Replace ssz with ssz2, adapt ssz_derive

eth2/utils/ssz/examples/struct_definition.rs

@@ -0,0 +1,62 @@
+use ssz::{Decodable, DecodeError, Encodable, SszDecoderBuilder, SszStream};
+
+#[derive(Debug, PartialEq)]
+pub struct Foo {
+    a: u16,
+    b: Vec<u8>,
+    c: u16,
+}
+
+impl Encodable for Foo {
+    fn is_ssz_fixed_len() -> bool {
+        <u16 as Encodable>::is_ssz_fixed_len() && <Vec<u16> as Encodable>::is_ssz_fixed_len()
+    }
+
+    fn as_ssz_bytes(&self) -> Vec<u8> {
+        let mut stream = SszStream::new();
+
+        stream.append(&self.a);
+        stream.append(&self.b);
+        stream.append(&self.c);
+
+        stream.drain()
+    }
+}
+
+impl Decodable for Foo {
+    fn is_ssz_fixed_len() -> bool {
+        <u16 as Decodable>::is_ssz_fixed_len() && <Vec<u16> as Decodable>::is_ssz_fixed_len()
+    }
+
+    fn from_ssz_bytes(bytes: &[u8]) -> Result<Self, DecodeError> {
+        let mut builder = SszDecoderBuilder::new(bytes);
+
+        builder.register_type::<u16>()?;
+        builder.register_type::<Vec<u8>>()?;
+        builder.register_type::<u16>()?;
+
+        let mut decoder = builder.build()?;
+
+        Ok(Self {
+            a: decoder.decode_next()?,
+            b: decoder.decode_next()?,
+            c: decoder.decode_next()?,
+        })
+    }
+}
+
+fn main() {
+    let foo = Foo {
+        a: 42,
+        b: vec![0, 1, 2, 3],
+        c: 11,
+    };
+
+    let bytes = vec![42, 0, 8, 0, 0, 0, 11, 0, 0, 1, 2, 3];
+
+    assert_eq!(foo.as_ssz_bytes(), bytes);
+
+    let decoded_foo = Foo::from_ssz_bytes(&bytes).unwrap();
+
+    assert_eq!(foo, decoded_foo);
+}