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Diffstat (limited to 'third_party/abseil_cpp/absl/container/internal/btree.h')
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diff --git a/third_party/abseil_cpp/absl/container/internal/btree.h b/third_party/abseil_cpp/absl/container/internal/btree.h deleted file mode 100644 index f2fc31df8d41..000000000000 --- a/third_party/abseil_cpp/absl/container/internal/btree.h +++ /dev/null @@ -1,2587 +0,0 @@ -// Copyright 2018 The Abseil Authors. -// -// Licensed under the Apache License, Version 2.0 (the "License"); -// you may not use this file except in compliance with the License. -// You may obtain a copy of the License at -// -// https://www.apache.org/licenses/LICENSE-2.0 -// -// Unless required by applicable law or agreed to in writing, software -// distributed under the License is distributed on an "AS IS" BASIS, -// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. -// See the License for the specific language governing permissions and -// limitations under the License. - -// A btree implementation of the STL set and map interfaces. A btree is smaller -// and generally also faster than STL set/map (refer to the benchmarks below). -// The red-black tree implementation of STL set/map has an overhead of 3 -// pointers (left, right and parent) plus the node color information for each -// stored value. So a set<int32_t> consumes 40 bytes for each value stored in -// 64-bit mode. This btree implementation stores multiple values on fixed -// size nodes (usually 256 bytes) and doesn't store child pointers for leaf -// nodes. The result is that a btree_set<int32_t> may use much less memory per -// stored value. For the random insertion benchmark in btree_bench.cc, a -// btree_set<int32_t> with node-size of 256 uses 5.1 bytes per stored value. -// -// The packing of multiple values on to each node of a btree has another effect -// besides better space utilization: better cache locality due to fewer cache -// lines being accessed. Better cache locality translates into faster -// operations. -// -// CAVEATS -// -// Insertions and deletions on a btree can cause splitting, merging or -// rebalancing of btree nodes. And even without these operations, insertions -// and deletions on a btree will move values around within a node. In both -// cases, the result is that insertions and deletions can invalidate iterators -// pointing to values other than the one being inserted/deleted. Therefore, this -// container does not provide pointer stability. This is notably different from -// STL set/map which takes care to not invalidate iterators on insert/erase -// except, of course, for iterators pointing to the value being erased. A -// partial workaround when erasing is available: erase() returns an iterator -// pointing to the item just after the one that was erased (or end() if none -// exists). - -#ifndef ABSL_CONTAINER_INTERNAL_BTREE_H_ -#define ABSL_CONTAINER_INTERNAL_BTREE_H_ - -#include <algorithm> -#include <cassert> -#include <cstddef> -#include <cstdint> -#include <cstring> -#include <functional> -#include <iterator> -#include <limits> -#include <new> -#include <string> -#include <type_traits> -#include <utility> - -#include "absl/base/macros.h" -#include "absl/container/internal/common.h" -#include "absl/container/internal/compressed_tuple.h" -#include "absl/container/internal/container_memory.h" -#include "absl/container/internal/layout.h" -#include "absl/memory/memory.h" -#include "absl/meta/type_traits.h" -#include "absl/strings/cord.h" -#include "absl/strings/string_view.h" -#include "absl/types/compare.h" -#include "absl/utility/utility.h" - -namespace absl { -ABSL_NAMESPACE_BEGIN -namespace container_internal { - -// A helper class that indicates if the Compare parameter is a key-compare-to -// comparator. -template <typename Compare, typename T> -using btree_is_key_compare_to = - std::is_convertible<absl::result_of_t<Compare(const T &, const T &)>, - absl::weak_ordering>; - -struct StringBtreeDefaultLess { - using is_transparent = void; - - StringBtreeDefaultLess() = default; - - // Compatibility