LevelDB store implementation

Cargo.toml

@@ -7,11 +7,28 @@ license = "Apache License 2.0"
 
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
-[dependencies]
+[dependencies.ciborium]
+version = "0.2.0"
+optional = true
+
+[dependencies.serde]
+version = "1.0.144"
+features = ["derive"]
 
 [dependencies.proptest]
 version = "1.0.0"
 optional = true
 
+[dependencies.rusty-leveldb]
+version = "= 1.0.4"
+optional = true
+
+[dependencies.blake2]
+version = "0.10.4"
+optional = true
+
 [features]
 default = []
+cbor = ["dep:ciborium"]
+blake2 = ["dep:blake2"]
+rusty-leveldb = ["dep:rusty-leveldb", "blake2", "cbor"]

src/blake2.rs

@@ -0,0 +1,39 @@
+// Copyright 2022 Jeremy Wall (Jeremy@marzhilsltudios.com)
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+use crate::hash::*;
+use blake2::digest::Digest;
+pub use blake2::{Blake2b512, Blake2s256};
+
+macro_rules! hash_writer_impl {
+    ($tname:ident, $size:expr) => {
+        impl HashWriter<$size> for $tname {
+            fn record<I: Iterator<Item = u8>>(&mut self, bs: I) {
+                let vec: Vec<u8> = bs.collect();
+                self.update(&vec);
+            }
+
+            fn hash(&self) -> [u8; $size] {
+                let mut out: [u8; $size] = Default::default();
+                // This is gross but Blake2 doesn't support the
+                // non consuming version of this.
+                let mut arr = self.clone().finalize();
+                arr.swap_with_slice(&mut out);
+                out
+            }
+        }
+    };
+}
+
+hash_writer_impl!(Blake2b512, 8);
+hash_writer_impl!(Blake2s256, 4);

src/dag.rs

@@ -15,9 +15,9 @@
 use std::{collections::BTreeSet, marker::PhantomData};
 
 use crate::{
-    hash::{ByteEncoder, HashWriter},
+    hash::HashWriter,
     node::Node,
-    store::{Store, StoreError},
+    store::{Result, Store, StoreError},
 };
 
 /// Node comparison values. In a given Merkle DAG a Node can come `After`, `Before`, be `Equivalent`, or `Uncomparable`.
@@ -44,22 +44,20 @@ pub enum NodeCompare {
 /// A merkle DAG instance is tied to a specific implementation of the HashWriter interface to ensure
 /// that all hash identifiers are of the same hash algorithm.
 #[derive(Clone, Debug)]
-pub struct Merkle<S, N, HW, const HASH_LEN: usize>
+pub struct Merkle<S, HW, const HASH_LEN: usize>
 where
-    N: ByteEncoder,
     HW: HashWriter<HASH_LEN>,
-    S: Store<N, HW, HASH_LEN>,
+    S: Store<HW, HASH_LEN>,
 {
     roots: BTreeSet<[u8; HASH_LEN]>,
     nodes: S,
-    _phantom_node: PhantomData<Node<N, HW, HASH_LEN>>,
+    _phantom_node: PhantomData<Node<HW, HASH_LEN>>,
 }
 
