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