feat: rlp enc/dec for requests (alloy-rs#728)

* feat: rlp enc/dec for requests

We need to encode/decode requests sent to us over P2P,
where they are RLP encoded.

* chore: no alloc decode

* decode as bytes

---------

Co-authored-by: Oliver Nordbjerg <[email protected]>

crates/consensus/src/request.rs

@@ -3,7 +3,7 @@ use alloy_eips::{
     eip7002::WithdrawalRequest,
     eip7685::{Decodable7685, Eip7685Error, Encodable7685},
 };
-use alloy_rlp::{Decodable, Encodable};
+use alloy_rlp::{Decodable, Encodable, Header};
 
 /// Ethereum execution layer requests.
 ///
@@ -86,3 +86,16 @@ impl Decodable7685 for Request {
         })
     }
 }
+
+impl Encodable for Request {
+    fn encode(&self, out: &mut dyn alloy_rlp::BufMut) {
+        self.encoded_7685().encode(out)
+    }
+}
+
+impl Decodable for Request {
+    fn decode(buf: &mut &[u8]) -> alloy_rlp::Result<Self> {
+        let mut data = Header::decode_bytes(buf, false)?;
+        Ok(Self::decode_7685(&mut data)?)
+    }
+}

crates/eips/src/eip7685.rs

@@ -43,6 +43,20 @@ impl From<alloy_rlp::Error> for Eip7685Error {
     }
 }
 
+impl From<Eip7685Error> for alloy_rlp::Error {
+    fn from(err: Eip7685Error) -> Self {
+        match err {
+            Eip7685Error::RlpError(err) => err,
+            Eip7685Error::MissingType => {
+                alloy_rlp::Error::Custom("eip7685 decoding failed: missing type")
+            }
+            Eip7685Error::UnexpectedType(_) => {
+                alloy_rlp::Error::Custom("eip7685 decoding failed: unexpected type")
+            }
+        }
+    }
+}
+
 /// Decoding trait for [EIP-7685] requests. The trait should be implemented for an envelope that
 /// wraps each possible request type.
 ///