-impl<S, N, HW, const HASH_LEN: usize> Merkle<S, N, HW, HASH_LEN>
+impl<S, HW, const HASH_LEN: usize> Merkle<S, HW, HASH_LEN>
 where
-    N: ByteEncoder,
     HW: HashWriter<HASH_LEN>,
-    S: Store<N, HW, HASH_LEN>,
+    S: Store<HW, HASH_LEN>,
 {
     /// Construct a new empty DAG. The empty DAG is also the default for a DAG.
     pub fn new() -> Self {
@@ -72,20 +70,20 @@ where
     ///
     /// One result of not constructing/adding nodes in this way is that we ensure that we always satisfy
     /// the implementation rule in the merkel-crdt's whitepaper.
-    pub fn add_node<'a>(
+    pub fn add_node<'a, N: Into<Vec<u8>>>(
         &'a mut self,
         item: N,
         dependency_ids: BTreeSet<[u8; HASH_LEN]>,
-    ) -> Result<[u8; HASH_LEN], StoreError> {
-        let node = Node::<N, HW, HASH_LEN>::new(item, dependency_ids.clone());
+    ) -> Result<[u8; HASH_LEN]> {
+        let node = Node::<HW, HASH_LEN>::new(item.into(), dependency_ids.clone());
         let id = node.id().clone();
-        if self.nodes.contains(&id) {
+        if self.nodes.contains(&id)? {
             // We've already added this node so there is nothing left to do.
             return Ok(id);
         }
         let mut root_removals = Vec::new();
         for dep_id in dependency_ids.iter() {
-            if !self.nodes.contains(dep_id) {
+            if !self.nodes.contains(dep_id)? {
                 return Err(StoreError::NoSuchDependents);
             }
             // If any of our dependencies is in the roots pointer list then
@@ -103,12 +101,12 @@ where
     }
 
     /// Check if we already have a copy of a node.
-    pub fn check_for_node(&self, id: &[u8; HASH_LEN]) -> bool {
+    pub fn check_for_node(&self, id: &[u8; HASH_LEN]) -> Result<bool> {
         return self.nodes.contains(id);
     }
 
     /// Get a node from the DAG by it's hash identifier if it exists.
-    pub fn get_node_by_id(&self, id: &[u8; HASH_LEN]) -> Option<&Node<N, HW, HASH_LEN>> {
+    pub fn get_node_by_id(&self, id: &[u8; HASH_LEN]) -> Result<Option<Node<HW, HASH_LEN>>> {
         self.nodes.get(id)
     }
 
@@ -127,30 +125,30 @@ where
     /// then returns `NodeCompare::After`. If both id's are equal then the returns
     /// `NodeCompare::Equivalent`. If neither id are parts of the same subgraph then returns
     /// `NodeCompare::Uncomparable`.
-    pub fn compare(&self, left: &[u8; HASH_LEN], right: &[u8; HASH_LEN]) -> NodeCompare {
-        if left == right {
+    pub fn compare(&self, left: &[u8; HASH_LEN], right: &[u8; HASH_LEN]) -> Result<NodeCompare> {
+        Ok(if left == right {
             NodeCompare::Equivalent
         } else {
             // Is left node an ancestor of right node?
-            if self.search_graph(right, left) {
+            if self.search_graph(right, left)? {
                 NodeCompare::Before
                 // is right node an ancestor of left node?
-            } else if self.search_graph(left, right) {
+            } else if self.search_graph(left, right)? {
                 NodeCompare::After
             } else {
                 NodeCompare::Uncomparable
             }
-        }
+        })
     }
 
-    fn search_graph(&self, root_id: &[u8; HASH_LEN], search_id: &[u8; HASH_LEN]) -> bool {
+    fn search_graph(&self, root_id: &[u8; HASH_LEN], search_id: &[u8; HASH_LEN]) -> Result<bool> {
         if root_id == search_id {
-            return true;
+            return Ok(true);
         }
-        let root_node = match self.get_node_by_id(root_id) {
+        let root_node = match self.get_node_by_id(root_id)? {
             Some(n) => n,
             None => {
-                return false;
+                return Ok(false);
             }
         };
         let mut stack = vec![root_node];
@@ -159,23 +157,22 @@ where
             let deps = node.dependency_ids();
             for dep in deps {
                 if search_id == dep {
-                    return true;
+                    return Ok(true);
                 }
-                stack.push(match self.get_node_by_id(dep) {
+                stack.push(match self.get_node_by_id(dep)? {
                     Some(n) => n,
                     None => panic!("Invalid DAG STATE encountered"),
                 })
             }
         }
-        return false;
+        return Ok(false);
     }
 }
 
