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#![no_std]
use core::fmt;
use core::mem::MaybeUninit;
use core::ptr;
use core::sync::atomic::Ordering::{Relaxed, SeqCst};
use interrupt::CriticalSection;
use util::*;
pub struct AchOption<T> {
val: MaybeUninit<T>,
state: AtomicMemoryState,
}
impl<T> AchOption<T> {
pub const fn new() -> Self {
Self {
val: MaybeUninit::uninit(),
state: AtomicMemoryState::new(MemoryState::Uninitialized),
}
}
pub const fn new_with(init: T) -> Self {
Self {
val: MaybeUninit::new(init),
state: AtomicMemoryState::new(MemoryState::Initialized),
}
}
fn ptr(&self) -> *mut T {
self.val.as_ptr() as *mut T
}
pub fn into_inner(self) -> Option<T> {
self.take()
}
pub fn is_some(&self) -> bool {
let state = self.state.load(SeqCst);
state.is_initialized()
}
pub fn is_none(&self) -> bool {
let state = self.state.load(SeqCst);
state.is_uninitialized()
}
pub fn try_take(&self) -> Result<Option<T>, Error<()>> {
let _cs = CriticalSection::new();
if let Err(state) = self.state.fetch_update(SeqCst, Relaxed, |x| {
if x.is_initialized() {
Some(MemoryState::Erasing)
} else {
None
}
}) {
if state.is_uninitialized() {
Ok(None)
} else {
Err(Error {
state,
input: (),
retry: state.is_transient(),
})
}
} else {
let ret = unsafe { ptr::read(self.ptr()) };
self.state.store(MemoryState::Uninitialized.into(), SeqCst);
Ok(Some(ret))
}
}
pub fn take(&self) -> Option<T> {
unwrap(|_| self.try_take(), ())
}
pub fn try_set(&self, value: T) -> Result<(), Error<T>> {
let _cs = CriticalSection::new();
if let Err(state) = self.state.compare_exchange(
MemoryState::Uninitialized.into(),
MemoryState::Initializing.into(),
SeqCst,
Relaxed,
) {
Err(Error {
state,
input: value,
retry: state.is_erasing(),
})
} else {
unsafe { ptr::write(self.ptr(), value) };
self.state.store(MemoryState::Initialized.into(), SeqCst);
Ok(())
}
}
pub fn set(&self, value: T) -> Result<(), Error<T>> {
retry(|val| self.try_set(val), value)
}
pub fn try_replace(&self, value: T) -> Result<Option<T>, Error<T>> {
let _cs = CriticalSection::new();
match self.state.fetch_update(SeqCst, Relaxed, |x| {
if x.is_uninitialized() || x.is_initialized() {
Some(MemoryState::Initializing.into())
} else {
None
}
}) {
Ok(state) => {
let ret = if state.is_uninitialized() {
None
} else {
Some(unsafe { ptr::read(self.ptr()) })
};
unsafe { ptr::write(self.ptr(), value) };
self.state.store(MemoryState::Initialized.into(), SeqCst);
Ok(ret)
}
Err(state) => Err(Error {
state,
input: value,
retry: state.is_transient(),
}),
}
}
pub fn replace(&self, value: T) -> Option<T> {
unwrap(|val| self.try_replace(val), value)
}
}
impl<'a, T: fmt::Debug> fmt::Debug for AchOption<T> {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
let v = if self.is_some() {
Some(unsafe { self.val.assume_init_ref() })
} else {
None
};
fmt::Debug::fmt(&v, f)
}
}
impl<T> Drop for AchOption<T> {
fn drop(&mut self) {
let _ = self.take();
}
}