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//! This crate defines a channel for requesting and receiving data. Each //! channel has only one requesting end, but it can have multiple responding //! ends. It is useful for implementing work sharing. //! //! The two ends of the channel are asynchronous with respect to each other, //! so it is kinda nonblocking. However, if multiple responding ends try to //! respond to the same request, only one will succeed; the rest will //! return errors. //! //! # Design //! //! ## Overview //! //! `reqchan` is built around the two halves of the channel: `Requester` //! and `Responder`. Both implement methods, `Requester::try_request()` and //! `Responder::try_respond()`, that, when succesful, lock their corresponding //! side of the channel and return contracts. `RequestContract` **requires** the //! user to either successfully receive a datum or cancel the request. //! `ResponseContract` requires the user to send a datum. These requirements //! prevent the system from losing data sent through the channel. //! //! ## Locking //! //! `Responder::try_response()` locks the responding side to prevent other //! potential responders from responding to the same request. However, //! `Requester::try_request()` locks the requesting side of the channel //! to prevent the user from trying to issue multiple outstanding requests. //! Both locks are dropped when their corresponding contract object is dropped. //! //! ## Contracts //! //! `Requester::try_request()` has to issue a `RequestContract` so the //! thread of execution does not block waiting for a response. However, //! that reason does not apply to `Responder::try_response()`. I originally //! made `Responder::try_response()` send the datum. However, that required //! the user to have the datum available to send even if it could not be sent, //! and it required the user to handle the returned datum if it could not be //! sent. If the datum was, say, half the contents of a `Vec`, this might entail //! lots of expensive memory allocation. Therefore, I made `Responder::try_response()` //! return a `ResponseContract` indicating that the responder *could* and *would* //! respond to the request. This way the user only has to perform the necessary //! steps to send the datum if the datum must be sent. //! //! # Examples //! //! ## Simple Example //! //! This simple, single-threaded example demonstrates most of the API. //! The only thing left out is `RequestContract::try_cancel()`. //! //! ``` //! extern crate reqchan; //! //! // Create channel. //! let (requester, responder) = reqchan::channel::<u32>(); //! //! // Issue request. //! let mut request_contract = requester.try_request().unwrap(); //! //! // Respond with number. //! responder.try_respond().unwrap().send(5); //! //! // Receive and print number. //! println!("Number is {}", request_contract.try_receive().unwrap()); //! ``` //! //! ## More Complex Example //! //! This more complex example demonstrates more "real-world" usage. //! One thread requests a 'task' (i.e. a closure to run), and the //! other two threads fight over who gets to respond with their //! own personal task. Meanwhile, the requesting thread is polling //! for a task, and if it gets one in time, it runs it. Regardless of //! whether or not the receiver got a task or timed out, the receiver //! notifies other threads to stop running, and stops itself. //! //! ``` //! extern crate reqchan as chan; //! //! use std::sync::Arc; //! use std::sync::atomic::{AtomicBool, AtomicUsize, Ordering}; //! use std::thread; //! use std::time::{Duration, Instant}; //! //! // Stuff to make it easier to pass around closures. //! trait FnBox { //! fn call_box(self: Box<Self>); //! } //! impl<F: FnOnce()> FnBox for F { //! fn call_box(self: Box<F>) { //! (*self)() //! } //! } //! type Task = Box<FnBox + Send + 'static>; //! //! // Variable used to test calling a `Task` sent between threads. //! let test_var = Arc::new(AtomicUsize::new(0)); //! let test_var2 = test_var.clone(); //! let test_var3 = test_var.clone(); //! //! // Variable needed to stop `responder` thread if `requester` times out //! let should_exit = Arc::new(AtomicBool::new(false)); //! let should_exit_copy_1 = should_exit.clone(); //! let should_exit_copy_2 = should_exit.clone(); //! //! let (requester, responder) = chan::channel::<Task>(); //! let