1 files changed, 66 insertions, 0 deletions
diff --git a/vendor/der/src/asn1/optional.rs b/vendor/der/src/asn1/optional.rs
new file mode 100644
index 0000000..ecda4f8
--- /dev/null
+++ b/vendor/der/src/asn1/optional.rs
@@ -0,0 +1,66 @@
+//! ASN.1 `OPTIONAL` as mapped to Rust's `Option` type
+
+use crate::{Choice, Decode, DerOrd, Encode, Length, Reader, Result, Tag, Writer};
+use core::cmp::Ordering;
+
+impl<'a, T> Decode<'a> for Option<T>
+where
+    T: Choice<'a>, // NOTE: all `Decode + Tagged` types receive a blanket `Choice` impl
+{
+    fn decode<R: Reader<'a>>(reader: &mut R) -> Result<Option<T>> {
+        if let Some(byte) = reader.peek_byte() {
+            if T::can_decode(Tag::try_from(byte)?) {
+                return T::decode(reader).map(Some);
+            }
+        }
+
+        Ok(None)
+    }
+}
+
+impl<T> DerOrd for Option<T>
+where
+    T: DerOrd,
+{
+    fn der_cmp(&self, other: &Self) -> Result<Ordering> {
+        match self {
+            Some(a) => match other {
+                Some(b) => a.der_cmp(b),
+                None => Ok(Ordering::Greater),
+            },
+            None => Ok(Ordering::Less),
+        }
+    }
+}
+
+impl<T> Encode for Option<T>
+where
+    T: Encode,
+{
+    fn encoded_len(&self) -> Result<Length> {
+        (&self).encoded_len()
+    }
+
+    fn encode(&self, writer: &mut impl Writer) -> Result<()> {
+        (&self).encode(writer)
+    }
+}
+
+impl<T> Encode for &Option<T>
+where
+    T: Encode,
+{
+    fn encoded_len(&self) -> Result<Length> {
+        match self {
+            Some(encodable) => encodable.encoded_len(),
+            None => Ok(0u8.into()),
+        }
+    }
+
+    fn encode(&self, encoder: &mut impl Writer) -> Result<()> {
+        match self {
+            Some(encodable) => encodable.encode(encoder),
+            None => Ok(()),
+        }
+    }
+}