Implement Linux kernel-inspired generic cyclic doubly linked list interface

[xonotic/darkplaces.git] / com_list.c

diff --git a/com_list.c b/com_list.c
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+/*
+Copyright (C) 2020 David "Cloudwalk" Knapp
+
+This program is free software; you can redistribute it and/or
+modify it under the terms of the GNU General Public License
+as published by the Free Software Foundation; either version 2
+of the License, or (at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+
+See the GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program; if not, write to the Free Software
+Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
+
+*/
+
+// com_list.c - generic doubly linked list interface, inspired by Linux list.h
+
+#include "qtypes.h"
+#include "com_list.h"
+
+/*
+ * Insert a node between two known nodes.
+ * 
+ * Only use when prev and next are known.
+ */
+static void __List_Add(llist_t *node, llist_t *prev, llist_t *next)
+{
+       next->prev = node;
+       node->next = next;
+       node->prev = prev;
+       prev->next = node;
+}
+
+/*
+ * Insert a node immediately after head.
+ */
+void List_Add(llist_t *node, llist_t *head)
+{
+       __List_Add(node, head, head->next);
+}
+
+/*
+ * Insert a node immediately before head.
+ */
+void List_Add_Tail(llist_t *node, llist_t *head)
+{
+       __List_Add(node, head->prev, head);
+}
+
+/*
+ * Bridge prev and next together, when removing the parent of them.
+ */
+static void __List_Delete(llist_t *prev, llist_t *next)
+{
+       next->prev = prev;
+       prev->next = next;
+}
+
+/*
+ * Redundant?
+ */
+static void __List_Delete_Node(llist_t *node)
+{
+       __List_Delete(node->prev, node->next);
+}
+
+/*
+ * Removes a node from its list.
+ */
+void List_Delete(llist_t *node)
+{
+       __List_Delete_Node(node);
+       node->next = node->prev = node;
+}
+
+/*
+ * Replace old with new. Old is overwritten if empty.
+ */
+void List_Replace(llist_t *old, llist_t *_new)
+{
+       _new->next = old->next;
+       _new->next->prev = _new;
+       _new->prev = old->prev;
+       _new->prev->next = _new;
+       old->next = old->prev = old;
+}
+
+/*
+ * Swap node1 with node2 in place.
+ */
+void List_Swap(llist_t *node1, llist_t *node2)
+{
+       llist_t *pos = node2->prev;
+       List_Delete(node2);
+       List_Replace(node1, node2);
+       if(pos == node1)
+               pos = node2;
+       List_Add(node1, pos);
+}
+
+/*
+ * Delete list from its... list, then insert after head.
+ */
+void List_Move(llist_t *list, llist_t *head)
+{
+       __List_Delete_Node(list);
+       List_Add(list, head);
+}
+
+/*
+ * Delete list from its... list, then insert before head.
+ */
+void List_Move_Tail(llist_t *list, llist_t *head)
+{
+       __List_Delete_Node(list);
+       List_Add_Tail(list, head);
+}
+
+/*
+ * Move the first node of a range of nodes immediately after head.
+ * All three parameters must belong to the same list.
+ */
+
+void List_Bulk_Move_Tail(llist_t *head, llist_t *first, llist_t *last)
+{
+       first->prev->next = last->next;
+       last->next->prev = first->prev;
+
+       head->prev->next = first;
+       first->prev = head->prev;
+
+       last->next = head;
+       head->prev = last;
+}
+
+/*
+ * Shift the head to the right (like rotating a wheel counterclockwise).
+ * The node immediately to the right becomes the new head.
+ */
+void List_Rotate_Left(llist_t *head)
+{
+       llist_t *first;
+
+       if (!List_IsEmpty(head))
+       {
+               first = head->next;
+               List_Move_Tail(first, head);
+       }
+}
+
+/*
+ * Make list the new head.
+ */
+void List_Rotate_To_Front(llist_t *list, llist_t *head)
+{
+       List_Move_Tail(head, list);
+}
+
+/*
+ * Concatenate two lists. The head of list will be discarded.
+ */
+static void __List_Splice(const llist_t *list, llist_t *prev, llist_t *next)
+{
+       llist_t *first = list->next;
+       llist_t *last = list->prev;
+
+       first->prev = prev;
+       prev->next = first;
+
+       last->next = next;
+       next->prev = last;
+}
+
+/*
+ * Concatenate two lists. The first node of list will be inserted after head.
+ */
+void List_Splice(const llist_t *list, llist_t *head)
+{
+       if(!List_IsEmpty(list))
+               __List_Splice(list, head, head->next);
+}
+
+/*
+ * Concatenate two lists. The tail of list will be inserted before head.
+ */
+void List_Splice_Tail(const llist_t *list, llist_t *head)
+{
+       if (!List_IsEmpty(list))
+               __List_Splice(list, head->prev, head);
+}
+
+qboolean List_IsFirst(llist_t *list, llist_t *start)
+{
+       return list->prev == start;
+}
+
+qboolean List_IsLast(llist_t *list, llist_t *start)
+{
+       return list->next == start;
+}
+
+qboolean List_IsEmpty(const llist_t *list)
+{
+       return list->next == list;
+}
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