responder2 = responder.clone(); //! //! // requesting thread //! let requester_handle = thread::spawn(move || { //! let start_time = Instant::now(); //! let timeout = Duration::new(0, 1000000); //! //! let mut contract = requester.try_request().unwrap(); //! //! loop { //! // Try to cancel request and stop threads if runtime //! // has exceeded `timeout`. //! if start_time.elapsed() >= timeout { //! // Try to cancel request. //! // This should only fail if `responder` has started responding. //! if contract.try_cancel() { //! // Notify other threads to stop. //! should_exit.store(true, Ordering::SeqCst); //! break; //! } //! } //! //! // Try getting `task` from `responder`. //! match contract.try_receive() { //! // `contract` received `task`. //! Ok(task) => { //! task.call_box(); //! // Notify other threads to stop. //! should_exit.store(true, Ordering::SeqCst); //! break; //! }, //! // Continue looping if `responder` has not yet sent `task`. //! Err(chan::TryReceiveError::Empty) => {}, //! // The only other error is `chan::TryReceiveError::Done`. //! // This only happens if we call `contract.try_receive()` //! // after either receiving data or cancelling the request. //! _ => unreachable!(), //! } //! } //! }); //! //! // responding thread 1 //! let responder_1_handle = thread::spawn(move || { //! let mut tasks = vec![Box::new(move || { //! test_var2.fetch_add(1, Ordering::SeqCst); //! }) as Task]; //! //! loop { //! // Exit loop if `receiver` has timed out. //! if should_exit_copy_1.load(Ordering::SeqCst) { //! break; //! } //! //! // Send `task` to `receiver` if it has issued a request. //! match responder2.try_respond() { //! // `responder2` can respond to request. //! Ok(contract) => { //! contract.send(tasks.pop().unwrap()); //! break; //! }, //! // Either `requester` has not yet made a request, //! // or `responder2` already handled the request. //! Err(chan::TryRespondError::NoRequest) => {}, //! // `responder2` is processing request.. //! Err(chan::TryRespondError::Locked) => { break; }, //! } //! } //! }); //! //! // responding thread 2 //! let responder_2_handle = thread::spawn(move || { //! let mut tasks = vec![Box::new(move || { //! test_var3.fetch_add(2, Ordering::SeqCst); //! }) as Task]; //! //! loop { //! // Exit loop if `receiver` has timed out. //! if should_exit_copy_2.load(Ordering::SeqCst) { //! break; //! } //! //! // Send `task` to `receiver` if it has issued a request. //! match responder.try_respond() { //! // `responder2` can respond to request. //! Ok(contract) => { //! contract.send(tasks.pop().unwrap()); //! break; //! }, //! // Either `requester` has not yet made a request, //! // or `responder` already handled the request. //! Err(chan::TryRespondError::NoRequest) => {}, //! // `responder` is processing request. //! Err(chan::TryRespondError::Locked) => { break; }, //! } //! } //! }); //! //! requester_handle.join().unwrap(); //! responder_1_handle.join().unwrap(); //! responder_2_handle.join().unwrap(); //! //! // `num` can be 0, 1 or 2. //! let num = test_var.load(Ordering::SeqCst); //! println!("Number is {}", num); //! ``` use std::cell::UnsafeCell; use std::sync::Arc; use std::sync::atomic::{AtomicBool, Ordering}; /// This function creates a `reqchan` and returns a tuple containing the /// two ends of this bidirectional request->response channel. /// /// # Example /// /// ``` /// extern crate reqchan; /// /// #[allow(unused_variables)] /// let (requester, responder) = reqchan::channel::<u32>(); /// ``` pub fn channel<T>() -> (Requester<T>, Responder<T>) { let inner = Arc::new(Inner { has_request_lock: AtomicBool::new(false), has_response_lock: AtomicBool::new(false), has_request: AtomicBool::new(false), has_datum: AtomicBool::new(false), datum: UnsafeCell::new(None), }); ( Requester { inner: inner.clone() }, Responder { inner: inner.clone() }, ) } /// This end of the channel requests and receives data from its `Responder`(s). pub struct Requester<T> { inner: Arc<Inner<T>>, } impl<T> Requester<T> { /// This methods tries to request item(s) from one or more `Responder`(s). /// If successful, it returns a `RequestContract` to either poll for data or /// cancel the request. /// /// # Warning /// /// Only **one** `RequestContract` may be active at a time. /// /// # Example /// /// ``` /// extern crate reqchan as chan; /// /// let (requester, responder) = chan::channel::<u32>(); /// /// // Create request. /// let mut request_contract = requester.try_request().unwrap(); /// /// // We have to wait for `request_contract` to go out of scope /// // before we can make another request. /// // match requester.try_request() { /// // Err(chan::TryRequestError::Locked) => { /// // println!