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use core::num::Wrapping;
pub trait Encoding<T>: From<T> + Into<T>
where
Self: Copy,
{
const ZERO: Self;
}
pub fn as_byte_slice<E: Encoding<T>, T>(x: &[E]) -> &[u8] {
unsafe {
core::slice::from_raw_parts(x.as_ptr() as *const u8, x.len() * core::mem::size_of::<E>())
}
}
pub trait ArrayEncoding<T> {
fn as_byte_array(&self) -> &T;
}
pub trait FromByteArray<T> {
fn from_byte_array(a: &T) -> Self;
}
macro_rules! define_endian {
($endian:ident) => {
#[repr(transparent)]
pub struct $endian<T>(T);
impl<T> $endian<T> {
#[deprecated]
pub fn into_raw_value(self) -> T {
self.0
}
}
impl<T> Copy for $endian<T> where T: Copy {}
impl<T> Clone for $endian<T>
where
T: Clone,
{
fn clone(&self) -> Self {
Self(self.0.clone())
}
}
};
}
macro_rules! impl_from_byte_array {
($endian:ident, $base:ident, $elems:expr) => {
impl FromByteArray<[u8; $elems * core::mem::size_of::<$base>()]>
for [$endian<$base>; $elems]
{
fn from_byte_array(a: &[u8; $elems * core::mem::size_of::<$base>()]) -> Self {
unsafe { core::mem::transmute_copy(a) }
}
}
};
}
macro_rules! impl_array_encoding {
($endian:ident, $base:ident, $elems:expr) => {
impl ArrayEncoding<[u8; $elems * core::mem::size_of::<$base>()]>
for [$endian<$base>; $elems]
{
fn as_byte_array(&self) -> &[u8; $elems * core::mem::size_of::<$base>()] {
let as_bytes_ptr =
self.as_ptr() as *const [u8; $elems * core::mem::size_of::<$base>()];
unsafe { &*as_bytes_ptr }
}
}
impl_from_byte_array!($endian, $base, $elems);
};
}
macro_rules! impl_endian {
($endian:ident, $base:ident, $to_endian:ident, $from_endian:ident, $size:expr) => {
impl Encoding<$base> for $endian<$base> {
const ZERO: Self = Self(0);
}
impl From<[u8; $size]> for $endian<$base> {
#[inline]
fn from(bytes: [u8; $size]) -> Self {
Self($base::from_ne_bytes(bytes))
}
}
impl From<$endian<$base>> for [u8; $size] {
#[inline]
fn from(encoded: $endian<$base>) -> Self {
$base::to_ne_bytes(encoded.0)
}
}
impl From<$base> for $endian<$base> {
#[inline]
fn from(value: $base) -> Self {
Self($base::$to_endian(value))
}
}
impl From<Wrapping<$base>> for $endian<$base> {
#[inline]
fn from(Wrapping(value): Wrapping<$base>) -> Self {
Self($base::$to_endian(value))
}
}
impl From<$endian<$base>> for $base {
#[inline]
fn from($endian(value): $endian<$base>) -> Self {
$base::$from_endian(value)
}
}
impl_array_encoding!($endian, $base, 1);
impl_array_encoding!($endian, $base, 2);
impl_array_encoding!($endian, $base, 3);
impl_array_encoding!($endian, $base, 4);
impl_array_encoding!($endian, $base, 8);
};
}
define_endian!(BigEndian);
define_endian!(LittleEndian);
impl_endian!(BigEndian, u32, to_be, from_be, 4);
impl_endian!(BigEndian, u64, to_be, from_be, 8);
impl_endian!(LittleEndian, u32, to_le, from_le, 4);
impl_endian!(LittleEndian, u64, to_le, from_le, 8);
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_big_endian() {
let x = BigEndian::from(1u32);
assert_eq!(u32::from(x), 1);
}
}