1 files changed, 65 insertions, 0 deletions
diff --git a/third_party/rust/midir/examples/test_forward.rs b/third_party/rust/midir/examples/test_forward.rs
new file mode 100644
index 0000000000..1ecb142c2e
--- /dev/null
+++ b/third_party/rust/midir/examples/test_forward.rs
@@ -0,0 +1,65 @@
+extern crate midir;
+
+use std::io::{stdin, stdout, Write};
+use std::error::Error;
+
+use midir::{MidiInput, MidiOutput, MidiIO, Ignore};
+
+fn main() {
+    match run() {
+        Ok(_) => (),
+        Err(err) => println!("Error: {}", err)
+    }
+}
+
+#[cfg(not(target_arch = "wasm32"))] // conn_out is not `Send` in Web MIDI, which means it cannot be passed to connect
+fn run() -> Result<(), Box<dyn Error>> {
+    let mut midi_in = MidiInput::new("midir forwarding input")?;
+    midi_in.ignore(Ignore::None);
+    let midi_out = MidiOutput::new("midir forwarding output")?;
+
+    let in_port = select_port(&midi_in, "input")?;
+    println!();
+    let out_port = select_port(&midi_out, "output")?;
+
+    println!("\nOpening connections");
+    let in_port_name = midi_in.port_name(&in_port)?;
+    let out_port_name = midi_out.port_name(&out_port)?;
+
+    let mut conn_out = midi_out.connect(&out_port, "midir-forward")?;
+
+    // _conn_in needs to be a named parameter, because it needs to be kept alive until the end of the scope
+    let _conn_in = midi_in.connect(&in_port, "midir-forward", move |stamp, message, _| {
+        conn_out.send(message).unwrap_or_else(|_| println!("Error when forwarding message ..."));
+        println!("{}: {:?} (len = {})", stamp, message, message.len());
+    }, ())?;
+
+    println!("Connections open, forwarding from '{}' to '{}' (press enter to exit) ...", in_port_name, out_port_name);
+
+    let mut input = String::new();
+    stdin().read_line(&mut input)?; // wait for next enter key press
+
+    println!("Closing connections");
+    Ok(())
+}
+
+fn select_port<T: MidiIO>(midi_io: &T, descr: &str) -> Result<T::Port, Box<dyn Error>> {
+    println!("Available {} ports:", descr);
+    let midi_ports = midi_io.ports();
+    for (i, p) in midi_ports.iter().enumerate() {
+        println!("{}: {}", i, midi_io.port_name(p)?);
+    }
+    print!("Please select {} port: ", descr);
+    stdout().flush()?;
+    let mut input = String::new();
+    stdin().read_line(&mut input)?;
+    let port = midi_ports.get(input.trim().parse::<usize>()?)
+                         .ok_or("Invalid port number")?;
+    Ok(port.clone())
+}
+
+#[cfg(target_arch = "wasm32")]
+fn run() -> Result<(), Box<dyn Error>> {
+    println!("test_forward cannot run on Web MIDI");
+    Ok(())
+}