1/*	$OpenBSD: backupfile.c,v 1.20 2009/10/27 23:59:41 deraadt 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;
57	int	highest_backup;
58
59	if (backup_type == simple)
60		return concat(file, simple_backup_suffix);
61	base_versions = concat(basename((char *)file), ".~");
62	if (base_versions == NULL)
63		return NULL;
64	dir = dirname((char *)file);
65	if (dir == NULL) {
66		free(base_versions);
67		return NULL;
68	}
69	highest_backup = max_backup_version(base_versions, dir);
70	free(base_versions);
71	if (backup_type == numbered_existing && highest_backup == 0)
72		return concat(file, simple_backup_suffix);
73	return make_version_name(file, highest_backup + 1);
74}
75
76/*
77 * Return the number of the highest-numbered backup file for file FILE in
78 * directory DIR.  If there are no numbered backups of FILE in DIR, or an
79 * error occurs reading DIR, return 0. FILE should already have ".~" appended
80 * to it.
81 */
82static int
83max_backup_version(const char *file, const char *dir)
84{
85	DIR	*dirp;
86	struct dirent	*dp;
87	int	highest_version, this_version;
88	size_t	file_name_length;
89
90	dirp = opendir(dir);
91	if (dirp == NULL)
92		return 0;
93
94	highest_version = 0;
95	file_name_length = strlen(file);
96
97	while ((dp = readdir(dirp)) != NULL) {
98		if (dp->d_namlen <= file_name_length)
99			continue;
100
101		this_version = version_number(file, dp->d_name, file_name_length);
102		if (this_version > highest_version)
103			highest_version = this_version;
104	}
105	closedir(dirp);
106	return highest_version;
107}
108
109/*
110 * Return a string, allocated with malloc, containing "FILE.~VERSION~".
111 * Return 0 if out of memory.
112 */
113static char *
114make_version_name(const char *file, int version)
115{
116	char	*backup_name;
117
118	if (asprintf(&backup_name, "%s.~%d~", file, version) == -1)
119		return NULL;
120	return backup_name;
121}
122
123/*
124 * If BACKUP is a numbered backup of BASE, return its version number;
125 * otherwise return 0.  BASE_LENGTH is the length of BASE. BASE should
126 * already have ".~" appended to it.
127 */
128static int
129version_number(const char *base, const char *backup, size_t base_length)
130{
131	int		version;
132	const char	*p;
133
134	version = 0;
135	if (!strncmp(base, backup, base_length) && ISDIGIT(backup[base_length])) {
136		for (p = &backup[base_length]; ISDIGIT(*p); ++p)
137			version = version * 10 + *p - '0';
138		if (p[0] != '~' || p[1])
139			version = 0;
140	}
141	return version;
142}
143
144/*
145 * Return the newly-allocated concatenation of STR1 and STR2. If out of
146 * memory, return 0.
147 */
148static char  *
149concat(const char *str1, const char *str2)
150{
151	char	*newstr;
152
153	if (asprintf(&newstr, "%s%s", str1, str2) == -1)
154		return NULL;
155	return newstr;
156}
157
158/*
159 * If ARG is an unambiguous match for an element of the null-terminated array
160 * OPTLIST, return the index in OPTLIST of the matched element, else -1 if it
161 * does not match any element or -2 if it is ambiguous (is a prefix of more
162 * than one element).
163 */
164static int
165argmatch(const char *arg, const char **optlist)
166{
167	int	i;	/* Temporary index in OPTLIST. */
168	size_t	arglen;	/* Length of ARG. */
169	int	matchind = -1;	/* Index of first nonexact match. */
170	int	ambiguous = 0;	/* If nonzero, multiple nonexact match(es). */
171
172	arglen = strlen(arg);
173
174	/* Test all elements for either exact match or abbreviated matches.  */
175	for (i = 0; optlist[i]; i++) {
176		if (!strncmp(optlist[i], arg, arglen)) {
177			if (strlen(optlist[i]) == arglen)
178				/* Exact match found.  */
179				return i;
180			else if (matchind == -1)
181				/* First nonexact match found.  */
182				matchind = i;
183			else
184				/* Second nonexact match found.  */
185				ambiguous = 1;
186		}
187	}
188	if (ambiguous)
189		return -2;
190	else
191		return matchind;
192}
193
194/*
195 * Error reporting for argmatch. KIND is a description of the type of entity
196 * that was being matched. VALUE is the invalid value that was given. PROBLEM
197 * is the return value from argmatch.
198 */
199static void
200invalid_arg(const char *kind, const char *value, int problem)
201{
202	fprintf(stderr, "patch: ");
203	if (problem == -1)
204		fprintf(stderr, "invalid");
205	else			/* Assume -2. */
206		fprintf(stderr, "ambiguous");
207	fprintf(stderr, " %s `%s'\n", kind, value);
208}
209
210static const char *backup_args[] = {
211	"never", "simple", "nil", "existing", "t", "numbered", 0
212};
213
214static enum backup_type backup_types[] = {
215	simple, simple, numbered_existing,
216	numbered_existing, numbered, numbered
217};
218
219/*
220 * Return the type of backup indicated by VERSION. Unique abbreviations are
221 * accepted.
222 */
223enum backup_type
224get_version(const char *version)
225{
226	int	i;
227
228	if (version == NULL || *version == '\0')
229		return numbered_existing;
230	i = argmatch(version, backup_args);
231	if (i >= 0)
232		return backup_types[i];
233	invalid_arg("version control type", version, i);
234	exit(2);
235}
236