/* Return the canonical absolute name of a given file.

   Copyright (C) 1996-2018 Free Software Foundation, Inc.

   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or

   modify it under the terms of the GNU Lesser General Public

   License as published by the Free Software Foundation; either

   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library 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

   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public

   License along with the GNU C Library; if not, see

   <http://www.gnu.org/licenses/>.  */

#include <assert.h>

#include <stdlib.h>

#include <string.h>

#include <unistd.h>

#include <limits.h>

#include <sys/stat.h>

#include <errno.h>

#include <stddef.h>

#include <eloop-threshold.h>

#include <shlib-compat.h>

/* Return the canonical absolute name of file NAME.  A canonical name

   does not contain any `.', `..' components nor any repeated path

   separators ('/') or symlinks.  All path components must exist.  If

   RESOLVED is null, the result is malloc'd; otherwise, if the

   canonical name is PATH_MAX chars or more, returns null with `errno'

   set to ENAMETOOLONG; if the name fits in fewer than PATH_MAX chars,

   returns the name in RESOLVED.  If the name cannot be resolved and

   RESOLVED is non-NULL, it contains the path of the first component

   that cannot be resolved.  If the path can be resolved, RESOLVED

   holds the same value as the value returned.  */

char *

__realpath (const char *name, char *resolved)

{

  char *rpath, *dest, *extra_buf = NULL;

  const char *start, *end, *rpath_limit;

  long int path_max;

  int num_links = 0;

  if (name == NULL)

    {

      /* As per Single Unix Specification V2 we must return an error if

	 either parameter is a null pointer.  We extend this to allow

	 the RESOLVED parameter to be NULL in case the we are expected to

	 allocate the room for the return value.  */

      __set_errno (EINVAL);

      return NULL;

    }

  if (name[0] == '\0')

    {

      /* As per Single Unix Specification V2 we must return an error if

	 the name argument points to an empty string.  */

      __set_errno (ENOENT);

      return NULL;

    }

#ifdef PATH_MAX

  path_max = PATH_MAX;

#else

  path_max = __pathconf (name, _PC_PATH_MAX);

  if (path_max <= 0)

    path_max = 1024;

#endif

  if (resolved == NULL)

    {

      rpath = malloc (path_max);

      if (rpath == NULL)

	return NULL;

    }

  else

    rpath = resolved;

  rpath_limit = rpath + path_max;

  if (name[0] != '/')

    {

      if (!__getcwd (rpath, path_max))

	{

	  rpath[0] = '\0';

	  goto error;

	}

      dest = __rawmemchr (rpath, '\0');

    }

  else

    {

      rpath[0] = '/';

      dest = rpath + 1;

    }

  for (start = end = name; *start; start = end)

    {

      struct stat64 st;

      int n;

      /* Skip sequence of multiple path-separators.  */

      while (*start == '/')

	++start;

      /* Find end of path component.  */

      for (end = start; *end && *end != '/'; ++end)

	/* Nothing.  */;

      if (end - start == 0)

	break;

      else if (end - start == 1 && start[0] == '.')

	/* nothing */;

      else if (end - start == 2 && start[0] == '.' && start[1] == '.')

	{

	  /* Back up to previous component, ignore if at root already.  */

	  if (dest > rpath + 1)

	    while ((--dest)[-1] != '/');

	}

      else

	{

	  size_t new_size;

	  if (dest[-1] != '/')

	    *dest++ = '/';

	  if (dest + (end - start) >= rpath_limit)

	    {

	      ptrdiff_t dest_offset = dest - rpath;

	      char *new_rpath;

	      if (resolved)

		{

		  __set_errno (ENAMETOOLONG);

		  if (dest > rpath + 1)

		    dest--;

		  *dest = '\0';

		  goto error;

		}

	      new_size = rpath_limit - rpath;

	      if (end - start + 1 > path_max)

		new_size += end - start + 1;

	      else

		new_size += path_max;

	      new_rpath = (char *) realloc (rpath, new_size);

	      if (new_rpath == NULL)

		goto error;

	      rpath = new_rpath;

	      rpath_limit = rpath + new_size;

	      dest = rpath + dest_offset;

	    }

	  dest = __mempcpy (dest, start, end - start);

	  *dest = '\0';

	  if (__lxstat64 (_STAT_VER, rpath, &st) < 0)

	    goto error;

	  if (S_ISLNK (st.st_mode))

	    {

	      char *buf = __alloca (path_max);

	      size_t len;

	      if (++num_links > __eloop_threshold ())

		{

		  __set_errno (ELOOP);

		  goto error;

		}

	      n = __readlink (rpath, buf, path_max - 1);

	      if (n < 0)

		goto error;

	      buf[n] = '\0';

	      if (!extra_buf)

		extra_buf = __alloca (path_max);

	      len = strlen (end);

	      if (path_max - n <= len)

		{

		  __set_errno (ENAMETOOLONG);

		  goto error;

		}

	      /* Careful here, end may be a pointer into extra_buf... */

	      memmove (&extra_buf[n], end, len + 1);

	      name = end = memcpy (extra_buf, buf, n);

	      if (buf[0] == '/')

		dest = rpath + 1;	/* It's an absolute symlink */

	      else

		/* Back up to previous component, ignore if at root already: */

		if (dest > rpath + 1)

		  while ((--dest)[-1] != '/');

	    }

	  else if (!S_ISDIR (st.st_mode) && *end != '\0')

	    {

	      __set_errno (ENOTDIR);

	      goto error;

	    }

	}

    }

  if (dest > rpath + 1 && dest[-1] == '/')

    --dest;

  *dest = '\0';

  assert (resolved == NULL || resolved == rpath);

  return rpath;

error:

  assert (resolved == NULL || resolved == rpath);

  if (resolved == NULL)

    free (rpath);

  return NULL;

}

libc_hidden_def (__realpath)

versioned_symbol (libc, __realpath, realpath, GLIBC_2_3);

#if SHLIB_COMPAT(libc, GLIBC_2_0, GLIBC_2_3)

char *

attribute_compat_text_section

__old_realpath (const char *name, char *resolved)

{

  if (resolved == NULL)

    {

      __set_errno (EINVAL);

      return NULL;

    }

  return __realpath (name, resolved);

}

compat_symbol (libc, __old_realpath, realpath, GLIBC_2_0);

#endif

char *

__canonicalize_file_name (const char *name)

{

  return __realpath (name, NULL);

}

weak_alias (__canonicalize_file_name, canonicalize_file_name)