("We already have a request contract!"); /// // }, /// // _ => unreachable!(), /// // } /// /// responder.try_respond().unwrap().send(5); /// println!("Got number {}", request_contract.try_receive().unwrap()); /// ``` pub fn try_request(&self) -> Result<RequestContract<T>, TryRequestError> { // First, try to lock the requesting side. if !self.inner.try_lock_request() { return Err(TryRequestError::Locked); } // Next, flag a request. self.inner.flag_request(); // Then return a `RequestContract`. Ok(RequestContract { inner: self.inner.clone(), done: false, }) } } /// This is the contract returned by a successful `Requester::try_request()`. /// It represents the caller's exclusive access to the requesting side of /// the channel. The user can either try to get a datum from the responding side /// or *attempt* to cancel the request. To prevent data loss, `RequestContract` /// will panic if the user has not received a datum or cancelled the request. pub struct RequestContract<T> { inner: Arc<Inner<T>>, done: bool, } impl<T> RequestContract<T> { /// This method attempts to receive a datum from one or more responder(s). /// /// # Warning /// /// It returns `Err(TryReceiveError::Done)` if the user called it /// after either receiving a datum or cancelling the request. /// /// # Example /// /// ``` /// extern crate reqchan as chan; /// /// let (requester, responder) = chan::channel::<u32>(); /// /// let mut request_contract = requester.try_request().unwrap(); /// /// // The responder has not responded yet. /// match request_contract.try_receive() { /// Err(chan::TryReceiveError::Empty) => { println!("No Data yet!"); }, /// _ => unreachable!(), /// } /// /// responder.try_respond().unwrap().send(6); /// /// // The responder has responded now. /// match request_contract.try_receive() { /// Ok(num) => { println!("Number: {}", num); }, /// _ => unreachable!(), /// } /// /// // We need to issue another request to receive more data. /// match request_contract.try_receive() { /// Err(chan::TryReceiveError::Done) => { /// println!("We already received data!"); /// }, /// _ => unreachable!(), /// } /// ``` pub fn try_receive(&mut self) -> Result<T, TryReceiveError> { // Do not try to receive anything if the contract already received data. if self.done { return Err(TryReceiveError::Done); } match self.inner.try_get_datum() { Ok(datum) => { self.done = true; Ok(datum) }, Err(err) => Err(err), } } /// This method attempts to cancel a request. This is useful for /// implementing a timeout. /// /// # Return /// /// * `true` - Cancelled request /// * `false` - `Responder` started processing request first /// /// # Warning /// /// It also returns `false` if the user called it after /// either receiving a datum or cancelling the request. /// /// # Example /// /// ``` /// extern crate reqchan as chan; /// /// let (requester, responder) = chan::channel::<u32>(); /// /// { /// let mut contract = requester.try_request().unwrap(); /// /// // We can cancel the request since `responder` has not /// // yet responded to it. /// assert_eq!(contract.try_cancel(), true); /// /// // Both contracts go out of scope here /// } /// /// { /// let mut request_contract = requester.try_request().unwrap(); /// /// responder.try_respond().unwrap().send(7); /// /// // It is too late to cancel the request! /// if !request_contract.try_cancel() { /// println!("Number: {}", request_contract.try_receive().unwrap()); /// } /// /// // Both contracts go out of scope here /// } /// ``` pub fn try_cancel(&mut self) -> bool { // Do not try to unsend if the contract already received data. if self.done { return false; } match self.inner.try_unflag_request() { true => { self.done = true; true }, false => false, } } } impl<T> Drop for RequestContract<T> { fn drop(&mut self) { if !self.done { panic!