der: add ApplicationExplicit, ContextSpecificExplicit, PrivateExplicit wrappers

Author: dishmaker

der/src/asn1.rs

@@ -35,18 +35,18 @@ mod videotex_string;
 
 pub use self::{
     any::AnyRef,
-    application::{Application, ApplicationRef},
+    application::{Application, ApplicationExplicit, ApplicationRef},
     bit_string::{BitStringIter, BitStringRef},
     choice::Choice,
-    context_specific::{ContextSpecific, ContextSpecificRef},
+    context_specific::{ContextSpecific, ContextSpecificExplicit, ContextSpecificRef},
     general_string::GeneralStringRef,
     generalized_time::GeneralizedTime,
     ia5_string::Ia5StringRef,
     integer::{int::IntRef, uint::UintRef},
     null::Null,
     octet_string::OctetStringRef,
     printable_string::PrintableStringRef,
-    private::{Private, PrivateRef},
+    private::{Private, PrivateExplicit, PrivateRef},
     sequence::{Sequence, SequenceRef},
     sequence_of::{SequenceOf, SequenceOfIter},
     set_of::{SetOf, SetOfIter},

der/src/asn1/application.rs

@@ -2,8 +2,8 @@
 
 use crate::{
     Choice, Class, Decode, DecodeValue, DerOrd, Encode, EncodeValue, EncodeValueRef, EncodingRules,
-    Error, Header, Length, Reader, Tag, TagMode, TagNumber, Tagged, ValueOrd, Writer, asn1::AnyRef,
-    tag::IsConstructed,
+    Error, FixedTag, Header, Length, Reader, Tag, TagMode, TagNumber, Tagged, ValueOrd, Writer,
+    asn1::AnyRef, tag::IsConstructed,
 };
 use core::cmp::Ordering;
 
@@ -12,3 +12,10 @@ use crate::ErrorKind;
 
 impl_custom_class!(Application, Application, "APPLICATION", "0b01000000");
 impl_custom_class_ref!(ApplicationRef, Application, "APPLICATION", "0b01000000");
+
+impl_custom_class_explicit!(
+    ApplicationExplicit,
+    Application,
+    "APPLICATION",
+    "0b01000000"
+);

der/src/asn1/context_specific.rs

@@ -2,8 +2,8 @@
 
 use crate::{
     Choice, Class, Decode, DecodeValue, DerOrd, Encode, EncodeValue, EncodeValueRef, EncodingRules,
-    Error, Header, Length, Reader, Tag, TagMode, TagNumber, Tagged, ValueOrd, Writer, asn1::AnyRef,
-    tag::IsConstructed,
+    Error, FixedTag, Header, Length, Reader, Tag, TagMode, TagNumber, Tagged, ValueOrd, Writer,
+    asn1::AnyRef, tag::IsConstructed,
 };
 use core::cmp::Ordering;
 
@@ -23,13 +23,23 @@ impl_custom_class_ref!(
     "0b10000000"
 );
 
+impl_custom_class_explicit!(
+    ContextSpecificExplicit,
+    ContextSpecific,
+    "CONTEXT-SPECIFIC",
+    "0b10000000"
+);
+
 #[cfg(test)]
 #[allow(clippy::unwrap_used)]
 mod tests {
     use super::ContextSpecific;
     use crate::{
         Decode, Encode, SliceReader, TagMode, TagNumber,
-        asn1::{BitStringRef, ContextSpecificRef, SetOf, Utf8StringRef},
+        asn1::{
+            BitStringRef, ContextSpecificRef, SetOf, Utf8StringRef,
+            context_specific::ContextSpecificExplicit,
+        },
     };
     use hex_literal::hex;
 
@@ -194,4 +204,34 @@ mod tests {
         assert_eq!(field.value.get(0).cloned(), Some(hello));
         assert_eq!(field.value.get(1).cloned(), Some(world));
     }
+
+    #[test]
+    fn round_trip_explicit() {
+        let field =
+            ContextSpecificExplicit::<1, BitStringRef<'_>>::from_der(EXAMPLE_BYTES).unwrap();
+        assert_eq!(
+            field.value,
+            BitStringRef::from_bytes(&EXAMPLE_BYTES[5..]).unwrap()
+        );
+        assert_eq!(
+            ContextSpecificExplicit::<1, BitStringRef<'_>>::tag_mode(),
+            TagMode::Explicit
+        );
+        assert_eq!(
+            ContextSpecificExplicit::<1, BitStringRef<'_>>::tag_number(),
+            TagNumber(1)
+        );
+
+        let mut buf = [0u8; 128];
+        let encoded = field.encode_to_slice(&mut buf).unwrap();
+        assert_eq!(encoded, EXAMPLE_BYTES);
+
+        // should not decode as tag CONTEXT-SPECIFIC [2]
+        assert!(ContextSpecificExplicit::<2, BitStringRef<'_>>::from_der(EXAMPLE_BYTES).is_err());
+
+        // should be different than CONTEXT-SPECIFIC [1]
+        let invalid_field = ContextSpecificExplicit::<2, BitStringRef<'_>> { value: field.value };
+        let invalid_encoded = invalid_field.encode_to_slice(&mut buf).unwrap();
+        assert_ne!(invalid_encoded, EXAMPLE_BYTES);
+    }
 }

