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use crate::sync::SgxThreadMutex;
use crate::sys_common;
use alloc_crate::sync::Arc;
use core::cell::{Cell, UnsafeCell};
use core::ptr;
pub struct Lazy<T> {
lock: SgxThreadMutex,
ptr: Cell<*mut Arc<T>>,
}
#[inline]
const fn done<T>() -> *mut Arc<T> {
1_usize as *mut _
}
unsafe impl<T> Sync for Lazy<T> {}
impl<T> Lazy<T> {
pub const fn new() -> Lazy<T> {
Lazy {
lock: SgxThreadMutex::new(),
ptr: Cell::new(ptr::null_mut()),
}
}
}
impl<T: Send + Sync + 'static> Lazy<T> {
pub unsafe fn get(&'static self, init: fn() -> Arc<T>) -> Option<Arc<T>> {
let r = self.lock.lock();
if r.is_err() {
return None;
}
let ptr = self.ptr.get();
let ret = if ptr.is_null() {
Some(self.init(init))
} else if ptr == done() {
None
} else {
Some((*ptr).clone())
};
self.lock.unlock();
ret
}
unsafe fn init(&'static self, init: fn() -> Arc<T>) -> Arc<T> {
let registered = sys_common::at_exit(move || {
self.lock.lock();
let ptr = self.ptr.replace(done());
self.lock.unlock();
drop(Box::from_raw(ptr))
});
let ret = init();
if registered.is_ok() {
self.ptr.set(Box::into_raw(Box::new(ret.clone())));
}
ret
}
}
#[allow(dead_code)]
pub struct LazyStatic<T> {
lock: SgxThreadMutex,
opt: UnsafeCell<Option<Arc<T>>>,
}
unsafe impl<T> Sync for LazyStatic<T> {}
#[allow(dead_code)]
impl<T> LazyStatic<T> {
pub const fn new() -> LazyStatic<T> {
LazyStatic {
lock: SgxThreadMutex::new(),
opt: UnsafeCell::new(None),
}
}
}
#[allow(dead_code)]
impl<T: Send + Sync + 'static> LazyStatic<T> {
pub unsafe fn get(&'static self, init: fn() -> Arc<T>) -> Option<Arc<T>> {
let r = self.lock.lock();
if r.is_err() {
return None;
}
let ret = match *self.opt.get() {
Some(ref arc) => Some(arc.clone()),
None => Some(self.init(init)),
};
self.lock.unlock();
ret
}
unsafe fn init(&'static self, init: fn() -> Arc<T>) -> Arc<T> {
let ret = init();
*self.opt.get() = Some(ret.clone());
ret
}
}