+++ /dev/null
-/* provide a chdir function that tries not to fail due to ENAMETOOLONG
- Copyright (C) 2004, 2005, 2006, 2007, 2008 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 3 of the License, 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, see <http://www.gnu.org/licenses/>. */
-
-/* written by Jim Meyering */
-
-#include <config.h>
-
-#include "chdir-long.h"
-
-#include <fcntl.h>
-#include <stdlib.h>
-#include <stdbool.h>
-#include <string.h>
-#include <errno.h>
-#include <stdio.h>
-#include <assert.h>
-
-#include "openat.h"
-
-#ifndef PATH_MAX
-# error "compile this file only if your system defines PATH_MAX"
-#endif
-
-struct cd_buf
-{
- int fd;
-};
-
-static inline void
-cdb_init (struct cd_buf *cdb)
-{
- cdb->fd = AT_FDCWD;
-}
-
-static inline int
-cdb_fchdir (struct cd_buf const *cdb)
-{
- return fchdir (cdb->fd);
-}
-
-static inline void
-cdb_free (struct cd_buf const *cdb)
-{
- if (0 <= cdb->fd)
- {
- bool close_fail = close (cdb->fd);
- assert (! close_fail);
- }
-}
-
-/* Given a file descriptor of an open directory (or AT_FDCWD), CDB->fd,
- try to open the CDB->fd-relative directory, DIR. If the open succeeds,
- update CDB->fd with the resulting descriptor, close the incoming file
- descriptor, and return zero. Upon failure, return -1 and set errno. */
-static int
-cdb_advance_fd (struct cd_buf *cdb, char const *dir)
-{
- int new_fd = openat (cdb->fd, dir,
- O_RDONLY | O_DIRECTORY | O_NOCTTY | O_NONBLOCK);
- if (new_fd < 0)
- return -1;
-
- cdb_free (cdb);
- cdb->fd = new_fd;
-
- return 0;
-}
-
-/* Return a pointer to the first non-slash in S. */
-static inline char *
-find_non_slash (char const *s)
-{
- size_t n_slash = strspn (s, "/");
- return (char *) s + n_slash;
-}
-
-/* This is a function much like chdir, but without the PATH_MAX limitation
- on the length of the directory name. A significant difference is that
- it must be able to modify (albeit only temporarily) the directory
- name. It handles an arbitrarily long directory name by operating
- on manageable portions of the name. On systems without the openat
- syscall, this means changing the working directory to more and more
- `distant' points along the long directory name and then restoring
- the working directory. If any of those attempts to save or restore
- the working directory fails, this function exits nonzero.
-
- Note that this function may still fail with errno == ENAMETOOLONG, but
- only if the specified directory name contains a component that is long
- enough to provoke such a failure all by itself (e.g. if the component
- has length PATH_MAX or greater on systems that define PATH_MAX). */
-
-int
-chdir_long (char *dir)
-{
- int e = chdir (dir);
- if (e == 0 || errno != ENAMETOOLONG)
- return e;
-
- {
- size_t len = strlen (dir);
- char *dir_end = dir + len;
- struct cd_buf cdb;
- size_t n_leading_slash;
-
- cdb_init (&cdb);
-
- /* If DIR is the empty string, then the chdir above
- must have failed and set errno to ENOENT. */
- assert (0 < len);
- assert (PATH_MAX <= len);
-
- /* Count leading slashes. */
- n_leading_slash = strspn (dir, "/");
-
- /* Handle any leading slashes as well as any name that matches
- the regular expression, m!^//hostname[/]*! . Handling this
- prefix separately usually results in a single additional
- cdb_advance_fd call, but it's worthwhile, since it makes the
- code in the following loop cleaner. */
- if (n_leading_slash == 2)
- {
- int err;
- /* Find next slash.
- We already know that dir[2] is neither a slash nor '\0'. */
- char *slash = memchr (dir + 3, '/', dir_end - (dir + 3));
- if (slash == NULL)
- {
- errno = ENAMETOOLONG;
- return -1;
- }
- *slash = '\0';
- err = cdb_advance_fd (&cdb, dir);
- *slash = '/';
- if (err != 0)
- goto Fail;
- dir = find_non_slash (slash + 1);
- }
- else if (n_leading_slash)
- {
- if (cdb_advance_fd (&cdb, "/") != 0)
- goto Fail;
- dir += n_leading_slash;
- }
-
- assert (*dir != '/');
- assert (dir <= dir_end);
-
- while (PATH_MAX <= dir_end - dir)
- {
- int err;
- /* Find a slash that is PATH_MAX or fewer bytes away from dir.
- I.e. see if there is a slash that will give us a name of
- length PATH_MAX-1 or less. */
- char *slash = memrchr (dir, '/', PATH_MAX);
- if (slash == NULL)
- {
- errno = ENAMETOOLONG;
- return -1;
- }
-
- *slash = '\0';
- assert (slash - dir < PATH_MAX);
- err = cdb_advance_fd (&cdb, dir);
- *slash = '/';
- if (err != 0)
- goto Fail;
-
- dir = find_non_slash (slash + 1);
- }
-
- if (dir < dir_end)
- {
- if (cdb_advance_fd (&cdb, dir) != 0)
- goto Fail;
- }
-
- if (cdb_fchdir (&cdb) != 0)
- goto Fail;
-
- cdb_free (&cdb);
- return 0;
-
- Fail:
- {
- int saved_errno = errno;
- cdb_free (&cdb);
- errno = saved_errno;
- return -1;
- }
- }
-}
-
-#if TEST_CHDIR
-
-# include "closeout.h"
-# include "error.h"
-
-char *program_name;
-
-int
-main (int argc, char *argv[])
-{
- char *line = NULL;
- size_t n = 0;
- int len;
-
- program_name = argv[0];
- atexit (close_stdout);
-
- len = getline (&line, &n, stdin);
- if (len < 0)
- {
- int saved_errno = errno;
- if (feof (stdin))
- exit (0);
-
- error (EXIT_FAILURE, saved_errno,
- "reading standard input");
- }
- else if (len == 0)
- exit (0);
-
- if (line[len-1] == '\n')
- line[len-1] = '\0';
-
- if (chdir_long (line) != 0)
- error (EXIT_FAILURE, errno,
- "chdir_long failed: %s", line);
-
- if (argc <= 1)
- {
- /* Using `pwd' here makes sense only if it is a robust implementation,
- like the one in coreutils after the 2004-04-19 changes. */
- char const *cmd = "pwd";
- execlp (cmd, (char *) NULL);
- error (EXIT_FAILURE, errno, "%s", cmd);
- }
-
- fclose (stdin);
- fclose (stderr);
-
- exit (EXIT_SUCCESS);
-}
-#endif
-
-/*
-Local Variables:
-compile-command: "gcc -DTEST_CHDIR=1 -g -O -W -Wall chdir-long.c libcoreutils.a"
-End:
-*/
projects / debian / tar / blobdiff