Implement SSZ decode for H256

Cargo.toml

@@ -12,7 +12,8 @@ boolean-bitfield = { path = "boolean-bitfield" }
 bytes = ""
 crypto-mac = "^0.6.2"
 clap = "2.32.0"
-ethereum-types = ""
+dirs = "1.0.3"
+ethereum-types = "0.4.0"
 futures = "0.1.23"
 network-libp2p = { path = "network-libp2p" }
 rand = "0.3"

ssz/src/impl_decode.rs

@@ -1,7 +1,10 @@
+use super::ethereum_types::H256;
 use super::{
     DecodeError,
     Decodable,
 };
+
+
 macro_rules! impl_decodable_for_uint {
     ($type: ident, $bit_size: expr) => {
         impl Decodable for $type {
@@ -33,14 +36,58 @@ impl_decodable_for_uint!(u32, 32);
 impl_decodable_for_uint!(u64, 64);
 impl_decodable_for_uint!(usize, 64);
 
+impl Decodable for H256 {
+    fn ssz_decode(bytes: &[u8], index: usize)
+        -> Result<(Self, usize), DecodeError>
+    {
+        if bytes.len() < 32 {
+            return Err(DecodeError::TooShort)
+        }
+        else if bytes.len() - 32 < index {
+            return Err(DecodeError::TooShort)
+        }
+        else {
+            return Ok((H256::from(&bytes[index..(index + 32)]),
+                       index + 32));
+        }
+    }
+}
 
 #[cfg(test)]
 mod tests {
+    use super::*;
     use super::super::{
         DecodeError,
         decode_ssz,
     };
 
+    #[test]
+    fn test_ssz_decode_h256() {
+        /*
+         * Input is exact length
+         */
+        let input = vec![42_u8; 32];
+        let (decoded, i) = H256::ssz_decode(&input, 0).unwrap();
+        assert_eq!(decoded.to_vec(), input);
+        assert_eq!(i, 32);
+
+        /*
+         * Input is too long
+         */
+        let mut input = vec![42_u8; 32];
+        input.push(12);
+        let (decoded, i) = H256::ssz_decode(&input, 0).unwrap();
+        assert_eq!(decoded.to_vec()[..], input[0..32]);
+        assert_eq!(i, 32);
+
+        /*
+         * Input is too short
+         */
+        let input = vec![42_u8; 31];
+        let res = H256::ssz_decode(&input, 0);
+        assert_eq!(res, Err(DecodeError::TooShort));
+    }
+
     #[test]
     fn test_ssz_decode_u16() {
         let ssz = vec![0, 0];

ssz/src/lib.rs

@@ -20,6 +20,7 @@ pub use decode::{
     Decodable,
     DecodeError,
     decode_ssz,
+    decode_ssz_list,
 };
 pub use encode::{
     Encodable,