[kvm-unit-tests PATCH v2 1/7] lib/list: Add double linked list management functions

From: Claudio Imbrenda <imbrenda@linux.ibm.com>
To: kvm@vger.kernel.org, pbonzini@redhat.com
Cc: frankja@linux.ibm.com, david@redhat.com, thuth@redhat.com,
	cohuck@redhat.com, lvivier@redhat.com
Subject: [kvm-unit-tests PATCH v2 1/7] lib/list: Add double linked list management functions
Date: Fri,  2 Oct 2020 17:44:14 +0200	[thread overview]
Message-ID: <20201002154420.292134-2-imbrenda@linux.ibm.com> (raw)
In-Reply-To: <20201002154420.292134-1-imbrenda@linux.ibm.com>

Add simple double linked lists.

Apart from the struct itself, there are functions to add and remove
items, and check for emptyness.

Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
---
 lib/list.h | 53 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 53 insertions(+)
 create mode 100644 lib/list.h

diff --git a/lib/list.h b/lib/list.h
new file mode 100644
index 0000000..702a78c
--- /dev/null
+++ b/lib/list.h
@@ -0,0 +1,53 @@
+#ifndef LIST_H
+#define LIST_H
+
+#include <stdbool.h>
+
+/*
+ * Simple double linked list. The pointer to the list is a list item itself,
+ * like in the kernel implementation.
+ */
+struct linked_list {
+	struct linked_list *prev;
+	struct linked_list *next;
+};
+
+/*
+ * An empty list is a list item whose prev and next both point to itself.
+ * Returns true if the list is empty.
+ */
+static inline bool is_list_empty(struct linked_list *p)
+{
+	return !p->next || !p->prev || p == p->next || p == p->prev;
+}
+
+/*
+ * Remove the given element from the list, if the list is not already empty.
+ * The removed element is returned.
+ */
+static inline struct linked_list *list_remove(struct linked_list *l)
+{
+	if (is_list_empty(l))
+		return NULL;
+
+	l->prev->next = l->next;
+	l->next->prev = l->prev;
+	l->prev = l->next = NULL;
+
+	return l;
+}
+
+/*
+ * Add the given element after the given list head.
+ */
+static inline void list_add(struct linked_list *head, struct linked_list *li)
+{
+	assert(li);
+	assert(head);
+	li->prev = head;
+	li->next = head->next;
+	head->next->prev = li;
+	head->next = li;
+}
+
+#endif
-- 
2.26.2

