From 58a1ca115f942191b12262e3e6ba431aa4277679 Mon Sep 17 00:00:00 2001
From: "Christoph J. Scherr" <Christoph.Scherr@newtec.de>
Date: Wed, 28 Feb 2024 11:24:03 +0100
Subject: [PATCH] mpsc

---
 Cargo.lock               |  7 +++++
 Cargo.toml               |  2 ++
 members/mpsc/Cargo.toml  |  9 ++++++
 members/mpsc/src/main.rs | 60 ++++++++++++++++++++++++++++++++++++++++
 4 files changed, 78 insertions(+)
 create mode 100644 members/mpsc/Cargo.toml
 create mode 100644 members/mpsc/src/main.rs

diff --git a/Cargo.lock b/Cargo.lock
index 2caa857..e569c6f 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -890,6 +890,13 @@ dependencies = [
  "windows-sys 0.48.0",
 ]
 
+[[package]]
+name = "mpsc"
+version = "0.1.0"
+dependencies = [
+ "anyhow",
+]
+
 [[package]]
 name = "nom"
 version = "7.1.3"
diff --git a/Cargo.toml b/Cargo.toml
index 061bb8e..52c1ace 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -14,10 +14,12 @@ members = [
   "members/tokio-send-sync",
   "members/matchmatchmatch",
   "members/future_stream",
+  "members/mpsc",
 ]
 default-members = [
   ".",
   "members/revsqrt",
+  "members/mpsc",
   "members/criterion-demo",
   "members/shortc",
   "members/pest-demo",
diff --git a/members/mpsc/Cargo.toml b/members/mpsc/Cargo.toml
new file mode 100644
index 0000000..62e2f7b
--- /dev/null
+++ b/members/mpsc/Cargo.toml
@@ -0,0 +1,9 @@
+[package]
+name = "mpsc"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+anyhow.workspace = true
diff --git a/members/mpsc/src/main.rs b/members/mpsc/src/main.rs
new file mode 100644
index 0000000..58ff9a6
--- /dev/null
+++ b/members/mpsc/src/main.rs
@@ -0,0 +1,60 @@
+use anyhow::Result;
+use std::io::Write;
+use std::str::FromStr;
+use std::sync::{Arc, Barrier};
+use std::{sync::mpsc, thread};
+
+#[derive(Clone, Debug)]
+struct Message {
+    payload: String,
+}
+
+impl std::fmt::Display for Message {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "Message {{{}}}", self.payload)
+    }
+}
+
+impl std::str::FromStr for Message {
+    type Err = std::convert::Infallible;
+    fn from_str(s: &str) -> std::prelude::v1::Result<Self, Self::Err> {
+        Ok(Self {
+            payload: s.to_string(),
+        })
+    }
+}
+
+fn printer(receiver: mpsc::Receiver<Message>, barrier: Arc<Barrier>) -> Result<()> {
+    let mut stdout = std::io::stdout();
+    loop {
+        let msg = receiver.recv()?;
+        println!("{msg}");
+        stdout.flush()?;
+        barrier.wait(); // wait until the main thread wants us to print
+    }
+}
+
+fn main() -> Result<()> {
+    let (sender, receiver) = mpsc::channel();
+    let barrier = Arc::new(Barrier::new(2));
+    let barrier_printer = barrier.clone();
+    thread::spawn(|| printer(receiver, barrier_printer).expect("printer error"));
+    let mut msg;
+    let mut buf = String::new();
+    let stdin = std::io::stdin();
+    let mut stdout = std::io::stdout();
+    loop {
+        buf.clear();
+        print!("> ");
+        stdout.flush()?;
+        let _ = stdin.read_line(&mut buf)?;
+        buf = buf.replace('\n', "");
+        if buf.is_empty() {
+            continue;
+        }
+        msg = Message::from_str(&buf).unwrap();
+        sender.send(msg)?;
+        barrier.wait(); // wait until the printer is done printing the message, so we dont mix
+                        // stdout prints (we use print instead of println)
+    }
+}