lib/path-concat.c

   1 /* path-concat.c -- concatenate two arbitrary pathnames
   2    Copyright (C) 1996, 1997, 1998, 1999, 2000 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
  30 #if HAVE_STRING_H
  31 # if !STDC_HEADERS && HAVE_MEMORY_H
  32 #  include <memory.h>
  33 # endif
  34 # include <string.h>
  35 #else
  36 # if HAVE_STRINGS_H
  37 #  include <strings.h>
  38 # endif
  39 #endif
  40 #if HAVE_STDLIB_H
  41 # include <stdlib.h>
  42 #endif
  43 #if HAVE_UNISTD_H
  44 # include <unistd.h>
  45 #endif
  46
  47 #ifndef HAVE_DECL_MALLOC
  48 "this configure-time declaration test was not run"
  49 #endif
  50 #if !HAVE_DECL_MALLOC
  51 char *malloc ();
  52 #endif
  53
  54 #ifndef strdup
  55 char *strdup ();
  56 #endif
  57
  58 #ifndef DIRECTORY_SEPARATOR
  59 # define DIRECTORY_SEPARATOR '/'
  60 #endif
  61
  62 #ifndef ISSLASH
  63 # define ISSLASH(C) ((C) == DIRECTORY_SEPARATOR)
  64 #endif
  65
  66 #include "xalloc.h"
  67 #include "path-concat.h"
  68
  69 /* Concatenate two pathname components, DIR and BASE, in
  70    newly-allocated storage and return the result.  Return 0 if out of
  71    memory.  Add a slash between DIR and BASE in the result if neither
  72    would contribute one.  If each would contribute at least one, elide
  73    one from the end of DIR.  Otherwise, simply concatenate DIR and
  74    BASE.  In any case, if BASE_IN_RESULT is non-NULL, set
  75    *BASE_IN_RESULT to point to the copy of BASE in the returned
  76    concatenation.
  77
  78    DIR may be NULL, BASE must not be.
  79
  80    Return NULL if memory is exhausted.  */
  81
  82 char *
  83 path_concat (const char *dir, const char *base, char **base_in_result)
  84 {
  85   char *p;
  86   char *p_concat;
  87   size_t base_len;
  88   size_t dir_len;
  89
  90   if (!dir)
  91     {
  92       p_concat = strdup (base);
  93       if (base_in_result)
  94         *base_in_result = p_concat;
  95       return p_concat;
  96     }
  97
  98   /* DIR is not empty. */
  99   base_len = strlen (base);
 100   dir_len = strlen (dir);
 101
 102   p_concat = malloc (dir_len + base_len + 2);
 103   if (!p_concat)
 104     return 0;
 105
 106   p = mempcpy (p_concat, dir, dir_len);
 107
 108   if (dir_len > 0)
 109     {
 110       if (ISSLASH (*(p - 1)) && ISSLASH(*base))
 111         --p;
 112       else if (!ISSLASH (*(p - 1)) && !ISSLASH(*base))
 113         *p++ = DIRECTORY_SEPARATOR;
 114     }
 115
 116   if (base_in_result)
 117     *base_in_result = p;
 118
 119   memcpy (p, base, base_len + 1);
 120
 121   return p_concat;
 122 }
 123
 124 /* Same, but die when memory is exhausted. */
 125
 126 char *
 127 xpath_concat (const char *dir, const char *base, char **base_in_result)
 128 {
 129   char *res = path_concat (dir, base, base_in_result);
 130   if (res)
 131     return res;
 132   xalloc_die ();
 133 }