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use core::marker::{PhantomData, Unsize};
use core::ptr::{self, Shared};
use BufferFullError;
use ring_buffer::RingBuffer;
impl<T, A> RingBuffer<T, A>
where
A: Unsize<[T]>,
{
pub fn split(&mut self) -> (Producer<T, A>, Consumer<T, A>) {
(
Producer {
rb: unsafe { Shared::new_unchecked(self) },
_marker: PhantomData,
},
Consumer {
rb: unsafe { Shared::new_unchecked(self) },
_marker: PhantomData,
},
)
}
}
pub struct Consumer<'a, T, A>
where
A: Unsize<[T]>,
{
rb: Shared<RingBuffer<T, A>>,
_marker: PhantomData<&'a ()>,
}
impl<'a, T, A> Consumer<'a, T, A>
where
A: Unsize<[T]>,
{
pub fn dequeue(&mut self) -> Option<T> {
let rb = unsafe { self.rb.as_ref() };
let n = rb.capacity() + 1;
let buffer: &[T] = unsafe { rb.buffer.as_ref() };
let tail = rb.tail.load_acquire();
let head = rb.head.load_relaxed();
if head != tail {
let item = unsafe { ptr::read(buffer.get_unchecked(head)) };
rb.head.store_release((head + 1) % n);
Some(item)
} else {
None
}
}
}
unsafe impl<'a, T, A> Send for Consumer<'a, T, A>
where
A: Unsize<[T]>,
T: Send,
{
}
pub struct Producer<'a, T, A>
where
A: Unsize<[T]>,
{
rb: Shared<RingBuffer<T, A>>,
_marker: PhantomData<&'a ()>,
}
impl<'a, T, A> Producer<'a, T, A>
where
A: Unsize<[T]>,
{
pub fn enqueue(&mut self, item: T) -> Result<(), BufferFullError> {
let rb = unsafe { self.rb.as_mut() };
let n = rb.capacity() + 1;
let buffer: &mut [T] = unsafe { rb.buffer.as_mut() };
let tail = rb.tail.load_relaxed();
let head = rb.head.load_acquire();
let next_tail = (tail + 1) % n;
if next_tail != head {
unsafe { ptr::write(buffer.get_unchecked_mut(tail), item) }
rb.tail.store_release(next_tail);
Ok(())
} else {
Err(BufferFullError)
}
}
}
unsafe impl<'a, T, A> Send for Producer<'a, T, A>
where
A: Unsize<[T]>,
T: Send,
{
}
#[cfg(test)]
mod tests {
use RingBuffer;
#[test]
fn sanity() {
static mut RB: RingBuffer<i32, [i32; 2]> = RingBuffer::new();
let (mut p, mut c) = unsafe { RB.split() };
assert_eq!(c.dequeue(), None);
p.enqueue(0).unwrap();
assert_eq!(c.dequeue(), Some(0));
}
}