Networking and in-memory client (#38)

* Networking crate draft

* Started work on syncing algo

* Fixed query range

* BlockCollection tests

* In-mem client backend

* Fixed tests

* Renamed Transaction

* Removed stray println

* Docs

substrate/state_machine/src/backend.rs

@@ -59,7 +59,7 @@ impl error::Error for Void {
 
 /// In-memory backend. Fully recomputes tries on each commit but useful for
 /// tests.
-#[derive(Default)]
+#[derive(Default, Clone)]
 pub struct InMemory {
 	inner: MemoryState, // keeps all the state in memory.
 }
@@ -67,7 +67,7 @@ pub struct InMemory {
 impl Backend for InMemory {
 	type Error = Void;
 
-	fn storage(&self, key: &[u8]) -> Result<&[u8], Void> {
+	fn storage(&self, key: &[u8]) -> Result<&[u8], Self::Error> {
 		Ok(self.inner.storage(key).unwrap_or(&[]))
 	}
 

substrate/state_machine/src/lib.rs

@@ -43,7 +43,7 @@ pub enum Update {
 }
 
 // in-memory section of the state.
-#[derive(Default)]
+#[derive(Default, Clone)]
 struct MemoryState {
 	storage: HashMap<Vec<u8>, Vec<u8>>,
 }
@@ -152,7 +152,7 @@ pub trait Externalities {
 }
 
 /// Code execution engine.
-pub trait CodeExecutor: Sized {
+pub trait CodeExecutor: Sized + Send + Sync {
 	/// Externalities error type.
 	type Error: Error;