utimens: add lutimens interface

Wraps utimensat(,AT_SYMLINK_NOFOLLOW) or lutimes, when supported;
otherwise fail with ENOSYS.  Allows coreutils' copy.c to preserve
symlink timestamps on more systems.  Note that cygwin's lstat
changes atime of symlinks, but mtime can reliably be set.

* lib/utimens.c (lutimens): New function.
* m4/utimens.m4 (gl_UTIMENS): Check for lutimes.
* lib/utimens.h (lutimens): Declare new interface.
* tests/test-utimens.c (main): Enhance test.
* tests/test-lutimens.h (test_lutimens): New file.
* modules/utimens-tests (Files): Distribute it.
(Depends-on): Add symlink.
(configure.ac): Check for usleep.

Signed-off-by: Eric Blake <ebb9@byu.net>

1 files changed, 152 insertions, 0 deletions

diff --git a/tests/test-lutimens.h b/tests/test-lutimens.h
new file mode 100644
index 0000000000..18cf75fa25
--- /dev/null
+++ b/tests/test-lutimens.h
@@ -0,0 +1,152 @@
+/* Test of file timestamp modification functions.
+   Copyright (C) 2009 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 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/>.  */
+
+/* This file assumes that BASE and ASSERT are already defined.  */
+
+#ifndef GL_TEST_UTIMENS
+# define GL_TEST_UTIMENS
+
+#include <fcntl.h>
+#include <errno.h>
+#include <string.h>
+#include <unistd.h>
+
+#include "stat-time.h"
+#include "timespec.h"
+#include "utimecmp.h"
+
+enum {
+  BILLION = 1000 * 1000 * 1000,
+
+  Y2K = 946684800, /* Jan 1, 2000, in seconds since epoch.  */
+
+  /* Bogus positive and negative tv_nsec values closest to valid
+     range, but without colliding with UTIME_NOW or UTIME_OMIT.  */
+  UTIME_BOGUS_POS = BILLION + ((UTIME_NOW == BILLION || UTIME_OMIT == BILLION)
+                               ? (1 + (UTIME_NOW == BILLION + 1)
+                                  + (UTIME_OMIT == BILLION + 1))
+                               : 0),
+  UTIME_BOGUS_NEG = -1 - ((UTIME_NOW == -1 || UTIME_OMIT == -1)
+                          ? (1 + (UTIME_NOW == -2) + (UTIME_OMIT == -2))
+                          : 0)
+};
+
+#endif /* GL_TEST_UTIMENS */
+
+/* This function is designed to test both lutimens(a,b) and
+   utimensat(AT_FDCWD,a,b,AT_SYMLINK_NOFOLLOW).  FUNC is the function
+   to test.  If PRINT, warn before skipping tests with status 77.  */
+static int
+test_lutimens (int (*func) (char const *, struct timespec const *), bool print)
+{
+  int result;
+  struct stat st1;
+  struct stat st2;
+  bool atime_supported = true;
+
+  if (symlink ("nowhere", BASE "link"))
+    {
+      if (print)
+        fputs ("skipping test: symlinks not supported on this file system\n",
+               stderr);
+      return 77;
+    }
+  errno = 0;
+  result = func (BASE "link", NULL);
+  if (result == -1 && errno == ENOSYS)
+    {
+      ASSERT (unlink (BASE "link") == 0);
+      if (print)
+        fputs ("skipping test: "
+               "setting symlink time not supported on this file system\n",
+               stderr);
+      return 77;
+    }
+  ASSERT (!result);
+  ASSERT (lstat (BASE "link", &st1) == 0);
+#if HAVE_USLEEP
+  /* On Cygwin, the mere act of lstat changes symlink atime, even
+     though POSIX says that only readlink is allowed to do that.
+     Sleeping for one millisecond is enough to expose this.  Platforms
+     without usleep either don't have symlinks, or are immune.  */
+  usleep (1000);
+#endif
+  ASSERT (lstat (BASE "link", &st2) == 0);
+  if (st1.st_atime != st2.st_atime
+      || get_stat_atime_ns (&st1) != get_stat_atime_ns (&st2))
+     atime_supported = false;
+
+  /* Invalid arguments.  */
+  errno = 0;
+  ASSERT (func ("no_such", NULL) == -1);
+  ASSERT (errno == ENOENT);
+  errno = 0;
+  ASSERT (func ("", NULL) == -1);
+  ASSERT (errno == ENOENT);
+  {
+    struct timespec ts[2] = { { Y2K, UTIME_BOGUS_POS }, { Y2K, 0 } };
+    errno = 0;
+    ASSERT (func (BASE "link", ts) == -1);
+    ASSERT (errno == EINVAL);
+  }
+  {
+    struct timespec ts[2] = { { Y2K, 0 }, { Y2K, UTIME_BOGUS_NEG } };
+    errno = 0;
+    ASSERT (func (BASE "link", ts) == -1);
+    ASSERT (errno == EINVAL);
+  }
+  ASSERT (lstat (BASE "link", &st2) == 0);
+  if (atime_supported)
+    {
+      ASSERT (st1.st_atime == st2.st_atime);
+      ASSERT (get_stat_atime_ns (&st1) == get_stat_atime_ns (&st2));
+    }
+  ASSERT (utimecmp (BASE "link", &st1, &st2, 0) == 0);
+
+  /* Set both times.  */
+  {
+    struct timespec ts[2] = { { Y2K, BILLION / 2 - 1 }, { Y2K, BILLION - 1 } };
+    ASSERT (func (BASE "link", ts) == 0);
+    ASSERT (lstat (BASE "link", &st2) == 0);
+    if (atime_supported)
+      {
+        ASSERT (st2.st_atime == Y2K);
+        ASSERT (0 <= get_stat_atime_ns (&st2));
+        ASSERT (get_stat_atime_ns (&st2) < BILLION / 2);
+      }
+    ASSERT (st2.st_mtime == Y2K);
+    ASSERT (0 <= get_stat_mtime_ns (&st2));
+    ASSERT (get_stat_mtime_ns (&st2) < BILLION);
+  }
+
+  /* Play with UTIME_OMIT, UTIME_NOW.  */
+  {
+    struct timespec ts[2] = { { BILLION, UTIME_OMIT }, { 0, UTIME_NOW } };
+    ASSERT (func (BASE "link", ts) == 0);
+    ASSERT (lstat (BASE "link", &st2) == 0);
+    if (atime_supported)
+      {
+        ASSERT (st2.st_atime == Y2K);
+        ASSERT (0 <= get_stat_atime_ns (&st2));
+        ASSERT (get_stat_atime_ns (&st2) < BILLION / 2);
+      }
+    ASSERT (utimecmp (BASE "link", &st1, &st2, 0) <= 0);
+  }
+
+  /* Cleanup.  */
+  ASSERT (unlink (BASE "link") == 0);
+  return 0;
+}