constructor. - StringBtreeDefaultLess(std::less<std::string>) {} // NOLINT - StringBtreeDefaultLess(std::less<string_view>) {} // NOLINT - - absl::weak_ordering operator()(absl::string_view lhs, - absl::string_view rhs) const { - return compare_internal::compare_result_as_ordering(lhs.compare(rhs)); - } - StringBtreeDefaultLess(std::less<absl::Cord>) {} // NOLINT - absl::weak_ordering operator()(const absl::Cord &lhs, - const absl::Cord &rhs) const { - return compare_internal::compare_result_as_ordering(lhs.Compare(rhs)); - } - absl::weak_ordering operator()(const absl::Cord &lhs, - absl::string_view rhs) const { - return compare_internal::compare_result_as_ordering(lhs.Compare(rhs)); - } - absl::weak_ordering operator()(absl::string_view lhs, - const absl::Cord &rhs) const { - return compare_internal::compare_result_as_ordering(-rhs.Compare(lhs)); - } -}; - -struct StringBtreeDefaultGreater { - using is_transparent = void; - - StringBtreeDefaultGreater() = default; - - StringBtreeDefaultGreater(std::greater<std::string>) {} // NOLINT - StringBtreeDefaultGreater(std::greater<string_view>) {} // NOLINT - - absl::weak_ordering operator()(absl::string_view lhs, - absl::string_view rhs) const { - return compare_internal::compare_result_as_ordering(rhs.compare(lhs)); - } - StringBtreeDefaultGreater(std::greater<absl::Cord>) {} // NOLINT - absl::weak_ordering operator()(const absl::Cord &lhs, - const absl::Cord &rhs) const { - return compare_internal::compare_result_as_ordering(rhs.Compare(lhs)); - } - absl::weak_ordering operator()(const absl::Cord &lhs, - absl::string_view rhs) const { - return compare_internal::compare_result_as_ordering(-lhs.Compare(rhs)); - } - absl::weak_ordering operator()(absl::string_view lhs, - const absl::Cord &rhs) const { - return compare_internal::compare_result_as_ordering(rhs.Compare(lhs)); - } -}; - -// A helper class to convert a boolean comparison into a three-way "compare-to" -// comparison that returns an `absl::weak_ordering`. This helper -// class is specialized for less<std::string>, greater<std::string>, -// less<string_view>, greater<string_view>, less<absl::Cord>, and -// greater<absl::Cord>. -// -// key_compare_to_adapter is provided so that btree users -// automatically get the more efficient compare-to code when using common -// Abseil string types with common comparison functors. -// These string-like specializations also turn on heterogeneous lookup by -// default. -template <typename Compare> -struct key_compare_to_adapter { - using type = Compare; -}; - -template <> -struct key_compare_to_adapter<std::less<std::string>> { - using type = StringBtreeDefaultLess; -}; - -template <> -struct key_compare_to_adapter<std::greater<std::string>> { - using type = StringBtreeDefaultGreater; -}; - -template <> -struct key_compare_to_adapter<std::less<absl::string_view>> { - using type = StringBtreeDefaultLess; -}; - -template <> -struct key_compare_to_adapter<std::greater<absl::string_view>> { - using type = StringBtreeDefaultGreater; -}; - -template <> -struct key_compare_to_adapter<std::less<absl::Cord>> { - using type = StringBtreeDefaultLess; -}; - -template <> -struct key_compare_to_adapter<std::greater<absl::Cord>> { - using type = StringBtreeDefaultGreater; -}; - -// Detects an 'absl_btree_prefer_linear_node_search' member. This is -// a protocol used as an opt-in or opt-out of linear search. -// -// For example, this would be useful for key types that wrap an integer -// and define their own cheap operator<(). For example: -// -// class K { -// public: -// using absl_btree_prefer_linear_node_search = std::true_type; -// ... -// private: -// friend bool operator<(K a, K b) { return a.k_ < b.k_; } -// int k_; -// }; -// -// btree_map<K, V> m; // Uses linear search -// -// If T has the preference tag, then it has a preference. -// Btree will use the tag's truth value. -template <typename T, typename = void> -struct has_linear_node_search_preference : std::false_type {}; -template <typename T, typename = void> -struct prefers_linear_node_search : std::false_type {}; -template <typename T> -struct has_linear_node_search_preference< - T, absl::void_t<typename