Deduplicating crate dependencies (part 2 of n, slab) (#11613)

The change includes only `slab` module.

Cargo.lock

@@ -1474,7 +1474,7 @@ dependencies = [
  "secp256k1",
  "serde",
  "serde_json",
- "slab 0.2.0",
+ "slab 0.4.2",
  "tempfile",
  "tiny-keccak 1.5.0",
 ]
@@ -4591,12 +4591,6 @@ version = "0.3.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "8e88f89a550c01e4cd809f3df4f52dc9e939f3273a2017eabd5c6d12fd98bb23"
 
-[[package]]
-name = "slab"
-version = "0.2.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6dbdd334bd28d328dad1c41b0ea662517883d8880d8533895ef96c8003dec9c4"
-
 [[package]]
 name = "slab"
 version = "0.3.0"

util/io/Cargo.toml

@@ -13,7 +13,7 @@ mio = { version = "0.6.19", optional = true }
 crossbeam-deque = "0.7.3"
 parking_lot = "0.10.0"
 log = "0.4"
-slab = "0.4"
+slab = "0.4.2"
 num_cpus = "1.8"
 timer = "0.2"
 time = "0.1"

util/network-devp2p/Cargo.toml

@@ -33,7 +33,7 @@ rlp = "0.4.0"
 secp256k1 = "0.17"
 serde = { version = "1.0", features = ["derive"] }
 serde_json = "1.0"
-slab = "0.2"
+slab = "0.4.2"
 tiny-keccak = "1.4"
 
 [dev-dependencies]

util/network-devp2p/src/host.rs

@@ -24,6 +24,7 @@ use std::str::FromStr;
 use std::sync::Arc;
 use std::sync::atomic::{AtomicBool, Ordering as AtomicOrdering};
 use std::time::Duration;
+use slab::Slab;
 
 use ethereum_types::H256;
 use keccak_hash::keccak;
@@ -55,8 +56,6 @@ use crate::{
 	session::{Session, SessionData}
 };
 
-type Slab<T> = ::slab::Slab<T, usize>;
-
 const MAX_SESSIONS: usize = 2048 + MAX_HANDSHAKES;
 const MAX_HANDSHAKES: usize = 1024;
 
@@ -339,7 +338,7 @@ impl Host {
 			discovery: Mutex::new(None),
 			udp_socket: Mutex::new(None),
 			tcp_listener: Mutex::new(tcp_listener),
-			sessions: Arc::new(RwLock::new(Slab::new_starting_at(FIRST_SESSION, MAX_SESSIONS))),
+			sessions: Arc::new(RwLock::new(Slab::with_capacity(MAX_SESSIONS))),
 			nodes: RwLock::new(NodeTable::new(path)),
 			handlers: RwLock::new(HashMap::new()),
 			timers: RwLock::new(HashMap::new()),
@@ -399,7 +398,7 @@ impl Host {
 				// disconnect all non-reserved peers here.
 				let reserved: HashSet<NodeId> = self.reserved_nodes.read().clone();
 				let mut to_kill = Vec::new();
-				for e in self.sessions.read().iter() {
+				for (_, e) in self.sessions.read().iter() {
 					let mut s = e.lock();
 					{
 						let id = s.id();
@@ -439,7 +438,7 @@ impl Host {
 	pub fn stop(&self, io: &IoContext<NetworkIoMessage>) {
 		self.stopping.store(true, AtomicOrdering::Release);
 		let mut to_kill = Vec::new();
-		for e in self.sessions.read().iter() {
+		for (_, e) in self.sessions.read().iter() {
 			let mut s = e.lock();
 			s.disconnect(io, DisconnectReason::ClientQuit);
 			to_kill.push(s.token());
@@ -456,7 +455,7 @@ impl Host {
 		let sessions = self.sessions.read();
 		let sessions = &*sessions;
 
-		let mut peers = Vec::with_capacity(sessions.count());
+		let mut peers = Vec::with_capacity(sessions.len());
 		for i in (0..MAX_SESSIONS).map(|x| x + FIRST_SESSION) {
 			if sessions.get(i).is_some() {
 				peers.push(i);
@@ -533,7 +532,7 @@ impl Host {
 	}
 
 	fn have_session(&self, id: &NodeId) -> bool {
-		self.sessions.read().iter().any(|e| e.lock().info.id == Some(*id))
+		self.sessions.read().iter().any(|(_, e)| e.lock().info.id == Some(*id))
 	}
 
 	// returns (handshakes, egress, ingress)
@@ -541,7 +540,7 @@ impl Host {
 		let mut handshakes = 0;
 		let mut egress = 0;
 		let mut ingress = 0;
-		for s in self.sessions.read().iter() {
+		for (_, s) in self.sessions.read().iter() {
 			match s.try_lock() {
 				Some(ref s) if s.is_ready() && s.info.originated => egress += 1,
 				Some(ref s) if s.is_ready() && !s.info.originated => ingress += 1,
@@ -552,12 +551,12 @@ impl Host {
 	}
 
 	fn connecting_to(&self, id: &NodeId) -> bool {
-		self.sessions.read().iter().any(|e| e.lock().id() == Some(id))
+		self.sessions.read().iter().any(|(_, e)| e.lock().id() == Some(id))
 	}
 
 	fn keep_alive(&self, io: &IoContext<NetworkIoMessage>) {
 		let mut to_kill = Vec::new();
-		for e in self.sessions.read().iter() {
+		for (_, e) in self.sessions.read().iter() {
 			let mut s = e.lock();
 			if !s.keep_alive(io) {
 				s.disconnect(io, DisconnectReason::PingTimeout);
@@ -674,21 +673,18 @@ impl Host {
 		let nonce = self.info.write().next_nonce();
 		let mut sessions = self.sessions.write();
 
-		let token = sessions.insert_with_opt(|token| {
+		let entry = sessions.vacant_entry();
-			trace!(target: "network", "{}: Initiating session {:?}", token, id);
+		let key = entry.key();
-			match Session::new(io, socket, token, id, &nonce, &self.info.read()) {
+
-				Ok(s) => Some(Arc::new(Mutex::new(s))),
+		trace!(target: "network", "{}: Initiating session {:?}", key, id);
+
+		match Session::new(io, socket, key, id, &nonce, &self.info.read()) {
+			Ok(session) => {
+				entry.insert(Arc::new(Mutex::new(session)));
+				io.register_stream(key).map(|_| ()).map_err(Into::into)
+			},
 			Err(e) => {
 				debug!(target: "network", "Session create error: {:?}", e);
-					None
-				}
-			}
-		});
-
-		match token {
-			Some(t) => io.register_stream(t).map(|_| ()).map_err(Into::into),
-			None => {
-				debug!(target: "network", "Max sessions reached");
 				Ok(())
 			}
 		}
@@ -854,7 +850,7 @@ impl Host {
 
 			let handlers = self.handlers.read();
 			if !ready_data.is_empty() {
-				let duplicate = self.sessions.read().iter().any(|e| {
+				let duplicate = self.sessions.read().iter().any(|(_, e)| {
 					let session = e.lock();
 					session.token() != token && session.info.id == ready_id
 				});
@@ -992,7 +988,7 @@ impl Host {
 		let mut to_remove: Vec<PeerId> = Vec::new();
 		{
 			let sessions = self.sessions.read();
-			for c in sessions.iter() {
+			for (_, c) in sessions.iter() {
 				let s = c.lock();
 				if let Some(id) = s.id() {
 					if node_changes.removed.contains(id) {