Initial community commit

Src/replicant/nu/lfmpscq.c

@@ -0,0 +1,50 @@
+#include "lfmpscq.h"
+#include "foundation/atomics.h"
+
+void mpscq_init(mpscq_t* self)
+{
+	self->head = &self->stub;
+	self->tail = &self->stub;
+	self->stub.Next = 0;
+}
+
+int mpscq_push(mpscq_t *self, queue_node_t *n)
+{
+	queue_node_t *prev;
+	n->Next = 0;
+	prev = nx_atomic_swap_pointer(n, (void * volatile *)&self->head);
+	//(*)
+	prev->Next = n;
+	return prev!=&self->stub;
+}
+
+queue_node_t *mpscq_pop(mpscq_t *self)
+{
+	queue_node_t* tail = self->tail;
+	queue_node_t* next = tail->Next;
+	queue_node_t* head;
+	if (tail == &self->stub)
+	{
+		if (0 == next)
+			return 0;
+		self->tail = next;
+		tail = next;
+		next = next->Next;
+	}
+	if (next)
+	{
+		self->tail = next;
+		return tail;
+	}
+	head = self->head;
+	if (tail != head)
+		return (queue_node_t *)1;
+	mpscq_push(self, &self->stub);
+	next = tail->Next;
+	if (next)
+	{
+		self->tail = next;
+		return tail;
+	}
+	return 0;
+}