Macro custom_print::define_flush

macro_rules! define_flush {
    ( $( #[$meta:meta] )* $name:ident, $($args:tt)* ) => { ... };
}

Defines flush macro that calls flush method of the specified writer.

Use define_try_flush if you need to define a fallible flush macro.

The macro is intentionally defined instead of a function because of the custom result type specified by the writer.

Examples

use std::io::{self, LineWriter, Write};
use std::sync::Mutex;

let written: Mutex<Vec<u8>> = Mutex::default();

#[derive(Clone, Debug)]
struct CustomWriter<'a>(&'a Mutex<Vec<u8>>);

impl Write for CustomWriter<'_> {
    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
        let mut written = self.0.lock().unwrap();
        written.extend_from_slice(buf);
        Ok(buf.len())
    }

    fn flush(&mut self) -> io::Result<()> {
        Ok(())
    }
}

let custom_writer = CustomWriter(&written);
let mut line_writer = LineWriter::new(custom_writer);

custom_print::define_print!(cprint, line_writer);
custom_print::define_flush!(flush, line_writer);

assert_eq!(cprint!("first,"), ());
assert_eq!(*written.lock().unwrap(), b"");
assert_eq!(cprint!("second\nthird,"), ());
assert_eq!(*written.lock().unwrap(), b"first,second\n");
assert_eq!(flush!(), ());
assert_eq!(*written.lock().unwrap(), b"first,second\nthird,");