T::absl_btree_prefer_linear_node_search>> - : std::true_type {}; -template <typename T> -struct prefers_linear_node_search< - T, absl::void_t<typename T::absl_btree_prefer_linear_node_search>> - : T::absl_btree_prefer_linear_node_search {}; - -template <typename Key, typename Compare, typename Alloc, int TargetNodeSize, - bool Multi, typename SlotPolicy> -struct common_params { - // If Compare is a common comparator for a string-like type, then we adapt it - // to use heterogeneous lookup and to be a key-compare-to comparator. - using key_compare = typename key_compare_to_adapter<Compare>::type; - // True when key_compare has been adapted to StringBtreeDefault{Less,Greater}. - using is_key_compare_adapted = - absl::negation<std::is_same<key_compare, Compare>>; - // A type which indicates if we have a key-compare-to functor or a plain old - // key-compare functor. - using is_key_compare_to = btree_is_key_compare_to<key_compare, Key>; - - using allocator_type = Alloc; - using key_type = Key; - using size_type = std::make_signed<size_t>::type; - using difference_type = ptrdiff_t; - - // True if this is a multiset or multimap. - using is_multi_container = std::integral_constant<bool, Multi>; - - using slot_policy = SlotPolicy; - using slot_type = typename slot_policy::slot_type; - using value_type = typename slot_policy::value_type; - using init_type = typename slot_policy::mutable_value_type; - using pointer = value_type *; - using const_pointer = const value_type *; - using reference = value_type &; - using const_reference = const value_type &; - - enum { - kTargetNodeSize = TargetNodeSize, - - // Upper bound for the available space for values. This is largest for leaf - // nodes, which have overhead of at least a pointer + 4 bytes (for storing - // 3 field_types and an enum). - kNodeValueSpace = - TargetNodeSize - /*minimum overhead=*/(sizeof(void *) + 4), - }; - - // This is an integral type large enough to hold as many - // ValueSize-values as will fit a node of TargetNodeSize bytes. - using node_count_type = - absl::conditional_t<(kNodeValueSpace / sizeof(value_type) > - (std::numeric_limits<uint8_t>::max)()), - uint16_t, uint8_t>; // NOLINT - - // The following methods are necessary for passing this struct as PolicyTraits - // for node_handle and/or are used within btree. - static value_type &element(slot_type *slot) { - return slot_policy::element(slot); - } - static const value_type &element(const slot_type *slot) { - return slot_policy::element(slot); - } - template <class... Args> - static void construct(Alloc *alloc, slot_type *slot, Args &&... args) { - slot_policy::construct(alloc, slot, std::forward<Args>(args)...); - } - static void construct(Alloc *alloc, slot_type *slot, slot_type *other) { - slot_policy::construct(alloc, slot, other); - } - static void destroy(Alloc *alloc, slot_type *slot) { - slot_policy::destroy(alloc, slot); - } - static void transfer(Alloc *alloc, slot_type *new_slot, slot_type *old_slot) { - construct(alloc, new_slot, old_slot); - destroy(alloc, old_slot); - } - static void swap(Alloc *alloc, slot_type *a, slot_type *b) { - slot_policy::swap(alloc, a, b); - } - static void move(Alloc *alloc, slot_type *src, slot_type *dest) { - slot_policy::move(alloc, src, dest); - } -}; - -// A parameters structure for holding the type parameters for a btree_map. -// Compare and Alloc should be nothrow copy-constructible. -template <typename Key, typename Data, typename Compare, typename Alloc, - int TargetNodeSize, bool Multi> -struct map_params : common_params<Key, Compare, Alloc, TargetNodeSize, Multi, - map_slot_policy<Key, Data>> { - using super_type = typename map_params::common_params; - using mapped_type = Data; - // This type allows us to move keys when it is safe to do so. It is safe - // for maps in which value_type and mutable_value_type are layout compatible. - using slot_policy = typename super_type::slot_policy; - using slot_type = typename super_type::slot_type; - using value_type = typename super_type::value_type; - using init_type = typename super_type::init_type; - - using key_compare = typename super_type::key_compare; - // Inherit