-impl<S, N, HW, const HASH_LEN: usize> Default for Merkle<S, N, HW, HASH_LEN>
+impl<S, HW, const HASH_LEN: usize> Default for Merkle<S, HW, HASH_LEN>
 where
-    N: ByteEncoder,
     HW: HashWriter<HASH_LEN>,
-    S: Store<N, HW, HASH_LEN>,
+    S: Store<HW, HASH_LEN>,
 {
     fn default() -> Self {
         Self {

src/hash.rs

@@ -11,15 +11,9 @@
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.
-
+use std::collections::hash_map::DefaultHasher;
 use std::hash::Hasher;
 
-/// Utility Trait to specify that payloads must be serializable into bytes.
-pub trait ByteEncoder {
-    /// Serialize self into bytes.
-    fn bytes(&self) -> Vec<u8>;
-}
-
 /// Utility Trait to specify the hashing algorithm and provide a common
 /// interface for that algorithm to provide. This interface is expected to
 /// be stateful.
@@ -28,15 +22,10 @@ pub trait HashWriter<const LEN: usize>: Default {
     fn record<I: Iterator<Item = u8>>(&mut self, bs: I);
 
     /// Provide the current hash value based on the bytes that have so far been recorded.
-    /// It is expected that you can call this method multiple times while recording the
-    /// the bytes for input into the hash.
     fn hash(&self) -> [u8; LEN];
 }
 
-impl<H> HashWriter<8> for H
-where
-    H: Hasher + Default,
-{
+impl HashWriter<8> for DefaultHasher {
     fn record<I: Iterator<Item = u8>>(&mut self, iter: I) {
         let bytes = iter.collect::<Vec<u8>>();
         self.write(bytes.as_slice());
@@ -46,12 +35,3 @@ where
         self.finish().to_le_bytes()
     }
 }
-
-impl<V> ByteEncoder for V
-where
-    V: Into<Vec<u8>> + Clone,
-{
-    fn bytes(&self) -> Vec<u8> {
-        <Self as Into<Vec<u8>>>::into(self.clone())
-    }
-}

src/leveldb/mod.rs

@@ -0,0 +1,75 @@
+// Copyright 2022 Jeremy Wall (Jeremy@marzhilsltudios.com)
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+use std::cell::RefCell;
+use std::path::Path;
+
+use crate::{
+    node::Node,
+    store::{Result, Store, StoreError},
+};
+
+use crate::blake2::*;
+use ciborium;
+use rusty_leveldb;
+
+// TODO(jwall): Add leveldb backing store for a Merkle-DAG
+
+pub struct LevelStore {
+    store: RefCell<rusty_leveldb::DB>,
+}
+
+impl LevelStore {
+    pub fn open<P: AsRef<Path>>(path: P) -> std::result::Result<Self, rusty_leveldb::Status> {
+        let opts = Default::default();
+        Ok(Self {
+            store: RefCell::new(rusty_leveldb::DB::open(path, opts)?),
+        })
+    }
+}
+impl Store<Blake2b512, 8> for LevelStore {
+    fn contains(&self, id: &[u8; 8]) -> Result<bool> {
+        Ok(self.store.borrow_mut().get(id).is_some())
+    }
+
+    fn get(&self, id: &[u8; 8]) -> Result<Option<Node<Blake2b512, 8>>> {
+        Ok(match self.store.borrow_mut().get(id) {
+            Some(bs) => ciborium::de::from_reader(bs.as_slice())
+                .map_err(|e| StoreError::StoreFailure(format!("Invalid serialization {:?}", e)))?,
+            None => None,
+        })
+    }
+
+    fn store(&mut self, node: Node<Blake2b512, 8>) -> Result<()> {
+        let mut buf = Vec::new();
+        ciborium::ser::into_writer(&node, &mut buf).unwrap();
+        self.store.borrow_mut().put(node.id(), &buf)?;
+        Ok(())
+    }
+}
+
+impl From<rusty_leveldb::Status> for StoreError {
+    fn from(status: rusty_leveldb::Status) -> Self {
+        StoreError::StoreFailure(format!("{}", status))
+    }
+}
+
+impl Default for LevelStore {
+    fn default() -> Self {
+        Self {
+            store: RefCell::new(
+                rusty_leveldb::DB::open("memory", rusty_leveldb::in_memory()).unwrap(),
+            ),
+        }
+    }
+}

