1 /* Concatenate two arbitrary file names.
2 
3    Copyright (C) 1996-2007, 2009-2015 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 <http://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 "dirname.h"
29 
30 #if ! HAVE_MEMPCPY && ! defined mempcpy
31 # define mempcpy(D, S, N) ((void *) ((char *) memcpy (D, S, N) + (N)))
32 #endif
33 
34 /* Return the longest suffix of F that is a relative file name.
35    If it has no such suffix, return the empty string.  */
36 
37 static char const * _GL_ATTRIBUTE_PURE
38 longest_relative_suffix (char const *f)
39 {
40   for (f += FILE_SYSTEM_PREFIX_LEN (f); ISSLASH (*f); f++)
41     continue;
42   return f;
43 }
44 
45 /* Concatenate two file name components, DIR and ABASE, in
46    newly-allocated storage and return the result.
47    The resulting file name F is such that the commands "ls F" and "(cd
48    DIR; ls BASE)" refer to the same file, where BASE is ABASE with any
49    file system prefixes and leading separators removed.
50    Arrange for a directory separator if necessary between DIR and BASE
51    in the result, removing any redundant separators.
52    In any case, if BASE_IN_RESULT is non-NULL, set
53    *BASE_IN_RESULT to point to the copy of ABASE in the returned
54    concatenation.  However, if ABASE begins with more than one slash,
55    set *BASE_IN_RESULT to point to the sole corresponding slash that
56    is copied into the result buffer.
57 
58    Return NULL if malloc fails.  */
59 
60 char *
61 mfile_name_concat (char const *dir, char const *abase, char **base_in_result)
62 {
63   char const *dirbase = last_component (dir);
64   size_t dirbaselen = base_len (dirbase);
65   size_t dirlen = dirbase - dir + dirbaselen;
66   size_t needs_separator = (dirbaselen && ! ISSLASH (dirbase[dirbaselen - 1]));
67 
68   char const *base = longest_relative_suffix (abase);
69   size_t baselen = strlen (base);
70 
71   char *p_concat = malloc (dirlen + needs_separator + baselen + 1);
72   char *p;
73 
74   if (p_concat == NULL)
75     return NULL;
76 
77   p = mempcpy (p_concat, dir, dirlen);
78   *p = DIRECTORY_SEPARATOR;
79   p += needs_separator;
80 
81   if (base_in_result)
82     *base_in_result = p - IS_ABSOLUTE_FILE_NAME (abase);
83 
84   p = mempcpy (p, base, baselen);
85   *p = '\0';
86 
87   return p_concat;
88 }
89