contrib/tar/lib/xgetcwd.c

   1 /* xgetcwd.c -- return current directory with unlimited length
   2    Copyright (C) 1992, 1996, 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 David MacKenzie <djm@gnu.ai.mit.edu>.  */
  19
  20 #if HAVE_CONFIG_H
  21 # include <config.h>
  22 #endif
  23
  24 #include <stdio.h>
  25 #include <errno.h>
  26 #ifndef errno
  27 extern int errno;
  28 #endif
  29
  30 #include <sys/types.h>
  31
  32 #if HAVE_STDLIB_H
  33 # include <stdlib.h>
  34 #endif
  35 #if HAVE_UNISTD_H
  36 # include <unistd.h>
  37 #endif
  38
  39 #if HAVE_GETCWD
  40 char *getcwd ();
  41 #else
  42 # include "pathmax.h"
  43 # define INITIAL_BUFFER_SIZE (PATH_MAX + 1)
  44 char *getwd ();
  45 # define getcwd(Buf, Max) getwd (Buf)
  46 #endif
  47
  48 #include "xalloc.h"
  49
  50 /* Return the current directory, newly allocated, arbitrarily long.
  51    Return NULL and set errno on error. */
  52
  53 char *
  54 xgetcwd ()
  55 {
  56 #if HAVE_GETCWD_NULL
  57   char *cwd = getcwd (NULL, 0);
  58   if (! cwd && errno == ENOMEM)
  59     xalloc_die ();
  60   return cwd;
  61 #else
  62
  63   /* The initial buffer size for the working directory.  A power of 2
  64      detects arithmetic overflow earlier, but is not required.  */
  65 # ifndef INITIAL_BUFFER_SIZE
  66 #  define INITIAL_BUFFER_SIZE 128
  67 # endif
  68
  69   size_t buf_size = INITIAL_BUFFER_SIZE;
  70
  71   while (1)
  72     {
  73       char *buf = xmalloc (buf_size);
  74       char *cwd = getcwd (buf, buf_size);
  75       int saved_errno;
  76       if (cwd)
  77         return cwd;
  78       saved_errno = errno;
  79       free (buf);
  80       if (saved_errno != ERANGE)
  81         return NULL;
  82       buf_size *= 2;
  83       if (buf_size == 0)
  84         xalloc_die ();
  85     }
  86 #endif
  87 }