lib/path-concat.c

   1 /* path-concat.c -- concatenate two arbitrary pathnames
   2    Copyright (C) 1996, 1997, 1998, 1999, 2000, 2001 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 FILESYSTEM_PREFIX_LEN
  63 # define FILESYSTEM_PREFIX_LEN(Filename) 0
  64 #endif
  65
  66 #ifndef ISSLASH
  67 # define ISSLASH(C) ((C) == DIRECTORY_SEPARATOR)
  68 #endif
  69
  70 #include "xalloc.h"
  71 #include "path-concat.h"
  72
  73 /* Concatenate two pathname components, DIR and BASE, in
  74    newly-allocated storage and return the result.  Return 0 if out of
  75    memory.  Add a slash between DIR and BASE in the result if neither
  76    would contribute one.  If each would contribute at least one, elide
  77    one from the end of DIR.  Otherwise, simply concatenate DIR and
  78    BASE.  In any case, if BASE_IN_RESULT is non-NULL, set
  79    *BASE_IN_RESULT to point to the copy of BASE in the returned
  80    concatenation.
  81
  82    DIR may be NULL, BASE must not be.
  83
  84    Return NULL if memory is exhausted.  */
  85
  86 char *
  87 path_concat (const char *dir, const char *base, char **base_in_result)
  88 {
  89   char *p;
  90   char *p_concat;
  91   size_t base_len;
  92   size_t dir_len;
  93
  94   if (!dir)
  95     {
  96       p_concat = strdup (base);
  97       if (base_in_result)
  98         *base_in_result = p_concat;
  99       return p_concat;
 100     }
 101
 102   /* DIR is not empty. */
 103   base_len = strlen (base);
 104   dir_len = strlen (dir);
 105
 106   p_concat = malloc (dir_len + base_len + 2);
 107   if (!p_concat)
 108     return 0;
 109
 110   p = mempcpy (p_concat, dir, dir_len);
 111
 112   if (dir_len > FILESYSTEM_PREFIX_LEN (dir))
 113     {
 114       if (ISSLASH (*(p - 1)) && ISSLASH (*base))
 115         --p;
 116       else if (!ISSLASH (*(p - 1)) && !ISSLASH (*base))
 117         *p++ = DIRECTORY_SEPARATOR;
 118     }
 119
 120   if (base_in_result)
 121     *base_in_result = p;
 122
 123   memcpy (p, base, base_len + 1);
 124
 125   return p_concat;
 126 }
 127
 128 /* Same, but die when memory is exhausted. */
 129
 130 char *
 131 xpath_concat (const char *dir, const char *base, char **base_in_result)
 132 {
 133   char *res = path_concat (dir, base, base_in_result);
 134   if (res)
 135     return res;
 136   xalloc_die ();
 137 }