xref: /freebsd/usr.bin/patch/backupfile.c (revision 9768746b)
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 
26 #include "backupfile.h"
27 
28 
29 #define ISDIGIT(c) (isascii ((unsigned char)c) && isdigit ((unsigned char)c))
30 
31 /* Which type of backup file names are generated. */
32 enum backup_type backup_type = none;
33 
34 /*
35  * The extension added to file names to produce a simple (as opposed to
36  * numbered) backup file name.
37  */
38 const char	*simple_backup_suffix = "~";
39 
40 static char	*concat(const char *, const char *);
41 static char	*make_version_name(const char *, int);
42 static int	max_backup_version(const char *, const char *);
43 static int	version_number(const char *, const char *, size_t);
44 static int	argmatch(const char *, const char **);
45 static void	invalid_arg(const char *, const char *, int);
46 
47 /*
48  * Return the name of the new backup file for file FILE, allocated with
49  * malloc.  Return 0 if out of memory. FILE must not end with a '/' unless it
50  * is the root directory. Do not call this function if backup_type == none.
51  */
52 char *
53 find_backup_file_name(const char *file)
54 {
55 	char	*dir, *base_versions, *tmp_file;
56 	int	highest_backup;
57 
58 	if (backup_type == simple)
59 		return concat(file, simple_backup_suffix);
60 	tmp_file = strdup(file);
61 	if (tmp_file == NULL)
62 		return NULL;
63 	base_versions = concat(basename(tmp_file), ".~");
64 	free(tmp_file);
65 	if (base_versions == NULL)
66 		return NULL;
67 	tmp_file = strdup(file);
68 	if (tmp_file == NULL) {
69 		free(base_versions);
70 		return NULL;
71 	}
72 	dir = dirname(tmp_file);
73 	if (dir == NULL) {
74 		free(base_versions);
75 		free(tmp_file);
76 		return NULL;
77 	}
78 	highest_backup = max_backup_version(base_versions, dir);
79 	free(base_versions);
80 	free(tmp_file);
81 	if (backup_type == numbered_existing && highest_backup == 0)
82 		return concat(file, simple_backup_suffix);
83 	return make_version_name(file, highest_backup + 1);
84 }
85 
86 /*
87  * Return the number of the highest-numbered backup file for file FILE in
88  * directory DIR.  If there are no numbered backups of FILE in DIR, or an
89  * error occurs reading DIR, return 0. FILE should already have ".~" appended
90  * to it.
91  */
92 static int
93 max_backup_version(const char *file, const char *dir)
94 {
95 	DIR	*dirp;
96 	struct dirent	*dp;
97 	int	highest_version, this_version;
98 	size_t	file_name_length;
99 
100 	dirp = opendir(dir);
101 	if (dirp == NULL)
102 		return 0;
103 
104 	highest_version = 0;
105 	file_name_length = strlen(file);
106 
107 	while ((dp = readdir(dirp)) != NULL) {
108 		if (dp->d_namlen <= file_name_length)
109 			continue;
110 
111 		this_version = version_number(file, dp->d_name, file_name_length);
112 		if (this_version > highest_version)
113 			highest_version = this_version;
114 	}
115 	closedir(dirp);
116 	return highest_version;
117 }
118 
119 /*
120  * Return a string, allocated with malloc, containing "FILE.~VERSION~".
121  * Return 0 if out of memory.
122  */
123 static char *
124 make_version_name(const char *file, int version)
125 {
126 	char	*backup_name;
127 
128 	if (asprintf(&backup_name, "%s.~%d~", file, version) == -1)
129 		return NULL;
130 	return backup_name;
131 }
132 
133 /*
134  * If BACKUP is a numbered backup of BASE, return its version number;
135  * otherwise return 0.  BASE_LENGTH is the length of BASE. BASE should
136  * already have ".~" appended to it.
137  */
138 static int
139 version_number(const char *base, const char *backup, size_t base_length)
140 {
141 	int		version;
142 	const char	*p;
143 
144 	version = 0;
145 	if (!strncmp(base, backup, base_length) && ISDIGIT(backup[base_length])) {
146 		for (p = &backup[base_length]; ISDIGIT(*p); ++p)
147 			version = version * 10 + *p - '0';
148 		if (p[0] != '~' || p[1])
149 			version = 0;
150 	}
151 	return version;
152 }
153 
154 /*
155  * Return the newly-allocated concatenation of STR1 and STR2. If out of
156  * memory, return 0.
157  */
158 static char  *
159 concat(const char *str1, const char *str2)
160 {
161 	char	*newstr;
162 
163 	if (asprintf(&newstr, "%s%s", str1, str2) == -1)
164 		return NULL;
165 	return newstr;
166 }
167 
168 /*
169  * If ARG is an unambiguous match for an element of the null-terminated array
170  * OPTLIST, return the index in OPTLIST of the matched element, else -1 if it
171  * does not match any element or -2 if it is ambiguous (is a prefix of more
172  * than one element).
173  */
174 static int
175 argmatch(const char *arg, const char **optlist)
176 {
177 	int	i;	/* Temporary index in OPTLIST. */
178 	size_t	arglen;	/* Length of ARG. */
179 	int	matchind = -1;	/* Index of first nonexact match. */
180 	int	ambiguous = 0;	/* If nonzero, multiple nonexact match(es). */
181 
182 	arglen = strlen(arg);
183 
184 	/* Test all elements for either exact match or abbreviated matches.  */
185 	for (i = 0; optlist[i]; i++) {
186 		if (!strncmp(optlist[i], arg, arglen)) {
187 			if (strlen(optlist[i]) == arglen)
188 				/* Exact match found.  */
189 				return i;
190 			else if (matchind == -1)
191 				/* First nonexact match found.  */
192 				matchind = i;
193 			else
194 				/* Second nonexact match found.  */
195 				ambiguous = 1;
196 		}
197 	}
198 	if (ambiguous)
199 		return -2;
200 	else
201 		return matchind;
202 }
203 
204 /*
205  * Error reporting for argmatch. KIND is a description of the type of entity
206  * that was being matched. VALUE is the invalid value that was given. PROBLEM
207  * is the return value from argmatch.
208  */
209 static void
210 invalid_arg(const char *kind, const char *value, int problem)
211 {
212 	fprintf(stderr, "patch: ");
213 	if (problem == -1)
214 		fprintf(stderr, "invalid");
215 	else			/* Assume -2. */
216 		fprintf(stderr, "ambiguous");
217 	fprintf(stderr, " %s `%s'\n", kind, value);
218 }
219 
220 static const char *backup_args[] = {
221 	"none", "never", "simple", "nil", "existing", "t", "numbered", 0
222 };
223 
224 static enum backup_type backup_types[] = {
225 	none, simple, simple, numbered_existing,
226 	numbered_existing, numbered, numbered
227 };
228 
229 /*
230  * Return the type of backup indicated by VERSION. Unique abbreviations are
231  * accepted.
232  */
233 enum backup_type
234 get_version(const char *version)
235 {
236 	int	i;
237 
238 	if (version == NULL || *version == '\0')
239 		return numbered_existing;
240 	i = argmatch(version, backup_args);
241 	if (i >= 0)
242 		return backup_types[i];
243 	invalid_arg("version control type", version, i);
244 	exit(2);
245 }
246