lib/interval_tree.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 #include <linux/interval_tree.h>
   3 #include <linux/interval_tree_generic.h>
   4 #include <linux/compiler.h>
   5 #include <linux/export.h>
   6
   7 #define START(node) ((node)->start)
   8 #define LAST(node)  ((node)->last)
   9
  10 INTERVAL_TREE_DEFINE(struct interval_tree_node, rb,
  11                      unsigned long, __subtree_last,
  12                      START, LAST,, interval_tree)
  13
  14 EXPORT_SYMBOL_GPL(interval_tree_insert);
  15 EXPORT_SYMBOL_GPL(interval_tree_remove);
  16 EXPORT_SYMBOL_GPL(interval_tree_iter_first);
  17 EXPORT_SYMBOL_GPL(interval_tree_iter_next);
  18
  19 #ifdef CONFIG_INTERVAL_TREE_SPAN_ITER
  20 /*
  21  * Roll nodes[1] into nodes[0] by advancing nodes[1] to the end of a contiguous
  22  * span of nodes. This makes nodes[0]->last the end of that contiguous used span
  23  * indexes that started at the original nodes[1]->start. nodes[1] is now the
  24  * first node starting the next used span. A hole span is between nodes[0]->last
  25  * and nodes[1]->start. nodes[1] must be !NULL.
  26  */
  27 static void
  28 interval_tree_span_iter_next_gap(struct interval_tree_span_iter *state)
  29 {
  30         struct interval_tree_node *cur = state->nodes[1];
  31
  32         state->nodes[0] = cur;
  33         do {
  34                 if (cur->last > state->nodes[0]->last)
  35                         state->nodes[0] = cur;
  36                 cur = interval_tree_iter_next(cur, state->first_index,
  37                                               state->last_index);
  38         } while (cur && (state->nodes[0]->last >= cur->start ||
  39                          state->nodes[0]->last + 1 == cur->start));
  40         state->nodes[1] = cur;
  41 }
  42
  43 void interval_tree_span_iter_first(struct interval_tree_span_iter *iter,
  44                                    struct rb_root_cached *itree,
  45                                    unsigned long first_index,
  46                                    unsigned long last_index)
  47 {
  48         iter->first_index = first_index;
  49         iter->last_index = last_index;
  50         iter->nodes[0] = NULL;
  51         iter->nodes[1] =
  52                 interval_tree_iter_first(itree, first_index, last_index);
  53         if (!iter->nodes[1]) {
  54                 /* No nodes intersect the span, whole span is hole */
  55                 iter->start_hole = first_index;
  56                 iter->last_hole = last_index;
  57                 iter->is_hole = 1;
  58                 return;
  59         }
  60         if (iter->nodes[1]->start > first_index) {
  61                 /* Leading hole on first iteration */
  62                 iter->start_hole = first_index;
  63                 iter->last_hole = iter->nodes[1]->start - 1;
  64                 iter->is_hole = 1;
  65                 interval_tree_span_iter_next_gap(iter);
  66                 return;
  67         }
  68
  69         /* Starting inside a used */
  70         iter->start_used = first_index;
  71         iter->is_hole = 0;
  72         interval_tree_span_iter_next_gap(iter);
  73         iter->last_used = iter->nodes[0]->last;
  74         if (iter->last_used >= last_index) {
  75                 iter->last_used = last_index;
  76                 iter->nodes[0] = NULL;
  77                 iter->nodes[1] = NULL;
  78         }
  79 }
  80 EXPORT_SYMBOL_GPL(interval_tree_span_iter_first);
  81
  82 void interval_tree_span_iter_next(struct interval_tree_span_iter *iter)
  83 {
  84         if (!iter->nodes[0] && !iter->nodes[1]) {
  85                 iter->is_hole = -1;
  86                 return;
  87         }
  88
  89         if (iter->is_hole) {
  90                 iter->start_used = iter->last_hole + 1;
  91                 iter->last_used = iter->nodes[0]->last;
  92                 if (iter->last_used >= iter->last_index) {
  93                         iter->last_used = iter->last_index;
  94                         iter->nodes[0] = NULL;
  95                         iter->nodes[1] = NULL;
  96                 }
  97                 iter->is_hole = 0;
  98                 return;
  99         }
 100
 101         if (!iter->nodes[1]) {
 102                 /* Trailing hole */
 103                 iter->start_hole = iter->nodes[0]->last + 1;
 104                 iter->last_hole = iter->last_index;
 105                 iter->nodes[0] = NULL;
 106                 iter->is_hole = 1;
 107                 return;
 108         }
 109
 110         /* must have both nodes[0] and [1], interior hole */
 111         iter->start_hole = iter->nodes[0]->last + 1;
 112         iter->last_hole = iter->nodes[1]->start - 1;
 113         iter->is_hole = 1;
 114         interval_tree_span_iter_next_gap(iter);
 115 }
 116 EXPORT_SYMBOL_GPL(interval_tree_span_iter_next);
 117
 118 /*
 119  * Advance the iterator index to a specific position. The returned used/hole is
 120  * updated to start at new_index. This is faster than calling
 121  * interval_tree_span_iter_first() as it can avoid full searches in several
 122  * cases where the iterator is already set.
 123  */
 124 void interval_tree_span_iter_advance(struct interval_tree_span_iter *iter,
 125                                      struct rb_root_cached *itree,
 126                                      unsigned long new_index)
 127 {
 128         if (iter->is_hole == -1)
 129                 return;
 130
 131         iter->first_index = new_index;
 132         if (new_index > iter->last_index) {
 133                 iter->is_hole = -1;
 134                 return;
 135         }
 136
 137         /* Rely on the union aliasing hole/used */
 138         if (iter->start_hole <= new_index && new_index <= iter->last_hole) {
 139                 iter->start_hole = new_index;
 140                 return;
 141         }
 142         if (new_index == iter->last_hole + 1)
 143                 interval_tree_span_iter_next(iter);
 144         else
 145                 interval_tree_span_iter_first(iter, itree, new_index,
 146                                               iter->last_index);
 147 }
 148 EXPORT_SYMBOL_GPL(interval_tree_span_iter_advance);
 149 #endif