lib/path-concat.c

   1 /* path-concat.c -- concatenate two arbitrary pathnames
   2    Copyright (C) 1996, 1997, 1998, 1999 Free Software Foundation, Inc.
   3
   4    This program is free software; you can redistribute it and/or modify
   5    it under the terms of the GNU General Public License as published by
   6    the Free Software Foundation; either version 2, or (at your option)
   7    any later version.
   8
   9    This program is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12    GNU General Public License for more details.
  13
  14    You should have received a copy of the GNU General Public License
  15    along with this program; if not, write to the Free Software Foundation,
  16    Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
  17
  18 /* Written by Jim Meyering.  */
  19
  20 #if HAVE_CONFIG_H
  21 # include <config.h>
  22 #endif
  23
  24 #ifndef HAVE_MEMPCPY
  25 # define mempcpy(D, S, N) ((void *) ((char *) memcpy (D, S, N) + (N)))
  26 #endif
  27
  28 #include <stdio.h>
  29 #if HAVE_STRING_H
  30 # include <string.h>
  31 #endif
  32 #include <sys/types.h>
  33
  34 char *malloc ();
  35
  36 #ifndef DIRECTORY_SEPARATOR
  37 # define DIRECTORY_SEPARATOR '/'
  38 #endif
  39
  40 #ifndef ISSLASH
  41 # define ISSLASH(C) ((C) == DIRECTORY_SEPARATOR)
  42 #endif
  43
  44 #include "xalloc.h"
  45 #include "path-concat.h"
  46
  47 /* Concatenate two pathname components, DIR and BASE, in
  48    newly-allocated storage and return the result.  Return 0 if out of
  49    memory.  Add a slash between DIR and BASE in the result if neither
  50    would contribute one.  If each would contribute at least one, elide
  51    one from the end of DIR.  Otherwise, simply concatenate DIR and
  52    BASE.  In any case, if BASE_IN_RESULT is non-NULL, set
  53    *BASE_IN_RESULT to point to the copy of BASE in the returned
  54    concatenation.
  55
  56    DIR may be NULL, BASE must not be.
  57
  58    Return NULL if memory is exhausted.  */
  59
  60 char *
  61 path_concat (const char *dir, const char *base, char **base_in_result)
  62 {
  63   char *p;
  64   char *p_concat;
  65   size_t base_len;
  66   size_t dir_len;
  67
  68   if (!dir)
  69     {
  70       p_concat = strdup (base);
  71       if (base_in_result)
  72         *base_in_result = p_concat;
  73       return p_concat;
  74     }
  75
  76   /* DIR is not empty. */
  77   base_len = strlen (base);
  78   dir_len = strlen (dir);
  79
  80   p_concat = malloc (dir_len + base_len + 2);
  81   if (!p_concat)
  82     return 0;
  83
  84   p = mempcpy (p_concat, dir, dir_len);
  85
  86   if (ISSLASH (*(p - 1)) && ISSLASH(*base))
  87     --p;
  88   else if (!ISSLASH (*(p - 1)) && !ISSLASH(*base))
  89     *p++ = DIRECTORY_SEPARATOR;
  90
  91   if (base_in_result)
  92     *base_in_result = p;
  93
  94   memcpy (p, base, base_len + 1);
  95
  96   return p_concat;
  97 }
  98
  99 /* Same, but die when memory is exhausted. */
 100
 101 char *
 102 xpath_concat (const char *dir, const char *base, char **base_in_result)
 103 {
 104   char *res = path_concat (dir, base, base_in_result);
 105   if (res)
 106     return res;
 107   xalloc_die ();
 108 }