Add serde functions for nanosecond timestamps

src/datetime.rs

@@ -992,6 +992,167 @@ pub mod serde {
         }
     }
 
+    /// Ser/de to/from timestamps in nanoseconds
+    ///
+    /// Intended for use with `serde`'s `with` attribute.
+    ///
+    /// # Example:
+    ///
+    /// ```rust
+    /// # // We mark this ignored so that we can test on 1.13 (which does not
+    /// # // support custom derive), and run tests with --ignored on beta and
+    /// # // nightly to actually trigger these.
+    /// #
+    /// # #[macro_use] extern crate serde_derive;
+    /// # #[macro_use] extern crate serde_json;
+    /// # extern crate chrono;
+    /// # use chrono::{TimeZone, DateTime, Utc};
+    /// use chrono::serde::ts_nano_seconds;
+    /// #[derive(Deserialize, Serialize)]
+    /// struct S {
+    ///     #[serde(with = "ts_nano_seconds")]
+    ///     time: DateTime<Utc>
+    /// }
+    ///
+    /// # fn example() -> Result<S, serde_json::Error> {
+    /// let time = Utc.ymd(2018, 5, 17).and_hms_nano(02, 04, 59, 918355733);
+    /// let my_s = S {
+    ///     time: time.clone(),
+    /// };
+    ///
+    /// let as_string = serde_json::to_string(&my_s)?;
+    /// assert_eq!(as_string, r#"{"time":1526522699918355733}"#);
+    /// let my_s: S = serde_json::from_str(&as_string)?;
+    /// assert_eq!(my_s.time, time);
+    /// # Ok(my_s)
+    /// # }
+    /// # fn main() { example().unwrap(); }
+    /// ```
+    pub mod ts_nano_seconds {
+        use std::fmt;
+        use serdelib::{ser, de};
+
+        use {DateTime, Utc};
+        use offset::{LocalResult, TimeZone};
+
+        /// Deserialize a `DateTime` from a nanosecond timestamp
+        ///
+        /// Intended for use with `serde`s `deserialize_with` attribute.
+        ///
+        /// # Example:
+        ///
+        /// ```rust
+        /// # // We mark this ignored so that we can test on 1.13 (which does not
+        /// # // support custom derive), and run tests with --ignored on beta and
+        /// # // nightly to actually trigger these.
+        /// #
+        /// # #[macro_use] extern crate serde_derive;
+        /// # #[macro_use] extern crate serde_json;
+        /// # extern crate chrono;
+        /// # use chrono::{DateTime, Utc};
+        /// use chrono::serde::ts_nano_seconds::deserialize as from_nano_ts;
+        /// #[derive(Deserialize)]
+        /// struct S {
+        ///     #[serde(deserialize_with = "from_nano_ts")]
+        ///     time: DateTime<Utc>
+        /// }
+        ///
+        /// # fn example() -> Result<S, serde_json::Error> {
+        /// let my_s: S = serde_json::from_str(r#"{ "time": 1526522699918355733 }"#)?;
+        /// # Ok(my_s)
+        /// # }
+        /// # fn main() { example().unwrap(); }
+        /// ```
+        pub fn deserialize<'de, D>(d: D) -> Result<DateTime<Utc>, D::Error>
+            where D: de::Deserializer<'de>
+        {
+            Ok(try!(d.deserialize_i64(NanoSecondsTimestampVisitor)))
+        }
+
+        /// Serialize a UTC datetime into an integer number of nanoseconds since the epoch
+        ///
+        /// Intended for use with `serde`s `serialize_with` attribute.
+        ///
+        /// # Example:
+        ///
+        /// ```rust
+        /// # // We mark this ignored so that we can test on 1.13 (which does not
+        /// # // support custom derive), and run tests with --ignored on beta and
+        /// # // nightly to actually trigger these.
+        /// #
+        /// # #[macro_use] extern crate serde_derive;
+        /// # #[macro_use] extern crate serde_json;
+        /// # extern crate chrono;
+        /// # use chrono::{TimeZone, DateTime, Utc};
+        /// use chrono::serde::ts_nano_seconds::serialize as to_nano_ts;
+        /// #[derive(Serialize)]
+        /// struct S {
+        ///     #[serde(serialize_with = "to_nano_ts")]
+        ///     time: DateTime<Utc>
+        /// }
+        ///
+        /// # fn example() -> Result<String, serde_json::Error> {
+        /// let my_s = S {
+        ///     time: Utc.ymd(2018, 5, 17).and_hms_nano(02, 04, 59, 918355733),
+        /// };
+        /// let as_string = serde_json::to_string(&my_s)?;
+        /// assert_eq!(as_string, r#"{"time":1526522699918355733}"#);
+        /// # Ok(as_string)
+        /// # }
+        /// # fn main() { example().unwrap(); }
+        /// ```
+        pub fn serialize<S>(dt: &DateTime<Utc>, serializer: S) -> Result<S::Ok, S::Error>
+            where S: ser::Serializer
+        {
+            serializer.serialize_i64(dt.timestamp_nanos())
+        }
+
+        struct NanoSecondsTimestampVisitor;
+
+        impl<'de> de::Visitor<'de> for NanoSecondsTimestampVisitor {
+            type Value = DateTime<Utc>;
+
+            fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result
+            {
+                write!(formatter, "a unix timestamp in seconds")
+            }
+
+            /// Deserialize a timestamp in seconds since the epoch
+            fn visit_i64<E>(self, value: i64) -> Result<DateTime<Utc>, E>
+                where E: de::Error
+            {
+                from(Utc.timestamp_opt(value / 1_000_000_000,
+                                       (value % 1_000_000_000) as u32),
+                     &value)
+            }
+
+            /// Deserialize a timestamp in seconds since the epoch
+            fn visit_u64<E>(self, value: u64) -> Result<DateTime<Utc>, E>
+                where E: de::Error
+            {
+                from(Utc.timestamp_opt(value as i64 / 1_000_000_000,
+                                       (value as i64 % 1_000_000_000) as u32),
+                     &value)
+            }
+        }
+
+        // try!-like function to convert a LocalResult into a serde-ish Result
+        fn from<T, E, V>(me: LocalResult<T>, ts: &V) -> Result<T, E>
+            where E: de::Error,
+                  V: fmt::Display,
+                  T: fmt::Display,
+        {
+            match me {
+                LocalResult::None => Err(E::custom(
+                    format!("value is not a legal timestamp: {}", ts))),
+                LocalResult::Ambiguous(min, max) => Err(E::custom(
+                    format!("value is an ambiguous timestamp: {}, could be either of {}, {}",
+                            ts, min, max))),
+                LocalResult::Single(val) => Ok(val)
+            }
+        }
+    }
+
     impl<Tz: TimeZone> ser::Serialize for DateTime<Tz> {
         /// Serialize into a rfc3339 time string
         ///