Michel Lespinasse | fff3fd8 | 2012-10-08 16:31:23 -0700 | [diff] [blame^] | 1 | #include <linux/init.h> |
| 2 | #include <linux/interval_tree.h> |
| 3 | |
| 4 | /* Callbacks for augmented rbtree insert and remove */ |
| 5 | |
| 6 | static inline unsigned long |
| 7 | compute_subtree_last(struct interval_tree_node *node) |
| 8 | { |
| 9 | unsigned long max = node->last, subtree_last; |
| 10 | if (node->rb.rb_left) { |
| 11 | subtree_last = rb_entry(node->rb.rb_left, |
| 12 | struct interval_tree_node, rb)->__subtree_last; |
| 13 | if (max < subtree_last) |
| 14 | max = subtree_last; |
| 15 | } |
| 16 | if (node->rb.rb_right) { |
| 17 | subtree_last = rb_entry(node->rb.rb_right, |
| 18 | struct interval_tree_node, rb)->__subtree_last; |
| 19 | if (max < subtree_last) |
| 20 | max = subtree_last; |
| 21 | } |
| 22 | return max; |
| 23 | } |
| 24 | |
| 25 | RB_DECLARE_CALLBACKS(static, augment_callbacks, struct interval_tree_node, rb, |
| 26 | unsigned long, __subtree_last, compute_subtree_last) |
| 27 | |
| 28 | /* Insert / remove interval nodes from the tree */ |
| 29 | |
| 30 | void interval_tree_insert(struct interval_tree_node *node, |
| 31 | struct rb_root *root) |
| 32 | { |
| 33 | struct rb_node **link = &root->rb_node, *rb_parent = NULL; |
| 34 | unsigned long start = node->start, last = node->last; |
| 35 | struct interval_tree_node *parent; |
| 36 | |
| 37 | while (*link) { |
| 38 | rb_parent = *link; |
| 39 | parent = rb_entry(rb_parent, struct interval_tree_node, rb); |
| 40 | if (parent->__subtree_last < last) |
| 41 | parent->__subtree_last = last; |
| 42 | if (start < parent->start) |
| 43 | link = &parent->rb.rb_left; |
| 44 | else |
| 45 | link = &parent->rb.rb_right; |
| 46 | } |
| 47 | |
| 48 | node->__subtree_last = last; |
| 49 | rb_link_node(&node->rb, rb_parent, link); |
| 50 | rb_insert_augmented(&node->rb, root, &augment_callbacks); |
| 51 | } |
| 52 | |
| 53 | void interval_tree_remove(struct interval_tree_node *node, |
| 54 | struct rb_root *root) |
| 55 | { |
| 56 | rb_erase_augmented(&node->rb, root, &augment_callbacks); |
| 57 | } |
| 58 | |
| 59 | /* |
| 60 | * Iterate over intervals intersecting [start;last] |
| 61 | * |
| 62 | * Note that a node's interval intersects [start;last] iff: |
| 63 | * Cond1: node->start <= last |
| 64 | * and |
| 65 | * Cond2: start <= node->last |
| 66 | */ |
| 67 | |
| 68 | static struct interval_tree_node * |
| 69 | subtree_search(struct interval_tree_node *node, |
| 70 | unsigned long start, unsigned long last) |
| 71 | { |
| 72 | while (true) { |
| 73 | /* |
| 74 | * Loop invariant: start <= node->__subtree_last |
| 75 | * (Cond2 is satisfied by one of the subtree nodes) |
| 76 | */ |
| 77 | if (node->rb.rb_left) { |
| 78 | struct interval_tree_node *left = |
| 79 | rb_entry(node->rb.rb_left, |
| 80 | struct interval_tree_node, rb); |
| 81 | if (start <= left->__subtree_last) { |
| 82 | /* |
| 83 | * Some nodes in left subtree satisfy Cond2. |
| 84 | * Iterate to find the leftmost such node N. |
| 85 | * If it also satisfies Cond1, that's the match |
| 86 | * we are looking for. Otherwise, there is no |
| 87 | * matching interval as nodes to the right of N |
| 88 | * can't satisfy Cond1 either. |
| 89 | */ |
| 90 | node = left; |
| 91 | continue; |
| 92 | } |
| 93 | } |
| 94 | if (node->start <= last) { /* Cond1 */ |
| 95 | if (start <= node->last) /* Cond2 */ |
| 96 | return node; /* node is leftmost match */ |
| 97 | if (node->rb.rb_right) { |
| 98 | node = rb_entry(node->rb.rb_right, |
| 99 | struct interval_tree_node, rb); |
| 100 | if (start <= node->__subtree_last) |
| 101 | continue; |
| 102 | } |
| 103 | } |
| 104 | return NULL; /* No match */ |
| 105 | } |
| 106 | } |
| 107 | |
| 108 | struct interval_tree_node * |
| 109 | interval_tree_iter_first(struct rb_root *root, |
| 110 | unsigned long start, unsigned long last) |
| 111 | { |
| 112 | struct interval_tree_node *node; |
| 113 | |
| 114 | if (!root->rb_node) |
| 115 | return NULL; |
| 116 | node = rb_entry(root->rb_node, struct interval_tree_node, rb); |
| 117 | if (node->__subtree_last < start) |
| 118 | return NULL; |
| 119 | return subtree_search(node, start, last); |
| 120 | } |
| 121 | |
| 122 | struct interval_tree_node * |
| 123 | interval_tree_iter_next(struct interval_tree_node *node, |
| 124 | unsigned long start, unsigned long last) |
| 125 | { |
| 126 | struct rb_node *rb = node->rb.rb_right, *prev; |
| 127 | |
| 128 | while (true) { |
| 129 | /* |
| 130 | * Loop invariants: |
| 131 | * Cond1: node->start <= last |
| 132 | * rb == node->rb.rb_right |
| 133 | * |
| 134 | * First, search right subtree if suitable |
| 135 | */ |
| 136 | if (rb) { |
| 137 | struct interval_tree_node *right = |
| 138 | rb_entry(rb, struct interval_tree_node, rb); |
| 139 | if (start <= right->__subtree_last) |
| 140 | return subtree_search(right, start, last); |
| 141 | } |
| 142 | |
| 143 | /* Move up the tree until we come from a node's left child */ |
| 144 | do { |
| 145 | rb = rb_parent(&node->rb); |
| 146 | if (!rb) |
| 147 | return NULL; |
| 148 | prev = &node->rb; |
| 149 | node = rb_entry(rb, struct interval_tree_node, rb); |
| 150 | rb = node->rb.rb_right; |
| 151 | } while (prev == rb); |
| 152 | |
| 153 | /* Check if the node intersects [start;last] */ |
| 154 | if (last < node->start) /* !Cond1 */ |
| 155 | return NULL; |
| 156 | else if (start <= node->last) /* Cond2 */ |
| 157 | return node; |
| 158 | } |
| 159 | } |