src/lib.rs

@@ -11,8 +11,12 @@
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.
+#[cfg(feature = "blake2")]
+pub mod blake2;
 pub mod dag;
 pub mod hash;
+#[cfg(feature = "rusty-leveldb")]
+pub mod leveldb;
 pub mod node;
 pub mod prelude;
 pub mod store;

src/node.rs

@@ -13,7 +13,9 @@
 // limitations under the License.
 use std::{collections::BTreeSet, marker::PhantomData};
 
-use crate::hash::{ByteEncoder, HashWriter};
+use serde::{de::Visitor, ser::SerializeStruct, Deserialize, Deserializer, Serialize, Serializer};
+
+use crate::hash::HashWriter;
 
 /// A node in a merkle DAG. Nodes are composed of a payload item and a set of dependency_ids.
 /// They provide a unique identifier that is formed from the bytes of the payload as well
@@ -25,32 +27,221 @@ use crate::hash::{ByteEncoder, HashWriter};
 /// Nodes are tied to a specific implementation of the HashWriter trait which is itself tied
 /// to the DAG they are stored in guaranteeing that the same Hashing implementation is used
 /// for each node in the DAG.
-#[derive(Debug, PartialEq, Clone)]
-pub struct Node<N, HW, const HASH_LEN: usize>
+#[derive(Debug, PartialEq)]
+pub struct Node<HW, const HASH_LEN: usize>
 where
-    N: ByteEncoder,
     HW: HashWriter<HASH_LEN>,
 {
     id: [u8; HASH_LEN],
-    item: N,
+    item: Vec<u8>,
     item_id: [u8; HASH_LEN],
     dependency_ids: BTreeSet<[u8; HASH_LEN]>,
     _phantom: PhantomData<HW>,
 }
 