("Dropping RequestContract without receiving data!"); } self.inner.unlock_request(); } } /// This end of the channel sends data in response to requests from /// its `Requester`. pub struct Responder<T> { inner: Arc<Inner<T>>, } impl<T> Responder<T> { /// This method signals the intent of `Responder` to respond to a request. /// If successful, it returns a `ResponseContract` to ensure the user sends /// a datum. /// /// # Warning /// /// Only **one** `ResponseContract` may be active at a time. /// /// # Example /// /// ``` /// extern crate reqchan as chan; /// /// let (requester, responder) = chan::channel::<u32>(); /// /// // `requester` has not yet issued a request. /// match responder.try_respond() { /// Err(chan::TryRespondError::NoRequest) => { /// println!("There is no request!"); /// }, /// _ => unreachable!(), /// } /// /// let mut request_contract = requester.try_request().unwrap(); /// /// // `requester` has issued a request. /// let mut response_contract = responder.try_respond().unwrap(); /// /// // We cannot issue another response to the request. /// match responder.try_respond() { /// Err(chan::TryRespondError::Locked) => { /// println!("We cannot issue multiple responses to a request!"); /// }, /// _ => unreachable!(), /// } /// /// response_contract.send(8); /// /// println!("Number is {}", request_contract.try_receive().unwrap()); /// ``` pub fn try_respond(&self) -> Result<ResponseContract<T>, TryRespondError> { // First try to lock the responding side. if !self.inner.try_lock_response() { return Err(TryRespondError::Locked); } // Next, atomically check for a request and signal a response to it. // If no request exists, drop the lock and return the data. if !self.inner.try_unflag_request() { self.inner.unlock_response(); return Err(TryRespondError::NoRequest); } Ok(ResponseContract { inner: self.inner.clone(), done: false, }) } } impl<T> Clone for Responder<T> { fn clone(&self) -> Self { Responder { inner: self.inner.clone(), } } } /// This is the contract returned by a successful `Responder::try_response()`. /// It represents the caller's exclusive access to the responding side of /// the channel. It ensures the user sends a datum by panicking if they have not. pub struct ResponseContract<T> { inner: Arc<Inner<T>>, done: bool, } impl<T> ResponseContract<T> { /// This method tries to send a datum to the requesting end of the channel. /// It will then consume itself, thereby freeing the responding side of /// the channel. /// /// # Arguments /// /// * `datum` - The item(s) to send /// /// # Example /// /// ``` /// extern crate reqchan as chan; /// /// let (requester, responder) = chan::channel::<u32>(); /// /// let mut request_contract = requester.try_request().unwrap(); /// /// let mut response_contract = responder.try_respond().unwrap(); /// /// // We send data to the requesting end. /// response_contract.send(9); /// /// println!("Number is {}", request_contract.try_receive().unwrap()); /// ``` pub fn send(mut self, datum: T) { self.inner.set_datum(datum); self.done = true; } } impl<T> Drop for ResponseContract<T> { fn drop(&mut self) { if !self.done { panic!("Dropping ResponseContract without sending data!"); } self.inner.unlock_response(); } } #[doc(hidden)] struct Inner<T> { has_request_lock: AtomicBool, has_response_lock: AtomicBool, has_request: AtomicBool, has_datum: AtomicBool, datum: UnsafeCell<Option<T>>, } unsafe impl<T> Sync for Inner<T> {} #[doc(hidden)] impl<T> Inner<T> { /// This method indicates that the requesting side has made a request. /// /// # Warning /// /// **ONLY** the requesting side of the channel should call it. /// /// # Invariant /// /// * self.has_request_lock == true #[inline] fn flag_request(&self) { self.has_request.store(true, Ordering::SeqCst); } /// This method atomically checks to see if the requesting end /// issued a request and unflag the request. #[inline] fn try_unflag_request(&self) -> bool { let (old, new) = (true, false); self.has_request.compare_and_swap(old, new, Ordering::SeqCst) == old } /// This method sets the inner datum to the specified value. /// /// # Arguments /// /// * datum - The datum to set /// /// # Warning /// /// **ONLY** the responding side of the channel should call it. /// /// # Invariant /// /// * self.has_response_lock == true /// /// * (*self.datum.get()).is_none() == true /// /// * self.has_datum == false #[inline] fn set_datum(&self, data: T) { // First update inner datum. unsafe { *self.datum.get() = Some(data); } // Then indicate the presence of a new datum. self.has_datum.store(true, Ordering::SeqCst); } /// This method tries to get the datum