lib/libc/gen/dirname.c

   1 /*
   2  * Copyright (c) 2015-2016 Nuxi, https://nuxi.nl/
   3  *
   4  * Redistribution and use in source and binary forms, with or without
   5  * modification, are permitted provided that the following conditions
   6  * are met:
   7  * 1. Redistributions of source code must retain the above copyright
   8  *    notice, this list of conditions and the following disclaimer.
   9  * 2. Redistributions in binary form must reproduce the above copyright
  10  *    notice, this list of conditions and the following disclaimer in the
  11  *    documentation and/or other materials provided with the distribution.
  12  *
  13  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  14  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  15  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  16  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  17  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  18  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  19  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  20  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  21  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  22  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  23  * SUCH DAMAGE.
  24  */
  25 #include <errno.h>
  26 #include <libgen.h>
  27 #include <stdlib.h>
  28 #include <string.h>
  29 #include <sys/param.h>
  30
  31 char *
  32 dirname(char *path)
  33 {
  34         char *end;
  35
  36         /*
  37          * If path is a null pointer or points to an empty string,
  38          * dirname() shall return a pointer to the string ".".
  39          */
  40         if (path == NULL || *path == '\0')
  41                 return (__DECONST(char *, "."));
  42
  43         /* Find end of last pathname component. */
  44         end = path + strlen(path);
  45         while (end > path + 1 && end[-1] == '/')
  46                 --end;
  47
  48         /* Strip off the last pathname component. */
  49         while (end > path && end[-1] != '/')
  50                 --end;
  51
  52         /*
  53          * If path does not contain a '/', then dirname() shall return a
  54          * pointer to the string ".".
  55          */
  56         if (end == path) {
  57                 path[0] = '.';
  58                 path[1] = '\0';
  59                 return (path);
  60         }
  61
  62         /*
  63          * Remove trailing slashes from the resulting directory name. Ensure
  64          * that at least one character remains.
  65          */
  66         while (end > path + 1 && end[-1] == '/')
  67                 --end;
  68
  69         /* Null terminate directory name and return it. */
  70         *end = '\0';
  71         return (path);
  72 }