1 files changed, 40 insertions, 0 deletions
diff --git a/libcr_ipc/chan.c b/libcr_ipc/chan.c
new file mode 100644
index 0000000..7dd1132
--- /dev/null
+++ b/libcr_ipc/chan.c
@@ -0,0 +1,40 @@
+/* libcr_ipc/chan.c - Simple channels for libcr
+ *
+ * Copyright (C) 2024-2025  Luke T. Shumaker <lukeshu@lukeshu.com>
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+#include <libcr_ipc/chan.h>
+
+void _cr_chan_dequeue(void *_ch, size_t) {
+	struct _cr_chan *ch = _ch;
+	_cr_ipc_dll_pop_from_front(&ch->waiters);
+}
+
+void _cr_chan_xfer(enum _cr_chan_waiter_typ self_typ, struct _cr_chan *ch, void *val_ptr, size_t val_size) {
+	assert(ch);
+	assert(val_ptr);
+
+	if (ch->waiters.front && ch->waiter_typ != self_typ) { /* non-blocking fast-path */
+		/* Copy.  */
+		struct _cr_chan_waiter *front = _cr_ipc_dll_node_cast(struct _cr_chan_waiter, ch->waiters.front);
+		if (self_typ == _CR_CHAN_SENDER)
+			memcpy(front->val_ptr, val_ptr, val_size);
+		else
+			memcpy(val_ptr, front->val_ptr, val_size);
+		cr_unpause(front->cid);
+		front->dequeue(front->dequeue_arg1,
+		               front->dequeue_arg2);
+		cr_yield();
+	} else { /* blocking slow-path */
+		struct _cr_chan_waiter self = {
+			.cid          = cr_getcid(),
+			.val_ptr      = val_ptr,
+			.dequeue      = _cr_chan_dequeue,
+			.dequeue_arg1 = ch,
+		};
+		_cr_ipc_dll_push_to_rear(&ch->waiters, &self);
+		ch->waiter_typ = self_typ;
+		cr_pause_and_yield();
+	}
+}