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use core::hint;
#[macro_export]
macro_rules! xref {
($e:expr) => {
$crate::__xref!($crate::__entropy!(stringify!($e), 1) as usize, $crate::__entropy!(stringify!($e), 2), $e)
};
}
#[doc(hidden)]
#[macro_export]
macro_rules! __xref {
($offset:expr, $seed:expr, $e:expr) => {
$crate::xref::xref::<_, {$offset}, {$seed}>($e)
};
}
#[inline(always)]
const fn non_zero(rand: usize) -> usize {
if rand == 0 { 1 } else { rand }
}
#[inline(always)]
const fn obfchoice(v: usize, seed: u64) -> usize {
let rand = (seed >> 32) as i32 as usize;
match seed & 7 {
0 => v.wrapping_add(rand),
1 => rand.wrapping_sub(v),
2 => v ^ rand,
3 => v ^ v.rotate_left(non_zero(rand & 7) as u32),
4 => !v,
5 => v ^ (v >> non_zero(rand & 31)),
6 => v.wrapping_mul(non_zero(rand)),
7 => v.wrapping_neg(),
_ => unsafe { hint::unreachable_unchecked() }
}
}
#[inline(always)]
const fn obfuscate<const SEED: u64>(mut v: usize) -> usize {
let mut seed = SEED;
use crate::splitmix;
seed = splitmix(seed);
v = obfchoice(v, seed);
seed = splitmix(seed);
v = obfchoice(v, seed);
seed = splitmix(seed);
v = obfchoice(v, seed);
seed = splitmix(seed);
v = obfchoice(v, seed);
seed = splitmix(seed);
return obfchoice(v, seed & 0xffffffff00000000 | 3) & 0xffff
}
#[inline(never)]
fn inner<const SEED: u64>(p: *const u8, offset: usize) -> *const u8 {
p.wrapping_add(obfuscate::<SEED>(offset))
}
#[inline(always)]
pub fn xref<T: ?Sized, const OFFSET: usize, const SEED: u64>(p: &'static T) -> &'static T {
unsafe {
let mut p: *const T = p;
let val = inner::<SEED>(hint::black_box((p as *const u8).wrapping_sub(obfuscate::<SEED>(OFFSET))), hint::black_box(OFFSET));
*(&mut p as *mut *const T as *mut *const u8) = val;
&*p
}
}
#[macro_export]
macro_rules! xref_mut {
($e:expr) => {
$crate::__xref_mut!($crate::__entropy!(stringify!($e), 1) as usize, $crate::__entropy!(stringify!($e), 2), $e)
};
}
#[doc(hidden)]
#[macro_export]
macro_rules! __xref_mut {
($offset:expr, $seed:expr, $e:expr) => {
$crate::xref::xref_mut::<_, {$offset}, {$seed}>($e)
};
}
#[inline(never)]
fn inner_mut<const SEED: u64>(p: *mut u8, offset: usize) -> *mut u8 {
p.wrapping_add(obfuscate::<SEED>(offset))
}
#[inline(always)]
pub fn xref_mut<T: ?Sized, const OFFSET: usize, const SEED: u64>(p: &'static mut T) -> &'static mut T {
unsafe {
let mut p: *mut T = p;
let val = inner_mut::<SEED>(hint::black_box((p as *mut u8).wrapping_sub(obfuscate::<SEED>(OFFSET))), hint::black_box(OFFSET));
*(&mut p as *mut *mut T as *mut *mut u8) = val;
&mut *p
}
}
#[test]
fn test_xref_slice() {
static FOO: [i32; 42] = [13; 42];
let foo = xref!(&FOO[..]);
assert_eq!(foo as *const _, &FOO as *const _);
assert_eq!(xref!("Hello world!"), "Hello world!");
assert_eq!(xref!(b"Byte array"), b"Byte array");
}
#[test]
fn regression1() {
let v = obfuscate::<{(-4272872662024917058i64) as u64}>(4898264233338431333usize);
assert_ne!(v, 0);
}