from key_compare for empty base class optimization. - struct value_compare : private key_compare { - value_compare() = default; - explicit value_compare(const key_compare &cmp) : key_compare(cmp) {} - - template <typename T, typename U> - auto operator()(const T &left, const U &right) const - -> decltype(std::declval<key_compare>()(left.first, right.first)) { - return key_compare::operator()(left.first, right.first); - } - }; - using is_map_container = std::true_type; - - template <typename V> - static auto key(const V &value) -> decltype(value.first) { - return value.first; - } - static const Key &key(const slot_type *s) { return slot_policy::key(s); } - static const Key &key(slot_type *s) { return slot_policy::key(s); } - // For use in node handle. - static auto mutable_key(slot_type *s) - -> decltype(slot_policy::mutable_key(s)) { - return slot_policy::mutable_key(s); - } - static mapped_type &value(value_type *value) { return value->second; } -}; - -// This type implements the necessary functions from the -// absl::container_internal::slot_type interface. -template <typename Key> -struct set_slot_policy { - using slot_type = Key; - using value_type = Key; - using mutable_value_type = Key; - - static value_type &element(slot_type *slot) { return *slot; } - static const value_type &element(const slot_type *slot) { return *slot; } - - template <typename Alloc, class... Args> - static void construct(Alloc *alloc, slot_type *slot, Args &&... args) { - absl::allocator_traits<Alloc>::construct(*alloc, slot, - std::forward<Args>(args)...); - } - - template <typename Alloc> - static void construct(Alloc *alloc, slot_type *slot, slot_type *other) { - absl::allocator_traits<Alloc>::construct(*alloc, slot, std::move(*other)); - } - - template <typename Alloc> - static void destroy(Alloc *alloc, slot_type *slot) { - absl::allocator_traits<Alloc>::destroy(*alloc, slot); - } - - template <typename Alloc> - static void swap(Alloc * /*alloc*/, slot_type *a, slot_type *b) { - using std::swap; - swap(*a, *b); - } - - template <typename Alloc> - static void move(Alloc * /*alloc*/, slot_type *src, slot_type *dest) { - *dest = std::move(*src); - } -}; - -// A parameters structure for holding the type parameters for a btree_set. -// Compare and Alloc should be nothrow copy-constructible. -template <typename Key, typename Compare, typename Alloc, int TargetNodeSize, - bool Multi> -struct set_params : common_params<Key, Compare, Alloc, TargetNodeSize, Multi, - set_slot_policy<Key>> { - using value_type = Key; - using slot_type = typename set_params::common_params::slot_type; - using value_compare = typename set_params::common_params::key_compare; - using is_map_container = std::false_type; - - template <typename V> - static const V &key(const V &value) { return value; } - static const Key &key(const slot_type *slot) { return *slot; } - static const Key &key(slot_type *slot) { return *slot; } -}; - -// An adapter class that converts a lower-bound compare into an upper-bound -// compare. Note: there is no need to make a version of this adapter specialized -// for key-compare-to functors because the upper-bound (the first value greater -// than the input) is never an exact match. -template <typename Compare> -struct upper_bound_adapter { - explicit upper_bound_adapter(const Compare &c) : comp(c) {} - template <typename K1, typename K2> - bool operator()(const K1 &a, const K2 &b) const { - // Returns true when a is not greater than b. - return !compare_internal::compare_result_as_less_than(comp(b, a)); - } - - private: - Compare comp; -}; - -enum class MatchKind : uint8_t { kEq, kNe }; - -template <typename V, bool IsCompareTo> -struct SearchResult { - V value; - MatchKind match; - - static constexpr bool HasMatch() { return true; } - bool IsEq() const { return match == MatchKind::kEq; } -}; - -// When we don't use CompareTo, `match` is not present. -// This ensures that callers can't use it accidentally when it provides no -// useful information. -template <typename V> -struct SearchResult<V, false> { - SearchResult() {} - explicit SearchResult(V value) : value(value) {} - SearchResult(V