contrib/diffutils/lib/filenamecat-lgpl.c

   1 /* Concatenate two arbitrary file names.
   2
   3    Copyright (C) 1996-2007, 2009-2013 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 }