Dynamic dispatch for Storage, no generics in Feed

This removes the generic argument from the Feed struct, making it
simpler to work with. Instead, the Storage is internally put into a
Box<dyn DynStorage>, where DynStorage is an async trait with the public
Storage functions.

Author: Frando

Cargo.toml

@@ -38,6 +38,7 @@ tree-index = "0.6.0"
 bitfield-rle = "0.1.1"
 futures = "0.3.4"
 async-std = "1.5.0"
+async-trait = "0.1.30"
 
 [dev-dependencies]
 quickcheck = "0.9.2"

examples/async.rs

@@ -1,27 +1,18 @@
 use async_std::task;
 use hypercore::Feed;
-use random_access_storage::RandomAccess;
-use std::fmt::Debug;
 
-async fn append<T>(feed: &mut Feed<T>, content: &[u8])
-where
-    T: RandomAccess<Error = Box<dyn std::error::Error + Send + Sync>> + Debug + Send,
-{
+async fn append(feed: &mut Feed, content: &[u8]) {
     feed.append(content).await.unwrap();
 }
 
-async fn print<T>(feed: &mut Feed<T>)
-where
-    T: RandomAccess<Error = Box<dyn std::error::Error + Send + Sync>> + Debug + Send,
-{
+async fn print(feed: &mut Feed) {
     println!("{:?}", feed.get(0).await);
     println!("{:?}", feed.get(1).await);
 }
 
 fn main() {
     task::block_on(task::spawn(async {
-        let mut feed = Feed::default();
-
+        let mut feed = Feed::open_in_memory().await.unwrap();
         append(&mut feed, b"hello").await;
         append(&mut feed, b"world").await;
         print(&mut feed).await;

src/feed.rs

@@ -2,7 +2,9 @@
 
 use crate::feed_builder::FeedBuilder;
 use crate::replicate::{Message, Peer};
-pub use crate::storage::{Node, NodeTrait, Storage, Store};
+pub use crate::storage::{
+    storage_disk, storage_memory, BoxStorage, Node, NodeTrait, Storage, Store,
+};
 
 use crate::audit::Audit;
 use crate::bitfield::Bitfield;
@@ -12,12 +14,8 @@ use anyhow::{bail, ensure, Result};
 use ed25519_dalek::{PublicKey, SecretKey, Signature};
 use flat_tree as flat;
 use pretty_hash::fmt as pretty_fmt;
-use random_access_disk::RandomAccessDisk;
-use random_access_memory::RandomAccessMemory;
-use random_access_storage::RandomAccess;
 use tree_index::TreeIndex;
 
-use std::borrow::Borrow;
 use std::cmp;
 use std::fmt::{self, Debug, Display};
 use std::ops::Range;
@@ -26,15 +24,12 @@ use std::sync::Arc;
 
 /// Append-only log structure.
 #[derive(Debug)]
-pub struct Feed<T>
-where
-    T: RandomAccess<Error = Box<dyn std::error::Error + Send + Sync>> + Debug,
-{
+pub struct Feed {
     /// Merkle tree instance.
     pub(crate) merkle: Merkle,
     pub(crate) public_key: PublicKey,
     pub(crate) secret_key: Option<SecretKey>,
-    pub(crate) storage: Storage<T>,
+    pub(crate) storage: BoxStorage,
     /// Total length of data stored.
     pub(crate) byte_length: u64,
     /// TODO: description. Length of... roots?
@@ -45,12 +40,9 @@ where
     pub(crate) peers: Vec<Peer>,
 }
 
-impl<T> Feed<T>
-where
-    T: RandomAccess<Error = Box<dyn std::error::Error + Send + Sync>> + Debug + Send,
-{
+impl Feed {
     /// Create a new instance with a custom storage backend.
-    pub async fn with_storage(mut storage: crate::storage::Storage<T>) -> Result<Self> {
+    pub async fn with_storage(mut storage: BoxStorage) -> Result<Self> {
         match storage.read_partial_keypair().await {
             Some(partial_keypair) => {
                 let builder = FeedBuilder::new(partial_keypair.public, storage);
@@ -76,10 +68,26 @@ where
     }
 
     /// Starts a `FeedBuilder` with the provided `Keypair` and `Storage`.
-    pub fn builder(public_key: PublicKey, storage: Storage<T>) -> FeedBuilder<T> {
+    pub fn builder(public_key: PublicKey, storage: BoxStorage) -> FeedBuilder {
         FeedBuilder::new(public_key, storage)
     }
 
