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#![no_std]
use core::cmp::Ordering;
use core::fmt;
use core::hash::{Hash, Hasher};
use core::marker::PhantomData as marker;
use core::mem::MaybeUninit;
use core::ops::Add;
#[repr(transparent)]
pub struct Offset<Base, Field> {
value: u32,
marker: marker<*const (Base, Field)>,
}
unsafe impl<Base, Field> Send for Offset<Base, Field> {}
unsafe impl<Base, Field> Sync for Offset<Base, Field> {}
#[macro_export]
macro_rules! field_ptr {
($base_ptr:ident.$field:ident) => {
&(*$base_ptr).$field as *const _
};
}
#[macro_export]
macro_rules! offset_of {
($ty:ident::$field:ident) => {
$crate::offset_of!(<$ty>::$field)
};
(<$ty:path>::$field:ident) => {{
#[inline(always)]
const unsafe fn offset<Base, Field>(
value: u32,
_ptr: *const Field,
) -> $crate::Offset<Base, Field> {
$crate::Offset::new_unchecked(value)
}
#[allow(unsafe_code)]
#[allow(unused_unsafe)]
{
unsafe {
let _ = |value: &$ty| {
let $ty { $field: _, .. } = *value;
};
let uninit = <core::mem::MaybeUninit<$ty>>::uninit();
let base_ptr = uninit.as_ptr();
let field_ptr = $crate::field_ptr!(base_ptr.$field);
offset::<$ty, _>(
(field_ptr as *const u8).offset_from(base_ptr as *const u8) as u32,
field_ptr,
)
}
}
}};
}
impl<Base, Field> Offset<Base, Field> {
#[inline(always)]
pub const unsafe fn new_unchecked(value: u32) -> Self {
Self { value, marker }
}
#[inline(always)]
pub const fn uninit(self) -> Offset<MaybeUninit<Base>, MaybeUninit<Field>> {
Offset {
value: self.value,
marker,
}
}
pub const fn as_u32(self) -> u32 {
self.value
}
#[inline(always)]
pub fn index_in(self, base: &Base) -> &Field {
unsafe { &*((base as *const Base as *const u8).add(self.value as usize) as *const Field) }
}
#[inline(always)]
pub fn index_mut_in(self, base: &mut Base) -> &mut Field {
unsafe { &mut *((base as *mut Base as *mut u8).add(self.value as usize) as *mut Field) }
}
}
impl<A, B, C> Add<Offset<B, C>> for Offset<A, B> {
type Output = Offset<A, C>;
#[inline(always)]
fn add(self, other: Offset<B, C>) -> Self::Output {
Offset {
value: self.value + other.value,
marker,
}
}
}
impl<Base, Field> Copy for Offset<Base, Field> {}
impl<Base, Field> Clone for Offset<Base, Field> {
#[inline(always)]
fn clone(&self) -> Self {
*self
}
}
impl<Base, Field> Eq for Offset<Base, Field> {}
impl<Base, Field> PartialEq for Offset<Base, Field> {
#[inline(always)]
fn eq(&self, other: &Self) -> bool {
self.value == other.value
}
}
impl<Base, Field> PartialEq<&Self> for Offset<Base, Field> {
#[inline(always)]
fn eq(&self, other: &&Self) -> bool {
self == *other
}
}
impl<Base, Field> PartialEq<u32> for Offset<Base, Field> {
#[inline(always)]
fn eq(&self, other: &u32) -> bool {
self.value == *other
}
}
impl<Base, Field> PartialEq<&u32> for Offset<Base, Field> {
#[inline(always)]
fn eq(&self, other: &&u32) -> bool {
self.value == **other
}
}
impl<Base, Field> Ord for Offset<Base, Field> {
#[inline(always)]
fn cmp(&self, other: &Self) -> Ordering {
self.value.cmp(&other.value)
}
}
impl<Base, Field> PartialOrd for Offset<Base, Field> {
#[inline(always)]
fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
Some(self.cmp(other))
}
}
impl<Base, Field> PartialOrd<&Self> for Offset<Base, Field> {
#[inline(always)]
fn partial_cmp(&self, other: &&Self) -> Option<Ordering> {
Some(self.cmp(&**other))
}
}
impl<Base, Field> PartialOrd<u32> for Offset<Base, Field> {
#[inline(always)]
fn partial_cmp(&self, other: &u32) -> Option<Ordering> {
self.value.partial_cmp(other)
}
}
impl<Base, Field> PartialOrd<&u32> for Offset<Base, Field> {
#[inline(always)]
fn partial_cmp(&self, other: &&u32) -> Option<Ordering> {
self.value.partial_cmp(other)
}
}
impl<Base, Field> Hash for Offset<Base, Field> {
#[inline(always)]
fn hash<H>(&self, state: &mut H)
where
H: Hasher,
{
self.value.hash(state);
}
}
impl<Base, Field> fmt::Debug for Offset<Base, Field>
where
Base: DescribeOffset,
{
fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
Base::describe_offset(self.value, fmt)
}
}
pub trait DescribeOffset {
fn describe_offset(offset: u32, fmt: &mut fmt::Formatter) -> fmt::Result;
}
macro_rules! trivial_fmt_impl {
($($t:ident),*) => {
$(impl<Base, Field> fmt::$t for Offset<Base, Field> {
fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
self.value.fmt(fmt)
}
})*
}
}
trivial_fmt_impl!(Binary, Display, LowerHex, Octal, UpperHex);
impl<Base, Field> From<Offset<Base, Field>> for u32 {
#[inline(always)]
fn from(offset: Offset<Base, Field>) -> Self {
offset.value
}
}