Nucleus

diff --git a/lib/object/list.c b/lib/object/list.c
new file mode 100644
index 0000000..6af7a72
--- /dev/null
+++ b/lib/object/list.c
@@ -0,0 +1,314 @@
+/*
+ * This file implements Object Lists.  Objects can be a part of multiple lists
+ * that can be managed automatically by the Object Manager.  This prevents
+ * subsystems having to implement their own object lists for sub-objects.  Each
+ * list is implemented as an Object itself, which allows the common object
+ * routines to be used on them.
+ */
+
+#include <stdarg.h>
+#include <nucleus/kernel.h>
+#include <nucleus/memory.h>
+#include <nucleus/object.h>
+
+/* Structure for a List Entry */
+struct ListEntry {
+	struct ListEntry *prev, *next;
+	Object *obj;
+};
+/* Structure for an Object List */
+struct ObjectList {
+	struct ListEntry *start, *end;
+	size_t entries;
+	ObjectType *type;
+	enum ListMode mode;
+	compare_callback_t compare;
+	Spinlock lock;
+};
+/* Iterator */
+struct Iterator {
+	ObjectList *list;
+	struct ListEntry *prev, *entry, *next;
+	off_t pos;
+};
+
+void init_lock(Spinlock *lock);
+void acquire(Spinlock *lock);
+void release(Spinlock *lock);
+
+/* Create an Object List */
+ObjectList *
+create_list(ObjectType *type, enum ListMode mode, ...)
+{
+	ObjectList *list = kmalloc(sizeof(ObjectList));
+	init_lock(&list->lock);
+	list->type = type;
+	list->mode = mode;
+
+	if (mode == LIST_ORDERED) {
+		va_list args;
+		va_start(args, mode);
+		list->compare = va_arg(args, compare_callback_t);
+		va_end(args);
+	}
+
+	return list;
+}
+
+/* Destroy an Object List */
+void
+destroy_list(ObjectList *list)
+{
+	while (list->entries > 0)
+		remove(list, list->start->obj);
+}
+
+/* Add an Object to a List */
+void
+add(ObjectList *list, void *addr)
+{
+	Object *obj = addr;
+	ASSERT(obj->magic == OBJECT_MAGIC);
+	if (list->type && obj->type != list->type)
+		return;
+
+	if (list->mode != LIST_LOCKLESS)
+		acquire(&list->lock);
+
+	struct ListEntry *entry, *next;
+	entry = kmalloc(sizeof(struct ListEntry));
+	entry->obj = get(obj);
+	list->entries++;
+
+	if (!list->start) {
+		/* Only item in list */
+		list->start = list->end = entry;
+	} else if (list->compare) {
+		/* Find next item */
+		for (next = list->start; next; next = next->next) {
+			if (list->compare(next->obj, obj) > 0)
+				break;
+		}
+		if (!next)
+			goto end;
+		/* Add in */
+		entry->prev = next->prev;
+		entry->next = next;
+		next->prev = entry;
+		if (entry->prev)
+			entry->prev->next = entry;
+		else
+			list->start = entry;
+	} else {
+end:
+		/* Add to end of list */
+		list->end->next = entry;
+		entry->prev = list->end;
+		list->end = entry;
+	}
+
+	if (list->mode != LIST_LOCKLESS)
+		release(&list->lock);
+}
+
+/* Remove an Object from a List */
+void
+remove(ObjectList *list, void *addr)
+{
+	Object *obj = addr;
+	ASSERT(obj->magic == OBJECT_MAGIC);
+	if (!list->start)
+		return;
+	if (list->type && obj->type != list->type)
+		return;
+	if (list->mode != LIST_LOCKLESS)
+		acquire(&list->lock);
+
+	/* Search for object */
+	struct ListEntry *entry;
+	for (entry = list->start;
+	     entry && entry->obj != obj;
+	     entry = entry->next);
+	if (!entry) {
+		release(&list->lock);
+		return;
+	}
+
+	/* Unlink list */
+	if (list->start == entry)
+		list->start = entry->next;
+	if (list->end == entry)
+		list->end = entry->prev;
+
+	/* Unlink neighbours */
+	if (entry->prev)
+		entry->prev->next = entry->next;
