From 2006536959fb2c5580b8cb14d0dfc8b5710c1559 Mon Sep 17 00:00:00 2001
From: Drew DeVault <sir@cmpwn.com>
Date: Tue, 18 May 2021 18:11:46 -0400
Subject: [PATCH] linux::io_uring: add CQE-related functions

Signed-off-by: Drew DeVault <sir@cmpwn.com>

---
 io_uring/queue.ha | 30 ++++++++++++++++++++++++++++--

diff --git a/io_uring/queue.ha b/io_uring/queue.ha
index 1df8a71d816739eaadbc10ab995622a8400903d7..db43998643dab79581a255a1f75748b328b0877b 100644
--- a/io_uring/queue.ha
+++ b/io_uring/queue.ha
@@ -82,6 +82,32 @@ 		return submitted;
 	};
 };
 
+// Advances the completion queue by N items.
+export fn cq_advance(ring: *io_uring, n: uint) void = {
+	*ring.cq.khead = *ring.cq.khead + n;
+};
+
+// Call after processing a [[cqe]]. The cqe is returned to the pool and cannot
+// be used by the application again.
+export fn cqe_seen(ring: *io_uring, cqe: *cqe) void = cq_advance(ring, 1);
+
+// Waits until a CQE is available, then returns it. The caller must pass the
+// returned CQE to [[cqe_seen]] to advance the queue.
+export fn wait(ring: *io_uring) (*cqe | error) = {
+	return match (get_cqe(ring, 0, 1)) {
+		err: error => err,
+		cq: nullable *cqe => {
+			assert(cq != null); // XXX: Correct?
+			cq: *cqe;
+		},
+	};
+};
+
+// Peeks the next CQE from the queue and returns it, or null if none are
+// pending. The caller must pass the returned CQE to [[cqe_seen]] to advance the
+// queue.
+export fn peek(ring: *io_uring) (nullable *cqe | error) = get_cqe(ring, 0, 0);
+
 fn peek_cqe(ring: *io_uring) (nullable *cqe, uint) = {
 	let head = *ring.cq.khead;
 	let tail = *ring.cq.ktail;
@@ -93,11 +119,11 @@ 	};
 	return (&ring.cq.cqes[head & mask], avail);
 };
 
-export fn get_cqe(
+fn get_cqe(
 	ring: *io_uring,
 	submit: uint,
 	wait: uint,
-) (nullable *cqe | errors::opaque) = {
+) (nullable *cqe | error) = {
 	let cq: nullable *cqe = null;
 	for (cq == null) {
 		let enter = false, overflow = false;

-- 
2.48.1