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-rw-r--r--absl/container/internal/btree.h203
1 files changed, 137 insertions, 66 deletions
diff --git a/absl/container/internal/btree.h b/absl/container/internal/btree.h
index 047055a2..996afa61 100644
--- a/absl/container/internal/btree.h
+++ b/absl/container/internal/btree.h
@@ -255,6 +255,10 @@ struct common_params {
static void move(Alloc *alloc, slot_type *src, slot_type *dest) {
slot_policy::move(alloc, src, dest);
}
+ static void move(Alloc *alloc, slot_type *first, slot_type *last,
+ slot_type *result) {
+ slot_policy::move(alloc, first, last, result);
+ }
};
// A parameters structure for holding the type parameters for a btree_map.
@@ -332,6 +336,13 @@ struct set_slot_policy {
static void move(Alloc * /*alloc*/, slot_type *src, slot_type *dest) {
*dest = std::move(*src);
}
+
+ template <typename Alloc>
+ static void move(Alloc *alloc, slot_type *first, slot_type *last,
+ slot_type *result) {
+ for (slot_type *src = first, *dest = result; src != last; ++src, ++dest)
+ move(alloc, src, dest);
+ }
};
// A parameters structure for holding the type parameters for a btree_set.
@@ -748,10 +759,14 @@ class btree_node {
template <typename... Args>
void emplace_value(size_type i, allocator_type *alloc, Args &&... args);
- // Removes the values at positions [i, i + to_erase), shifting all existing
- // values and children after that range to the left by to_erase. Clears all
- // children between [i, i + to_erase).
- void remove_values(field_type i, field_type to_erase, allocator_type *alloc);
+ // Removes the value at position i, shifting all existing values and children
+ // at positions > i to the left by 1.
+ void remove_value(int i, allocator_type *alloc);
+
+ // Removes the values at positions [i, i + to_erase), shifting all values
+ // after that range to the left by to_erase. Does not change children at all.
+ void remove_values_ignore_children(int i, int to_erase,
+ allocator_type *alloc);
// Rebalances a node with its right sibling.
void rebalance_right_to_left(int to_move, btree_node *right,
@@ -763,7 +778,7 @@ class btree_node {
void split(int insert_position, btree_node *dest, allocator_type *alloc);
// Merges a node with its right sibling, moving all of the values and the
- // delimiting key in the parent node onto itself, and deleting the src node.
+ // delimiting key in the parent node onto itself.
void merge(btree_node *src, allocator_type *alloc);
// Node allocation/deletion routines.
@@ -784,27 +799,9 @@ class btree_node {
absl::container_internal::SanitizerPoisonMemoryRegion(
&mutable_child(start()), (kNodeValues + 1) * sizeof(btree_node *));
}
-
- // Deletes a node and all of its children.
- // TODO(ezb): don't use recursion here to avoid potential stack overflows.
- static void clear_and_delete(btree_node *node, allocator_type *alloc) {
- const field_type start = node->start();
- const field_type finish = node->finish();
- for (field_type i = start; i < finish; ++i) {
- node->value_destroy(i, alloc);
- }
- if (node->leaf()) {
- absl::container_internal::Deallocate<Alignment()>(
- alloc, node, LeafSize(node->max_count()));
- } else {
- // If the node is empty, then there are no children so don't try clearing.
- if (start < finish) {
- for (field_type i = start; i <= finish; ++i) {
- clear_and_delete(node->child(i), alloc);
- }
- }
- absl::container_internal::Deallocate<Alignment()>(alloc, node,
- InternalSize());
+ void destroy(allocator_type *alloc) {
+ for (int i = start(); i < finish(); ++i) {
+ value_destroy(i, alloc);
}
}
@@ -1426,8 +1423,25 @@ class btree {
}
// Deletion helper routines.
+ void erase_same_node(iterator begin, iterator end);
+ iterator erase_from_leaf_node(iterator begin, size_type to_erase);
iterator rebalance_after_delete(iterator iter);
+ // Deallocates a node of a certain size in bytes using the allocator.
+ void deallocate(const size_type size, node_type *node) {
+ absl::container_internal::Deallocate<node_type::Alignment()>(
+ mutable_allocator(), node, size);
+ }
+
+ void delete_internal_node(node_type *node) {
+ node->destroy(mutable_allocator());
+ deallocate(node_type::InternalSize(), node);
+ }
+ void delete_leaf_node(node_type *node) {
+ node->destroy(mutable_allocator());
+ deallocate(node_type::LeafSize(node->max_count()), node);
+ }
+
// Rebalances or splits the node iter points to.
void rebalance_or_split(iterator *iter);
@@ -1496,6 +1510,9 @@ class btree {
template <typename K>
iterator internal_find(const K &key) const;
+ // Deletes a node and all of its children.