+	if (entry->next)
+		entry->next->prev = entry->prev;
+
+	/* Release resources */
+	if (__builtin_expect(!!(obj->usage), 1))
+		put(obj);
+	list->entries--;
+	kfree(entry);
+	if (list->mode != LIST_LOCKLESS)
+		release(&list->lock);
+}
+
+/* Pop the first Object in a List */
+void *
+pop_from_start(ObjectList *list)
+{
+	if (!list->start)
+		return NULL;
+	if (list->mode != LIST_LOCKLESS)
+		acquire(&list->lock);
+	Object *head = get(list->start->obj);
+	remove(list, head);
+	if (list->mode != LIST_LOCKLESS)
+		release(&list->lock);
+	return head;
+}
+
+/* Pop the last Object in a List */
+void *
+pop_from_end(ObjectList *list)
+{
+	if (!list->end)
+		return NULL;
+	if (list->mode != LIST_LOCKLESS)
+		acquire(&list->lock);
+	Object *tail = get(list->end->obj);
+	remove(list, tail);
+	if (list->mode != LIST_LOCKLESS)
+		release(&list->lock);
+	return tail;
+}
+
+/* Count the number of Objects in a List */
+size_t
+count(ObjectList *list)
+{
+	return list->entries;
+}
+
+/* Get the nth Object in a List */
+void *
+get_nth_item(ObjectList *list, off_t n)
+{
+	if (n > list->entries - 1)
+		return NULL;
+
+	struct ListEntry *entry;
+	if (n < (list->entries >> 1)) {
+		for (entry = list->start; entry; entry = entry->next)
+			if (n-- == 0)
+				break;
+	} else {
+		n = list->entries - 1 - n;
+		for (entry = list->end; entry; entry = entry->prev)
+			if (n-- == 0)
+				break;
+	}
+	return entry->obj;
+}
+
+/* Copy list */
+ObjectList *
+copy_list(ObjectList *list)
+{
+	ObjectList *newlist = create_list(list->type, list->mode,
+	                                  list->compare);
+	if (list->mode != LIST_LOCKLESS)
+		acquire(&list->lock);
+	struct ListEntry *entry;
+	for (entry = list->start; entry; entry = entry->next)
+		add(newlist, entry->obj);
+	if (list->mode != LIST_LOCKLESS)
+		release(&list->lock);
+	return newlist;
+}
+
+/* Concatenate one list onto the end of another */
+void
+concat_list(ObjectList *src, ObjectList *dest)
+{
+	if (src->mode != LIST_LOCKLESS)
+		acquire(&src->lock);
+	struct ListEntry *entry;
+	for (entry = src->start; entry; entry = entry->next)
+		add(dest, entry->obj);
+	if (src->mode != LIST_LOCKLESS)
+		release(&src->lock);
+}
+
+/* Iterate a List */
+Iterator *
+iterate(ObjectList *list)
+{
+	Iterator *i = kmalloc(sizeof(Iterator));
+	i->list = list;
+	return i;
+}
+
+/* Get first iteratable element */
+void *
+first(Iterator *iter)
+{
+	iter->entry = iter->list->start;
+	if (iter->entry) {
+		iter->next = iter->entry->next;
+		iter->pos = 0;
+		return iter->entry->obj;
+	}
+	return NULL;
+}
+
+/* Get last iteratable element */
+void *
+last(Iterator *iter)
+{
+	iter->entry = iter->list->end;
+	if (iter->entry) {
+		iter->prev = iter->entry->prev;
+		iter->pos = iter->list->entries - 1;
+		return iter->entry->obj;
+	}
+	return NULL;
+}
+
+/* Get next iteratable element */
+void *
+next(Iterator *iter)
+{
+	iter->entry = iter->next;
+	if (iter->entry) {
+		iter->prev = iter->entry->prev;
+		iter->next = iter->entry->next;
+		iter->pos++;
+		return iter->entry->obj;
+	}
+	return NULL;
+}
+
+/* Get previous iteratable element */
+void *
+prev(Iterator *iter)
+{
+	iter->entry = iter->prev;
+	if (iter->entry) {
+		iter->prev = iter->entry->prev;
+		iter->next = iter->entry->next;
+		iter->pos--;
+		return iter->entry->obj;
+	}
+	return NULL;
+}
+
+/* End iteration */
+int
+done_iterating(Iterator *iter)
+{
+	kfree(iter);
+	return 0;
+}