1 files changed, 68 insertions, 0 deletions
diff --git a/libcr_ipc/waitgroup.c b/libcr_ipc/waitgroup.c
new file mode 100644
index 0000000..e76db01
--- /dev/null
+++ b/libcr_ipc/waitgroup.c
@@ -0,0 +1,68 @@
+/* libcr_ipc/waitgroup.c - Go-like WaitGroups for libcr
+ *
+ * Copyright (C) 2025  Luke T. Shumaker <lukeshu@lukeshu.com>
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+#include <libcr/coroutine.h> /* for cid_t, cr_* */
+
+#define IMPLEMENTATION_FOR_LIBCR_IPC_WAITGROUP_H YES
+#include <libcr_ipc/waitgroup.h>
+
+#include "_linkedlist.h"
+
+struct cr_waitgroup_waiter {
+	cr_ipc_sll_node;
+	cid_t                    cid;
+};
+
+void cr_waitgroup_wait(cr_waitgroup_t *wg) {
+	assert(wg);
+	cr_assert_in_coroutine();
+
+	struct cr_waitgroup_waiter self = {
+		.cid = cr_getcid(),
+	};
+	cr_ipc_sll_push_to_rear(&wg->waiters, &self);
+	if (wg->waiters.front != &self.cr_ipc_sll_node || wg->count > 0)
+		cr_pause_and_yield();
+	assert(wg->waiters.front == &self.cr_ipc_sll_node);
+
+	cr_ipc_sll_pop_from_front(&wg->waiters);
+	if (wg->waiters.front) {
+		assert(wg->unpausing);
+		cr_unpause(cr_ipc_sll_node_cast(struct cr_waitgroup_waiter, wg->waiters.front)->cid);
+	} else {
+		wg->unpausing = false;
+	}
+}
+
+void cr_waitgroup_add(cr_waitgroup_t *wg, int delta) {
+	assert(wg);
+	cr_assert_in_coroutine();
+
+	if (delta == 0)
+		return;
+	bool saved = cr_save_and_disable_interrupts();
+	wg->count += delta;
+	assert(wg->count >= 0);
+	if (wg->count == 0 && !wg->unpausing && wg->waiters.front) {
+		wg->unpausing = true;
+		cr_unpause(cr_ipc_sll_node_cast(struct cr_waitgroup_waiter, wg->waiters.front)->cid);
+	}
+	cr_restore_interrupts(saved);
+}
+
+void cr_waitgroup_add_from_intrhandler(cr_waitgroup_t *wg, int delta) {
+	assert(wg);
+	cr_assert_in_intrhandler();
+
+	if (delta == 0)
+		return;
+	wg->count += delta;
+	assert(wg->count >= 0);
+	if (wg->count == 0 && !wg->unpausing && wg->waiters.front) {
+		wg->unpausing = true;
+		cr_unpause_from_intrhandler(cr_ipc_sll_node_cast(struct cr_waitgroup_waiter, wg->waiters.front)->cid);
+	}
+}