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//! Implements the `print!`, `println!` and `dbg!` macros so they can be used in the kernel without the use of an allocator.
//!
//! By default the macros are prefixed with `kernel_`. If you want to remove the prefix, you can enable the `std_name` feature.
//!
//! ## Usage
//!
//! Exactly as you'd use the original macros from the standard library.
//!
//! ```no_run
//! #![no_std]
//!
//! // ...
//!
//! kernel_dbg!(2 + 2);
//! kernel_print!("{} + {} = {}\n", 2, 2, 2 + 2);
//! kernel_println!("{} + {} = {}", 2, 2, 2 + 2);
//! ```
//!
//! ## Features
//!
//! - `std_name`: Allows you to use the macros without the `kernel_` prefix.
//! - `format`: Uses the `format!` macro instead of the `core::fmt::Write` trait to convert the passed data into a string.

#![no_std]

extern crate alloc;

#[doc(hidden)]
pub mod writer;

#[cfg(feature = "std_name")]
#[doc(hidden)]
pub mod std_name {
    pub use super::kernel_dbg as dbg;
    pub use super::kernel_print as print;
    pub use super::kernel_println as println;
}

#[cfg(feature = "std_name")]
pub use std_name::*;

/// Macro for printing the value of a given expression for quick and dirty debugging.
///
/// Does not panic on failure to write - instead silently ignores errors.
///
/// See [`dbg!`](https://doc.rust-lang.org/std/macro.dbg.html) for full documentation.
#[macro_export]
macro_rules! kernel_dbg {
    () => {
        $crate::kernel_println!("[{}:{}]", file!(), line!());
    };
    ($val:expr) => {
        // Use of `match` here is intentional because it affects the lifetimes
        // of temporaries - https://stackoverflow.com/a/48732525/1063961
        match $val {
            tmp => {
                $crate::kernel_println!("[{}:{}] {} = {:#?}",
                    file!(), line!(), stringify!($val), &tmp);
                tmp
            }
        }
    };
    // Trailing comma with single argument is ignored
    ($val:expr,) => { $crate::kernel_dbg!($val) };
    ($($val:expr),+ $(,)?) => {
        ($($crate::kernel_dbg!($val)),+,)
    };
}

/// Prints to the standard output.
///
/// Does not panic on failure to write - instead silently ignores errors.
///
/// See [`print!`](https://doc.rust-lang.org/std/macro.print.html) for full documentation.
#[macro_export]
macro_rules! kernel_print {
    ($($arg:tt)*) => {
        $crate::__impl_print!($($arg)*);
    };
}

#[cfg(not(feature = "format"))]
#[macro_export]
#[doc(hidden)]
macro_rules! __impl_print {
    ($($arg:tt)*) => {
        {
            let mut writer = $crate::writer::KernelWriter::new();
            let _ = writer.write_fmt(format_args!($($arg)*));
        }
    };
}

#[cfg(feature = "format")]
#[macro_export]
#[doc(hidden)]
macro_rules! __impl_print {
    ($($arg:tt)*) => {
        {
            let out = alloc::format!($($arg)*);
            let _ = $crate::writer::__kernel_println(out);
        }
    };
}

/// Prints to the standard output, with a newline.
///
/// Does not panic on failure to write - instead silently ignores errors.
///
/// See [`println!`](https://doc.rust-lang.org/std/macro.println.html) for full documentation.
#[macro_export]
macro_rules! kernel_println {
    () => {
        $crate::kernel_println!("")
    };
    ($($arg:tt)*) => {
        $crate::__impl_println!($($arg)*);
    };
}

#[cfg(not(feature = "format"))]
#[macro_export]
#[doc(hidden)]
macro_rules! __impl_println {
    ($($arg:tt)*) => {
        {
            let mut writer = $crate::writer::KernelWriter::new();
            let _ = writer.write_fmt(format_args!($($arg)*));
            let _ = writer.write_nl();
        }
    };
}

#[cfg(feature = "format")]
#[macro_export]
#[doc(hidden)]
macro_rules! __impl_println {
    ($($arg:tt)*) => {
        {
            let out = {
                let mut out = alloc::format!($($arg)*);
                out.push('\n');
                out
            };
            let _ = $crate::writer::__kernel_println(out);
        }
    };
}