--- /dev/null
+/* Save and restore the working directory, possibly using a child process.
+
+ Copyright (C) 2006 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 2, 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, write to the Free Software Foundation,
+ Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
+
+/* Written by Paul Eggert. */
+
+#include <config.h>
+
+#include "savewd.h"
+
+#include <assert.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <stdbool.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+#include "exit.h"
+#include "dirname.h"
+#include "fcntl-safer.h"
+
+
+/* Save the working directory into *WD, if it hasn't been saved
+ already. Return true if a child has been forked to do the real
+ work. */
+static bool
+savewd_save (struct savewd *wd)
+{
+ switch (wd->state)
+ {
+ case INITIAL_STATE:
+ /* Save the working directory, or prepare to fall back if possible. */
+ {
+ int fd = open_safer (".", O_RDONLY);
+ if (0 <= fd)
+ {
+ wd->state = FD_STATE;
+ wd->val.fd = fd;
+ break;
+ }
+ if (errno != EACCES)
+ {
+ wd->state = ERROR_STATE;
+ wd->val.errnum = errno;
+ break;
+ }
+ }
+ wd->state = FORKING_STATE;
+ wd->val.child = -1;
+ /* Fall through. */
+ case FORKING_STATE:
+ if (wd->val.child < 0)
+ {
+ /* "Save" the initial working directory by forking a new
+ subprocess that will attempt all the work from the chdir
+ until until the next savewd_restore. */
+ wd->val.child = fork ();
+ if (wd->val.child != 0)
+ {
+ if (0 < wd->val.child)
+ return true;
+ wd->state = ERROR_STATE;
+ wd->val.errnum = errno;
+ }
+ }
+ break;
+
+ case FD_STATE:
+ case FD_POST_CHDIR_STATE:
+ case ERROR_STATE:
+ case FINAL_STATE:
+ break;
+
+ default:
+ assert (false);
+ }
+
+ return false;
+}
+
+int
+savewd_chdir (struct savewd *wd, char const *dir, int options,
+ int open_result[2])
+{
+ int fd = -1;
+ int result = 0;
+
+ /* Open the directory if requested, or if avoiding a race condition
+ is requested and possible. */
+ if (open_result || (options & (O_NOFOLLOW ? SAVEWD_CHDIR_NOFOLLOW : 0)))
+ {
+ fd = open (dir,
+ (O_RDONLY | O_DIRECTORY | O_NOCTTY | O_NONBLOCK
+ | (options & SAVEWD_CHDIR_NOFOLLOW ? O_NOFOLLOW : 0)));
+
+ if (open_result)
+ {
+ open_result[0] = fd;
+ open_result[1] = errno;
+ }
+
+ if (fd < 0 && (errno != EACCES || (options & SAVEWD_CHDIR_READABLE)))
+ result = -1;
+ }
+
+ if (result == 0 && ! (0 <= fd && options & SAVEWD_CHDIR_SKIP_READABLE))
+ {
+ if (savewd_save (wd))
+ {
+ open_result = NULL;
+ result = -2;
+ }
+ else
+ {
+ result = (fd < 0 ? chdir (dir) : fchdir (fd));
+
+ if (result == 0)
+ switch (wd->state)
+ {
+ case FD_STATE:
+ wd->state = FD_POST_CHDIR_STATE;
+ break;
+
+ case ERROR_STATE:
+ case FD_POST_CHDIR_STATE:
+ case FINAL_STATE:
+ break;
+
+ case FORKING_STATE:
+ assert (wd->val.child == 0);
+ break;
+
+ default:
+ assert (false);
+ }
+ }
+ }
+
+ if (0 <= fd && ! open_result)
+ {
+ int e = errno;
+ close (fd);
+ errno = e;
+ }
+
+ return result;
+}
+
+int
+savewd_restore (struct savewd *wd, int status)
+{
+ switch (wd->state)
+ {
+ case INITIAL_STATE:
+ case FD_STATE:
+ /* The working directory is the desired directory, so there's no
+ work to do. */
+ break;
+
+ case FD_POST_CHDIR_STATE:
+ /* Restore the working directory using fchdir. */
+ if (fchdir (wd->val.fd) == 0)
+ {
+ wd->state = FD_STATE;
+ break;
+ }
+ else
+ {
+ int chdir_errno = errno;
+ close (wd->val.fd);
+ wd->state = ERROR_STATE;
+ wd->val.errnum = chdir_errno;
+ }
+ /* Fall through. */
+ case ERROR_STATE:
+ /* Report an error if asked to restore the working directory. */
+ errno = wd->val.errnum;
+ return -1;
+
+ case FORKING_STATE:
+ /* "Restore" the working directory by waiting for the subprocess
+ to finish. */
+ {
+ pid_t child = wd->val.child;
+ if (child == 0)
+ _exit (status);
+ if (0 < child)
+ {
+ int status;
+ while (waitpid (child, &status, 0) < 0)
+ assert (errno == EINTR);
+ wd->val.child = -1;
+ if (! WIFEXITED (status))
+ raise (WTERMSIG (status));
+ return WEXITSTATUS (status);
+ }
+ }
+ break;
+
+ default:
+ assert (false);
+ }
+
+ return 0;
+}
+
+void
+savewd_finish (struct savewd *wd)
+{
+ switch (wd->state)
+ {
+ case INITIAL_STATE:
+ case ERROR_STATE:
+ break;
+
+ case FD_STATE:
+ case FD_POST_CHDIR_STATE:
+ close (wd->val.fd);
+ break;
+
+ case FORKING_STATE:
+ assert (wd->val.child < 0);
+ break;
+
+ default:
+ assert (false);
+ }
+
+ wd->state = FINAL_STATE;
+}
+
+/* Return true if the actual work is currently being done by a
+ subprocess.
+
+ A true return means that the caller and the subprocess should
+ resynchronize later with savewd_restore, using only their own
+ memory to decide when to resynchronize; they should not consult the
+ file system to decide, because that might lead to race conditions.
+ This is why savewd_chdir is broken out into another function;
+ savewd_chdir's callers _can_ inspect the file system to decide
+ whether to call savewd_chdir. */
+static inline bool
+savewd_delegating (struct savewd const *wd)
+{
+ return wd->state == FORKING_STATE && 0 < wd->val.child;
+}
+
+int
+savewd_process_files (int n_files, char **file,
+ int (*act) (char *, struct savewd *, void *),
+ void *options)
+{
+ int i = 0;
+ int last_relative;
+ int exit_status = EXIT_SUCCESS;
+ struct savewd wd;
+ savewd_init (&wd);
+
+ for (last_relative = n_files - 1; 0 <= last_relative; last_relative--)
+ if (! IS_ABSOLUTE_FILE_NAME (file[last_relative]))
+ break;
+
+ for (; i < last_relative; i++)
+ {
+ if (! savewd_delegating (&wd))
+ {
+ int s = act (file[i], &wd, options);
+ if (exit_status < s)
+ exit_status = s;
+ }
+
+ if (! IS_ABSOLUTE_FILE_NAME (file[i + 1]))
+ {
+ int r = savewd_restore (&wd, exit_status);
+ if (exit_status < r)
+ exit_status = r;
+ }
+ }
+
+ savewd_finish (&wd);
+
+ for (; i < n_files; i++)
+ {
+ int s = act (file[i], &wd, options);
+ if (exit_status < s)
+ exit_status = s;
+ }
+
+ return exit_status;
+}
projects / gnulib.git / blobdiff