coreutils/lib/xgetcwd.c

/* xgetcwd.c -- return current directory with unlimited length
   Copyright (C) 1992, 1996, 2000, 2001, 2003 Free Software Foundation, Inc.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2, or (at your option)
   any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software Foundation,
   Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */

/* Written by David MacKenzie <djm@gnu.ai.mit.edu>.  */

#if HAVE_CONFIG_H
# include <config.h>
#endif

#include <stdio.h>
#include <errno.h>
#include <sys/types.h>
#include <stdlib.h>

#if HAVE_UNISTD_H
# include <unistd.h>
#endif

#if HAVE_GETCWD
char *getcwd ();
#else
# include "pathmax.h"
# define INITIAL_BUFFER_SIZE (PATH_MAX + 1)
char *getwd ();
# define getcwd(Buf, Max) getwd (Buf)
#endif

#include "xalloc.h"
#include "xgetcwd.h"

/* Return the current directory, newly allocated, assuming it fits
   within PATH_MAX bytes -- this is a common system-imposed limit
   on how getcwd works.
   Upon an out-of-memory error, call xalloc_die.
   Upon any other type of error, return NULL.  */

char *
xgetcwd (void)
{
#if HAVE_GETCWD_NULL
  char *cwd = getcwd (NULL, 0);
  if (! cwd && errno == ENOMEM)
    xalloc_die ();
  return cwd;
#else

  /* The initial buffer size for the working directory.  A power of 2
     detects arithmetic overflow earlier, but is not required.  */
# ifndef INITIAL_BUFFER_SIZE
#  define INITIAL_BUFFER_SIZE 128
# endif

  size_t buf_size = INITIAL_BUFFER_SIZE;

  while (1)
    {
      char *buf = xmalloc (buf_size);
      char *cwd = getcwd (buf, buf_size);
      int saved_errno;
      if (cwd)
	return cwd;
      saved_errno = errno;
      free (buf);
      if (saved_errno != ERANGE)
	return NULL;
      buf_size *= 2;
      if (buf_size == 0)
	xalloc_die ();
    }
#endif
}