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//! Common utilities.
#![no_std]
use core::{
fmt,
mem::size_of,
ops::{Deref, DerefMut},
};
/// Creates an ad-hoc `Debug` instance.
pub fn debug(f: impl Fn(&mut fmt::Formatter) -> fmt::Result) -> impl fmt::Debug {
struct Debug<F>(F);
impl<F: Fn(&mut fmt::Formatter) -> fmt::Result> fmt::Debug for Debug<F> {
fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
(self.0)(fmt)
}
}
Debug(f)
}
/// A hint that this branch is unlikely to be called.
#[cold]
#[inline(always)]
pub fn cold() {}
/// A hint that `b` is likely to be true. See `core::intrinsics::likely`.
#[inline(always)]
pub fn likely(b: bool) -> bool {
if !b {
cold()
}
b
}
/// A hint that `b` is likely to be false. See `core::intrinsics::unlikely`.
#[inline(always)]
pub fn unlikely(b: bool) -> bool {
if b {
cold()
}
b
}
/// A version of `std::dbg` built on top of `log::debug` instead of
/// `std::eprintln`.
///
/// This code is copied from libstd, and inherits its copyright.
#[macro_export]
macro_rules! dbg {
// NOTE: We cannot use `concat!` to make a static string as a format
// argument of `log::debug!` because the `$expr` expression could be a
// block (`{ .. }`), in which case the format string will be malformed.
() => {
log::debug!("")
};
($expr:expr $(,)?) => {
// Use of `match` here is intentional because it affects the lifetimes
// of temporaries - https://stackoverflow.com/a/48732525/1063961
match $expr {
tmp => {
log::debug!("{} = {:#?}", core::stringify!($expr), &tmp);
tmp
}
}
};
($($expr:expr),+ $(,)?) => {
($($crate::dbg!($expr)),+,)
};
}
/// A wrapper type that promises that its contents are Send.
pub struct BelieveMeSend<T>(pub T);
impl<T> Deref for BelieveMeSend<T> {
type Target = T;
fn deref(&self) -> &T {
&self.0
}
}
impl<T> DerefMut for BelieveMeSend<T> {
fn deref_mut(&mut self) -> &mut T {
&mut self.0
}
}
unsafe impl<T> Send for BelieveMeSend<T> {}
/// A trait for types that can be converted to from big-endian or little-endian byte slices.
pub trait FromEndianBytes {
/// Converts from a big-endian byte slice.
fn from_big_endian_bytes(bytes: &[u8]) -> Self;
/// Converts from a little-endian byte slice.
fn from_little_endian_bytes(bytes: &[u8]) -> Self;
}
macro_rules! impl_FromEndianBytes {
($($ty:ty),* $(,)?) => {
$(impl FromEndianBytes for $ty {
fn from_big_endian_bytes(bytes: &[u8]) -> $ty {
let chunk = match bytes.last_chunk() {
Some(chunk) => *chunk,
None => {
let mut chunk = [0; size_of::<$ty>()];
chunk[size_of::<$ty>() - bytes.len()..]
.copy_from_slice(bytes);
chunk
},
};
<$ty>::from_be_bytes(chunk)
}
fn from_little_endian_bytes(bytes: &[u8]) -> $ty {
let chunk = match bytes.first_chunk() {
Some(chunk) => *chunk,
None => {
let mut chunk = [0; size_of::<$ty>()];
chunk[.. bytes.len()].copy_from_slice(bytes);
chunk
},
};
<$ty>::from_le_bytes(chunk)
}
})*
};
}
impl_FromEndianBytes!(i8, i16, i32, i64, isize, u8, u16, u32, u64, usize);
/// Runs the body block the first time it is encountered.
#[macro_export]
macro_rules! first_time {
($($stmt:stmt)*) => {{
use spin::lazy::Lazy;
static LAZY: Lazy<()> = Lazy::new(|| {
$($stmt)*
});
*Lazy::force(&LAZY)
}};
}
|
