uefi: fs: Add file times plumbing

- Add plumbing to allow conversions to and from UEFI Time to Rust
  SystemTime.
- Also add FileTimes implementation.

Signed-off-by: Ayush Singh <[email protected]>

Author: Ayush1325

library/std/src/sys/fs/uefi.rs

@@ -17,6 +17,8 @@ pub struct File(!);
 pub struct FileAttr {
     attr: u64,
     size: u64,
+    created: SystemTime,
+    times: FileTimes,
 }
 
 pub struct ReadDir(!);
@@ -31,8 +33,11 @@ pub struct OpenOptions {
     create_new: bool,
 }
 
-#[derive(Copy, Clone, Debug, Default)]
-pub struct FileTimes {}
+#[derive(Copy, Clone, Debug)]
+pub struct FileTimes {
+    accessed: SystemTime,
+    modified: SystemTime,
+}
 
 #[derive(Clone, PartialEq, Eq, Debug)]
 // Bool indicates if file is readonly
@@ -59,15 +64,15 @@ impl FileAttr {
     }
 
     pub fn modified(&self) -> io::Result<SystemTime> {
-        unsupported()
+        Ok(self.times.modified)
     }
 
     pub fn accessed(&self) -> io::Result<SystemTime> {
-        unsupported()
+        Ok(self.times.accessed)
     }
 
     pub fn created(&self) -> io::Result<SystemTime> {
-        unsupported()
+        Ok(self.created)
     }
 }
 
@@ -91,8 +96,19 @@ impl FilePermissions {
 }
 
 impl FileTimes {
-    pub fn set_accessed(&mut self, _t: SystemTime) {}
-    pub fn set_modified(&mut self, _t: SystemTime) {}
+    pub fn set_accessed(&mut self, t: SystemTime) {
+        self.accessed = t;
+    }
+
+    pub fn set_modified(&mut self, t: SystemTime) {
+        self.modified = t;
+    }
+}
+
+impl Default for FileTimes {
+    fn default() -> Self {
+        Self { modified: SystemTime::ZERO, accessed: SystemTime::ZERO }
+    }
 }
 
 impl FileType {

library/std/src/sys/pal/uefi/time.rs

@@ -40,11 +40,22 @@ impl Instant {
 }
 
 impl SystemTime {
+    pub(crate) const ZERO: SystemTime = SystemTime(Duration::ZERO);
+
+    pub(crate) const fn new(t: r_efi::efi::Time) -> Self {
+        Self(system_time_internal::uefi_time_to_duration(t))
+    }
+
     pub fn now() -> SystemTime {
         system_time_internal::now()
             .unwrap_or_else(|| panic!("time not implemented on this platform"))
     }
 
+    #[expect(dead_code)]
+    pub(crate) const fn to_uefi_time(&self, daylight: u8, timezone: i16) -> r_efi::efi::Time {
+        system_time_internal::uefi_time_from_duration(self.0, daylight, timezone)
+    }
+
     pub fn sub_time(&self, other: &SystemTime) -> Result<Duration, Duration> {
         self.0.checked_sub(other.0).ok_or_else(|| other.0 - self.0)
     }
@@ -79,7 +90,7 @@ pub(crate) mod system_time_internal {
 
         let t = unsafe { t.assume_init() };
 
-        Some(SystemTime(uefi_time_to_duration(t)))
+        Some(SystemTime::new(t))
     }
 
     // This algorithm is based on the one described in the post
@@ -112,6 +123,48 @@ pub(crate) mod system_time_internal {
 
         Duration::new(utc_epoch, t.nanosecond)
     }
+
+    /// This algorithm is taken from: http://howardhinnant.github.io/date_algorithms.html
+    pub(crate) const fn uefi_time_from_duration(
+        dur: crate::time::Duration,
+        daylight: u8,
+        timezone: i16,
+    ) -> r_efi::system::Time {
+        const SECS_IN_MINUTE: u64 = 60;
+        const SECS_IN_HOUR: u64 = SECS_IN_MINUTE * 60;
+        const SECS_IN_DAY: u64 = SECS_IN_HOUR * 24;
+
+        let secs = dur.as_secs();
+        let days = secs / SECS_IN_DAY;
+        let remaining_secs = secs % SECS_IN_DAY;
+        let z = days + 719468;
+        let era = z / 146097;
+        let doe = z - (era * 146097);
+        let yoe = (doe - doe / 1460 + doe / 36524 - doe / 146096) / 365;
+        let mut y = yoe + era * 400;
+        let doy = doe - (365 * yoe + yoe / 4 - yoe / 100);
+        let mp = (5 * doy + 2) / 153;
+        let d = doy - (153 * mp + 2) / 5 + 1;
+        let m = if mp < 10 { mp + 3 } else { mp - 9 };
+
+        if m <= 2 {
+            y += 1;
+        }
+
+        r_efi::system::Time {
+            year: y as u16,
+            month: m as u8,
+            day: d as u8,
+            hour: (remaining_secs / SECS_IN_HOUR) as u8,
+            minute: ((remaining_secs % SECS_IN_HOUR) / SECS_IN_MINUTE) as u8,
+            second: ((remaining_secs % SECS_IN_HOUR) % SECS_IN_MINUTE) as u8,
+            pad1: 0,
+            nanosecond: dur.subsec_nanos(),
+            timezone,
+            daylight,
+            pad2: 0,
+        }
+    }
 }
 
 pub(crate) mod instant_internal {