out of `Inner`. /// /// # Warning /// /// **ONLY** the requesting side of the channel should call it. /// /// # Invariant /// /// * self.has_request_lock == true /// /// * if self.has_datum == true then (*self.datum.get()).is_some() == true #[inline] fn try_get_datum(&self) -> Result<T, TryReceiveError> { // First check to see if data exists. let (old, new) = (true, false); if self.has_datum.compare_and_swap(old, new, Ordering::SeqCst) == old { // If so, retrieve the data and unwrap it from its Option container. unsafe { Ok((*self.datum.get()).take().unwrap()) } } else { Err(TryReceiveError::Empty) } } /// This method tries to lock the requesting side of the channel. /// It returns a `boolean` indicating whether or not it succeeded. #[inline] fn try_lock_request(&self) -> bool { let (old, new) = (false, true); self.has_request_lock.compare_and_swap(old, new, Ordering::SeqCst) == old } /// This method unlocks the requesting side of the channel. #[inline] fn unlock_request(&self) { self.has_request_lock.store(false, Ordering::SeqCst); } /// This method tries to lock the responding side of the channel. /// It returns a `boolean` indicating whether or not it succeeded. #[inline] fn try_lock_response(&self) -> bool { let (old, new) = (false, true); self.has_response_lock.compare_and_swap(old, new, Ordering::SeqCst) == old } /// This method unlocks the responding side of the channel. #[inline] fn unlock_response(&self) { self.has_response_lock.store(false, Ordering::SeqCst); } } #[derive(Debug)] pub enum TryRequestError { Locked, } #[derive(Debug)] pub enum TryReceiveError { Empty, Done, } #[derive(Debug)] pub enum TryRespondError { NoRequest, Locked, } #[cfg(test)] mod tests { use std::sync::Arc; use std::sync::atomic::{AtomicUsize, Ordering}; use super::*; trait FnBox { fn call_box(self: Box<Self>); } impl<F: FnOnce()> FnBox for F { fn call_box(self: Box<F>) { (*self)() } } type Task = Box<FnBox + Send + 'static>; #[test] fn test_channel() { #[allow(unused_variables)] let (rqst, resp) = channel::<Task>(); } #[test] fn test_inner_try_lock_request() { #[allow(unused_variables)] let (rqst, resp) = channel::<Task>(); assert_eq!(rqst.inner.try_lock_request(), true); assert_eq!(resp.inner.has_request_lock.load(Ordering::SeqCst), true); } #[test] fn test_inner_try_lock_request_multiple() { #[allow(unused_variables)] let (rqst, resp) = channel::<Task>(); rqst.inner.try_lock_request(); assert_eq!(rqst.inner.try_lock_request(), false); } #[test] fn test_inner_try_unlock_request() { #[allow(unused_variables)] let (rqst, resp) = channel::<Task>(); rqst.inner.has_request_lock.store(true, Ordering::SeqCst); rqst.inner.unlock_request(); assert_eq!(resp.inner.has_request_lock.load(Ordering::SeqCst), false); } #[test] fn test_inner_try_lock_response() { #[allow(unused_variables)] let (rqst, resp) = channel::<Task>(); assert_eq!(rqst.inner.try_lock_response(), true); assert_eq!(resp.inner.has_response_lock.load(Ordering::SeqCst), true); } #[test] fn test_inner_try_lock_response_multiple() { #[allow(unused_variables)] let (rqst, resp) = channel::<Task>(); rqst.inner.try_lock_response(); assert_eq!(rqst.inner.try_lock_response(), false); } #[test] fn test_inner_try_unlock_response() { #[allow(unused_variables)] let (rqst, resp) = channel::<Task>(); rqst.inner.has_response_lock.store(true, Ordering::SeqCst); rqst.inner.unlock_response(); assert_eq!(resp.inner.has_response_lock.load(Ordering::SeqCst), false); } #[test] fn test_inner_flag_request() { #[allow(unused_variables)] let (rqst, resp) = channel::<Task>(); rqst.inner.flag_request(); assert_eq!(resp.inner.has_request.load(Ordering::SeqCst), true); } #[test] fn test_inner_try_unflag_request() { #[allow(unused_variables)] let (rqst, resp) = channel::<Task>(); resp.inner.has_request.store(true, Ordering::SeqCst); assert_eq!(rqst.inner.try_unflag_request(), true); assert_eq!(resp.inner.has_request.load(Ordering::SeqCst), false); assert_eq!(rqst.inner.try_unflag_request(), false); } #[test] fn test_inner_try_unflag_request_multiple() { #[allow(unused_variables)] let (rqst, resp) = channel::<Task>(); resp.inner.has_request.store(true, Ordering::SeqCst); rqst.inner.try_unflag_request(); assert_eq!(rqst.inner.try_unflag_request(), false); } #[test] fn test_inner_set_datum() { #[allow(unused_variables)] let (rqst, resp) = channel::<Task>(); let task = Box::new(move || { println!