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/* Return the canonical absolute name of a given file.
Copyright (C) 1996 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 Library General Public License as
published by the Free Software Foundation; either version 2 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
Library General Public License for more details.
You should have received a copy of the GNU Library General Public
License along with the GNU C Library; see the file COPYING.LIB. If
not, write to the Free Software Foundation, Inc., 675 Mass Ave,
Cambridge, MA 02139, USA. */
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <limits.h>
#include <sys/stat.h>
#include <errno.h>
/* Return the canonical absolute name of file NAME. The last file name
component need not exist, and may be a symlink to a nonexistent file.
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. */
static char *
canonicalize (const char *name, char *resolved)
{
struct stat st;
const char *p;
long int path_max;
char *result, *dir, *end;
size_t namelen;
if (! resolved)
path_max = 0;
else
{
#ifdef PATH_MAX
path_max = PATH_MAX;
#else
path_max = sysconf (_SC_PATH_MAX);
if (path_max <= 0)
path_max = 1024;
#endif
}
p = strrchr (name, '/');
if (!p)
{
dir = (char *) ".";
p = name;
}
else
{
if (p++ == name)
dir = (char *) "/";
else
{
dir = __alloca (p - name);
memcpy (dir, name, p - name - 1);
dir[p - name] = '\0';
}
}
result = __canonicalize_directory_name_internal (dir, resolved, path_max);
if (!result)
return NULL;
/* Reconstruct the file name in the canonicalized directory. */
namelen = strlen (name);
end = strchr (result, '\0');
if (resolved)
{
/* Make sure the name is not too long. */
if (end - result + namelen > path_max)
{
errno = ENAMETOOLONG;
return NULL;
}
}
else
{
/* The name is dynamically allocated. Extend it. */
char *new = realloc (result, end - result + namelen + 1);
if (! new)
{
free (result);
return NULL;
}
end = new + (end - result);
result = new;
}
memcpy (end, name, namelen + 1);
while (__lstat (result, &st) == 0 && S_ISLNK (st.st_mode))
{
/* The file is a symlink. Read its contents. */
ssize_t n;
read_link_contents:
n = readlink (result, end,
resolved ? result + path_max - end : namelen + 1);
if (n < 0)
/* Error reading the link contents. */
return NULL;
if (end[0] == '/')
{
/* Absolute symlink. */
if (resolved ? (end + n < result + path_max) : (n < namelen + 1))
{
/* It fit in our buffer, so we have the whole thing. */
memcpy (result, end, n);
result[n] = '\0';
}
else if (resolved)
{
/* It didn't fit in the remainder of the buffer. Either it
fits in the entire buffer, or it doesn't. Copy back the
unresolved name onto the canonical directory and try once
more. */
memcpy (end, name, namelen + 1);
n = readlink (result, result, path_max);
if (n < 0)
return NULL;
if (n == path_max)
{
errno = ENAMETOOLONG;
return NULL;
}
result[n] = '\0';
}
else
/* Try again with a bigger buffer. */
goto extend_buffer;
/* Check the resolved name for being a symlink too. */
continue;
}
if (resolved)
{
if (end + n == result + path_max)
{
/* The link contents we read fill the buffer completely.
There may be even more to read, and there is certainly no
space for the null terminator. */
errno = ENAMETOOLONG;
return NULL;
}
}
else if (n == namelen + 1)
extend_buffer:
{
/* The name buffer is dynamically allocated. Extend it. */
char *new;
/* Copy back the unresolved name onto the canonical directory. */
memcpy (end, name, namelen + 1);
/* Make more space for readlink. */
namelen *= 2;
new = realloc (result, end - result + namelen + 1);
if (! new)
{
free (result);
return NULL;
}
end = new + (end - result);
result = new;
goto read_link_contents;
}
/* Terminate the string; readlink does not. */
end[n] = '\0';
}
return result;
}
weak_alias (canonicalize, realpath)
char *
canonicalize_file_name (const char *name)
{
return canonicalize (name, NULL);
}
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