Encoding relations API

encoding/src/traits.rs

@@ -3,12 +3,16 @@ use std::future::Future;
 use crate::error::DecodeError;
 use ufotofu::local_nb::{BulkConsumer, BulkProducer};
 
-/// A type that can be encoded to a bytestring, ensuring that any value of `Self` maps to exactly one bytestring.
+/// A type which can be asynchronously encoded to bytes consumed by a [`ufotofu::local_nb::BulkConsumer`]
 ///
 /// [Definition](https://willowprotocol.org/specs/encodings/index.html#encodings_what)
 pub trait Encodable {
-    /// Encode a value to a bytestring in a specific way that is best described over at [willowprotocol.org](https://willowprotocol.org/specs/encodings/index.html#encodings_what).
+    /// Encode the value with an [encoding function](https://macromania--channelclosing.deno.dev/specs/encodings/index.html#encoding_function) for the set of `Self`, ensuring that any value of `Self` maps to exactly one bytestring, such that there exists a _decoding_ function such that:
     ///
+    /// - for every value `s` in `Self` and every bytestring `b` that starts with `encode_s(s)`, we have `decode_s(b)=s`, and
+    /// - for every `s` in `Self` and every bytestring b that does not start with `encode_s(s)`, we have `decode_s(b) ≠ s`.
+    ///
+    /// The encoded bytestring will be consumed to the provided [`ufotofu::local_nb::BulkConsumer`].
     /// [Definition](https://willowprotocol.org/specs/encodings/index.html#encode_s)
     fn encode<Consumer>(
         &self,
@@ -18,11 +22,16 @@ pub trait Encodable {
         Consumer: BulkConsumer<Item = u8>;
 }
 
-/// A type that can be decoded from a bytestring, ensuring that every valid encoding maps to exactly one member of `Self`.
+/// A type which can be asynchronously decoded from bytes produced by a [`ufotofu::local_nb::BulkProducer`]
 ///
 /// [Definition](https://willowprotocol.org/specs/encodings/index.html#encodings_what)
 pub trait Decodable {
-    /// Decade a value to a bytestring in a specific way that is best described over at [willowprotocol.org](https://willowprotocol.org/specs/encodings/index.html#encodings_what).
+    /// Decode a bytestring created with an [encoding function](https://macromania--channelclosing.deno.dev/specs/encodings/index.html#encoding_function) for the set of `Self`, ensuring that any value of `Self` maps to exactly one bytestring, such that there exists a _decoding_ function (provided by this trait!) such that:
+    ///
+    /// - for every value `s` in `Self` and every bytestring `b` that starts with `encode_s(s)`, we have `decode_s(b)=s`, and
+    /// - for every `s` in `Self` and every bytestring `b` that does not start with `encode_s(s)`, we have `decode_s(b) ≠ s`.
+    ///
+    /// Will return an error if the encoding correlates to the **encoding relation** and not the result of the aforementioned encoding function.
     ///
     /// [Definition](https://willowprotocol.org/specs/encodings/index.html#decode_s)
     fn decode<Producer>(
@@ -31,12 +40,31 @@ pub trait Decodable {
     where
         Producer: BulkProducer<Item = u8>,
         Self: Sized;
+
+    /// Decode a bytestring belonging to the **encoding relation** on the set of `Self` and the set of bytestrings, such that:
+    ///
+    /// - for every `s` in `Self`, there is at least one bytestring in relation with `s`, and
+    /// - no bytestring in the relation is a prefix of another bytestring in the relation.
+    ///
+    /// [Definition](https://willowprotocol.org/specs/encodings/index.html#decode_s)
+    fn decode_relation<Producer>(
+        producer: &mut Producer,
+    ) -> impl Future<Output = Result<Self, DecodeError<Producer::Error>>>
+    where
+        Producer: BulkProducer<Item = u8>,
+        Self: Sized;
 }
 
