lib/basename.c

   1 /* basename.c -- return the last element in a file name
   2
   3    Copyright (C) 1990, 1998-2001, 2003-2006, 2009-2024 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 <https://www.gnu.org/licenses/>.  */
  18
  19 #include <config.h>
  20
  21 #include "dirname.h"
  22
  23 #include <string.h>
  24 #include "xalloc.h"
  25
  26 char *
  27 base_name (char const *name)
  28 {
  29   char const *base = last_component (name);
  30   idx_t length;
  31   int dotslash_len;
  32   if (*base)
  33     {
  34       length = base_len (base);
  35
  36       /* Collapse a sequence of trailing slashes into one.  */
  37       length += ISSLASH (base[length]);
  38
  39       /* On systems with drive letters, "a/b:c" must return "./b:c" rather
  40          than "b:c" to avoid confusion with a drive letter.  On systems
  41          with pure POSIX semantics, this is not an issue.  */
  42       dotslash_len = FILE_SYSTEM_PREFIX_LEN (base) != 0 ? 2 : 0;
  43     }
  44   else
  45     {
  46       /* There is no last component, so NAME is a file system root or
  47          the empty string.  */
  48       base = name;
  49       length = base_len (base);
  50       dotslash_len = 0;
  51     }
  52
  53   char *p = ximalloc (dotslash_len + length + 1);
  54   if (dotslash_len)
  55     {
  56       p[0] = '.';
  57       p[1] = '/';
  58     }
  59
  60   /* Finally, copy the basename.  */
  61   memcpy (p + dotslash_len, base, length);
  62   p[dotslash_len + length] = '\0';
  63   return p;
  64 }