From 7f80dcbeb09f4dd743cdccfb2cfed10bfdeb07ab Mon Sep 17 00:00:00 2001
From: Willow Barraco <contact@willowbarraco.fr>
Date: Fri, 13 Dec 2024 14:47:33 +0100
Subject: [PATCH] Controll concurrent events priority

This new file.prio parameter give some control to the user over
concurrent events.

Say that a timer expires, but a concurrent event would re-arm it, the
user have no way to predict if the timer callback will trigger.

Signed-off-by: Willow Barraco <contact@willowbarraco.fr>

---
 ev/+linux/file.ha | 22 ++++++++++++++++++++++
 ev/+linux/loop.ha |  3 +++

diff --git a/ev/+linux/file.ha b/ev/+linux/file.ha
index e79e35fa4a0892f71f30064ebdce8902ba85c8f9..b412408490d25c806f7a54d36cf5a3a99fc33155 100644
--- a/ev/+linux/file.ha
+++ b/ev/+linux/file.ha
@@ -38,6 +38,8 @@ 	cb: nullable *opaque,
 	cb2: nullable *opaque,
 	user: nullable *opaque,
 
+	prio: int,
+
 	// Operation-specific data
 	union {
 		struct {
@@ -151,6 +153,26 @@
 // Returns the event loop for a given file.
 export fn getloop(file: *file) *loop = {
 	return file.ev;
+};
+
+// Sets the priority on this file object. Used to priorize concurrent events,
+// starting on the next dispatch. The lowest run first.
+export fn setprio(file: *file, prio: int) void = {
+	file.prio = prio;
+};
+
+fn sort_events(a: const *opaque, b: const *opaque) int = {
+	const a = a: *rt::epoll_event;
+	const b = b: *rt::epoll_event;
+
+	if (a.data.fd == 0 || b.data.fd == 0) {
+		return 0;
+	};
+
+	const a = a.data.ptr: *file;
+	const b = b.data.ptr: *file;
+
+	return a.prio - b.prio;
 };
 
 // Updates epoll events for a given file. For internal use.
diff --git a/ev/+linux/loop.ha b/ev/+linux/loop.ha
index 98ff45a9033d908eb041a133a1e83665a8253b44..145273adf7db6f9b7949c5e73cef130ec32b5e75 100644
--- a/ev/+linux/loop.ha
+++ b/ev/+linux/loop.ha
@@ -1,6 +1,7 @@
 use errors;
 use io;
 use rt;
+use sort;
 use time;
 use types;
 use unix::signal;
@@ -151,6 +152,8 @@
 	if (nevent == 0) {
 		return true;
 	};
+
+	sort::sort(loop.events[..nevent], size(rt::epoll_event), &sort_events);
 
 	for (let ev &.. loop.events[..nevent]) {
 		const file = ev.data.ptr: *file;

-- 
2.48.1