-/// A type that can be used to encode `T` to a bytestring *encoded relative to `R`*.
-/// This can be used to create more compact encodings from which `T` can be derived by anyone with `R`.
+/// A type relative to a reference value of type `R` which can be asynchronously encoded to bytes consumed by a [`ufotofu::local_nb::BulkConsumer`]
+///
+/// [Definition](https://willowprotocol.org/specs/encodings/index.html#encodings_what)
+///
+/// [Definition](https://willowprotocol.org/specs/encodings/index.html#encodings_what)
 pub trait RelativeEncodable<R> {
-    /// Encode a value (relative to a reference value) to a bytestring in a specific way that is best described over at [willowprotocol.org](https://willowprotocol.org/specs/encodings/index.html#encodings_what).
+    /// Encode a pair of `Self` and `R` with the [encoding function](https://macromania--channelclosing.deno.dev/specs/encodings/index.html#encoding_function) for the set of `Self` relative to a value of the set of `R`, ensuring that any pair of `Self` and `R` maps to exactly one bytestring, such that there exists a _decoding_ function such that:
+    ///
+    /// - for every pair of `s` in `Self` and `r` in `R`, and every bytestring `b` that starts with `encode_s(s, r)`, we have `decode_s(b, r)=s`, and
+    /// - for every pair of `s` in `Self` and `r` in `R`, and every bytestring `b` that does not start with `encode_s(s, r)`, we have `decode_s(b, r) ≠ s`.
     fn relative_encode<Consumer>(
         &self,
         reference: &R,
@@ -46,15 +74,35 @@ pub trait RelativeEncodable<R> {
         Consumer: BulkConsumer<Item = u8>;
 }
 
-/// A type that can be used to decode `T` from a bytestring *encoded relative to `Self`*.
-/// This can be used to decode a compact encoding frow which `T` can be derived by anyone with `R`.
+/// A type relative to a value of type `R` which can be asynchronously decoded from bytes produced by a [`ufotofu::local_nb::BulkProducer`]
+///
+/// [Definition](https://willowprotocol.org/specs/encodings/index.html#encodings_what)
 pub trait RelativeDecodable<R> {
-    /// Decode a value (relative to a reference value) to a bytestring in a specific way that is best described over at [willowprotocol.org](https://willowprotocol.org/specs/encodings/index.html#encodings_what).
+    ///
+    /// Decode a bytestring created with an [encoding function](https://macromania--channelclosing.deno.dev/specs/encodings/index.html#encoding_function) for the set of `Self` relative to a value of the set of `R`, ensuring that any pair of `Self` and `R` maps to exactly one bytestring, such that there exists a _decoding_ function (provided by this trait!) such that:
+    ///
+    /// - for every pair of `s` in `Self` and `r` in `R`, and every bytestring `b` that starts with `encode_s(s, r)`, we have `decode_s(b, r)=s`, and
+    /// - for every pair of `s` in `Self` and `r` in `R`, and every bytestring `b` that does not start with `encode_s(s, r)`, we have `decode_s(b, r) ≠ s`.
+    ///
+    /// Will return an error if the encoding correlates to the **encoding relation** and not the result of the aforementioned encoding function.
+    ///
+    /// [Definition](https://willowprotocol.org/specs/encodings/index.html#decode_s)
     fn relative_decode<Producer>(
         reference: &R,
         producer: &mut Producer,
     ) -> impl Future<Output = Result<Self, DecodeError<Producer::Error>>>
     where
         Producer: BulkProducer<Item = u8>,
         Self: Sized;
+
+    /// Decode a bytestring belonging to the **encoding relation** on the set of `Self` relative to a value of the set of `R`, and the set of bytestrings, such that:
+    ///
+    /// - for every pair of `s` in `Self` and `r` in `R`, there is at least one bytestring in relation with the pair of `s` and `r`, and
+    /// - no bytestring in the relation is a prefix of another bytestring in the relation.
+    fn relative_decode_relation<Producer>(
+        producer: &mut Producer,
+    ) -> impl Future<Output = Result<Self, DecodeError<Producer::Error>>>
+    where
+        Producer: BulkProducer<Item = u8>,
+        Self: Sized;
 }