-impl<N, HW, const HASH_LEN: usize> Node<N, HW, HASH_LEN>
+impl<HW, const HASH_LEN: usize> Clone for Node<HW, HASH_LEN>
+where
+    HW: HashWriter<HASH_LEN>,
+{
+    fn clone(&self) -> Self {
+        Self {
+            id: self.id.clone(),
+            item: self.item.clone(),
+            item_id: self.item_id.clone(),
+            dependency_ids: self.dependency_ids.clone(),
+            _phantom: PhantomData,
+        }
+    }
+}
+
+impl<HW, const HASH_LEN: usize> Serialize for Node<HW, HASH_LEN>
+where
+    HW: HashWriter<HASH_LEN>,
+{
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        let mut structor = serializer.serialize_struct("Node", 4)?;
+        structor.serialize_field("id", self.id.as_slice())?;
+        structor.serialize_field("item", &self.item)?;
+        structor.serialize_field("item_id", self.item_id.as_slice())?;
+        // TODO(jwall): structor.serialize_field("dependency_ids", &self.dependency_ids)?;
+        structor.end()
+    }
+}
+
+fn coerce_array<const HASH_LEN: usize>(slice: &[u8]) -> Result<[u8; HASH_LEN], String> {
+    let mut coerced_item: [u8; HASH_LEN] = [0; HASH_LEN];
+    if slice.len() > coerced_item.len() {
+        return Err(format!(
+            "Expected slice of length: {} but got slice of length: {}",
+            coerced_item.len(),
+            slice.len()
+        ));
+    } else {
+        coerced_item.copy_from_slice(slice);
+    }
+    Ok(coerced_item)
+}
+
+fn coerce_set<const HASH_LEN: usize>(
+    set: BTreeSet<&[u8]>,
+) -> Result<BTreeSet<[u8; HASH_LEN]>, String> {
+    let mut coerced_item = BTreeSet::new();
+    for slice in set {
+        coerced_item.insert(coerce_array(slice)?);
+    }
+    Ok(coerced_item)
+}
+
+impl<'de, HW, const HASH_LEN: usize> Deserialize<'de> for Node<HW, HASH_LEN>
+where
+    HW: HashWriter<HASH_LEN>,
+{
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        #[derive(Deserialize)]
+        #[serde(field_identifier, rename_all = "lowercase")]
+        #[allow(non_camel_case_types)]
+        enum Field {
+            Id,
+            Item,
+            Item_Id,
+            Dependency_Ids,
+        }
+
+        struct NodeVisitor<HW, const HASH_LEN: usize>(PhantomData<HW>);
+
+        impl<'de, HW, const HASH_LEN: usize> Visitor<'de> for NodeVisitor<HW, HASH_LEN>
+        where
+            HW: HashWriter<HASH_LEN>,
+        {
+            type Value = Node<HW, HASH_LEN>;
+
+            fn expecting(&self, formatter: &mut std::fmt::Formatter) -> std::fmt::Result {
+                formatter.write_str("struct Node")
+            }
+
+            fn visit_seq<A>(self, mut seq: A) -> Result<Self::Value, A::Error>
+            where
+                A: serde::de::SeqAccess<'de>,
+            {
+                let id: [u8; HASH_LEN] = coerce_array(
+                    seq.next_element::<&[u8]>()?
+                        .ok_or_else(|| serde::de::Error::invalid_length(0, &self))?,
+                )
+                .map_err(serde::de::Error::custom)?;
+                let item = seq
+                    .next_element::<Vec<u8>>()?
+                    .ok_or_else(|| serde::de::Error::invalid_length(1, &self))?;
+                let item_id: [u8; HASH_LEN] = coerce_array(
+                    seq.next_element::<&[u8]>()?
+                        .ok_or_else(|| serde::de::Error::invalid_length(0, &self))?,
+                )
+                .map_err(serde::de::Error::custom)?;
+                let dependency_ids: BTreeSet<[u8; HASH_LEN]> = coerce_set(
+                    seq.next_element::<BTreeSet<&[u8]>>()?
+                        .ok_or_else(|| serde::de::Error::invalid_length(3, &self))?,
+                )
+                .map_err(serde::de::Error::custom)?;
+                Ok(Self::Value {
+                    id,
+                    item,
+                    item_id,
+                    dependency_ids,
+                    _phantom: PhantomData,
+                })
+            }
+
+            fn visit_map<A>(self, mut map: A) -> Result<Self::Value, A::Error>
+            where
+                A: serde::de::MapAccess<'de>,
+            {
+                let mut id: Option<[u8; HASH_LEN]> = None;
+                let mut item: Option<Vec<u8>> = None;
+                let mut item_id: Option<[u8; HASH_LEN]> = None;
+                let mut dependency_ids: Option<BTreeSet<[u8; HASH_LEN]>> = None;
+                while let Some(key) = map.next_key()? {
+                    match key {
+                        Field::Id => {
+                            if id.is_some() {
+                                return Err(serde::de::Error::duplicate_field("id"));
+                            } else {
+                                id = Some(
+                                    coerce_array(map.next_value()?)
+                                        .map_err(serde::de::Error::custom)?,
+                                );
+                            }
+                        }
+                        Field::Item => {
+                            if item.is_some() {
+                                return Err(serde::de::Error::duplicate_field("item"));
+                            } else {
+                                item = Some(map.next_value()?);
+                            }
+                        }
+                        Field::Item_Id => {
+                            if item_id.is_some() {
+                                return Err(serde::de::Error::duplicate_field("item_id"));
+                            } else {
+                                item_id = Some(
+                                    coerce_array(map.next_value()?)
+                                        .map_err(serde::de::Error::custom)?,
+                                );
+                            }
+                        }
+                        Field::Dependency_Ids => {
+                            if dependency_ids.is_some() {
+                                return Err(serde::de::Error::duplicate_field("dependency_ids"));
+                            } else {
+                                dependency_ids = Some(
+                                    coerce_set(map.next_value()?)
+                                        .map_err(serde::de::Error::custom)?,
+                                );
+                            }
+                        }
+                    }
+                }
+                let id = id.ok_or_else(|| serde::de::Error::missing_field("id"))?;
+                let item = item.ok_or_else(|| serde::de::Error::missing_field("item"))?;
+                let item_id = item_id.ok_or_else(|| serde::de::Error::missing_field("item_id"))?;
+                let dependency_ids = dependency_ids
+                    .ok_or_else(|| serde::de::Error::missing_field("dependency_ids"))?;
+
+                Ok(Self::Value {
+                    id,
+                    item,
+                    item_id,
+                    dependency_ids,
+                    _phantom: PhantomData,
+                })
+            }
+        }
+
+        const FIELDS: &'static [&'static str] = &["id", "item", "item_id", "dependency_ids"];
+        deserializer.deserialize_struct(
+            "Duration",
+            FIELDS,
+            NodeVisitor::<HW, HASH_LEN>(PhantomData),
+        )
+    }
+}
+
+impl<HW, const HASH_LEN: usize> Node<HW, HASH_LEN>
 where
-    N: ByteEncoder,
     HW: HashWriter<HASH_LEN>,
 {
     /// Construct a new node with a payload and a set of dependency_ids.
-    pub fn new(item: N, dependency_ids: BTreeSet<[u8; HASH_LEN]>) -> Self {
+    pub fn new<P: Into<Vec<u8>>>(item: P, dependency_ids: BTreeSet<[u8; HASH_LEN]>) -> Self {
         let mut hw = HW::default();
-
+        let item = item.into();
         // NOTE(jwall): The order here is important. Our reliable id creation must be stable
         // for multiple calls to this constructor. This means that we must *always*
         // 1. Record the `item_id` hash first.
-        hw.record(item.bytes().into_iter());
+        hw.record(item.iter().cloned());
         let item_id = hw.hash();
         // 2. Sort the dependency ids before recording them into our node id hash.
         let mut dependency_list = dependency_ids
@@ -75,7 +266,7 @@ where
         &self.id
     }
 
