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