+    /// Create a new instance that persists to disk at the location of `dir`.
+    // TODO: Ensure that dir is always a directory.
+    // NOTE: Should we `mkdirp` here?
+    // NOTE: Should we call these `data.bitfield` / `data.tree`?
+    pub async fn open_from_disk<P: AsRef<Path>>(path: P) -> Result<Self> {
+        let dir = path.as_ref().to_owned();
+        let storage = storage_disk(&dir).await?;
+        Self::with_storage(storage).await
+    }
+
+    /// Create a new in-memory instance.
+    pub async fn open_in_memory() -> Result<Self> {
+        let storage = storage_memory().await.unwrap();
+        Self::with_storage(storage).await
+    }
+
     /// Get the amount of entries in the feed.
     #[inline]
     pub fn len(&self) -> u64 {
@@ -116,7 +124,7 @@ where
         let hash = Hash::from_roots(self.merkle.roots());
         let index = self.length;
         let signature = sign(&self.public_key, key, hash.as_bytes());
-        self.storage.put_signature(index, signature).await?;
+        self.storage.put_signature(index, &signature).await?;
 
         for node in self.merkle.nodes() {
             self.storage.put_node(node).await?;
@@ -352,8 +360,7 @@ where
         }
 
         if let Some(sig) = sig {
-            let sig = sig.borrow();
-            self.storage.put_signature(index, sig).await?;
+            self.storage.put_signature(index, &sig).await?;
         }
 
         for node in nodes {
@@ -556,35 +563,18 @@ where
     }
 }
 
-impl Feed<RandomAccessDisk> {
-    /// Create a new instance that persists to disk at the location of `dir`.
-    // TODO: Ensure that dir is always a directory.
-    // NOTE: Should we `mkdirp` here?
-    // NOTE: Should we call these `data.bitfield` / `data.tree`?
-    pub async fn open<P: AsRef<Path>>(path: P) -> Result<Self> {
-        let dir = path.as_ref().to_owned();
-        let storage = Storage::new_disk(&dir).await?;
-        Self::with_storage(storage).await
-    }
-}
-
 /// Create a new instance with an in-memory storage backend.
 ///
 /// ## Panics
 /// Can panic if constructing the in-memory store fails, which is highly
 /// unlikely.
-impl Default for Feed<RandomAccessMemory> {
+impl Default for Feed {
     fn default() -> Self {
-        async_std::task::block_on(async {
-            let storage = Storage::new_memory().await.unwrap();
-            Self::with_storage(storage).await.unwrap()
-        })
+        async_std::task::block_on(async { Self::open_in_memory().await.unwrap() })
     }
 }
 
-impl<T: RandomAccess<Error = Box<dyn std::error::Error + Send + Sync>> + Debug + Send> Display
-    for Feed<T>
-{
+impl Display for Feed {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         // TODO: yay, we should find a way to convert this .unwrap() to an error
         // type that's accepted by `fmt::Result<(), fmt::Error>`.

src/feed_builder.rs

@@ -2,8 +2,7 @@ use ed25519_dalek::{PublicKey, SecretKey};
 
 use crate::bitfield::Bitfield;
 use crate::crypto::Merkle;
-use crate::storage::Storage;
-use random_access_storage::RandomAccess;
+use crate::storage::BoxStorage;
 use std::fmt::Debug;
 use tree_index::TreeIndex;
 
@@ -14,22 +13,16 @@ use anyhow::Result;
 // TODO: make this an actual builder pattern.
 // https://deterministic.space/elegant-apis-in-rust.html#builder-pattern
 #[derive(Debug)]
-pub struct FeedBuilder<T>
-where
-    T: RandomAccess + Debug,
-{
-    storage: Storage<T>,
+pub struct FeedBuilder {
+    storage: BoxStorage,
     public_key: PublicKey,
     secret_key: Option<SecretKey>,
 }
 
-impl<T> FeedBuilder<T>
-where
-    T: RandomAccess<Error = Box<dyn std::error::Error + Send + Sync>> + Debug,
-{
+impl FeedBuilder {
     /// Create a new instance.
     #[inline]
-    pub fn new(public_key: PublicKey, storage: Storage<T>) -> Self {
+    pub fn new(public_key: PublicKey, storage: BoxStorage) -> Self {
         Self {
             storage,
             public_key,
@@ -45,7 +38,7 @@ where
 
     /// Finalize the builder.
     #[inline]
-    pub fn build(self) -> Result<Feed<T>> {
+    pub fn build(self) -> Result<Feed> {
         Ok(Feed {
             merkle: Merkle::new(),
             byte_length: 0,

src/lib.rs

@@ -54,8 +54,6 @@ pub use ed25519_dalek::{PublicKey, SecretKey};
 use std::path::Path;
 
 /// Create a new Hypercore `Feed`.
-pub async fn open<P: AsRef<Path>>(
-    path: P,
-) -> anyhow::Result<Feed<random_access_disk::RandomAccessDisk>> {
-    Feed::open(path).await
+pub async fn open<P: AsRef<Path>>(path: P) -> anyhow::Result<Feed> {
+    Feed::open_from_disk(path).await
 }