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-rw-r--r--src/find-mount-point.c113
1 files changed, 113 insertions, 0 deletions
diff --git a/src/find-mount-point.c b/src/find-mount-point.c
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+++ b/src/find-mount-point.c
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+/* find-mount-point.c -- find the root mount point for a file.
+ Copyright (C) 2010-2022 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 <https://www.gnu.org/licenses/>. */
+
+#include <config.h>
+#include <sys/types.h>
+
+#include "system.h"
+#include "die.h"
+#include "error.h"
+#include "save-cwd.h"
+#include "xgetcwd.h"
+#include "find-mount-point.h"
+
+/* Return the root mountpoint of the file system on which FILE exists, in
+ malloced storage. FILE_STAT should be the result of stating FILE.
+ Give a diagnostic and return NULL if unable to determine the mount point.
+ Exit if unable to restore current working directory. */
+extern char *
+find_mount_point (char const *file, struct stat const *file_stat)
+{
+ struct saved_cwd cwd;
+ struct stat last_stat;
+ char *mp = NULL; /* The malloc'd mount point. */
+
+ if (save_cwd (&cwd) != 0)
+ {
+ error (0, errno, _("cannot get current directory"));
+ return NULL;
+ }
+
+ if (S_ISDIR (file_stat->st_mode))
+ /* FILE is a directory, so just chdir there directly. */
+ {
+ last_stat = *file_stat;
+ if (chdir (file) < 0)
+ {
+ error (0, errno, _("cannot change to directory %s"), quoteaf (file));
+ return NULL;
+ }
+ }
+ else
+ /* FILE is some other kind of file; use its directory. */
+ {
+ char *xdir = dir_name (file);
+ char *dir;
+ ASSIGN_STRDUPA (dir, xdir);
+ free (xdir);
+
+ if (chdir (dir) < 0)
+ {
+ error (0, errno, _("cannot change to directory %s"), quoteaf (dir));
+ return NULL;
+ }
+
+ if (stat (".", &last_stat) < 0)
+ {
+ error (0, errno, _("cannot stat current directory (now %s)"),
+ quoteaf (dir));
+ goto done;
+ }
+ }
+
+ /* Now walk up FILE's parents until we find another file system or /,
+ chdiring as we go. LAST_STAT holds stat information for the last place
+ we visited. */
+ while (true)
+ {
+ struct stat st;
+ if (stat ("..", &st) < 0)
+ {
+ error (0, errno, _("cannot stat %s"), quoteaf (".."));
+ goto done;
+ }
+ if (st.st_dev != last_stat.st_dev || st.st_ino == last_stat.st_ino)
+ /* cwd is the mount point. */
+ break;
+ if (chdir ("..") < 0)
+ {
+ error (0, errno, _("cannot change to directory %s"), quoteaf (".."));
+ goto done;
+ }
+ last_stat = st;
+ }
+
+ /* Finally reached a mount point, see what it's called. */
+ mp = xgetcwd ();
+
+done:
+ /* Restore the original cwd. */
+ {
+ int save_errno = errno;
+ if (restore_cwd (&cwd) != 0)
+ die (EXIT_FAILURE, errno,
+ _("failed to return to initial working directory"));
+ free_cwd (&cwd);
+ errno = save_errno;
+ }
+
+ return mp;
+}