+ void internal_clear(node_type *node);
+
// Verifies the tree structure of node.
int internal_verify(const node_type *node, const key_type *lo,
const key_type *hi) const;
@@ -1563,29 +1580,26 @@ inline void btree_node<P>::emplace_value(const size_type i,
}
template <typename P>
-inline void btree_node<P>::remove_values(const field_type i,
- const field_type to_erase,
- allocator_type *alloc) {
- // Transfer values after the removed range into their new places.
- const field_type orig_finish = finish();
- const field_type src_i = i + to_erase;
- for (field_type j = i; j < src_i; ++j) {
- value_destroy(j, alloc);
+inline void btree_node<P>::remove_value(const int i, allocator_type *alloc) {
+ if (!leaf() && finish() > i + 1) {
+ assert(child(i + 1)->count() == 0);
+ for (size_type j = i + 1; j < finish(); ++j) {
+ set_child(j, child(j + 1));
+ }
+ clear_child(finish());
}
- transfer_n(orig_finish - src_i, i, src_i, this, alloc);
- if (!leaf()) {
- // Delete all children between begin and end.
- for (field_type j = 0; j < to_erase; ++j) {
- clear_and_delete(child(i + j + 1), alloc);
- }
- // Rotate children after end into new positions.
- for (field_type j = i + to_erase + 1; j <= orig_finish; ++j) {
- set_child(j - to_erase, child(j));
- clear_child(j);
- }
+ remove_values_ignore_children(i, /*to_erase=*/1, alloc);
+}
+
+template <typename P>
+inline void btree_node<P>::remove_values_ignore_children(
+ const int i, const int to_erase, allocator_type *alloc) {
+ params_type::move(alloc, slot(i + to_erase), finish_slot(), slot(i));
+ for (int j = finish() - to_erase; j < finish(); ++j) {
+ value_destroy(j, alloc);
}
- set_finish(orig_finish - to_erase);
+ set_finish(finish() - to_erase);
}
template <typename P>
@@ -1737,8 +1751,8 @@ void btree_node<P>::merge(btree_node *src, allocator_type *alloc) {
set_finish(start() + 1 + count() + src->count());
src->set_finish(src->start());
- // Remove the value on the parent node and delete the src node.
- parent()->remove_values(position(), /*to_erase=*/1, alloc);
+ // Remove the value on the parent node.
+ parent()->remove_value(position(), alloc);
}
////
@@ -2020,7 +2034,7 @@ auto btree<P>::erase(iterator iter) -> iterator {
bool internal_delete = false;
if (!iter.node->leaf()) {
// Deletion of a value on an internal node. First, move the largest value
- // from our left child here, then delete that position (in remove_values()
+ // from our left child here, then delete that position (in remove_value()
// below). We can get to the largest value from our left child by
// decrementing iter.
iterator internal_iter(iter);
@@ -2032,7 +2046,7 @@ auto btree<P>::erase(iterator iter) -> iterator {
}
// Delete the key from the leaf.
- iter.node->remove_values(iter.position, /*to_erase=*/1, mutable_allocator());
+ iter.node->remove_value(iter.position, mutable_allocator());
--size_;
// We want to return the next value after the one we just erased. If we
@@ -2107,9 +2121,7 @@ auto btree<P>::erase_range(iterator begin, iterator end)
}
if (begin.node == end.node) {
- assert(end.position > begin.position);
- begin.node->remove_values(begin.position, end.position - begin.position,
- mutable_allocator());
+ erase_same_node(begin, end);
size_ -= count;
return {count, rebalance_after_delete(begin)};
}
@@ -2119,11 +2131,8 @@ auto btree<P>::erase_range(iterator begin, iterator end)
if (begin.node->leaf()) {
const size_type remaining_to_erase = size_ - target_size;
const size_type remaining_in_node = begin.node->finish() - begin.position;
- const size_type to_erase =
- (std::min)(remaining_to_erase, remaining_in_node);
- begin.node->remove_values(begin.position, to_erase, mutable_allocator());
- size_ -= to_erase;
- begin = rebalance_after_delete(begin);
+ begin = erase_from_leaf_node(
+ begin, (std::min)(remaining_to_erase, remaining_in_node));
} else {
begin = erase(begin);
}
@@ -2132,6 +2141,51 @@ auto btree<P>::erase_range(iterator begin, iterator end)
}
template <typename P>
+void btree<P>::erase_same_node(iterator begin, iterator end) {
+ assert(begin.node == end.node);
+ assert(end.position > begin.position);
+
+ node_type *node = begin.node;
+ size_type to_erase = end.position - begin.position;
+ if (!node->leaf()) {
+ // Delete all children between begin and end.
