1 /* Concatenate two arbitrary file names.
2
3 Copyright (C) 1996-2007, 2009-2020 Free Software Foundation, Inc.
4
5 This program is free software: you can redistribute it and/or modify
6 it under the terms of the GNU General Public License as published by
7 the Free Software Foundation; either version 3 of the License, or
8 (at your option) any later version.
9
10 This program is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 GNU General Public License for more details.
14
15 You should have received a copy of the GNU General Public License
16 along with this program. If not, see <https://www.gnu.org/licenses/>. */
17
18 /* Written by Jim Meyering. */
19
20 #include <config.h>
21
22 /* Specification. */
23 #include "filenamecat.h"
24
25 #include <stdlib.h>
26 #include <string.h>
27
28 #include "basename-lgpl.h"
29 #include "filename.h"
30
31 #if ! HAVE_MEMPCPY && ! defined mempcpy
32 # define mempcpy(D, S, N) ((void *) ((char *) memcpy (D, S, N) + (N)))
33 #endif
34
35 /* Concatenate two file name components, DIR and BASE, in
36 newly-allocated storage and return the result.
37 The resulting file name F is such that the commands "ls F" and "(cd
38 DIR; ls ./BASE)" refer to the same file. If necessary, put
39 a separator between DIR and BASE in the result. Typically this
40 separator is "/", but in rare cases it might be ".".
41 In any case, if BASE_IN_RESULT is non-NULL, set
42 *BASE_IN_RESULT to point to the copy of BASE at the end of the
43 returned concatenation.
44
45 If malloc fails, return NULL with errno set. */
46
47 char *
mfile_name_concat(char const * dir,char const * base,char ** base_in_result)48 mfile_name_concat (char const *dir, char const *base, char **base_in_result)
49 {
50 char const *dirbase = last_component (dir);
51 size_t dirbaselen = base_len (dirbase);
52 size_t dirlen = dirbase - dir + dirbaselen;
53 size_t baselen = strlen (base);
54 char sep = '\0';
55 if (dirbaselen)
56 {
57 /* DIR is not a file system root, so separate with / if needed. */
58 if (! ISSLASH (dir[dirlen - 1]) && ! ISSLASH (*base))
59 sep = '/';
60 }
61 else if (ISSLASH (*base))
62 {
63 /* DIR is a file system root and BASE begins with a slash, so
64 separate with ".". For example, if DIR is "/" and BASE is
65 "/foo" then return "/./foo", as "//foo" would be wrong on
66 some POSIX systems. A fancier algorithm could omit "." in
67 some cases but is not worth the trouble. */
68 sep = '.';
69 }
70
71 char *p_concat = malloc (dirlen + (sep != '\0') + baselen + 1);
72 if (p_concat == NULL)
73 return NULL;
74
75 {
76 char *p;
77
78 p = mempcpy (p_concat, dir, dirlen);
79 *p = sep;
80 p += sep != '\0';
81
82 if (base_in_result)
83 *base_in_result = p;
84
85 p = mempcpy (p, base, baselen);
86 *p = '\0';
87 }
88
89 return p_concat;
90 }
91