-    pub fn item(&self) -> &N {
+    pub fn item(&self) -> &[u8] {
         &self.item
     }
 

src/proptest.rs

@@ -17,7 +17,7 @@ use proptest::prelude::*;
 
 use crate::prelude::*;
 
-type TestDag = Merkle<BTreeMap<[u8; 8], Node<String, DefaultHasher, 8>>, String, DefaultHasher, 8>;
+type TestDag = Merkle<BTreeMap<[u8; 8], Node<DefaultHasher, 8>>, DefaultHasher, 8>;
 
 fn simple_edge_strategy(
     nodes_count: usize,
@@ -79,7 +79,7 @@ proptest! {
         let mut node_set = BTreeSet::new();
         for (idx, n) in nodes.iter().cloned().enumerate() {
             if !parent_idxs.contains(&idx) {
-                let node_id = dag.add_node(n, BTreeSet::new()).unwrap();
+                let node_id = dag.add_node(n.as_bytes(), BTreeSet::new()).unwrap();
                 node_set.insert(node_id.clone());
                 let parent = idx % parent_count;
                 if dependents.contains_key(&parent) {
@@ -114,7 +114,7 @@ proptest! {
                 continue;
             }
             for root in roots.iter() {
-                if let NodeCompare::After = dag.compare(root, node_id) {
+                if let NodeCompare::After = dag.compare(root, node_id).unwrap() {
                     // success
                     is_descendant = true;
                 }
@@ -125,7 +125,7 @@ proptest! {
         for left_root in roots.iter() {
             for right_root in roots.iter() {
                 if left_root != right_root {
-                    assert_eq!(dag.compare(left_root, right_root), NodeCompare::Uncomparable);
+                    assert_eq!(dag.compare(left_root, right_root).unwrap(), NodeCompare::Uncomparable);
                 }
             }
         }

src/store.rs

@@ -13,42 +13,38 @@
 // limitations under the License.
 use std::collections::BTreeMap;
 
