// SPDX-License-Identifier: GPL-2.0

  /*
   * Copyright (C) 2011 STRATO AG
   * written by Arne Jansen <sensille@gmx.net>

   */
  
  #include <linux/slab.h>

  #include "ulist.h"

  #include "ctree.h"

  
  /*
   * ulist is a generic data structure to hold a collection of unique u64
   * values. The only operations it supports is adding to the list and
   * enumerating it.
   * It is possible to store an auxiliary value along with the key.
   *

   * A sample usage for ulists is the enumeration of directed graphs without
   * visiting a node twice. The pseudo-code could look like this:
   *
   * ulist = ulist_alloc();
   * ulist_add(ulist, root);

   * ULIST_ITER_INIT(&uiter);

   *

   * while ((elem = ulist_next(ulist, &uiter)) {

   * 	for (all child nodes n in elem)
   *		ulist_add(ulist, n);
   *	do something useful with the node;
   * }
   * ulist_free(ulist);
   *

   * This assumes the graph nodes are addressable by u64. This stems from the

   * usage for tree enumeration in btrfs, where the logical addresses are
   * 64 bit.
   *
   * It is also useful for tree enumeration which could be done elegantly
   * recursively, but is not possible due to kernel stack limitations. The
   * loop would be similar to the above.
   */
  
  /**
   * ulist_init - freshly initialize a ulist
   * @ulist:	the ulist to initialize
   *
   * Note: don't use this function to init an already used ulist, use
   * ulist_reinit instead.
   */
  void ulist_init(struct ulist *ulist)
  {

  	INIT_LIST_HEAD(&ulist->nodes);

  	ulist->root = RB_ROOT;

  	ulist->nnodes = 0;

  }

  
  /**

   * ulist_release - free up additionally allocated memory for the ulist

   * @ulist:	the ulist from which to free the additional memory
   *
   * This is useful in cases where the base 'struct ulist' has been statically
   * allocated.
   */

  void ulist_release(struct ulist *ulist)

  {

  	struct ulist_node *node;
  	struct ulist_node *next;
  
  	list_for_each_entry_safe(node, next, &ulist->nodes, list) {
  		kfree(node);
  	}

  	ulist->root = RB_ROOT;

  	INIT_LIST_HEAD(&ulist->nodes);

  }

  
  /**
   * ulist_reinit - prepare a ulist for reuse
   * @ulist:	ulist to be reused
   *
   * Free up all additional memory allocated for the list elements and reinit
   * the ulist.
   */
  void ulist_reinit(struct ulist *ulist)
  {

  	ulist_release(ulist);

  	ulist_init(ulist);
  }

  
  /**
   * ulist_alloc - dynamically allocate a ulist
   * @gfp_mask:	allocation flags to for base allocation
   *
   * The allocated ulist will be returned in an initialized state.
   */

  struct ulist *ulist_alloc(gfp_t gfp_mask)

  {
  	struct ulist *ulist = kmalloc(sizeof(*ulist), gfp_mask);
  
  	if (!ulist)
  		return NULL;
  
  	ulist_init(ulist);
  
  	return ulist;
  }

  
  /**
   * ulist_free - free dynamically allocated ulist
   * @ulist:	ulist to free
   *

   * It is not necessary to call ulist_release before.

   */
  void ulist_free(struct ulist *ulist)
  {
  	if (!ulist)
  		return;

  	ulist_release(ulist);

  	kfree(ulist);
  }

  static struct ulist_node *ulist_rbtree_search(struct ulist *ulist, u64 val)
  {
  	struct rb_node *n = ulist->root.rb_node;
  	struct ulist_node *u = NULL;
  
  	while (n) {
  		u = rb_entry(n, struct ulist_node, rb_node);
  		if (u->val < val)
  			n = n->rb_right;
  		else if (u->val > val)
  			n = n->rb_left;
  		else
  			return u;
  	}
  	return NULL;
  }

  static void ulist_rbtree_erase(struct ulist *ulist, struct ulist_node *node)
  {
  	rb_erase(&node->rb_node, &ulist->root);
  	list_del(&node->list);
  	kfree(node);
  	BUG_ON(ulist->nnodes == 0);
  	ulist->nnodes--;
  }

  static int ulist_rbtree_insert(struct ulist *ulist, struct ulist_node *ins)
  {
  	struct rb_node **p = &ulist->root.rb_node;
  	struct rb_node *parent = NULL;
  	struct ulist_node *cur = NULL;
  
  	while (*p) {
  		parent = *p;
  		cur = rb_entry(parent, struct ulist_node, rb_node);
  
  		if (cur->val < ins->val)
  			p = &(*p)->rb_right;
  		else if (cur->val > ins->val)
  			p = &(*p)->rb_left;
  		else
  			return -EEXIST;
  	}
  	rb_link_node(&ins->rb_node, parent, p);
  	rb_insert_color(&ins->rb_node, &ulist->root);
  	return 0;
  }

