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#![doc = include_str!("../README.md")]
#![no_std]
#[cfg(feature = "log")]
pub mod log;
use core::cmp::min;
use core::fmt::{self, Write};
#[cfg(windows)]
use {
core::ptr::null_mut,
io_lifetimes::BorrowedHandle,
is_terminal::IsTerminal,
windows_sys::Win32::Foundation::{GetLastError, SetLastError, HANDLE},
windows_sys::Win32::Storage::FileSystem::WriteFile,
windows_sys::Win32::System::Console::STD_ERROR_HANDLE,
windows_sys::Win32::System::Console::{GetStdHandle, WriteConsoleW},
};
// No specific size is documented, so just pick a number.
#[cfg(windows)]
const BUF_LEN: usize = 4096;
struct Writer {
pos: usize,
// `PIPE_BUF` is the biggest buffer we can write atomically.
#[cfg(unix)]
buf: [u8; rustix::pipe::PIPE_BUF],
#[cfg(windows)]
buf: [u8; BUF_LEN],
// A buffer of UTF-16, for the Windows console.
#[cfg(windows)]
console_buf: [u16; BUF_LEN],
#[cfg(windows)]
console_pos: usize,
#[cfg(feature = "errno")]
#[cfg(unix)]
saved_errno: errno::Errno,
#[cfg(windows)]
saved_error: u32,
}
impl Writer {
fn new() -> Self {
Self {
pos: 0,
#[cfg(unix)]
buf: [0_u8; rustix::pipe::PIPE_BUF],
#[cfg(windows)]
buf: [0_u8; BUF_LEN],
#[cfg(windows)]
console_buf: [0_u16; BUF_LEN],
#[cfg(windows)]
console_pos: 0,
#[cfg(feature = "errno")]
#[cfg(unix)]
saved_errno: errno::errno(),
#[cfg(windows)]
saved_error: unsafe { GetLastError() },
}
}
fn flush(&mut self) {
#[cfg(unix)]
{
self.flush_buf().unwrap();
}
#[cfg(windows)]
{
let stderr = unsafe { GetStdHandle(STD_ERROR_HANDLE) };
if unsafe { BorrowedHandle::borrow_raw(stderr as _) }.is_terminal() {
self.flush_console(stderr)
} else {
self.flush_buf()
}
.unwrap();
}
}
fn flush_buf(&mut self) -> fmt::Result {
let mut s = &self.buf[..self.pos];
// SAFETY: Users using `dbg`/`eprintln`/`eprint` APIs should be aware
// that these assume that the stderr file descriptor is open and valid
// to write to.
#[cfg(unix)]
let stderr = unsafe { rustix::stdio::stderr() };
#[cfg(windows)]
let stderr = unsafe { GetStdHandle(STD_ERROR_HANDLE) };
while !s.is_empty() {
#[cfg(unix)]
match rustix::io::write(stderr, s) {
Ok(n) => s = &s[n..],
Err(rustix::io::Errno::INTR) => (),
Err(_) => return Err(fmt::Error),
}
#[cfg(windows)]
unsafe {
let mut n = 0;
if WriteFile(
stderr,
s.as_ptr().cast(),
min(s.len(), u32::MAX as usize) as u32,
&mut n,
null_mut(),
) == 0
{
return Err(fmt::Error);
}
s = &s[n as usize..];
}
}
self.pos = 0;
Ok(())
}
#[cfg(windows)]
fn flush_console(&mut self, handle: HANDLE) -> fmt::Result {
// Write `self.console_buf` to the console.
let mut s = &self.console_buf[..self.console_pos];
while !s.is_empty() {
unsafe {
let mut n16 = 0;
if WriteConsoleW(
handle,
s.as_ptr().cast(),
min(s.len(), u32::MAX as usize) as u32,
&mut n16,
null_mut(),
) == 0
{
return Err(fmt::Error);
}
s = &s[n16 as usize..];
}
}
self.console_pos = 0;
Ok(())
}
}
impl Drop for Writer {
fn drop(&mut self) {
#[cfg(feature = "errno")]
#[cfg(unix)]
errno::set_errno(self.saved_errno);
#[cfg(windows)]
unsafe {
SetLastError(self.saved_error);
}
}
}
impl fmt::Write for Writer {
fn write_str(&mut self, s: &str) -> fmt::Result {
// On Windows, to write Unicode to the console, we need to use some
// form of `WriteConsole` instead of `WriteFile`.