-use crate::{
-    hash::{ByteEncoder, HashWriter},
-    node::Node,
-};
+use crate::{hash::HashWriter, node::Node};
+
+pub type Result<T> = std::result::Result<T, StoreError>;
 
 #[derive(Debug, Clone)]
 pub enum StoreError {
-    StoreFailure,
+    StoreFailure(String),
     NoSuchDependents,
 }
 
-pub trait Store<N, HW, const HASH_LEN: usize>: Default
+pub trait Store<HW, const HASH_LEN: usize>: Default
 where
-    N: ByteEncoder,
     HW: HashWriter<HASH_LEN>,
 {
-    fn contains(&self, id: &[u8; HASH_LEN]) -> bool;
-    fn get(&self, id: &[u8; HASH_LEN]) -> Option<&Node<N, HW, HASH_LEN>>;
-    fn store(&mut self, node: Node<N, HW, HASH_LEN>) -> Result<(), StoreError>;
+    fn contains(&self, id: &[u8; HASH_LEN]) -> Result<bool>;
+    fn get(&self, id: &[u8; HASH_LEN]) -> Result<Option<Node<HW, HASH_LEN>>>;
+    fn store(&mut self, node: Node<HW, HASH_LEN>) -> Result<()>;
 }
 
-impl<N, HW, const HASH_LEN: usize> Store<N, HW, HASH_LEN>
-    for BTreeMap<[u8; HASH_LEN], Node<N, HW, HASH_LEN>>
+impl<HW, const HASH_LEN: usize> Store<HW, HASH_LEN> for BTreeMap<[u8; HASH_LEN], Node<HW, HASH_LEN>>
 where
-    N: ByteEncoder,
     HW: HashWriter<HASH_LEN>,
 {
-    fn contains(&self, id: &[u8; HASH_LEN]) -> bool {
-        self.contains_key(id)
+    fn contains(&self, id: &[u8; HASH_LEN]) -> Result<bool> {
+        Ok(self.contains_key(id))
     }
 
-    fn get(&self, id: &[u8; HASH_LEN]) -> Option<&Node<N, HW, HASH_LEN>> {
-        self.get(id)
+    fn get(&self, id: &[u8; HASH_LEN]) -> Result<Option<Node<HW, HASH_LEN>>> {
+        Ok(self.get(id).cloned())
     }
 
-    fn store(&mut self, node: Node<N, HW, HASH_LEN>) -> Result<(), StoreError> {
+    fn store(&mut self, node: Node<HW, HASH_LEN>) -> Result<()> {
         self.insert(node.id().clone(), node);
         Ok(())
     }

src/test.rs

@@ -17,8 +17,7 @@ use std::collections::{BTreeMap, BTreeSet};
 use crate::prelude::*;
 
 type TestDag<'a> = Merkle<
-    BTreeMap<[u8; 8], Node<&'a str, std::collections::hash_map::DefaultHasher, 8>>,
-    &'a str,
+    BTreeMap<[u8; 8], Node<std::collections::hash_map::DefaultHasher, 8>>,
     std::collections::hash_map::DefaultHasher,
     8,
 >;
@@ -29,7 +28,7 @@ fn test_root_pointer_hygiene() {
     let quax_node_id = dag.add_node("quax", BTreeSet::new()).unwrap();
     assert_eq!(
         quax_node_id,
-        *dag.get_node_by_id(&quax_node_id).unwrap().id()
+        *dag.get_node_by_id(&quax_node_id).unwrap().unwrap().id()
     );
     assert!(dag.get_roots().contains(&quax_node_id));
     let mut dep_set = BTreeSet::new();
@@ -39,13 +38,14 @@ fn test_root_pointer_hygiene() {
     assert!(dag.get_roots().contains(&quux_node_id));
     assert_eq!(
         quux_node_id,
-        *dag.get_node_by_id(&quux_node_id).unwrap().id()
+        *dag.get_node_by_id(&quux_node_id).unwrap().unwrap().id()
     );
 }
 