  /**
   * ulist_add - add an element to the ulist
   * @ulist:	ulist to add the element to
   * @val:	value to add to ulist
   * @aux:	auxiliary value to store along with val
   * @gfp_mask:	flags to use for allocation
   *
   * Note: locking must be provided by the caller. In case of rwlocks write
   *       locking is needed
   *
   * Add an element to a ulist. The @val will only be added if it doesn't
   * already exist. If it is added, the auxiliary value @aux is stored along with
   * it. In case @val already exists in the ulist, @aux is ignored, even if
   * it differs from the already stored value.
   *
   * ulist_add returns 0 if @val already exists in ulist and 1 if @val has been
   * inserted.
   * In case of allocation failure -ENOMEM is returned and the ulist stays
   * unaltered.
   */

  int ulist_add(struct ulist *ulist, u64 val, u64 aux, gfp_t gfp_mask)

  {

  	return ulist_add_merge(ulist, val, aux, NULL, gfp_mask);
  }

  int ulist_add_merge(struct ulist *ulist, u64 val, u64 aux,
  		    u64 *old_aux, gfp_t gfp_mask)

  {

  	int ret;
  	struct ulist_node *node;

  	node = ulist_rbtree_search(ulist, val);
  	if (node) {
  		if (old_aux)
  			*old_aux = node->aux;
  		return 0;

  	}

  	node = kmalloc(sizeof(*node), gfp_mask);
  	if (!node)
  		return -ENOMEM;

  	node->val = val;
  	node->aux = aux;

  	ret = ulist_rbtree_insert(ulist, node);
  	ASSERT(!ret);
  	list_add_tail(&node->list, &ulist->nodes);
  	ulist->nnodes++;

  
  	return 1;
  }

  /*
   * ulist_del - delete one node from ulist
   * @ulist:	ulist to remove node from
   * @val:	value to delete
   * @aux:	aux to delete
   *
   * The deletion will only be done when *BOTH* val and aux matches.
   * Return 0 for successful delete.
   * Return > 0 for not found.
   */
  int ulist_del(struct ulist *ulist, u64 val, u64 aux)
  {
  	struct ulist_node *node;
  
  	node = ulist_rbtree_search(ulist, val);
  	/* Not found */
  	if (!node)
  		return 1;
  
  	if (node->aux != aux)
  		return 1;
  
  	/* Found and delete */
  	ulist_rbtree_erase(ulist, node);
  	return 0;
  }

  /**
   * ulist_next - iterate ulist
   * @ulist:	ulist to iterate

   * @uiter:	iterator variable, initialized with ULIST_ITER_INIT(&iterator)

   *
   * Note: locking must be provided by the caller. In case of rwlocks only read
   *       locking is needed
   *

   * This function is used to iterate an ulist.
   * It returns the next element from the ulist or %NULL when the

   * end is reached. No guarantee is made with respect to the order in which
   * the elements are returned. They might neither be returned in order of
   * addition nor in ascending order.
   * It is allowed to call ulist_add during an enumeration. Newly added items
   * are guaranteed to show up in the running enumeration.
   */

  struct ulist_node *ulist_next(struct ulist *ulist, struct ulist_iterator *uiter)

  {

  	struct ulist_node *node;
  
  	if (list_empty(&ulist->nodes))

  		return NULL;

  	if (uiter->cur_list && uiter->cur_list->next == &ulist->nodes)

  		return NULL;

  	if (uiter->cur_list) {
  		uiter->cur_list = uiter->cur_list->next;
  	} else {
  		uiter->cur_list = ulist->nodes.next;

  	}
  	node = list_entry(uiter->cur_list, struct ulist_node, list);

  	return node;

  }