value, MatchKind /*match*/) : value(value) {} - - V value; - - static constexpr bool HasMatch() { return false; } - static constexpr bool IsEq() { return false; } -}; - -// A node in the btree holding. The same node type is used for both internal -// and leaf nodes in the btree, though the nodes are allocated in such a way -// that the children array is only valid in internal nodes. -template <typename Params> -class btree_node { - using is_key_compare_to = typename Params::is_key_compare_to; - using is_multi_container = typename Params::is_multi_container; - using field_type = typename Params::node_count_type; - using allocator_type = typename Params::allocator_type; - using slot_type = typename Params::slot_type; - - public: - using params_type = Params; - using key_type = typename Params::key_type; - using value_type = typename Params::value_type; - using pointer = typename Params::pointer; - using const_pointer = typename Params::const_pointer; - using reference = typename Params::reference; - using const_reference = typename Params::const_reference; - using key_compare = typename Params::key_compare; - using size_type = typename Params::size_type; - using difference_type = typename Params::difference_type; - - // Btree decides whether to use linear node search as follows: - // - If the comparator expresses a preference, use that. - // - If the key expresses a preference, use that. - // - If the key is arithmetic and the comparator is std::less or - // std::greater, choose linear. - // - Otherwise, choose binary. - // TODO(ezb): Might make sense to add condition(s) based on node-size. - using use_linear_search = std::integral_constant< - bool, - has_linear_node_search_preference<key_compare>::value - ? prefers_linear_node_search<key_compare>::value - : has_linear_node_search_preference<key_type>::value - ? prefers_linear_node_search<key_type>::value - : std::is_arithmetic<key_type>::value && - (std::is_same<std::less<key_type>, key_compare>::value || - std::is_same<std::greater<key_type>, - key_compare>::value)>; - - // This class is organized by gtl::Layout as if it had the following - // structure: - // // A pointer to the node's parent. - // btree_node *parent; - // - // // The position of the node in the node's parent. - // field_type position; - // // The index of the first populated value in `values`. - // // TODO(ezb): right now, `start` is always 0. Update insertion/merge - // // logic to allow for floating storage within nodes. - // field_type start; - // // The index after the last populated value in `values`. Currently, this - // // is the same as the count of values. - // field_type finish; - // // The maximum number of values the node can hold. This is an integer in - // // [1, kNodeValues] for root leaf nodes, kNodeValues for non-root leaf - // // nodes, and kInternalNodeMaxCount (as a sentinel value) for internal - // // nodes (even though there are still kNodeValues values in the node). - // // TODO(ezb): make max_count use only 4 bits and record log2(capacity) - // // to free extra bits for is_root, etc. - // field_type max_count; - // - // // The array of values. The capacity is `max_count` for leaf nodes and - // // kNodeValues for internal nodes. Only the values in - // // [start, finish) have been initialized and are valid. - // slot_type values[max_count]; - // - // // The array of child pointers. The keys in children[i] are all less - // // than key(i). The keys in children[i + 1] are all greater than key(i). - // // There are 0 children for leaf nodes and kNodeValues + 1 children for - // // internal nodes. - // btree_node *children[kNodeValues + 1]; - // - // This class is only constructed by EmptyNodeType. Normally, pointers to the - // layout above are allocated, cast to btree_node*, and de-allocated within - // the btree implementation. - ~btree_node() = default; - btree_node(btree_node const &) = delete; - btree_node &operator=(btree_node const &) = delete; - - // Public for EmptyNodeType. - constexpr static size_type Alignment() { - static_assert(LeafLayout(1).Alignment() == InternalLayout().Alignment(), - "Alignment of all nodes must be