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use std::future::Future;
use std::io;
use std::pin::Pin;
use std::task::{Poll, Context};
use std::thread;
use futures_core::ready;
use once_cell::sync::Lazy;
use parking_lot::Mutex;
const SQ_ENTRIES: u32 = 32;
const CQ_ENTRIES: usize = (SQ_ENTRIES * 2) as usize;
use access_queue::*;
use super::{Drive, Completion};
static SQ: Lazy<AccessQueue<Mutex<iou::SubmissionQueue<'static>>>> = Lazy::new(init_sq);
pub struct DemoDriver<'a> {
sq: Access<'a, Mutex<iou::SubmissionQueue<'static>>>,
}
impl Default for DemoDriver<'_> {
fn default() -> Self {
driver()
}
}
impl Drive for DemoDriver<'_> {
fn poll_prepare<'cx>(
mut self: Pin<&mut Self>,
ctx: &mut Context<'cx>,
prepare: impl FnOnce(iou::SubmissionQueueEvent<'_>, &mut Context<'cx>) -> Completion<'cx>,
) -> Poll<Completion<'cx>> {
let access = ready!(Pin::new(&mut self.sq).poll(ctx));
let (sq, access) = access.hold_and_reenqueue();
self.sq = access;
let mut sq = sq.lock();
loop {
match sq.next_sqe() {
Some(sqe) => return Poll::Ready(prepare(sqe, ctx)),
None => { let _ = sq.submit(); }
}
}
}
fn poll_submit(
self: Pin<&mut Self>,
_: &mut Context<'_>,
eager: bool,
) -> Poll<io::Result<usize>> {
let result = if eager {
self.sq.skip_queue().lock().submit()
} else {
Ok(0)
};
Poll::Ready(result)
}
}
pub fn driver() -> DemoDriver<'static> {
DemoDriver { sq: SQ.access() }
}
fn init_sq() -> AccessQueue<Mutex<iou::SubmissionQueue<'static>>> {
unsafe {
static mut RING: Option<iou::IoUring> = None;
RING = Some(iou::IoUring::new(SQ_ENTRIES).expect("TODO handle io_uring_init failure"));
let (sq, cq, _) = RING.as_mut().unwrap().queues();
thread::spawn(move || complete(cq));
AccessQueue::new(Mutex::new(sq), CQ_ENTRIES)
}
}
unsafe fn complete(mut cq: iou::CompletionQueue<'static>) {
while let Ok(cqe) = cq.wait_for_cqe() {
let mut ready = cq.ready() as usize + 1;
SQ.release(ready);
super::complete(cqe);
ready -= 1;
while let Some(cqe) = cq.peek_for_cqe() {
if ready == 0 {
ready = cq.ready() as usize + 1;
SQ.release(ready);
}
super::complete(cqe);
ready -= 1;
}
debug_assert!(ready == 0);
}
}