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//! # Allocate
/// # Initialize Queue
/// - Name: Symbol name
/// - Size: Number of elements
/// - Default: Default value
/// - Type: Data Type
macro_rules! init_queue {
($name:tt,$size:tt,$default:tt,$type:ty) => {
init_queue!{@gen [$name,$size,$default,$type,concat!("# ", stringify!($type), " Queue Allocator")]}
};
(@gen [$name:tt,$size:tt,$default:tt,$type:ty,$doc:expr]) => {
#[doc = $doc]
#[link_section = ".data.alloc"]
pub static $name: QueueAllocator<'static, $type, {$size+2}> = QueueAllocator::<$type, {$size+2}>{inner: NullLock::new([QueueItem{data: $default, next: None}; {$size+2}])};
};
}
use crate::sync::NullLock;
use crate::sync::interface::Mutex;
use core::fmt::{Debug,Formatter,Result};
#[derive(Copy,Clone)]
/// # Queue Item
///
/// Encapsulates a data element and a pointer to
/// the next `Queue` item
pub struct QueueItem<'a, T: Sized> {
/// # Data
///
/// The encapsulated data
data: T,
/// # Pointer to the next item
///
/// Stores either `None` or points
/// to the next item.
next: Option<*mut QueueItem<'a, T>>,
}
impl<T> QueueItem<'_,T> {
/// # Get the inner data
///
/// Returns a borrow of the underlying data.
pub fn inner(&mut self) -> &mut T {
&mut self.data
}
}
/// # Sharing Thread Safety for QueueItem
unsafe impl<T> Send for QueueItem<'_,T> {}
impl<T: Debug> Debug for QueueItem<'_,T> {
/// # Debug formatter for `QueueItem`
///
/// Output the encapsulated data
fn fmt(&self, f: &mut Formatter<'_>) -> Result {
write!(f, "{:?}", self.data)
}
}
/// # Queue Allocator
///
/// Structure to store a pool of allocated data structures.
pub struct QueueAllocator<'a, T: Sized, const COUNT: usize> {
/// # Synchronized Pool of items
///
/// Stores synchronization wrapper around the data pool
pub inner: NullLock<[QueueItem<'a, T>;COUNT]>,
}
/// # Sharing Thread Safety for QueueAllocator
unsafe impl<T,const COUNT: usize> Send for QueueAllocator<'_,T,COUNT> {}
impl<'a, T: Sized,const COUNT: usize> QueueAllocator<'a, T, COUNT> {
/// # Initialization of Fixed-Size Pool
///
/// Establishes the header and footer of the queue
/// as the first and second elements respectively.
/// All of the internal elements point to the next
/// one and the final element points to `None`
pub fn init(&self) {
self.inner.lock(|queue| {
for idx in 2..queue.len() {
if idx != queue.len()-1 {
queue[idx].next = Some(&mut queue[idx+1] as *mut QueueItem<'_, T>);
} else {
queue[idx].next = None;
}
}
queue[0].next = Some(&mut queue[2] as *mut QueueItem<'_, T>);
queue[1].next = Some(&mut queue[queue.len()-1] as *mut QueueItem<'_, T>);
});
}
/// # Allocate Data
///
/// If there is a data chunk available,
/// return it, otherwise return `None`
#[allow(dead_code)]
pub fn alloc(&self) -> Option<&mut QueueItem<'a,T>> {
return self.inner.lock(|pool| {
if let Some(entry) = pool[0].next {
pool[0].next = unsafe { (*entry).next };
unsafe {
(*entry).next = None;
}
match pool[0].next {
None => {
pool[1].next = None
}
_ => {}
}
return Some(unsafe{&mut *entry as &mut QueueItem<'a,T>});
} else {
return None;
}
});
}
/// # Free
///
/// Add the item to the end of the queue.
/// If there were no items, set it as the head.
#[allow(dead_code)]
pub fn free(&self, freed_item: &mut QueueItem<'a,T>) {
self.inner.lock(|pool| {
freed_item.next = None;
match pool[1].next {
None => {
pool[0].next = Some(freed_item as *mut QueueItem<'a,T>);
}
Some(entry) => {
unsafe {
if (entry as u32) == (freed_item as *mut QueueItem<'a,T> as u32) {
(*entry).next = Some(freed_item as *mut QueueItem<'a,T>);
}
}
}
}
pool[1].next = Some(freed_item as *mut QueueItem<'a,T>);
});
}
}
impl<T: Debug,const COUNT: usize> Debug for QueueAllocator<'_,T,COUNT> {
/// # Debug Formatted Output
///
/// Output each data point in the array with
/// its debug formatter.
fn fmt(&self, f: &mut Formatter<'_>) -> Result {
self.inner.lock(|queue| {
write!(f, "{:?}", queue)
})
}
}
/// Number of U64s to hand out
const U64_POOL_SIZE: usize = 2;
init_queue!(U64_QUEUE_ALLOCATOR, U64_POOL_SIZE, 0, u64);
|