#[cfg(windows)]
{
let stderr = unsafe { GetStdHandle(STD_ERROR_HANDLE) };
if unsafe { BorrowedHandle::borrow_raw(stderr as _) }.is_terminal() {
// If the stream switched on us, just fail.
if self.pos != 0 {
return Err(fmt::Error);
}
// Transcode `s` to UTF-16 and write it to the console.
for c in s.chars() {
if self.console_buf.len() - self.console_pos < 2 {
self.flush_console(stderr)?;
}
self.console_pos += c
.encode_utf16(&mut self.console_buf[self.console_pos..])
.len();
}
return Ok(());
}
// If the stream switched on us, just fail.
if self.console_pos != 0 {
return Err(fmt::Error);
}
}
let mut bytes = s.as_bytes();
while !bytes.is_empty() {
let mut sink = &mut self.buf[self.pos..];
if sink.is_empty() {
self.flush_buf()?;
sink = &mut self.buf;
}
let len = min(sink.len(), bytes.len());
let (now, later) = bytes.split_at(len);
sink[..len].copy_from_slice(now);
self.pos += len;
bytes = later;
}
Ok(())
}
}
#[doc(hidden)]
pub fn _eprint(args: fmt::Arguments<'_>) {
let mut writer = Writer::new();
writer.write_fmt(args).unwrap();
writer.flush();
}
#[doc(hidden)]
pub fn _eprintln(args: fmt::Arguments<'_>) {
let mut writer = Writer::new();
writer.write_fmt(args).unwrap();
writer.write_fmt(format_args!("\n")).unwrap();
writer.flush();
}
#[doc(hidden)]
pub struct _Dbg(Writer);
#[doc(hidden)]
pub fn _dbg_start() -> _Dbg {
_Dbg(Writer::new())
}
#[doc(hidden)]
pub fn _dbg_write(dbg: &mut _Dbg, file: &str, line: u32, name: &str, args: fmt::Arguments<'_>) {
writeln!(&mut dbg.0, "[{}:{}] {} = {}", file, line, name, args).unwrap();
}
#[doc(hidden)]
pub fn _dbg_finish(mut dbg: _Dbg) {
dbg.0.flush();
}
/// Prints to the standard error.
///
/// Similar to [`std::eprint`], except it:
/// - Writes atomically, up to the greatest length supported on the platform.
/// - Doesn't use locks (in userspace).
/// - Preserve libc's `errno` and Windows' last-error code value.
///
/// This allows it to be used to debug allocators, multi-threaded code,
/// synchronization routines, startup code, and more.
#[macro_export]
macro_rules! eprint {
($($arg:tt)*) => {
$crate::_eprint(core::format_args!($($arg)*))
};
}
/// Prints to the standard error, with a newline.
///
/// Similar to [`std::eprintln`], except it:
/// - Writes atomically, up to the greatest length supported on the platform.
/// - Doesn't use locks (in userspace).
/// - Preserve libc's `errno` and Windows' last-error code value.
///
/// This allows it to be used to debug allocators, multi-threaded code,
/// synchronization routines, startup code, and more.
#[macro_export]
macro_rules! eprintln {
() => {
$crate::eprint!("\n")
};
($($arg:tt)*) => {
// TODO: Use `format_args_nl` when it's stabilized.
$crate::_eprintln(core::format_args!($($arg)*))
};
}
/// Prints and returns the value of a given expression for quick and dirty
/// debugging.
///
/// Similar to [`std::dbg`], except it:
/// - Writes atomically, up to the greatest length supported on the platform.
/// - Doesn't use locks (in userspace).
/// - Preserve libc's `errno` and Windows' last-error code value.
///
/// This allows it to be used to debug allocators, multi-threaded code,
/// synchronization routines, startup code, and more.
#[macro_export]
macro_rules! dbg {
() => {
$crate::eprintln!("[{}:{}]", core::file!(), core::line!())
};
($val:expr $(,)?) => {
// Use the same `match` trick that `std` does.
match $val {
tmp => {
$crate::eprintln!("[{}:{}] {} = {:#?}",
core::file!(), core::line!(), core::stringify!($val), &tmp);
tmp
}
}
};
($($val:expr),+ $(,)?) => {
let mut dbg = $crate::_dbg_start();
// Use the same `match` trick that `std` does.
($(match $val {
tmp => {
$crate::_dbg_write(
&mut dbg,
core::file!(),
core::line!(),
core::stringify!($val),
core::format_args!("{:#?}", &tmp),
);
tmp
}
}),+);
$crate::_dbg_finish(dbg);
};
}