("Hello World!"); }) as Task; resp.inner.set_datum(task); assert_eq!(resp.inner.has_datum.load(Ordering::SeqCst), true); } #[test] fn test_inner_try_get_datum_with_data() { #[allow(unused_variables)] let (rqst, resp) = channel::<Task>(); let var = Arc::new(AtomicUsize::new(0)); let var2 = var.clone(); let task = Box::new(move || { var2.fetch_add(1, Ordering::SeqCst); }) as Task; unsafe { *resp.inner.datum.get() = Some(task); } resp.inner.has_datum.store(true, Ordering::SeqCst); match rqst.inner.try_get_datum() { Ok(t) => { t.call_box(); assert_eq!(var.load(Ordering::SeqCst), 1); }, _ => { assert!(false); }, } } #[test] fn test_inner_try_get_datum_no_data() { #[allow(unused_variables)] let (rqst, resp) = channel::<Task>(); match rqst.inner.try_get_datum() { Err(TryReceiveError::Empty) => {} _ => { assert!(false); }, } } #[test] fn test_requester_try_request() { #[allow(unused_variables)] let (rqst, resp) = channel::<Task>(); let mut contract = rqst.try_request().unwrap(); contract.done = true; } #[test] fn test_requester_try_request_multiple() { #[allow(unused_variables)] let (rqst, resp) = channel::<Task>(); rqst.inner.try_lock_request(); match rqst.try_request() { Err(TryRequestError::Locked) => {}, _ => { assert!(false); }, } } #[test] fn test_request_contract_try_receive() { let (rqst, resp) = channel::<Task>(); let var = Arc::new(AtomicUsize::new(0)); let var2 = var.clone(); let task = Box::new(move || { var2.fetch_add(1, Ordering::SeqCst); }) as Task; let mut contract = rqst.try_request().unwrap(); resp.inner.set_datum(task); match contract.try_receive() { Ok(task) => { task.call_box(); }, _ => { assert!(false); }, } assert_eq!(contract.done, true); assert_eq!(var.load(Ordering::SeqCst), 1); } #[test] fn test_request_contract_try_receive_no_data() { #[allow(unused_variables)] let (rqst, resp) = channel::<Task>(); let mut contract = rqst.try_request().unwrap(); match contract.try_receive() { Err(TryReceiveError::Empty) => {}, _ => { assert!(false); }, } assert_eq!(contract.done, false); contract.done = true; } #[test] fn test_request_contract_try_receive_done() { #[allow(unused_variables)] let (rqst, resp) = channel::<Task>(); let mut contract = rqst.try_request().unwrap(); contract.done = true; match contract.try_receive() { Err(TryReceiveError::Done) => {}, _ => { assert!(false); }, } } #[test] fn test_request_contract_try_cancel() { #[allow(unused_variables)] let (rqst, resp) = channel::<Task>(); let mut contract = rqst.try_request().unwrap(); assert_eq!(contract.try_cancel(), true); } #[test] fn test_request_contract_try_cancel_too_late() { #[allow(unused_variables)] let (rqst, resp) = channel::<Task>(); let mut contract = rqst.try_request().unwrap(); rqst.inner.try_unflag_request(); assert_eq!(contract.try_cancel(), false); assert_eq!(contract.done, false); contract.done = true; } #[test] fn test_request_contract_try_cancel_done() { #[allow(unused_variables)] let (rqst, resp) = channel::<Task>(); let mut contract = rqst.try_request().unwrap(); contract.done = true; assert_eq!(contract.try_cancel(), false); } #[test] #[should_panic] fn test_request_contract_drop_without_receiving_data() { #[allow(unused_variables)] let (rqst, resp) = channel::<Task>(); #[allow(unused_variables)] let contract = rqst.try_request().unwrap(); } #[test] fn test_responder_try_respond() { let (rqst, resp) = channel::<Task>(); rqst.inner.flag_request(); let mut contract = resp.try_respond().unwrap(); contract.done = true; } #[test] fn test_responder_try_respond_no_request() { #[allow(unused_variables)] let (rqst, resp) = channel::<Task>(); match resp.try_respond() { Err(TryRespondError::NoRequest) => {}, _ => { assert!(false); }, } } #[test] fn test_responder_try_respond_multiple() { #[allow(unused_variables)] let (rqst, resp) = channel::<Task>(); resp.inner.try_lock_response(); match resp.try_respond() { Err(TryRespondError::Locked) => {}, _ => { assert!(false); }, } } #[test] fn test_response_contract_send() { let (rqst, resp) = channel::<Task>(); rqst.inner.flag_request(); let contract = resp.try_respond().unwrap(); contract.send(Box::new(move || { println!("Hello World!"); }) as Task); } #[test] #[should_panic] fn test_response_contract_drop_without_sending_data() { #[allow(unused_variables)] let (rqst, resp) = channel::<Task>(); #[allow(unused_variables)] let contract = resp.try_respond().unwrap(); } }