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//! # FIFO Queue
//!
//! Provides the FIFO queue structure for allocations
use crate::sync::NullLock;
use crate::sync::interface::Mutex;
use crate::util::node::*;
use core::fmt;
use core::fmt::{Debug,Formatter};
/// # Initialize Queue
/// - Name: Symbol name
/// - Size: Number of elements
/// - Default: Default value
/// - Type: Data Type
#[macro_export]
macro_rules! init_fifo_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: FifoQueue<'static, $type, {$size+1}> = FifoQueue::new(NullLock::new([Node::new($default); {$size+1}]));
};
}
/// # Queue Allocator
///
/// Structure to store a pool of allocated data structures.
pub struct FifoQueue<'a, T: Sized, const COUNT: usize> {
/// # Synchronized Pool of items
///
/// Stores synchronization wrapper around the data pool
pub inner: NullLock<[Node<'a, T>;COUNT]>,
}
impl<'a, T: Sized, const COUNT: usize> FifoQueue<'a, T, COUNT> {
/// # Create new Fifo Queue
pub const fn new(initial: NullLock<[Node<'a, T>; COUNT]>) -> Self {
Self { inner: initial }
}
}
/// # Sharing Thread Safety for FifoQueue
unsafe impl<T,const COUNT: usize> Send for FifoQueue<'_,T,COUNT> {}
impl<'a, T: Sized,const COUNT: usize> FifoQueue<'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..COUNT {
if idx != COUNT-1 {
queue[idx].next = Some(&mut queue[idx+1] as *mut Node<'a, T>);
} else {
queue[idx].next = None;
}
}
queue[0].next = Some(&mut queue[2] as *mut Node<'a, T>);
queue[1].next = Some(&mut queue[COUNT-1] as *mut Node<'a, T>);
});
}
/// # Allocate Data
///
/// If there is a data chunk available,
/// return it, otherwise return `None`
#[allow(dead_code)]
pub fn alloc(&self) -> Option<&mut Node<'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 Node<'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 Node<'a,T>) {
self.inner.lock(|pool| {
freed_item.next = None;
match pool[1].next {
None => {
pool[0].next = Some(freed_item as *mut Node<'a,T>);
}
Some(entry) => {
unsafe {
(*entry).next = Some(freed_item as *mut Node<'a,T>);
}
}
}
pool[1].next = Some(freed_item as *mut Node<'a,T>);
});
}
}
impl<T: Debug,const COUNT: usize> Debug for FifoQueue<'_,T,COUNT> {
/// # Debug Formatted Output
///
/// Output each data point in the array with
/// its debug formatter.
fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
self.inner.lock(|queue| {
return write!(f, "{:?}", queue);
})
}
}
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