impl fastrlp traits for Signature (#1444)

Cargo.lock

@@ -1279,6 +1279,7 @@ dependencies = [
  "convert_case",
  "elliptic-curve",
  "ethabi",
+ "fastrlp",
  "generic-array 0.14.5",
  "hex",
  "hex-literal",
@@ -1512,6 +1513,31 @@ dependencies = [
  "instant",
 ]
 
+[[package]]
+name = "fastrlp"
+version = "0.1.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d6c60b758dc5bf92743e1b863ac88b84a4750bd096b19c2f524359659dc1f1ac"
+dependencies = [
+ "arrayvec 0.7.2",
+ "auto_impl",
+ "bytes",
+ "ethereum-types",
+ "fastrlp-derive",
+]
+
+[[package]]
+name = "fastrlp-derive"
+version = "0.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9499f20a2fa1a744422de24d1b4d1ec58f240147de1d0a3ceacadf2e240b4fc2"
+dependencies = [
+ "bytes",
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
 [[package]]
 name = "ff"
 version = "0.11.0"

ethers-core/Cargo.toml

@@ -10,6 +10,7 @@ repository = "https://github.com/gakonst/ethers-rs"
 keywords = ["ethereum", "web3", "celo", "ethers"]
 
 [dependencies]
+fastrlp = { version = "0.1.2", features = ["std", "derive", "ethereum-types"] }
 rlp = { version = "0.5.0", default-features = false, features = ["std"] }
 ethabi = { version = "17.1.0", default-features = false, features = ["full-serde", "rlp"] }
 arrayvec = { version = "0.7.2", default-features = false }

ethers-core/src/types/signature.rs

@@ -4,6 +4,7 @@ use crate::{
     utils::hash_message,
 };
 
+use fastrlp::Decodable;
 use serde::{Deserialize, Serialize};
 use std::{convert::TryFrom, fmt, str::FromStr};
 
@@ -53,7 +54,7 @@ pub enum RecoveryMessage {
     Hash(H256),
 }
 
-#[derive(Serialize, Deserialize, Debug, Clone, PartialEq, Eq, Copy)]
+#[derive(Serialize, Deserialize, Debug, Clone, PartialEq, Eq, Copy, Hash)]
 /// An ECDSA signature
 pub struct Signature {
     /// R value
@@ -141,6 +142,29 @@ impl Signature {
     pub fn to_vec(&self) -> Vec<u8> {
         self.into()
     }
+
+    /// Decodes a signature from RLP bytes, assuming no RLP header
+    pub(crate) fn decode_signature(buf: &mut &[u8]) -> Result<Self, fastrlp::DecodeError> {
+        let v = u64::decode(buf)?;
+        Ok(Self { r: U256::decode(buf)?, s: U256::decode(buf)?, v })
+    }
+}
+
+impl fastrlp::Decodable for Signature {
+    fn decode(buf: &mut &[u8]) -> Result<Self, fastrlp::DecodeError> {
+        Self::decode_signature(buf)
+    }
+}
+
+impl fastrlp::Encodable for Signature {
+    fn length(&self) -> usize {
+        self.r.length() + self.s.length() + self.v.length()
+    }
+    fn encode(&self, out: &mut dyn bytes::BufMut) {
+        self.v.encode(out);
+        self.r.encode(out);
+        self.s.encode(out);
+    }
 }
 
 fn normalize_recovery_id(v: u64) -> u8 {