feat(alonzo): small ergonomic improvements to lib api

pallas-alonzo/src/crypto.rs

@@ -29,7 +29,7 @@ pub fn hash_plutus_data(data: &PlutusData) -> Result<Hash32, Error> {
 
 #[cfg(test)]
 mod tests {
-    use crate::BlockWrapper;
+    use crate::{BlockWrapper, Fragment};
 
     use super::hash_transaction;
 
@@ -40,7 +40,7 @@ mod tests {
         let block_str = include_str!("test_data/test1.block");
 
         let block_bytes = hex::decode(block_str).expect(&format!("bad block file {}", block_idx));
-        let block_model: BlockWrapper = minicbor::decode(&block_bytes[..])
+        let block_model = BlockWrapper::decode_fragment(&block_bytes[..])
             .expect(&format!("error decoding cbor for file {}", block_idx));
 
         let valid_hashes = vec![

pallas-alonzo/src/framework.rs

@@ -0,0 +1,22 @@
+pub type Error = Box<dyn std::error::Error>;
+
+pub trait Fragment<'a>
+where
+    Self: Sized,
+{
+    fn encode_fragment(&self) -> Result<Vec<u8>, Error>;
+    fn decode_fragment(bytes: &'a [u8]) -> Result<Self, Error>;
+}
+
+impl<'a, T> Fragment<'a> for T
+where
+    T: minicbor::Encode + minicbor::Decode<'a> + Sized,
+{
+    fn encode_fragment(&self) -> Result<Vec<u8>, Error> {
+        minicbor::to_vec(self).map_err(|e| e.into())
+    }
+
+    fn decode_fragment(bytes: &'a [u8]) -> Result<Self, Error> {
+        minicbor::decode(bytes).map_err(|e| e.into())
+    }
+}

pallas-alonzo/src/lib.rs

@@ -1,4 +1,7 @@
 mod model;
+mod framework;
+
+pub use framework::*;
 pub use model::*;
 
 #[cfg(feature = "crypto")]

pallas-alonzo/src/model.rs

@@ -5,7 +5,7 @@
 use log::warn;
 use minicbor::{bytes::ByteVec, data::Tag};
 use minicbor_derive::{Decode, Encode};
-use std::collections::BTreeMap;
+use std::{collections::BTreeMap, ops::Deref};
 
 #[derive(Debug, PartialEq, PartialOrd, Eq, Ord)]
 pub struct SkipCbor<const N: usize> {}
@@ -1092,6 +1092,14 @@ impl minicbor::Encode for Metadatum {
 #[derive(Debug, PartialEq, Eq, PartialOrd, Ord)]
 pub struct Metadata(Vec<(Metadatum, Metadatum)>);
 
+impl Deref for Metadata {
+    type Target = Vec<(Metadatum, Metadatum)>;
+
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+
 impl<'b> minicbor::decode::Decode<'b> for Metadata {
     fn decode(d: &mut minicbor::Decoder<'b>) -> Result<Self, minicbor::decode::Error> {
         let items: Result<Vec<_>, _> = d.map_iter::<Metadatum, Metadatum>()?.collect();
@@ -1202,7 +1210,7 @@ pub struct BlockWrapper(#[n(0)] pub u16, #[n(1)] pub Block);
 
 #[cfg(test)]
 mod tests {
-    use crate::BlockWrapper;
+    use crate::{BlockWrapper, Fragment};
     use minicbor::{self, to_vec};
 
     #[test]
@@ -1221,7 +1229,7 @@ mod tests {
         for (idx, block_str) in test_blocks.iter().enumerate() {
             //println!("decoding test block {}", idx + 1);
             let bytes = hex::decode(block_str).expect(&format!("bad block file {}", idx));
-            let block: BlockWrapper = minicbor::decode(&bytes[..])
+            let block = BlockWrapper::decode_fragment(&bytes[..])
                 .expect(&format!("error decoding cbor for file {}", idx));
             let bytes2 =
                 to_vec(block).expect(&format!("error encoding block cbor for file {}", idx));