equal."); - return InternalLayout().Alignment(); - } - - protected: - btree_node() = default; - - private: - using layout_type = absl::container_internal::Layout<btree_node *, field_type, - slot_type, btree_node *>; - constexpr static size_type SizeWithNValues(size_type n) { - return layout_type(/*parent*/ 1, - /*position, start, finish, max_count*/ 4, - /*values*/ n, - /*children*/ 0) - .AllocSize(); - } - // A lower bound for the overhead of fields other than values in a leaf node. - constexpr static size_type MinimumOverhead() { - return SizeWithNValues(1) - sizeof(value_type); - } - - // Compute how many values we can fit onto a leaf node taking into account - // padding. - constexpr static size_type NodeTargetValues(const int begin, const int end) { - return begin == end ? begin - : SizeWithNValues((begin + end) / 2 + 1) > - params_type::kTargetNodeSize - ? NodeTargetValues(begin, (begin + end) / 2) - : NodeTargetValues((begin + end) / 2 + 1, end); - } - - enum { - kTargetNodeSize = params_type::kTargetNodeSize, - kNodeTargetValues = NodeTargetValues(0, params_type::kTargetNodeSize), - - // We need a minimum of 3 values per internal node in order to perform - // splitting (1 value for the two nodes involved in the split and 1 value - // propagated to the parent as the delimiter for the split). - kNodeValues = kNodeTargetValues >= 3 ? kNodeTargetValues : 3, - - // The node is internal (i.e. is not a leaf node) if and only if `max_count` - // has this value. - kInternalNodeMaxCount = 0, - }; - - // Leaves can have less than kNodeValues values. - constexpr static layout_type LeafLayout(const int max_values = kNodeValues) { - return layout_type(/*parent*/ 1, - /*position, start, finish, max_count*/ 4, - /*values*/ max_values, - /*children*/ 0); - } - constexpr static layout_type InternalLayout() { - return layout_type(/*parent*/ 1, - /*position, start, finish, max_count*/ 4, - /*values*/ kNodeValues, - /*children*/ kNodeValues + 1); - } - constexpr static size_type LeafSize(const int max_values = kNodeValues) { - return LeafLayout(max_values).AllocSize(); - } - constexpr static size_type InternalSize() { - return InternalLayout().AllocSize(); - } - - // N is the index of the type in the Layout definition. - // ElementType<N> is the Nth type in the Layout definition. - template <size_type N> - inline typename layout_type::template ElementType<N> *GetField() { - // We assert that we don't read from values that aren't there. - assert(N < 3 || !leaf()); - return InternalLayout().template Pointer<N>(reinterpret_cast<char *>(this)); - } - template <size_type N> - inline const typename layout_type::template ElementType<N> *GetField() const { - assert(N < 3 || !leaf()); - return InternalLayout().template Pointer<N>( - reinterpret_cast<const char *>(this)); - } - void set_parent(btree_node *p) { *GetField<0>() = p; } - field_type &mutable_finish() { return GetField<1>()[2]; } - slot_type *slot(int i) { return &GetField<2>()[i]; } - slot_type *start_slot() { return slot(start()); } - slot_type *finish_slot() { return slot(finish()); } - const slot_type *slot(int i) const { return &GetField<2>()[i]; } - void set_position(field_type v) { GetField<1>()[0] = v; } - void set_start(field_type v) { GetField<1>()[1] = v; } - void set_finish(field_type v) { GetField<1>()[2] = v; } - // This method is only called by the node init methods. - void set_max_count(field_type v) { GetField<1>()[3] = v; } - - public: - // Whether this is a leaf node or not. This value doesn't change after the - // node is created. - bool leaf() const { return GetField<1>()[3] != kInternalNodeMaxCount; } - - // Getter for the position of this node in its parent. - field_type position() const { return GetField<1>()[0]; } - - // Getter for the offset of the first value in the `values` array. - field_type start() const { - // TODO(ezb): when floating storage is implemented, return GetField<1>()[1]; - assert(GetField<1>()[1] == 0); - return 0; - } - - // Getter for the offset after the last value in the `values` array. - field_type finish() const { return GetField<1>()[2]; } - - // Getters for the number of values stored