LXR linux/fs/btrfs/ulist.h

   1/*
   2 * Copyright (C) 2011 STRATO AG
   3 * written by Arne Jansen <sensille@gmx.net>
   4 * Distributed under the GNU GPL license version 2.
   5 *
   6 */
   7
   8#ifndef __ULIST__
   9#define __ULIST__
  10
  11#include <linux/list.h>
  12#include <linux/rbtree.h>
  13
  14/*
  15 * ulist is a generic data structure to hold a collection of unique u64
  16 * values. The only operations it supports is adding to the list and
  17 * enumerating it.
  18 * It is possible to store an auxiliary value along with the key.
  19 *
  20 * The implementation is preliminary and can probably be sped up
  21 * significantly. A first step would be to store the values in an rbtree
  22 * as soon as ULIST_SIZE is exceeded.
  23 */
  24
  25/*
  26 * number of elements statically allocated inside struct ulist
  27 */
  28#define ULIST_SIZE 16
  29
  30struct ulist_iterator {
  31        int i;
  32};
  33
  34/*
  35 * element of the list
  36 */
  37struct ulist_node {
  38        u64 val;                /* value to store */
  39        u64 aux;                /* auxiliary value saved along with the val */
  40        struct rb_node rb_node; /* used to speed up search */
  41};
  42
  43struct ulist {
  44        /*
  45         * number of elements stored in list
  46         */
  47        unsigned long nnodes;
  48
  49        /*
  50         * number of nodes we already have room for
  51         */
  52        unsigned long nodes_alloced;
  53
  54        /*
  55         * pointer to the array storing the elements. The first ULIST_SIZE
  56         * elements are stored inline. In this case the it points to int_nodes.
  57         * After exceeding ULIST_SIZE, dynamic memory is allocated.
  58         */
  59        struct ulist_node *nodes;
  60
  61        struct rb_root root;
  62
  63        /*
  64         * inline storage space for the first ULIST_SIZE entries
  65         */
  66        struct ulist_node int_nodes[ULIST_SIZE];
  67};
  68
  69void ulist_init(struct ulist *ulist);
  70void ulist_fini(struct ulist *ulist);
  71void ulist_reinit(struct ulist *ulist);
  72struct ulist *ulist_alloc(gfp_t gfp_mask);
  73void ulist_free(struct ulist *ulist);
  74int ulist_add(struct ulist *ulist, u64 val, u64 aux, gfp_t gfp_mask);
  75int ulist_add_merge(struct ulist *ulist, u64 val, u64 aux,
  76                    u64 *old_aux, gfp_t gfp_mask);
  77struct ulist_node *ulist_next(struct ulist *ulist,
  78                              struct ulist_iterator *uiter);
  79
  80#define ULIST_ITER_INIT(uiter) ((uiter)->i = 0)
  81
  82#endif
  83