lib/path-concat.c

   1 /* path-concat.c -- concatenate two arbitrary pathnames
   2
   3    Copyright (C) 1996, 1997, 1998, 1999, 2000, 2001, 2002 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
  32 #if HAVE_STRING_H
  33 # if !STDC_HEADERS && HAVE_MEMORY_H
  34 #  include <memory.h>
  35 # endif
  36 # include <string.h>
  37 #else
  38 # if HAVE_STRINGS_H
  39 #  include <strings.h>
  40 # endif
  41 #endif
  42 #if HAVE_STDLIB_H
  43 # include <stdlib.h>
  44 #endif
  45 #if HAVE_UNISTD_H
  46 # include <unistd.h>
  47 #endif
  48
  49 #ifndef HAVE_DECL_MALLOC
  50 "this configure-time declaration test was not run"
  51 #endif
  52 #if !HAVE_DECL_MALLOC
  53 char *malloc ();
  54 #endif
  55
  56 #ifndef strdup
  57 char *strdup ();
  58 #endif
  59
  60 #include "dirname.h"
  61 #include "xalloc.h"
  62 #include "path-concat.h"
  63
  64 /* Concatenate two pathname components, DIR and BASE, in
  65    newly-allocated storage and return the result.  Return 0 if out of
  66    memory.  Add a slash between DIR and BASE in the result if neither
  67    would contribute one.  If each would contribute at least one, elide
  68    one from the end of DIR.  Otherwise, simply concatenate DIR and
  69    BASE.  In any case, if BASE_IN_RESULT is non-NULL, set
  70    *BASE_IN_RESULT to point to the copy of BASE in the returned
  71    concatenation.
  72
  73    DIR may be NULL, BASE must not be.
  74
  75    Return NULL if memory is exhausted.  */
  76
  77 char *
  78 path_concat (const char *dir, const char *base, char **base_in_result)
  79 {
  80   char *p;
  81   char *p_concat;
  82   size_t baselen;
  83   size_t dirlen;
  84
  85   if (!dir)
  86     {
  87       p_concat = strdup (base);
  88       if (base_in_result)
  89         *base_in_result = p_concat;
  90       return p_concat;
  91     }
  92
  93   /* DIR is not empty. */
  94   baselen = base_len (base);
  95   dirlen = strlen (dir);
  96
  97   p_concat = malloc (dirlen + baselen + 2);
  98   if (!p_concat)
  99     return 0;
 100
 101   p = mempcpy (p_concat, dir, dirlen);
 102
 103   if (FILESYSTEM_PREFIX_LEN (dir) < dirlen)
 104     {
 105       if (ISSLASH (*(p - 1)) && ISSLASH (*base))
 106         --p;
 107       else if (!ISSLASH (*(p - 1)) && !ISSLASH (*base))
 108         *p++ = DIRECTORY_SEPARATOR;
 109     }
 110
 111   if (base_in_result)
 112     *base_in_result = p;
 113
 114   memcpy (p, base, baselen);
 115   p[baselen] = '\0';
 116
 117   return p_concat;
 118 }
 119
 120 /* Same, but die when memory is exhausted. */
 121
 122 char *
 123 xpath_concat (const char *dir, const char *base, char **base_in_result)
 124 {
 125   char *res = path_concat (dir, base, base_in_result);
 126   if (! res)
 127     xalloc_die ();
 128   return res;
 129 }