Merge branch 'lukeshu/misc'

1 files changed, 102 insertions, 0 deletions

diff --git a/libcr_ipc/select.c b/libcr_ipc/select.c
new file mode 100644
index 0000000..4bd9067
--- /dev/null
+++ b/libcr_ipc/select.c
@@ -0,0 +1,102 @@
+/* libcr_ipc/select.c - Select between channels
+ *
+ * Copyright (C) 2024-2025  Luke T. Shumaker <lukeshu@lukeshu.com>
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+#include <libcr_ipc/select.h>
+
+static inline enum _cr_select_class _cr_select_getclass(struct cr_select_arg arg) {
+	switch (arg.op) {
+	case _CR_SELECT_OP_RECV:
+		if (arg.ch->waiters.front && arg.ch->waiter_typ == _CR_CHAN_SENDER)
+			return _CR_SELECT_CLASS_NONBLOCK;
+		else
+			return _CR_SELECT_CLASS_BLOCKING;
+	case _CR_SELECT_OP_SEND:
+		if (arg.ch->waiters.front && arg.ch->waiter_typ == _CR_CHAN_RECVER)
+			return _CR_SELECT_CLASS_NONBLOCK;
+		else
+			return _CR_SELECT_CLASS_BLOCKING;
+	case _CR_SELECT_OP_DEFAULT:
+		return _CR_SELECT_CLASS_DEFAULT;
+	default:
+		assert_notreached("invalid arg.op");
+	}
+}
+
+void _cr_select_dequeue(void *_waiters, size_t idx) {
+	struct _cr_select_waiters *waiters = _waiters;
+	for (size_t i = 0; i < waiters->cnt; i++)
+		_cr_ipc_dll_remove(&(waiters->args[i].ch->waiters),
+		                   &(waiters->nodes[i]));
+	waiters->cnt = idx;
+}
+
+size_t cr_select_v(size_t arg_cnt, struct cr_select_arg arg_vec[]) {
+	size_t  cnt_blocking = 0;
+	size_t  cnt_nonblock = 0;
+	size_t  cnt_default  = 0;
+
+	assert(arg_cnt);
+	assert(arg_vec);
+	cr_assert_in_coroutine();
+
+	for (size_t i = 0; i < arg_cnt; i++) {
+		switch (_cr_select_getclass(arg_vec[i])) {
+		case _CR_SELECT_CLASS_BLOCKING:
+			cnt_blocking++;
+			break;
+		case _CR_SELECT_CLASS_NONBLOCK:
+			cnt_nonblock++;
+			break;
+		case _CR_SELECT_CLASS_DEFAULT:
+			cnt_default++;
+			break;
+		}
+	}
+
+	if (cnt_nonblock) {
+		size_t choice = rand_uint63n(cnt_nonblock);
+		for (size_t i = 0, seen = 0; i < arg_cnt; i++) {
+			if (_cr_select_getclass(arg_vec[i]) == _CR_SELECT_CLASS_NONBLOCK) {
+				if (seen == choice) {
+					_cr_chan_xfer(arg_vec[i].op == _CR_SELECT_OP_RECV
+					              ? _CR_CHAN_RECVER
+					              : _CR_CHAN_SENDER,
+					              arg_vec[i].ch,
+					              arg_vec[i].val_ptr,
+					              arg_vec[i].val_siz);
+					return i;
+				}
+				seen++;
+			}
+		}
+		assert_notreached("should have returned from inside for() loop");
+	}
+
+	if (cnt_default) {
+		for (size_t i = 0; i < arg_cnt; i++)
+			if (_cr_select_getclass(arg_vec[i]) == _CR_SELECT_CLASS_DEFAULT)
+				return i;
+		assert_notreached("should have returned from inside for() loop");
+	}
+
+	struct _cr_select_waiters waiters = {
+		.cnt   = arg_cnt,
+		.args  = arg_vec,
+		.nodes = alloca(sizeof(struct _cr_chan_waiter) * arg_cnt),
+	};
+	for (size_t i = 0; i < arg_cnt; i++) {
+		waiters.nodes[i] = (struct _cr_chan_waiter){
+			.cid          = cr_getcid(),
+			.val_ptr      = arg_vec[i].val_ptr,
+			.dequeue      = _cr_select_dequeue,
+			.dequeue_arg1 = &waiters,
+			.dequeue_arg2 = i,
+		};
+		_cr_ipc_dll_push_to_rear(&arg_vec[i].ch->waiters, &waiters.nodes[i]);
+	}
+	cr_pause_and_yield();
+	return waiters.cnt;
+}