lib/xgetcwd.c

   1 /* xgetcwd.c -- return current directory with unlimited length
   2    Copyright (C) 1992, 1996, 2000, 2001, 2003 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 #include <stdlib.h>
  32
  33 #if HAVE_UNISTD_H
  34 # include <unistd.h>
  35 #endif
  36
  37 #if HAVE_GETCWD
  38 char *getcwd ();
  39 #else
  40 # include "pathmax.h"
  41 # define INITIAL_BUFFER_SIZE (PATH_MAX + 1)
  42 char *getwd ();
  43 # define getcwd(Buf, Max) getwd (Buf)
  44 #endif
  45
  46 #include "xalloc.h"
  47 #include "xgetcwd.h"
  48
  49 /* Return the current directory, newly allocated, assuming it fits
  50    within PATH_MAX bytes -- this is a common system-imposed limit
  51    on how getcwd works.
  52    Upon an out-of-memory error, call xalloc_die.
  53    Upon any other type of error, return NULL.  */
  54
  55 char *
  56 xgetcwd (void)
  57 {
  58 #if HAVE_GETCWD_NULL
  59   char *cwd = getcwd (NULL, 0);
  60   if (! cwd && errno == ENOMEM)
  61     xalloc_die ();
  62   return cwd;
  63 #else
  64
  65   /* The initial buffer size for the working directory.  A power of 2
  66      detects arithmetic overflow earlier, but is not required.  */
  67 # ifndef INITIAL_BUFFER_SIZE
  68 #  define INITIAL_BUFFER_SIZE 128
  69 # endif
  70
  71   size_t buf_size = INITIAL_BUFFER_SIZE;
  72
  73   while (1)
  74     {
  75       char *buf = xmalloc (buf_size);
  76       char *cwd = getcwd (buf, buf_size);
  77       int saved_errno;
  78       if (cwd)
  79         return cwd;
  80       saved_errno = errno;
  81       free (buf);
  82       if (saved_errno != ERANGE)
  83         return NULL;
  84       buf_size *= 2;
  85       if (buf_size == 0)
  86         xalloc_die ();
  87     }
  88 #endif
  89 }