1 files changed, 131 insertions, 0 deletions
diff --git a/kern/queue.c b/kern/queue.c
new file mode 100644
index 00000000..98b74c20
--- /dev/null
+++ b/kern/queue.c
@@ -0,0 +1,131 @@
+/* 
+ * Mach Operating System
+ * Copyright (c) 1991,1990,1989,1988,1987 Carnegie Mellon University
+ * All Rights Reserved.
+ * 
+ * Permission to use, copy, modify and distribute this software and its
+ * documentation is hereby granted, provided that both the copyright
+ * notice and this permission notice appear in all copies of the
+ * software, derivative works or modified versions, and any portions
+ * thereof, and that both notices appear in supporting documentation.
+ * 
+ * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
+ * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
+ * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
+ * 
+ * Carnegie Mellon requests users of this software to return to
+ * 
+ *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
+ *  School of Computer Science
+ *  Carnegie Mellon University
+ *  Pittsburgh PA 15213-3890
+ * 
+ * any improvements or extensions that they make and grant Carnegie Mellon
+ * the rights to redistribute these changes.
+ */
+/*
+ *	Routines to implement queue package.
+ */
+
+#include <kern/queue.h>
+
+
+
+/*
+ *	Insert element at head of queue.
+ */
+void enqueue_head(
+	register queue_t	que,
+	register queue_entry_t	elt)
+{
+	elt->next = que->next;
+	elt->prev = que;
+	elt->next->prev = elt;
+	que->next = elt;
+}
+
+/*
+ *	Insert element at tail of queue.
+ */
+void enqueue_tail(
+	register queue_t	que,
+	register queue_entry_t	elt)
+{
+	elt->next = que;
+	elt->prev = que->prev;
+	elt->prev->next = elt;
+	que->prev = elt;
+}
+
+/*
+ *	Remove and return element at head of queue.
+ */
+queue_entry_t dequeue_head(
+	register queue_t	que)
+{
+	register queue_entry_t	elt;
+
+	if (que->next == que)
+		return((queue_entry_t)0);
+
+	elt = que->next;
+	elt->next->prev = que;
+	que->next = elt->next;
+	return(elt);
+}
+
+/*
+ *	Remove and return element at tail of queue.
+ */
+queue_entry_t dequeue_tail(
+	register queue_t	que)
+{
+	register queue_entry_t	elt;
+
+	if (que->prev == que)
+		return((queue_entry_t)0);
+
+	elt = que->prev;
+	elt->prev->next = que;
+	que->prev = elt->prev;
+	return(elt);
+}
+
+/*
+ *	Remove arbitrary element from queue.
+ *	Does not check whether element is on queue - the world
+ *	will go haywire if it isn't.
+ */
+
+/*ARGSUSED*/
+void remqueue(
+	queue_t			que,
+	register queue_entry_t	elt)
+{
+	elt->next->prev = elt->prev;
+	elt->prev->next = elt->next;
+}
+
+/*
+ *	Routines to directly imitate the VAX hardware queue
+ *	package.
+ */
+void insque(
+	register struct queue_entry *entry,
+	register struct queue_entry *pred)
+{
+	entry->next = pred->next;
+	entry->prev = pred;
+	(pred->next)->prev = entry;
+	pred->next = entry;
+}
+
+struct queue_entry
+*remque(
+	register struct queue_entry *elt)
+{
+	(elt->next)->prev = elt->prev;
+	(elt->prev)->next = elt->next;
+	return(elt);
+}
+