der/src/asn1/internal_macros.rs

@@ -335,3 +335,73 @@ macro_rules! impl_custom_class_ref {
         }
     };
 }
+
+macro_rules! impl_custom_class_explicit {
+    ($explicit_class_type_name: ident, $class_enum_name: ident, $asn1_class_name: literal, $class_bits_str: literal) => {
+        #[doc = concat!("`", $asn1_class_name, "` field reference, with const `EXPLICIT` encoding.")]
+        ///
+        ///
+        /// This type encodes a field which is specific to a particular context
+        /// and is identified by a [`TagNumber`].
+        ///
+        /// Inner value might implement [`Encode`], [`Decode`] or both.
+        #[derive(Copy, Clone, Debug, Eq, PartialEq, PartialOrd, Ord)]
+        pub struct $explicit_class_type_name<const NUMBER: u32, T> {
+            /// Inner value might implement [`Encode`], [`Decode`] or both.
+            pub value: T,
+        }
+
+        impl<const NUMBER: u32, T> $explicit_class_type_name<NUMBER, T> {
+            #[doc = concat!("Returns const [`TagNumber`], associated with this `EXPLICIT` `", $asn1_class_name, "` wrapper.")]
+            pub const fn tag_number() -> TagNumber {
+                TagNumber(NUMBER)
+            }
+
+            #[doc = concat!("Returns const [`TagMode::Explicit`], associated with this `EXPLICIT` `", $asn1_class_name, "` wrapper.")]
+            pub const fn tag_mode() -> TagMode {
+                TagMode::Explicit
+            }
+        }
+
+        impl<const NUMBER: u32, T> EncodeValue for $explicit_class_type_name<NUMBER, T>
+        where
+            T: Encode,
+        {
+            fn value_len(&self) -> Result<Length, Error> {
+                self.value.encoded_len()
+            }
+
+            fn encode_value(&self, writer: &mut impl Writer) -> Result<(), Error> {
+                // Encode EXPLICIT value (with tag and length)
+                self.value.encode(writer)
+            }
+        }
+
+        impl<'a, const NUMBER: u32, T> DecodeValue<'a> for $explicit_class_type_name<NUMBER, T>
+        where
+            T: Decode<'a>,
+        {
+            type Error = T::Error;
+
+            fn decode_value<R: Reader<'a>>(
+                reader: &mut R,
+                header: Header,
+            ) -> Result<Self, Self::Error> {
+                // encoding shall be constructed
+                if !header.tag.is_constructed() {
+                    return Err(reader.error(header.tag.non_canonical_error()).into());
+                }
+                Ok(Self {
+                    value: T::decode(reader)?,
+                })
+            }
+        }
+
+        impl<const NUMBER: u32, T> FixedTag for $explicit_class_type_name<NUMBER, T> {
+            const TAG: Tag = Tag::$class_enum_name {
+                constructed: true,
+                number: Self::tag_number(),
+            };
+        }
+    };
+}

der/src/asn1/private.rs

@@ -2,8 +2,8 @@
 
 use crate::{
     Choice, Class, Decode, DecodeValue, DerOrd, Encode, EncodeValue, EncodeValueRef, EncodingRules,
-    Error, Header, Length, Reader, Tag, TagMode, TagNumber, Tagged, ValueOrd, Writer, asn1::AnyRef,
-    tag::IsConstructed,
+    Error, FixedTag, Header, Length, Reader, Tag, TagMode, TagNumber, Tagged, ValueOrd, Writer,
+    asn1::AnyRef, tag::IsConstructed,
 };
 use core::cmp::Ordering;
 
@@ -12,3 +12,4 @@ use crate::ErrorKind;
 
 impl_custom_class!(Private, Private, "PRIVATE", "0b11000000");
 impl_custom_class_ref!(PrivateRef, Private, "PRIVATE", "0b11000000");
+impl_custom_class_explicit!(PrivateExplicit, Private, "PRIVATE", "0b11000000");