ClientCirc: Move n_hops into a new Path type.

This will help with #415

crates/tor-proto/src/circuit.rs

@@ -41,6 +41,7 @@
 pub(crate) mod celltypes;
 pub(crate) mod halfcirc;
 mod halfstream;
+mod path;
 pub(crate) mod reactor;
 pub(crate) mod sendme;
 mod streammap;
@@ -68,7 +69,6 @@ use futures::channel::{mpsc, oneshot};
 use crate::circuit::sendme::StreamRecvWindow;
 use futures::SinkExt;
 use std::net::IpAddr;
-use std::sync::atomic::{AtomicU8, Ordering};
 use std::sync::Arc;
 use tor_cell::relaycell::StreamId;
 // use std::time::Duration;
@@ -88,7 +88,7 @@ pub const CIRCUIT_BUFFER_SIZE: usize = 128;
 /// they all actually communicate with the Reactor which contains the primary
 /// mutable state, and does the actual work.
 //
-// Effectively, this struct contains two Arcs: one for `hops` and one for
+// Effectively, this struct contains two Arcs: one for `path` and one for
 // `control` (which surely has something Arc-like in it).  We cannot unify
 // these by putting a single Arc around the whole struct, and passing
 // an Arc strong reference to the `Reactor`, because then `control` would
@@ -100,10 +100,8 @@ pub const CIRCUIT_BUFFER_SIZE: usize = 128;
 // two atomic refcount changes/checks.  Wrapping it in another Arc would
 // be overkill.
 pub struct ClientCirc {
-    /// Number of hops on this circuit.
-    ///
-    /// This value is incremented after the circuit successfully completes extending to a new hop.
-    hops: Arc<AtomicU8>,
+    /// Information about this circuit's path.
+    path: Arc<path::Path>,
     /// A unique identifier for this circuit.
     unique_id: UniqId,
     /// Channel to send control messages to the reactor.
@@ -239,7 +237,7 @@ impl ClientCirc {
         // TODO: Possibly this should take a hop, rather than just
         // assuming it's the last hop.
 
-        let num_hops = self.hops.load(Ordering::SeqCst);
+        let num_hops = self.path.n_hops();
         if num_hops == 0 {
             return Err(Error::from(internal!(
                 "Can't begin a stream at the 0th hop"
@@ -408,7 +406,7 @@ impl ClientCirc {
 
     #[cfg(test)]
     pub fn n_hops(&self) -> u8 {
-        self.hops.load(Ordering::SeqCst)
+        self.path.n_hops()
     }
 }
 
@@ -427,7 +425,7 @@ impl PendingClientCirc {
     ) -> (PendingClientCirc, reactor::Reactor) {
         let crypto_out = OutboundClientCrypt::new();
         let (control_tx, control_rx) = mpsc::unbounded();
-        let num_hops = Arc::new(AtomicU8::new(0));
+        let path = Arc::new(path::Path::default());
 
         let reactor = Reactor {
             control: control_rx,
@@ -440,11 +438,11 @@ impl PendingClientCirc {
             channel_id: id,
             crypto_out,
             meta_handler: None,
-            num_hops: Arc::clone(&num_hops),
+            path: Arc::clone(&path),
         };
 
         let circuit = ClientCirc {
-            hops: num_hops,
+            path,
             unique_id,
             control: control_tx,
             #[cfg(test)]

crates/tor-proto/src/circuit/path.rs

+//! Tracking for the path of a client circuit.
+
+use std::sync::atomic::{AtomicU8, Ordering};
+
+/// Helper struct that shares information
+#[derive(Debug, Default)]
+pub(super) struct Path {
+    /// Number of hops on this circuit.
+    ///
+    /// This value is incremented after the circuit successfully completes extending to a new hop.
+    n_hops: AtomicU8,
+}
+
+impl Path {
+    /// Return the number of hops in this path
+    pub(super) fn n_hops(&self) -> u8 {
+        self.n_hops.load(Ordering::SeqCst)
+    }
+
+    /// Add 1 to the number of hops in this path.
+    pub(super) fn inc_hops(&self) {
+        self.n_hops.fetch_add(1, Ordering::SeqCst);
+    }
+}

crates/tor-proto/src/circuit/reactor.rs

@@ -24,11 +24,11 @@ use futures::Sink;
 use futures::Stream;
 use tor_error::internal;
 
-use std::sync::atomic::{AtomicU8, Ordering};
 use std::sync::Arc;
 use std::task::{Context, Poll};
 
 use crate::channel::Channel;
+use crate::circuit::path;
 #[cfg(test)]
 use crate::circuit::sendme::CircTag;
 use crate::circuit::sendme::StreamSendWindow;
@@ -446,7 +446,7 @@ pub struct Reactor {
     /// List of hops state objects used by the reactor
     pub(super) hops: Vec<CircHop>,
     /// Shared atomic for the number of hops this circuit has.
-    pub(super) num_hops: Arc<AtomicU8>,
+    pub(super) path: Arc<path::Path>,
     /// An identifier for logging about this reactor's circuit.
     pub(super) unique_id: UniqId,
     /// This circuit's identifier on the upstream channel.
@@ -811,7 +811,7 @@ impl Reactor {
         self.hops.push(hop);
         self.crypto_in.add_layer(rev);
         self.crypto_out.add_layer(fwd);
-        self.num_hops.fetch_add(1, Ordering::SeqCst);
+        self.path.inc_hops();
     }
 
     /// Handle a RELAY cell on this circuit with stream ID 0.