Allow for completely lock-free access to Static values, and closed channels.

Cargo.toml

@@ -17,6 +17,7 @@ exclude = ["flake.nix", "flake.lock", ".envrc", "cliff.toml", "release-plz.toml"
 thiserror = "2.0"
 flume = { version = "0.11", optional = true }
 crossbeam-channel = { version = "0.5", optional = true }
+arc-swap = "1.7.1"
 
 [features]
 default = ["all"]

src/channel.rs

@@ -1,4 +1,5 @@
 use std::sync::atomic::{AtomicBool, Ordering};
+use std::sync::{Arc, Mutex};
 
 use crate::error::Error;
 use crate::sync::traits::{ChannelReceiver, ChannelSender};
@@ -68,8 +69,7 @@ where
 {
     /// Set a fixed value
     pub fn set_static(&self, value: T) -> Result<(), Error> {
-        let mut state = self.state.lock().map_err(|_| Error::InternalError)?;
+        self.state.swap(Arc::new(ValueSource::Static(value)));
-        *state = ValueSource::Static(value);
         Ok(())
     }
 
@@ -78,15 +78,16 @@ where
     where
         F: Fn() -> T + Send + Sync + 'static,
     {
-        let mut state = self.state.lock().map_err(|_| Error::InternalError)?;
+        self.state
-        *state = ValueSource::Dynamic(Box::new(closure));
+            .swap(Arc::new(ValueSource::Dynamic(Mutex::new(Box::new(
+                closure,
+            )))));
         Ok(())
     }
 
     /// Close the channel
     pub fn close(&self) -> Result<(), Error> {
-        let mut state = self.state.lock().map_err(|_| Error::InternalError)?;
+        self.state.swap(Arc::new(ValueSource::Cleared));
-        *state = ValueSource::Cleared;
         Ok(())
     }
 
@@ -103,8 +104,7 @@ where
                 }
                 Ok(Request::Close) => {
                     // Close channel
-                    let mut state = self.state.lock().map_err(|_| Error::InternalError)?;
+                    self.close()?;
-                    *state = ValueSource::Cleared;
                     break;
                 }
                 Err(_) => {
@@ -117,12 +117,13 @@ where
     }
 
     fn handle_get_value(&self) -> Result<Response<T>, Error> {
-        let mut state = self.state.lock().map_err(|_| Error::InternalError)?;
+        let state = self.state.load();
 
-        match &mut *state {
+        match &**state {
             ValueSource::Static(value) => Ok(Response::Value(value.clone())),
             ValueSource::Dynamic(closure) => {
-                let value = self.execute_closure_safely(closure);
+                let mut closure = closure.lock().unwrap();
+                let value = self.execute_closure_safely(&mut *closure);
                 match value {
                     Ok(v) => Ok(Response::Value(v)),
                     Err(_) => Ok(Response::NoSource), // Closure execution failed

src/sync/crossbeam.rs

@@ -1,6 +1,9 @@
+use std::sync::Arc;
+
 #[cfg(feature = "sync-crossbeam")]
 use crate::sync::traits::{ChannelError, ChannelReceiver, ChannelSender, ChannelType};
 use crate::types;
+use arc_swap::ArcSwap;
 use crossbeam_channel;
 
 type CrossbeamSucker<T> =
@@ -62,10 +65,10 @@ impl<T> CrossbeamSuck<T> {
         let (request_tx, request_rx) = CrossbeamChannel::create_request_channel();
         let (response_tx, response_rx) = CrossbeamChannel::create_response_channel::<T>();
 
-        let state = std::sync::Arc::new(std::sync::Mutex::new(crate::types::ValueSource::None));
+        let state = ArcSwap::new(Arc::new(crate::types::ValueSource::None));
 
         let sucker = crate::Sucker::new(request_tx, response_rx);
-        let sourcer = crate::Sourcer::new(request_rx, response_tx, std::sync::Arc::clone(&state));
+        let sourcer = crate::Sourcer::new(request_rx, response_tx, state);
 
         (sucker, sourcer)
     }

src/sync/flume.rs

@@ -1,6 +1,9 @@
+use std::sync::Arc;
+
 #[cfg(feature = "sync-flume")]
 use crate::sync::traits::{ChannelError, ChannelReceiver, ChannelSender, ChannelType};
 use crate::types;
+use arc_swap::ArcSwap;
 use flume;
 
 type FlumeSucker<T> =
@@ -62,10 +65,11 @@ impl<T> FlumeSuck<T> {
         let (request_tx, request_rx) = FlumeChannel::create_request_channel();
         let (response_tx, response_rx) = FlumeChannel::create_response_channel::<T>();
 
-        let state = std::sync::Arc::new(std::sync::Mutex::new(crate::types::ValueSource::None));
+        let state = Arc::new(crate::types::ValueSource::None);
+        let state = ArcSwap::new(state);
 
         let sucker = crate::Sucker::new(request_tx, response_rx);
-        let sourcer = crate::Sourcer::new(request_rx, response_tx, std::sync::Arc::clone(&state));
+        let sourcer = crate::Sourcer::new(request_rx, response_tx, state);
 
         (sucker, sourcer)
     }

src/sync/std.rs

@@ -1,5 +1,8 @@
+use arc_swap::ArcSwap;
+
 use crate::sync::traits::{ChannelError, ChannelReceiver, ChannelSender, ChannelType};
 use crate::types;
+use std::sync::Arc;
 #[cfg(feature = "sync-std")]
 use std::sync::mpsc;
 
@@ -60,10 +63,11 @@ impl<T> StdSuck<T> {
         let (request_tx, request_rx) = StdChannel::create_request_channel();
         let (response_tx, response_rx) = StdChannel::create_response_channel::<T>();
 
-        let state = std::sync::Arc::new(std::sync::Mutex::new(crate::types::ValueSource::None));
+        let state = Arc::new(crate::types::ValueSource::None);
+        let state = ArcSwap::new(state);
 
         let sucker = crate::Sucker::new(request_tx, response_rx);
-        let sourcer = crate::Sourcer::new(request_rx, response_tx, std::sync::Arc::clone(&state));
+        let sourcer = crate::Sourcer::new(request_rx, response_tx, state);
 
         (sucker, sourcer)
     }

src/types.rs

@@ -1,4 +1,6 @@
-use std::sync::{Arc, Mutex};
+use std::sync::Mutex;
+
+use arc_swap::ArcSwap;
 
 /// Request messages sent from consumer to producer
 pub enum Request {
@@ -16,10 +18,10 @@ pub enum Response<T> {
 /// Represents the source of values: either static or dynamic
 pub(crate) enum ValueSource<T> {
     Static(T),
-    Dynamic(Box<dyn FnMut() -> T + Send + Sync + 'static>),
+    Dynamic(Mutex<Box<dyn FnMut() -> T + Send + Sync + 'static>>),
     None,    // Never set
     Cleared, // Was set but cleared (closed)
 }
 
 /// Internal channel state shared between producer and consumer
-pub(crate) type ChannelState<T> = Arc<Mutex<ValueSource<T>>>;
+pub(crate) type ChannelState<T> = ArcSwap<ValueSource<T>>;