 #[test]
 fn test_insert_no_such_dependents_error() {
-    let missing_dependent = Node::<&str, DefaultHasher, 8>::new("missing", BTreeSet::new());
+    let missing_dependent =
+        Node::<DefaultHasher, 8>::new("missing".as_bytes().to_vec(), BTreeSet::new());
     let mut dag = TestDag::new();
     let mut dep_set = BTreeSet::new();
     dep_set.insert(*missing_dependent.id());
@@ -60,7 +60,7 @@ fn test_adding_nodes_is_idempotent() {
     let quax_node_id = dag.add_node("quax", BTreeSet::new()).unwrap();
     assert_eq!(
         quax_node_id,
-        *dag.get_node_by_id(&quax_node_id).unwrap().id()
+        *dag.get_node_by_id(&quax_node_id).unwrap().unwrap().id()
     );
     assert!(dag.get_roots().contains(&quax_node_id));
     let root_size = dag.get_roots().len();
@@ -97,7 +97,7 @@ fn test_node_comparison_equivalent() {
     let mut dag = TestDag::new();
     let quake_node_id = dag.add_node("quake", BTreeSet::new()).unwrap();
     assert_eq!(
-        dag.compare(&quake_node_id, &quake_node_id),
+        dag.compare(&quake_node_id, &quake_node_id).unwrap(),
         NodeCompare::Equivalent
     );
 }
@@ -113,11 +113,11 @@ fn test_node_comparison_before() {
         .add_node("quell", BTreeSet::from([qualm_node_id.clone()]))
         .unwrap();
     assert_eq!(
-        dag.compare(&quake_node_id, &qualm_node_id),
+        dag.compare(&quake_node_id, &qualm_node_id).unwrap(),
         NodeCompare::Before
     );
     assert_eq!(
-        dag.compare(&quake_node_id, &quell_node_id),
+        dag.compare(&quake_node_id, &quell_node_id).unwrap(),
         NodeCompare::Before
     );
 }
@@ -133,11 +133,11 @@ fn test_node_comparison_after() {
         .add_node("quell", BTreeSet::from([qualm_node_id.clone()]))
         .unwrap();
     assert_eq!(
-        dag.compare(&qualm_node_id, &quake_node_id),
+        dag.compare(&qualm_node_id, &quake_node_id).unwrap(),
         NodeCompare::After
     );
     assert_eq!(
-        dag.compare(&quell_node_id, &quake_node_id),
+        dag.compare(&quell_node_id, &quake_node_id).unwrap(),
         NodeCompare::After
     );
 }
@@ -149,15 +149,15 @@ fn test_node_comparison_no_shared_graph() {
     let qualm_node_id = dag.add_node("qualm", BTreeSet::new()).unwrap();
     let quell_node_id = dag.add_node("quell", BTreeSet::new()).unwrap();
     assert_eq!(
-        dag.compare(&qualm_node_id, &quake_node_id),
+        dag.compare(&qualm_node_id, &quake_node_id).unwrap(),
         NodeCompare::Uncomparable
     );
     assert_eq!(
-        dag.compare(&quell_node_id, &quake_node_id),
+        dag.compare(&quell_node_id, &quake_node_id).unwrap(),
         NodeCompare::Uncomparable
     );
     assert_eq!(
-        dag.compare(&quell_node_id, &qualm_node_id),
+        dag.compare(&quell_node_id, &qualm_node_id).unwrap(),
         NodeCompare::Uncomparable
     );
 }