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//! # Synchronization module
//!
//! Provides synchronization objects for thread-safe memory sharing.
use core::cell::UnsafeCell;
use core::marker::{Send, Sized, Sync};
use core::ops::FnOnce;
/// # Synchronization interfaces
///
/// Provides Synchronization traits.
pub mod interface {
use core::ops::FnOnce;
/// # Mutex Trait
///
/// Basic Locking primitive to allow single-process access to data
pub trait Mutex {
/// # The data
///
/// Each mutex protects some internal data from modification across
/// processes when it is in use. This is important if the process
/// is preempted while the function is using it.
type Data;
/// # Locking mechanism
///
/// Locks the mutex to access the data in a closure.
/// The data can be read and modified in this closure without worry
/// of poisoning the data across processes.
fn lock<'a, R>(&'a self, f: impl FnOnce(&'a mut Self::Data) -> R) -> R;
}
/// # Initializable
///
/// Initializable type
pub trait Initializable {
/// # Initialize structure
fn init(&mut self);
}
}
/// # Basic Lock Structure
pub struct NullLock<T>
where
T: ?Sized,
{
/// The internal data to safely share
data: UnsafeCell<T>,
}
/// # Allow thread sharing
unsafe impl<T> Send for NullLock<T> where T: ?Sized + Send {}
/// # Allow thread sharing
unsafe impl<T> Sync for NullLock<T> where T: ?Sized + Send {}
impl<T> NullLock<T> {
/// # Create a new instance of the lock
pub const fn new(data: T) -> Self {
Self {
data: UnsafeCell::new(data),
}
}
}
impl<T: interface::Initializable> NullLock<T> {
/// # Initialize NullLock
pub fn init(&self) {
use interface::Mutex;
self.lock(|initializable| {
initializable.init();
});
}
}
impl<T> interface::Mutex for NullLock<T> {
/// # Underlying data of the lock
type Data = T;
/// # Locking mechanism
///
/// Locks the Mutex, and passes a mutable reference
/// to the encapsulated data to a closure.
fn lock<'a, R>(&'a self, f: impl FnOnce(&'a mut T) -> R) -> R {
let data = unsafe { &mut *self.data.get() };
f(data)
}
}
use core::sync::atomic::{AtomicBool, Ordering};
/// # Spinlock
pub struct SpinLock<T>
where
T: Sized,
{
data: UnsafeCell<T>,
lock: AtomicBool,
}
unsafe impl<T> Send for SpinLock<T> where T: Sized + Send {}
unsafe impl<T> Sync for SpinLock<T> where T: Sized + Send {}
impl<T> SpinLock<T> {
/// # New lock
pub const fn new(data: T) -> Self {
Self {
data: UnsafeCell::new(data),
lock: AtomicBool::new(false),
}
}
}
impl<T: interface::Initializable> SpinLock<T> {
/// # Init
pub fn init(&self) {
use interface::Mutex;
self.lock(|init| {
init.init();
});
}
}
impl<T> interface::Mutex for SpinLock<T> {
/// # Data type
type Data = T;
/// # Lock
fn lock<'a, R>(&'a self, f: impl FnOnce(&'a mut T) -> R) -> R {
while let false = self.lock.swap(true, Ordering::SeqCst) {}
let data = unsafe { &mut *self.data.get() };
let res = f(data);
// Release the lock after finished with the underlying data
self.lock.store(false, Ordering::SeqCst);
res
}
}
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