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-rw-r--r--lib/interval_tree.c159
1 files changed, 159 insertions, 0 deletions
diff --git a/lib/interval_tree.c b/lib/interval_tree.c
new file mode 100644
index 00000000000..6fd540b1e49
--- /dev/null
+++ b/lib/interval_tree.c
@@ -0,0 +1,159 @@
+#include <linux/init.h>
+#include <linux/interval_tree.h>
+
+/* Callbacks for augmented rbtree insert and remove */
+
+static inline unsigned long
+compute_subtree_last(struct interval_tree_node *node)
+{
+ unsigned long max = node->last, subtree_last;
+ if (node->rb.rb_left) {
+ subtree_last = rb_entry(node->rb.rb_left,
+ struct interval_tree_node, rb)->__subtree_last;
+ if (max < subtree_last)
+ max = subtree_last;
+ }
+ if (node->rb.rb_right) {
+ subtree_last = rb_entry(node->rb.rb_right,
+ struct interval_tree_node, rb)->__subtree_last;
+ if (max < subtree_last)
+ max = subtree_last;
+ }
+ return max;
+}
+
+RB_DECLARE_CALLBACKS(static, augment_callbacks, struct interval_tree_node, rb,
+ unsigned long, __subtree_last, compute_subtree_last)
+
+/* Insert / remove interval nodes from the tree */
+
+void interval_tree_insert(struct interval_tree_node *node,
+ struct rb_root *root)
+{
+ struct rb_node **link = &root->rb_node, *rb_parent = NULL;
+ unsigned long start = node->start, last = node->last;
+ struct interval_tree_node *parent;
+
+ while (*link) {
+ rb_parent = *link;
+ parent = rb_entry(rb_parent, struct interval_tree_node, rb);
+ if (parent->__subtree_last < last)
+ parent->__subtree_last = last;
+ if (start < parent->start)
+ link = &parent->rb.rb_left;
+ else
+ link = &parent->rb.rb_right;
+ }
+
+ node->__subtree_last = last;
+ rb_link_node(&node->rb, rb_parent, link);
+ rb_insert_augmented(&node->rb, root, &augment_callbacks);
+}
+
+void interval_tree_remove(struct interval_tree_node *node,
+ struct rb_root *root)
+{
+ rb_erase_augmented(&node->rb, root, &augment_callbacks);
+}
+
+/*
+ * Iterate over intervals intersecting [start;last]
+ *
+ * Note that a node's interval intersects [start;last] iff:
+ * Cond1: node->start <= last
+ * and
+ * Cond2: start <= node->last
+ */
+
+static struct interval_tree_node *
+subtree_search(struct interval_tree_node *node,
+ unsigned long start, unsigned long last)
+{
+ while (true) {
+ /*
+ * Loop invariant: start <= node->__subtree_last
+ * (Cond2 is satisfied by one of the subtree nodes)
+ */
+ if (node->rb.rb_left) {
+ struct interval_tree_node *left =
+ rb_entry(node->rb.rb_left,
+ struct interval_tree_node, rb);
+ if (start <= left->__subtree_last) {
+ /*
+ * Some nodes in left subtree satisfy Cond2.
+ * Iterate to find the leftmost such node N.
+ * If it also satisfies Cond1, that's the match
+ * we are looking for. Otherwise, there is no
+ * matching interval as nodes to the right of N
+ * can't satisfy Cond1 either.
+ */
+ node = left;
+ continue;
+ }
+ }
+ if (node->start <= last) { /* Cond1 */
+ if (start <= node->last) /* Cond2 */
+ return node; /* node is leftmost match */
+ if (node->rb.rb_right) {
+ node = rb_entry(node->rb.rb_right,
+ struct interval_tree_node, rb);
+ if (start <= node->__subtree_last)
+ continue;
+ }
+ }
+ return NULL; /* No match */
+ }
+}
+
+struct interval_tree_node *
+interval_tree_iter_first(struct rb_root *root,
+ unsigned long start, unsigned long last)
+{
+ struct interval_tree_node *node;
+
+ if (!root->rb_node)
+ return NULL;
+ node = rb_entry(root->rb_node, struct interval_tree_node, rb);
+ if (node->__subtree_last < start)
+ return NULL;
+ return subtree_search(node, start, last);
+}
+
+struct interval_tree_node *
+interval_tree_iter_next(struct interval_tree_node *node,
+ unsigned long start, unsigned long last)
+{
+ struct rb_node *rb = node->rb.rb_right, *prev;
+
+ while (true) {
+ /*
+ * Loop invariants:
+ * Cond1: node->start <= last
+ * rb == node->rb.rb_right
+ *
+ * First, search right subtree if suitable
+ */
+ if (rb) {
+ struct interval_tree_node *right =
+ rb_entry(rb, struct interval_tree_node, rb);
+ if (start <= right->__subtree_last)
+ return subtree_search(right, start, last);
+ }
+
+ /* Move up the tree until we come from a node's left child */
+ do {
+ rb = rb_parent(&node->rb);
+ if (!rb)
+ return NULL;
+ prev = &node->rb;
+ node = rb_entry(rb, struct interval_tree_node, rb);
+ rb = node->rb.rb_right;
+ } while (prev == rb);
+
+ /* Check if the node intersects [start;last] */
+ if (last < node->start) /* !Cond1 */
+ return NULL;
+ else if (start <= node->last) /* Cond2 */
+ return node;
+ }
+}