backup_types[] = {
226	simple, simple, numbered_existing,
227	numbered_existing, numbered, numbered
228};
229
230/*
231 * Return the type of backup indicated by VERSION. Unique abbreviations are
232 * accepted.
233 */
234enum backup_type
235get_version(const char *version)
236{
237	int	i;
238
239	if (version == NULL || *version == '\0')
240		return numbered_existing;
241	i = argmatch(version, backup_args);
242	if (i >= 0)
243		return backup_types[i];
244	invalid_arg("version control type", version, i);
245	exit(2);
246}
247