feat: Add associated constants UTIME_OMIT UTIME_NOW to TimeSpec

changelog/1879.added.md

@@ -0,0 +1 @@
+Add associated constants `UTIME_OMIT` `UTIME_NOW` for `TimeSpec`

src/sys/stat.rs

@@ -376,6 +376,9 @@ pub fn lutimes<P: ?Sized + NixPath>(
 
 /// Change the access and modification times of the file specified by a file descriptor.
 ///
+/// If you want to set the timestamp to now, use `TimeSpec::UTIME_NOW`. Use
+/// `TimeSpec::UTIME_OMIT` if you don't want to change it.
+///
 /// # References
 ///
 /// [futimens(2)](https://pubs.opengroup.org/onlinepubs/9699919799/functions/futimens.html).
@@ -408,6 +411,9 @@ pub enum UtimensatFlags {
 /// `utimes(path, times)`. The latter is a deprecated API so prefer using the
 /// former if the platforms you care about support it.
 ///
+/// If you want to set the timestamp to now, use `TimeSpec::UTIME_NOW`. Use
+/// `TimeSpec::UTIME_OMIT` if you don't want to change it.
+///
 /// # References
 ///
 /// [utimensat(2)](https://pubs.opengroup.org/onlinepubs/9699919799/functions/utimens.html).
@@ -448,4 +454,4 @@ pub fn mkdirat<P: ?Sized + NixPath>(
     })?;
 
     Errno::result(res).map(drop)
-}
+}

src/sys/time.rs

@@ -329,6 +329,17 @@ impl TimeValLike for TimeSpec {
 }
 
 impl TimeSpec {
+    /// Leave the timestamp unchanged.
+    #[cfg(not(target_os = "redox"))]
+    // At the time of writing this PR, redox does not support this feature
+    pub const UTIME_OMIT: TimeSpec =
+        TimeSpec::new(0, libc::UTIME_OMIT as timespec_tv_nsec_t);
+    /// Update the timestamp to `Now`
+    // At the time of writing this PR, redox does not support this feature
+    #[cfg(not(target_os = "redox"))]
+    pub const UTIME_NOW: TimeSpec =
+        TimeSpec::new(0, libc::UTIME_NOW as timespec_tv_nsec_t);
+
     /// Construct a new `TimeSpec` from its components
     #[cfg_attr(target_env = "musl", allow(deprecated))] // https://github.com/rust-lang/libc/issues/1848
     pub const fn new(seconds: time_t, nanoseconds: timespec_tv_nsec_t) -> Self {

test/test_stat.rs

@@ -415,3 +415,75 @@ fn test_mknodat() {
     assert_eq!(mode & libc::S_IFREG, libc::S_IFREG);
     assert_eq!(mode & libc::S_IRWXU, libc::S_IRWXU);
 }
+
+#[test]
+#[cfg(not(any(target_os = "redox", target_os = "haiku")))]
+fn test_futimens_unchanged() {
+    let tempdir = tempfile::tempdir().unwrap();
+    let fullpath = tempdir.path().join("file");
+    drop(File::create(&fullpath).unwrap());
+    let fd = fcntl::open(&fullpath, fcntl::OFlag::empty(), stat::Mode::empty())
+        .unwrap();
+
+    let old_atime = fs::metadata(fullpath.as_path())
+        .unwrap()
+        .accessed()
+        .unwrap();
+    let old_mtime = fs::metadata(fullpath.as_path())
+        .unwrap()
+        .modified()
+        .unwrap();
+
+    futimens(fd, &TimeSpec::UTIME_OMIT, &TimeSpec::UTIME_OMIT).unwrap();
+
+    let new_atime = fs::metadata(fullpath.as_path())
+        .unwrap()
+        .accessed()
+        .unwrap();
+    let new_mtime = fs::metadata(fullpath.as_path())
+        .unwrap()
+        .modified()
+        .unwrap();
+    assert_eq!(old_atime, new_atime);
+    assert_eq!(old_mtime, new_mtime);
+}
+
+#[test]
+#[cfg(not(any(target_os = "redox", target_os = "haiku")))]
+fn test_utimensat_unchanged() {
+    let _dr = crate::DirRestore::new();
+    let tempdir = tempfile::tempdir().unwrap();
+    let filename = "foo.txt";
+    let fullpath = tempdir.path().join(filename);
+    drop(File::create(&fullpath).unwrap());
+    let dirfd =
+        fcntl::open(tempdir.path(), fcntl::OFlag::empty(), stat::Mode::empty())
+            .unwrap();
+
+    let old_atime = fs::metadata(fullpath.as_path())
+        .unwrap()
+        .accessed()
+        .unwrap();
+    let old_mtime = fs::metadata(fullpath.as_path())
+        .unwrap()
+        .modified()
+        .unwrap();
+    utimensat(
+        Some(dirfd),
+        filename,
+        &TimeSpec::UTIME_OMIT,
+        &TimeSpec::UTIME_OMIT,
+        UtimensatFlags::NoFollowSymlink,
+    )
+    .unwrap();
+    let new_atime = fs::metadata(fullpath.as_path())
+        .unwrap()
+        .accessed()
+        .unwrap();
+    let new_mtime = fs::metadata(fullpath.as_path())
+        .unwrap()
+        .modified()
+        .unwrap();
+    assert_eq!(old_atime, new_atime);
+    assert_eq!(old_mtime, new_mtime);
+}