1/* Concatenate two arbitrary file names.
2
3   Copyright (C) 1996-2007, 2009-2010 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
37static char const *
38longest_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
60char *
61mfile_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