lib/path-concat.c

   1 /* path-concat.c -- concatenate two arbitrary pathnames
   2
   3    Copyright (C) 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003 Free
   4    Software 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 2, or (at your option)
   9    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, write to the Free Software Foundation,
  18    Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
  19
  20 /* Written by Jim Meyering.  */
  21
  22 #if HAVE_CONFIG_H
  23 # include <config.h>
  24 #endif
  25
  26 #ifndef HAVE_MEMPCPY
  27 # define mempcpy(D, S, N) ((void *) ((char *) memcpy (D, S, N) + (N)))
  28 #endif
  29
  30 #include <stdio.h>
  31 #include <stdlib.h>
  32 #include <string.h>
  33
  34 #if HAVE_UNISTD_H
  35 # include <unistd.h>
  36 #endif
  37
  38 #ifndef strdup
  39 char *strdup ();
  40 #endif
  41
  42 #include "dirname.h"
  43 #include "xalloc.h"
  44 #include "path-concat.h"
  45
  46 /* Concatenate two pathname components, DIR and BASE, in
  47    newly-allocated storage and return the result.  Return 0 if out of
  48    memory.  Add a slash between DIR and BASE in the result if neither
  49    would contribute one.  If each would contribute at least one, elide
  50    one from the end of DIR.  Otherwise, simply concatenate DIR and
  51    BASE.  In any case, if BASE_IN_RESULT is non-NULL, set
  52    *BASE_IN_RESULT to point to the copy of BASE in the returned
  53    concatenation.
  54
  55    DIR may be NULL, BASE must not be.
  56
  57    Return NULL if memory is exhausted.  */
  58
  59 char *
  60 path_concat (const char *dir, const char *base, char **base_in_result)
  61 {
  62   char *p;
  63   char *p_concat;
  64   size_t baselen;
  65   size_t dirlen;
  66
  67   if (!dir)
  68     {
  69       p_concat = strdup (base);
  70       if (base_in_result)
  71         *base_in_result = p_concat;
  72       return p_concat;
  73     }
  74
  75   /* DIR is not empty. */
  76   baselen = base_len (base);
  77   dirlen = strlen (dir);
  78
  79   p_concat = malloc (dirlen + baselen + 2);
  80   if (!p_concat)
  81     return 0;
  82
  83   p = mempcpy (p_concat, dir, dirlen);
  84
  85   if (FILESYSTEM_PREFIX_LEN (dir) < dirlen)
  86     {
  87       if (ISSLASH (*(p - 1)) && ISSLASH (*base))
  88         --p;
  89       else if (!ISSLASH (*(p - 1)) && !ISSLASH (*base))
  90         *p++ = DIRECTORY_SEPARATOR;
  91     }
  92
  93   if (base_in_result)
  94     *base_in_result = p;
  95
  96   memcpy (p, base, baselen);
  97   p[baselen] = '\0';
  98
  99   return p_concat;
 100 }
 101
 102 /* Same, but die when memory is exhausted. */
 103
 104 char *
 105 xpath_concat (const char *dir, const char *base, char **base_in_result)
 106 {
 107   char *res = path_concat (dir, base, base_in_result);
 108   if (! res)
 109     xalloc_die ();
 110   return res;
 111 }