+ for (size_type i = 0; i < to_erase; ++i) {
+ internal_clear(node->child(begin.position + i + 1));
+ }
+ // Rotate children after end into new positions.
+ for (size_type i = begin.position + to_erase + 1; i <= node->finish();
+ ++i) {
+ node->set_child(i - to_erase, node->child(i));
+ node->clear_child(i);
+ }
+ }
+ node->remove_values_ignore_children(begin.position, to_erase,
+ mutable_allocator());
+
+ // Do not need to update rightmost_, because
+ // * either end == this->end(), and therefore node == rightmost_, and still
+ // exists
+ // * or end != this->end(), and therefore rightmost_ hasn't been erased, since
+ // it wasn't covered in [begin, end)
+}
+
+template <typename P>
+auto btree<P>::erase_from_leaf_node(iterator begin, size_type to_erase)
+ -> iterator {
+ node_type *node = begin.node;
+ assert(node->leaf());
+ assert(node->finish() > begin.position);
+ assert(begin.position + to_erase <= node->finish());
+
+ node->remove_values_ignore_children(begin.position, to_erase,
+ mutable_allocator());
+
+ size_ -= to_erase;
+
+ return rebalance_after_delete(begin);
+}
+
+template <typename P>
template <typename K>
auto btree<P>::erase_unique(const K &key) -> size_type {
const iterator iter = internal_find(key);
@@ -2159,7 +2213,7 @@ auto btree<P>::erase_multi(const K &key) -> size_type {
template <typename P>
void btree<P>::clear() {
if (!empty()) {
- node_type::clear_and_delete(root(), mutable_allocator());
+ internal_clear(root());
}
mutable_root() = EmptyNode();
rightmost_ = EmptyNode();
@@ -2300,7 +2354,12 @@ void btree<P>::rebalance_or_split(iterator *iter) {
template <typename P>
void btree<P>::merge_nodes(node_type *left, node_type *right) {
left->merge(right, mutable_allocator());
- if (rightmost_ == right) rightmost_ = left;
+ if (right->leaf()) {
+ if (rightmost_ == right) rightmost_ = left;
+ delete_leaf_node(right);
+ } else {
+ delete_internal_node(right);
+ }
}
template <typename P>
@@ -2357,20 +2416,20 @@ bool btree<P>::try_merge_or_rebalance(iterator *iter) {
template <typename P>
void btree<P>::try_shrink() {
- node_type *orig_root = root();
- if (orig_root->count() > 0) {
+ if (root()->count() > 0) {
return;
}
// Deleted the last item on the root node, shrink the height of the tree.
- if (orig_root->leaf()) {
+ if (root()->leaf()) {
assert(size() == 0);
+ delete_leaf_node(root());
mutable_root() = rightmost_ = EmptyNode();
} else {
- node_type *child = orig_root->start_child();
+ node_type *child = root()->start_child();
child->make_root();
+ delete_internal_node(root());
mutable_root() = child;
}
- node_type::clear_and_delete(orig_root, mutable_allocator());
}
template <typename P>
@@ -2415,7 +2474,7 @@ inline auto btree<P>::internal_emplace(iterator iter, Args &&... args)
old_root->start(), old_root, alloc);
new_root->set_finish(old_root->finish());
old_root->set_finish(old_root->start());
- node_type::clear_and_delete(old_root, alloc);
+ delete_leaf_node(old_root);
mutable_root() = rightmost_ = new_root;
} else {
rebalance_or_split(&iter);
@@ -2519,6 +2578,18 @@ auto btree<P>::internal_find(const K &key) const -> iterator {
}
template <typename P>
+void btree<P>::internal_clear(node_type *node) {
+ if (!node->leaf()) {
+ for (int i = node->start(); i <= node->finish(); ++i) {
+ internal_clear(node->child(i));
+ }
+ delete_internal_node(node);
+ } else {
+ delete_leaf_node(node);
+ }
+}
+
+template <typename P>
int btree<P>::internal_verify(const node_type *node, const key_type *lo,
const key_type *hi) const {
assert(node->count() > 0);