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      1 /* dirname.c -- return all but the last element in a file name
      2 
      3    Copyright (C) 1990, 1998, 2000-2001, 2003-2006, 2009-2012 Free Software
      4    Foundation, Inc.
      5 
      6    This program is free software: you can redistribute it and/or modify
      7    it under the terms of the GNU General Public License as published by
      8    the Free Software Foundation; either version 3 of the License, or
      9    (at your option) any later version.
     10 
     11    This program is distributed in the hope that it will be useful,
     12    but WITHOUT ANY WARRANTY; without even the implied warranty of
     13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
     14    GNU General Public License for more details.
     15 
     16    You should have received a copy of the GNU General Public License
     17    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
     18 
     19 #include <config.h>
     20 
     21 #include "dirname.h"
     22 
     23 #include <stdlib.h>
     24 #include <string.h>
     25 
     26 /* Return the length of the prefix of FILE that will be used by
     27    dir_name.  If FILE is in the working directory, this returns zero
     28    even though 'dir_name (FILE)' will return ".".  Works properly even
     29    if there are trailing slashes (by effectively ignoring them).  */
     30 
     31 size_t
     32 dir_len (char const *file)
     33 {
     34   size_t prefix_length = FILE_SYSTEM_PREFIX_LEN (file);
     35   size_t length;
     36 
     37   /* Advance prefix_length beyond important leading slashes.  */
     38   prefix_length += (prefix_length != 0
     39                     ? (FILE_SYSTEM_DRIVE_PREFIX_CAN_BE_RELATIVE
     40                        && ISSLASH (file[prefix_length]))
     41                     : (ISSLASH (file[0])
     42                        ? ((DOUBLE_SLASH_IS_DISTINCT_ROOT
     43                            && ISSLASH (file[1]) && ! ISSLASH (file[2])
     44                            ? 2 : 1))
     45                        : 0));
     46 
     47   /* Strip the basename and any redundant slashes before it.  */
     48   for (length = last_component (file) - file;
     49        prefix_length < length; length--)
     50     if (! ISSLASH (file[length - 1]))
     51       break;
     52   return length;
     53 }
     54 
     55 
     56 /* In general, we can't use the builtin 'dirname' function if available,
     57    since it has different meanings in different environments.
     58    In some environments the builtin 'dirname' modifies its argument.
     59 
     60    Return the leading directories part of FILE, allocated with malloc.
     61    Works properly even if there are trailing slashes (by effectively
     62    ignoring them).  Return NULL on failure.
     63 
     64    If lstat (FILE) would succeed, then { chdir (dir_name (FILE));
     65    lstat (base_name (FILE)); } will access the same file.  Likewise,
     66    if the sequence { chdir (dir_name (FILE));
     67    rename (base_name (FILE), "foo"); } succeeds, you have renamed FILE
     68    to "foo" in the same directory FILE was in.  */
     69 
     70 char *
     71 mdir_name (char const *file)
     72 {
     73   size_t length = dir_len (file);
     74   bool append_dot = (length == 0
     75                      || (FILE_SYSTEM_DRIVE_PREFIX_CAN_BE_RELATIVE
     76                          && length == FILE_SYSTEM_PREFIX_LEN (file)
     77                          && file[2] != '\0' && ! ISSLASH (file[2])));
     78   char *dir = malloc (length + append_dot + 1);
     79   if (!dir)
     80     return NULL;
     81   memcpy (dir, file, length);
     82   if (append_dot)
     83     dir[length++] = '.';
     84   dir[length] = '\0';
     85   return dir;
     86 }
     87