Adds simple single producer, single consumer crossbeam channel example. (#551)

Cargo.toml

@@ -16,6 +16,7 @@ cc = "1.0"
 chrono = "0.4"
 clap = "2.29"
 crossbeam = "0.5"
+crossbeam-channel = "0.3.9"
 csv = "1.0"
 data-encoding = "2.1.0"
 env_logger = "0.5"

src/concurrency.md

@@ -3,6 +3,7 @@
 | Recipe | Crates | Categories |
 |--------|--------|------------|
 | [Spawn a short-lived thread][ex-crossbeam-spawn] | [![crossbeam-badge]][crossbeam] | [![cat-concurrency-badge]][cat-concurrency] |
+| [Pass data between two threads][ex-crossbeam-spsc] | [![crossbeam-badge]][crossbeam] | [![cat-concurrency-badge]][cat-concurrency] |
 | [Maintain global mutable state][ex-global-mut-state] | [![lazy_static-badge]][lazy_static] | [![cat-rust-patterns-badge]][cat-rust-patterns] |
 | [Calculate SHA1 sum of *.iso files concurrently][ex-threadpool-walk]  | [![threadpool-badge]][threadpool] [![walkdir-badge]][walkdir] [![num_cpus-badge]][num_cpus] [![ring-badge]][ring] | [![cat-concurrency-badge]][cat-concurrency][![cat-filesystem-badge]][cat-filesystem] |
 | [Draw fractal dispatching work to a thread pool][ex-threadpool-fractal] | [![threadpool-badge]][threadpool] [![num-badge]][num] [![num_cpus-badge]][num_cpus] [![image-badge]][image] | [![cat-concurrency-badge]][cat-concurrency][![cat-science-badge]][cat-science][![cat-rendering-badge]][cat-rendering] |
@@ -15,6 +16,7 @@
 
 
 [ex-crossbeam-spawn]: concurrency/threads.html#spawn-a-short-lived-thread
+[ex-crossbeam-spsc]: concurrency/threads.html#pass-data-between-two-threads
 [ex-global-mut-state]: concurrency/threads.html#maintain-global-mutable-state
 [ex-threadpool-walk]: concurrency/threads.html#calculate-sha1-sum-of-iso-files-concurrently
 [ex-threadpool-fractal]: concurrency/threads.html#draw-fractal-dispatching-work-to-a-thread-pool

src/concurrency/thread/crossbeam-spsc.md

@@ -0,0 +1,41 @@
+# Pass data between two threads
+
+[![crossbeam-badge]][crossbeam] [![cat-concurrency-badge]][cat-concurrency]
+
+This example demonstrates the use of [crossbeam-channel] in a single producer, single
+consumer (SPSC) setting. We build off the [ex-crossbeam-spawn] example by using
+[`crossbeam::scope`] and [`Scope::spawn`] to manage the producer thread. Data is
+exchanged between the two threads using a [`crossbeam_channel::unbounded`]
+channel, meaning there is no limit to the number of storeable messages. The
+producer thread sleeps for half a second in between messages.
+
+```rust
+extern crate crossbeam;
+extern crate crossbeam_channel;
+
+use std::{thread, time};
+use crossbeam_channel::unbounded;
+
+fn main() {
+    let (snd, rcv) = unbounded();
+    let n_msgs = 5;
+    crossbeam::scope(|s| {
+        s.spawn(|_| {
+            for i in 0..n_msgs {
+                snd.send(i).unwrap();
+                thread::sleep(time::Duration::from_millis(100));
+            }
+        });
+    }).unwrap();
+    for _ in 0..n_msgs {
+        let msg = rcv.recv().unwrap();
+        println!("Received {}", msg);
+    }
+}
+```
+
+[crossbeam-channel]: https://docs.rs/crate/crossbeam-channel/
+[ex-crossbeam-spawn]: concurrency/threads.html#spawn-a-short-lived-thread
+[`crossbeam::scope`]: https://docs.rs/crossbeam/*/crossbeam/fn.scope.html
+[`Scope::spawn`]: https://docs.rs/crossbeam/*/crossbeam/thread/struct.Scope.html#method.spawn
+[`crossbeam_channel::unbounded`]: https://docs.rs/crossbeam-channel/*/crossbeam_channel/fn.unbounded.html

src/concurrency/threads.md

@@ -2,6 +2,8 @@
 
 {{#include thread/crossbeam-spawn.md}}
 
+{{#include thread/crossbeam-spsc.md}}
+
 {{#include thread/global-mut-state.md}}
 
 {{#include thread/threadpool-walk.md}}