app/src/dprintf.rs

// Copyright 2022 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

//! App-side dprintf macro that calls through to the debug_uart capsule.

use core::fmt;
use core2::io::{Cursor, Write};
use libtock::syscalls;
use matcha_config::*;

#[macro_export]
macro_rules! dprintf {
    ($msg:expr) => ({
        $crate::dprintf::vdprintf(format_args!($msg))
    });
    ($fmt:expr, $($arg:tt)+) => ({
        $crate::dprintf::vdprintf(format_args!($fmt, $($arg)+))
    });
}

pub fn vdprintf(args: fmt::Arguments) {
    let mut uart_buf = [0u8; 256];
    let mut cur = Cursor::new(&mut uart_buf[..]);
    if cur.write_fmt(args).is_ok() {
        let pos = cur.position();
        drop(cur);
        let allow = syscalls::allow(CAPSULE_DPRINTF, 0, &mut uart_buf);
        let _result = syscalls::command(CAPSULE_DPRINTF, CMD_DPRINTF_PRINT, pos as usize, 0);
        drop(allow);
    }
}