hare

commit db8164f92e9de3d54b92e4cc85c80151ac25770f
parent 725c6c8fc05b8883f30da4580f416711498992a3
Author: Drew DeVault <sir@cmpwn.com>
Date:   Tue, 19 Oct 2021 15:29:19 +0200

iobus: implement chain and serialize functions

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

Diffstat:
M
iobus/io_uring/handle.ha
 | 
29
+++++++++++++++++++++++++++++

1 file changed, 29 insertions(+), 0 deletions(-)
diff --git a/iobus/io_uring/handle.ha b/iobus/io_uring/handle.ha
@@ -27,3 +27,32 @@ export fn done(bus: *bus, res: result) void = {
 	free(handle.callbacks);
 	io_uring::cqe_seen(&bus.uring, res);
 };
+
+// Causes a series of I/O handles to be executed serially, waiting for the Nth
+// to complete before starting the N+1th. If any of the I/O operations fail, all
+// subsequent I/O handles in the chain will be cancelled, returning
+// [[errors::cancelled]]. A short read or write (including [[io::EOF]]) is
+// considered a failure for this purpose.
+//
+// All of the I/O handles must be provided as parameters in the order that they
+// were created, and must form a continuous sequence of I/O handles as obtained
+// from this bus. Discontinuous sequences are not permitted, such that 'h1 =
+// read(); h2 = read(); h3 = read(); serial(h1, h3)' is invalid. This function
+// must be called prior to any of the handles being submitted to the bus.
+export fn chain(items: *handle...) void = {
+	// TODO: Add assertions to enforce the constraints of this function
+	for (let i = 0z; i < len(items) - 1; i += 1) {
+		items[i].sqe.flags |= io_uring::flags::IO_LINK;
+	};
+};
+
+// Serialize behaves similarly to [[chain]], except that an error in I/O
+// execution does not cause the remainder of the chain to be cancelled. However,
+// a poorly formed I/O submission (such as for an invalid file handle) will
+// still cause the chain to be cancelled.
+export fn serialize(items: *handle...) void = {
+	// TODO: Add assertions to enforce the constraints of this function
+	for (let i = 0z; i < len(items) - 1; i += 1) {
+		items[i].sqe.flags |= io_uring::flags::IO_HARDLINK;
+	};
+};