Logging

JACK can communicate info and error messages. By default, the log crate is hooked up to output messages. However, other logging methods can be used with the set_logger function.

No Logging

Logging from jack can be disabled entirely by setting the logger to None.

#![allow(unused)]
fn main() {
jack::set_logger(jack::LoggerType::None);
}

Log Crate (default)

The log crate is the default logger if the log feature is enabled, which is enabled by default. The log crate provides a facade for logging; it provides macros to perform logging, but another mechanism or crate is required to actually perform the logging.

In the example below, we use the env_logger crate to display logging for info and error severity level messages.

#![allow(unused)]
fn main() {
env_logger::builder().filter(None, log::LevelFilter::Info).init();

// JACK may log things to `info!` or `error!`.
let (client, _status) =
      jack::Client::new("rust_jack_simple", jack::ClientOptions::default()).unwrap();
}

Stdio

If the log feature is not enabled, then jack will log info messages to stdout and error messages to stderr. These usually show up in the terminal.

#![allow(unused)]
fn main() {
jack::set_logger(jack::LoggerType::Stdio);
}

Custom

jack::LoggerType::Custom can be used to set a custom logger. Here is stdout/stderr implemented as a custom logger:

fn main() {
    jack::set_logger(jack::LoggerType::Custom{info: stdout_handler, error: stderr_handler});
    ...
}

unsafe extern "C" fn stdout_handler(msg: *const libc::c_char) {
    let res = std::panic::catch_unwind(|| match std::ffi::CStr::from_ptr(msg).to_str() {
        Ok(msg) => println!("{}", msg),
        Err(err) => println!("failed to log to JACK info: {:?}", err),
    });
    if let Err(err) = res {
        eprintln!("{err:?}");
        std::mem::forget(err); // Prevent from rethrowing panic.
    }
}

unsafe extern "C" fn stderr_handler(msg: *const libc::c_char) {
    let res = std::panic::catch_unwind(|| match std::ffi::CStr::from_ptr(msg).to_str() {
        Ok(msg) => eprintln!("{}", msg),
        Err(err) => eprintln!("failed to log to JACK error: {:?}", err),
    });
    if let Err(err) = res {
        eprintln!("{err:?}");
        std::mem::forget(err); // Prevent from rethrowing panic.
    }
}