RUST-475 adding getter for timestamp from ObjectId

Author: Utkarsh Mehta

src/oid.rs

@@ -13,6 +13,8 @@ use hex::{self, FromHexError};
 
 use rand::{thread_rng, Rng};
 
+use chrono::Utc;
+
 const TIMESTAMP_SIZE: usize = 4;
 const PROCESS_ID_SIZE: usize = 5;
 const COUNTER_SIZE: usize = 3;
@@ -114,6 +116,14 @@ impl ObjectId {
         }
     }
 
+    /// Retrieves the timestamp (chrono::DateTime) from an ObjectId.
+    pub fn timestamp(&self) -> chrono::DateTime<Utc> {
+        let seconds_since_epoch = BigEndian::read_u32(&self.id);
+        let naive_datetime = chrono::NaiveDateTime::from_timestamp(seconds_since_epoch as i64, 0);
+        let timestamp: chrono::DateTime<Utc> = chrono::DateTime::from_utc(naive_datetime, Utc);
+        timestamp
+    }
+
     /// Returns the raw byte representation of an ObjectId.
     pub fn bytes(&self) -> [u8; 12] {
         self.id
@@ -204,16 +214,40 @@ fn count_generated_is_big_endian() {
     assert_eq!(0x33u8, oid.bytes()[COUNTER_OFFSET + 2]);
 }
 
-#[test]
-fn test_display() {
-    let id = ObjectId::with_string("53e37d08776f724e42000000").unwrap();
+#[cfg(test)]
+mod test {
+    use chrono::{offset::TimeZone, Utc};
 
-    assert_eq!(format!("{}", id), "53e37d08776f724e42000000")
-}
+    #[test]
+    fn test_display() {
+        let id = super::ObjectId::with_string("53e37d08776f724e42000000").unwrap();
 
-#[test]
-fn test_debug() {
-    let id = ObjectId::with_string("53e37d08776f724e42000000").unwrap();
+        assert_eq!(format!("{}", id), "53e37d08776f724e42000000")
+    }
 
-    assert_eq!(format!("{:?}", id), "ObjectId(53e37d08776f724e42000000)")
+    #[test]
+    fn test_debug() {
+        let id = super::ObjectId::with_string("53e37d08776f724e42000000").unwrap();
+
+        assert_eq!(format!("{:?}", id), "ObjectId(53e37d08776f724e42000000)")
+    }
+
+    #[test]
+    fn test_timestamp() {
+        let id = super::ObjectId::with_string("000000000000000000000000").unwrap();
+        // "Jan 1st, 1970 00:00:00 UTC"
+        assert_eq!(Utc.ymd(1970, 1, 1).and_hms(0, 0, 0), id.timestamp());
+
+        let id = super::ObjectId::with_string("7FFFFFFF0000000000000000").unwrap();
+        // "Jan 19th, 2038 03:14:07 UTC"
+        assert_eq!(Utc.ymd(2038, 1, 19).and_hms(3, 14, 7), id.timestamp());
+
+        let id = super::ObjectId::with_string("800000000000000000000000").unwrap();
+        // "Jan 19th, 2038 03:14:08 UTC"
+        assert_eq!(Utc.ymd(2038, 1, 19).and_hms(3, 14, 8), id.timestamp());
+
+        let id = super::ObjectId::with_string("FFFFFFFF0000000000000000").unwrap();
+        // "Feb 7th, 2106 06:28:15 UTC"
+        assert_eq!(Utc.ymd(2106, 2, 7).and_hms(6, 28, 15), id.timestamp());
+    }
 }