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#![allow(dead_code)]
use core::sync::atomic::Ordering;
#[cfg(target_pointer_width = "64")]
use core::sync::atomic::AtomicU64;
#[cfg(target_pointer_width = "32")]
use core::sync::atomic::AtomicU32;
pub const fn set_bit(x: u64, bit: u32) -> u64 {
x | 1 << bit
}
pub const fn test_bit(x: u64, bit: u32) -> bool {
x & (1 << bit) != 0
}
const CACHE_CAPACITY: u32 = 63;
#[derive(Copy, Clone)]
pub struct Initializer(u64);
impl Default for Initializer {
fn default() -> Self {
Initializer(0)
}
}
impl Initializer {
#[allow(dead_code)]
pub fn test(&self, bit: u32) -> bool {
debug_assert!(
bit < CACHE_CAPACITY,
"too many features, time to increase the cache size!"
);
test_bit(self.0, bit)
}
pub fn set(&mut self, bit: u32) {
debug_assert!(
bit < CACHE_CAPACITY,
"too many features, time to increase the cache size!"
);
let v = self.0;
self.0 = set_bit(v, bit);
}
}
static CACHE: Cache = Cache::uninitialized();
#[cfg(target_pointer_width = "64")]
struct Cache(AtomicU64);
#[cfg(target_pointer_width = "64")]
impl Cache {
const fn uninitialized() -> Self {
Cache(AtomicU64::new(u64::max_value()))
}
pub fn is_uninitialized(&self) -> bool {
self.0.load(Ordering::Relaxed) == u64::max_value()
}
pub fn test(&self, bit: u32) -> bool {
test_bit(CACHE.0.load(Ordering::Relaxed), bit)
}
pub fn initialize(&self, value: Initializer) {
self.0.store(value.0, Ordering::Relaxed);
}
}
#[cfg(target_pointer_width = "32")]
struct Cache(AtomicU32, AtomicU32);
#[cfg(target_pointer_width = "32")]
impl Cache {
const fn uninitialized() -> Self {
Cache(
AtomicU32::new(u32::max_value()),
AtomicU32::new(u32::max_value()),
)
}
pub fn is_uninitialized(&self) -> bool {
self.1.load(Ordering::Relaxed) == u32::max_value()
}
pub fn test(&self, bit: u32) -> bool {
if bit < 32 {
test_bit(CACHE.0.load(Ordering::Relaxed) as u64, bit)
} else {
test_bit(CACHE.1.load(Ordering::Relaxed) as u64, bit - 32)
}
}
pub fn initialize(&self, value: Initializer) {
let lo: u32 = value.0 as u32;
let hi: u32 = (value.0 >> 32) as u32;
self.0.store(lo, Ordering::Relaxed);
self.1.store(hi, Ordering::Relaxed);
}
}
pub fn test<F>(bit: u32, f: F) -> bool
where
F: FnOnce() -> Initializer,
{
if CACHE.is_uninitialized() {
CACHE.initialize(f());
}
CACHE.test(bit)
}