1 files changed, 108 insertions, 0 deletions
diff --git a/src/datetime.rs b/src/datetime.rs
new file mode 100644
index 0000000..613b44b
--- /dev/null
+++ b/src/datetime.rs
@@ -0,0 +1,108 @@
+use crate::{Result, Tag};
+use alloc::format;
+use alloc::string::ToString;
+use core::fmt;
+#[cfg(feature = "datetime")]
+use time::OffsetDateTime;
+
+#[derive(Clone, Copy, Debug, Eq, PartialEq, PartialOrd, Ord)]
+pub enum ASN1TimeZone {
+    /// No timezone provided
+    Undefined,
+    /// Coordinated universal time
+    Z,
+    /// Local zone, with offset to coordinated universal time
+    ///
+    /// `(offset_hour, offset_minute)`
+    Offset(i8, i8),
+}
+
+#[derive(Clone, Debug, Eq, PartialEq, PartialOrd, Ord)]
+pub struct ASN1DateTime {
+    pub year: u32,
+    pub month: u8,
+    pub day: u8,
+    pub hour: u8,
+    pub minute: u8,
+    pub second: u8,
+    pub millisecond: Option<u16>,
+    pub tz: ASN1TimeZone,
+}
+
+impl ASN1DateTime {
+    #[allow(clippy::too_many_arguments)]
+    pub const fn new(
+        year: u32,
+        month: u8,
+        day: u8,
+        hour: u8,
+        minute: u8,
+        second: u8,
+        millisecond: Option<u16>,
+        tz: ASN1TimeZone,
+    ) -> Self {
+        ASN1DateTime {
+            year,
+            month,
+            day,
+            hour,
+            minute,
+            second,
+            millisecond,
+            tz,
+        }
+    }
+
+    #[cfg(feature = "datetime")]
+    fn to_time_datetime(
+        &self,
+    ) -> core::result::Result<OffsetDateTime, time::error::ComponentRange> {
+        use std::convert::TryFrom;
+        use time::{Date, Month, PrimitiveDateTime, Time, UtcOffset};
+
+        let month = Month::try_from(self.month)?;
+        let date = Date::from_calendar_date(self.year as i32, month, self.day)?;
+        let time = Time::from_hms_milli(
+            self.hour,
+            self.minute,
+            self.second,
+            self.millisecond.unwrap_or(0),
+        )?;
+        let primitive_date = PrimitiveDateTime::new(date, time);
+        let offset = match self.tz {
+            ASN1TimeZone::Offset(h, m) => UtcOffset::from_hms(h, m, 0)?,
+            ASN1TimeZone::Undefined | ASN1TimeZone::Z => UtcOffset::UTC,
+        };
+        Ok(primitive_date.assume_offset(offset))
+    }
+
+    #[cfg(feature = "datetime")]
+    pub fn to_datetime(&self) -> Result<OffsetDateTime> {
+        use crate::Error;
+
+        self.to_time_datetime().map_err(|_| Error::InvalidDateTime)
+    }
+}
+
+impl fmt::Display for ASN1DateTime {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        let fractional = match self.millisecond {
+            None => "".to_string(),
+            Some(v) => format!(".{}", v),
+        };
+        write!(
+            f,
+            "{:04}{:02}{:02}{:02}{:02}{:02}{}Z",
+            self.year, self.month, self.day, self.hour, self.minute, self.second, fractional,
+        )
+    }
+}
+
+/// Decode 2-digit decimal value
+pub(crate) fn decode_decimal(tag: Tag, hi: u8, lo: u8) -> Result<u8> {
+    if (b'0'..=b'9').contains(&hi) && (b'0'..=b'9').contains(&lo) {
+        Ok((hi - b'0') * 10 + (lo - b'0'))
+    } else {
+        Err(tag.invalid_value("expected digit"))
+    }
+}