From a2a652e521c12c28a0cc7b397216b78804b1142a Mon Sep 17 00:00:00 2001
From: Drew DeVault <sir@cmpwn.com>
Date: Wed, 19 May 2021 15:37:56 -0400
Subject: [PATCH] linux::io_uring: timeout operations

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

---
 io_uring/cqe.ha   | 12 ++++++++++--
 io_uring/sqe.ha   | 46 +++++++++++++++++++++++++++++++++++++++++++++-
 io_uring/uring.ha |  8 +++++++-

diff --git a/io_uring/cqe.ha b/io_uring/cqe.ha
index 9705b4ba94ba6b4da50fe33bd1318d8b0eab81e8..0f5b7d5df6fe93aaa0cb611f2e4d3c8f8e059eba 100644
--- a/io_uring/cqe.ha
+++ b/io_uring/cqe.ha
@@ -28,8 +28,16 @@ // queue.
 export fn peek(ring: *io_uring) (nullable *cqe | error) = get_cqe(ring, 0, 0);
 
 // Returns the result of a [[cqe]], or an error if unsuccessful.
-export fn result(cqe: *cqe) (int | error) =
-	if (cqe.res < 0) rt::wrap_errno(-cqe.res) else cqe.res;
+export fn result(cqe: *cqe) (int | error) = {
+	// TODO: Flesh out more errors
+	return if (cqe.res < 0) switch (-cqe.res) {
+		rt::ETIME => errors::timeout,
+		rt::ECANCELED => errors::cancelled,
+		* => errors::errno(rt::wrap_errno(-cqe.res)),
+	} else {
+		cqe.res;
+	};
+};
 
 // Gets the user data field of a [[cqe]]. See [[set_user]] for the corresponding
 // SQE function.
diff --git a/io_uring/sqe.ha b/io_uring/sqe.ha
index 6d47f8c5291ed49e0a155cb42724a3b2843364a7..975f71e49db23dd77ae09f1e6cca46ae62207b2f 100644
--- a/io_uring/sqe.ha
+++ b/io_uring/sqe.ha
@@ -148,7 +148,8 @@ 	assert(endian::host == &endian::little); // TODO?
 	sqe.poll32_events = poll_mask: u32;
 };
 
-// Removes an existing poll request by matching the SQE's user_data field.
+// Removes an existing poll request by matching the SQE's user_data field. See
+// [[setuser]].
 export fn poll_remove(sqe: *sqe, user_data: *void, flags: sqe_flags...) void = {
 	preprw(sqe, op::POLL_REMOVE, -1, null, 0, 0, flags...);
 	set_user(sqe, user_data);
@@ -209,3 +210,46 @@ 	assert(count <= types::U32_MAX);
 	preprw(sqe, op::RECV, fd, buf, count: u32, 0, flags...);
 	sqe.msg_flags = recv_flags;
 };
+
+// Prepares a timeout operation for an [[sqe]]. "ts" should be a timespec
+// describing the desired timeout, and "events" may optionally be used to define
+// a number of completion events to wake after (or zero to wake only after the
+// timeout expires). The caller must call [[setuser]] to provide a user data
+// field in order to use [[timeout_remove]] to cancel this timeout later.
+export fn timeout(
+	sqe: *sqe,
+	ts: *rt::timespec,
+	events: uint,
+	to_flags: timeout_flags,
+	flags: sqe_flags...
+) void = {
+	preprw(sqe, op::TIMEOUT, 0, ts, 1, events, flags...);
+	sqe.timeout_flags = to_flags;
+};
+
+// Removes an existing timeout request by matching the SQE's user_data field.
+// See [[setuser]].
+export fn timeout_remove(
+	sqe: *sqe,
+	user_data: *void,
+	to_flags: timeout_flags,
+	flags: sqe_flags...
+) void = {
+	preprw(sqe, op::TIMEOUT_REMOVE, 0, user_data, 0, 0, flags...);
+	sqe.timeout_flags = to_flags;
+};
+
+// Updates an existing timeout request by matching the SQE's user_data field.
+// See [[setuser]].
+export fn timeout_update(
+	sqe: *sqe,
+	user_data: *void,
+	ts: *rt::timespec,
+	events: uint,
+	to_flags: timeout_flags,
+	flags: sqe_flags...
+) void = {
+	preprw(sqe, op::TIMEOUT_REMOVE, 0, user_data, 0, events, flags...);
+	sqe.timeout_flags = to_flags | timeout_flags::UPDATE;
+	sqe.addr2 = ts;
+};
diff --git a/io_uring/uring.ha b/io_uring/uring.ha
index e6e7441f3cbd4dea81ac27fe91f7c825fe954df8..fec9360cd4afb006f9670b13d4c09ef926d02584 100644
--- a/io_uring/uring.ha
+++ b/io_uring/uring.ha
@@ -1,7 +1,7 @@
 use errors;
 
 // All errors which may be returned by this module.
-export type error = errors::opaque;
+export type error = (errors::timeout | errors::cancelled | errors::opaque);
 
 // Converts an [[error]] into a human-readable string.
 export fn strerror(err: error) const str = {
@@ -77,7 +77,13 @@ };
 
 // Flags for a timeout operation.
 export type timeout_flags = enum u32 {
+	// If set, the timeout will be "absolute", waiting until CLOCK_MONOTONIC
+	// reaches the time defined by the timespec. If unset, it will be
+	// interpted as a duration relative to the I/O submission.
 	ABS = 1 << 0,
+	// When combined with [[op::TIMEOUT_REMOVE]], causes the submission to
+	// update the timer rather than remove it.
+	UPDATE = 1 << 1,
 };
 
 // Flags for a splice operation.

-- 
2.48.1