feat: add Codec trait

Cargo.toml

@@ -12,7 +12,7 @@ categories = ["data-structures", "encoding"]
 
 [features]
 default = ["std"]
-# Makes the error implement `std::error::Error`.
+# Makes the error implement `std::error::Error` and the `Codec` trait available.
 std = ["cid/std", "serde?/std"]
 # Enables support for Serde serialization into/deserialization from the `Ipld` enum.
 serde = ["dep:serde", "cid/serde-codec"]

src/codec.rs

@@ -0,0 +1,43 @@
+//! This module contains traits to have a unified API across codecs.
+//!
+//! There are two traits defined, [`Codec`] and [`Links`]. Those are separate traits as the `Links`
+//! trait is not generic over a certain type.
+
+use cid::Cid;
+
+use std::io::{BufRead, Write};
+
+/// Each IPLD codec implementation should implement this Codec trait. This way codecs can be more
+/// easily exchanged or combined.
+pub trait Codec<T>: Links {
+    /// The multicodec code of the IPLD codec.
+    const CODE: u64;
+    /// The error that is returned if encoding or decoding fails.
+    type Error;
+
+    /// Decode a reader into the desired type.
+    fn decode<R: BufRead>(reader: R) -> Result<T, Self::Error>;
+    /// Encode a type into a writer.
+    fn encode<W: Write>(writer: W, data: &T) -> Result<(), Self::Error>;
+
+    /// Decode a slice into the desired type.
+    fn decode_from_slice(bytes: &[u8]) -> Result<T, Self::Error> {
+        Self::decode(bytes)
+    }
+
+    /// Encode a type into bytes.
+    fn encode_to_vec(data: &T) -> Result<Vec<u8>, Self::Error> {
+        let mut output = Vec::new();
+        Self::encode(&mut output, data)?;
+        Ok(output)
+    }
+}
+
+/// Trait for returning the links of a serialized IPLD data.
+pub trait Links {
+    /// The error that is returned if the link extraction fails.
+    type LinksError;
+
+    /// Return all links (CIDs) that the given encoded data contains.
+    fn links(bytes: &[u8]) -> Result<impl Iterator<Item = Cid>, Self::LinksError>;
+}

src/lib.rs

@@ -9,6 +9,8 @@
 
 extern crate alloc;
 
+#[cfg(feature = "std")]
+pub mod codec;
 pub mod convert;
 pub mod ipld;
 #[cfg(feature = "serde")]