1/* Concatenate two arbitrary file names.
2
3   Copyright (C) 1996-2007 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#include "xalloc.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/* Return the longest suffix of F that is a relative file name.
36   If it has no such suffix, return the empty string.  */
37
38static char const *
39longest_relative_suffix (char const *f)
40{
41  for (f += FILE_SYSTEM_PREFIX_LEN (f); ISSLASH (*f); f++)
42    continue;
43  return f;
44}
45
46/* Concatenate two file name components, DIR and ABASE, in
47   newly-allocated storage and return the result.
48   The resulting file name F is such that the commands "ls F" and "(cd
49   DIR; ls BASE)" refer to the same file, where BASE is ABASE with any
50   file system prefixes and leading separators removed.
51   Arrange for a directory separator if necessary between DIR and BASE
52   in the result, removing any redundant separators.
53   In any case, if BASE_IN_RESULT is non-NULL, set
54   *BASE_IN_RESULT to point to the copy of ABASE in the returned
55   concatenation.  However, if ABASE begins with more than one slash,
56   set *BASE_IN_RESULT to point to the sole corresponding slash that
57   is copied into the result buffer.
58
59   Return NULL if malloc fails.  */
60
61char *
62mfile_name_concat (char const *dir, char const *abase, char **base_in_result)
63{
64  char const *dirbase = last_component (dir);
65  size_t dirbaselen = base_len (dirbase);
66  size_t dirlen = dirbase - dir + dirbaselen;
67  size_t needs_separator = (dirbaselen && ! ISSLASH (dirbase[dirbaselen - 1]));
68
69  char const *base = longest_relative_suffix (abase);
70  size_t baselen = strlen (base);
71
72  char *p_concat = malloc (dirlen + needs_separator + baselen + 1);
73  char *p;
74
75  if (p_concat == NULL)
76    return NULL;
77
78  p = mempcpy (p_concat, dir, dirlen);
79  *p = DIRECTORY_SEPARATOR;
80  p += needs_separator;
81
82  if (base_in_result)
83    *base_in_result = p - IS_ABSOLUTE_FILE_NAME (abase);
84
85  p = mempcpy (p, base, baselen);
86  *p = '\0';
87
88  return p_concat;
89}
90
91/* Just like mfile_name_concat, above, except, rather than
92   returning NULL upon malloc failure, here, we report the
93   "memory exhausted" condition and exit.  */
94
95char *
96file_name_concat (char const *dir, char const *abase, char **base_in_result)
97{
98  char *p = mfile_name_concat (dir, abase, base_in_result);
99  if (p == NULL)
100    xalloc_die ();
101  return p;
102}
103