test_forward.rs - mozsearch

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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(())