in this node. - field_type count() const { - assert(finish() >= start()); - return finish() - start(); - } - field_type max_count() const { - // Internal nodes have max_count==kInternalNodeMaxCount. - // Leaf nodes have max_count in [1, kNodeValues]. - const field_type max_count = GetField<1>()[3]; - return max_count == field_type{kInternalNodeMaxCount} - ? field_type{kNodeValues} - : max_count; - } - - // Getter for the parent of this node. - btree_node *parent() const { return *GetField<0>(); } - // Getter for whether the node is the root of the tree. The parent of the - // root of the tree is the leftmost node in the tree which is guaranteed to - // be a leaf. - bool is_root() const { return parent()->leaf(); } - void make_root() { - assert(parent()->is_root()); - set_parent(parent()->parent()); - } - - // Getters for the key/value at position i in the node. - const key_type &key(int i) const { return params_type::key(slot(i)); } - reference value(int i) { return params_type::element(slot(i)); } - const_reference value(int i) const { return params_type::element(slot(i)); } - - // Getters/setter for the child at position i in the node. - btree_node *child(int i) const { return GetField<3>()[i]; } - btree_node *start_child() const { return child(start()); } - btree_node *&mutable_child(int i) { return GetField<3>()[i]; } - void clear_child(int i) { - absl::container_internal::SanitizerPoisonObject(&mutable_child(i)); - } - void set_child(int i, btree_node *c) { - absl::container_internal::SanitizerUnpoisonObject(&mutable_child(i)); - mutable_child(i) = c; - c->set_position(i); - } - void init_child(int i, btree_node *c) { - set_child(i, c); - c->set_parent(this); - } - - // Returns the position of the first value whose key is not less than k. - template <typename K> - SearchResult<int, is_key_compare_to::value> lower_bound( - const K &k, const key_compare &comp) const { - return use_linear_search::value ? linear_search(k, comp) - : binary_search(k, comp); - } - // Returns the position of the first value whose key is greater than k. - template <typename K> - int upper_bound(const K &k, const key_compare &comp) const { - auto upper_compare = upper_bound_adapter<key_compare>(comp); - return use_linear_search::value ? linear_search(k, upper_compare).value - : binary_search(k, upper_compare).value; - } - - template <typename K, typename Compare> - SearchResult<int, btree_is_key_compare_to<Compare, key_type>::value> - linear_search(const K &k, const Compare &comp) const { - return linear_search_impl(k, start(), finish(), comp, - btree_is_key_compare_to<Compare, key_type>()); - } - - template <typename K, typename Compare> - SearchResult<int, btree_is_key_compare_to<Compare, key_type>::value> - binary_search(const K &k, const Compare &comp) const { - return binary_search_impl(k, start(), finish(), comp, - btree_is_key_compare_to<Compare, key_type>()); - } - - // Returns the position of the first value whose key is not less than k using - // linear search performed using plain compare. - template <typename K, typename Compare> - SearchResult<int, false> linear_search_impl( - const K &k, int s, const int e, const Compare &comp, - std::false_type /* IsCompareTo */) const { - while (s < e) { - if (!comp(key(s), k)) { - break; - } - ++s; - } - return SearchResult<int, false>{s}; - } - - // Returns the position of the first value whose key is not less than k using - // linear search performed using compare-to. - template <typename K, typename Compare> - SearchResult<int, true> linear_search_impl( - const K &k, int s, const int e, const Compare &comp, - std::true_type /* IsCompareTo */) const { - while (s < e) { - const absl::weak_ordering c = comp(key(s), k); - if (c == 0) { - return {s, MatchKind::kEq}; - } else if (c > 0) { - break; - } - ++s; - } - return {s, MatchKind::kNe}; - } - - // Returns the position of the first value whose key is not less than k using - // binary search performed using plain compare. - template <typename K, typename Compare> - SearchResult<int, false> binary_search_impl( - const K &k, int s, int e, const Compare &comp, - std::false_type /* IsCompareTo */) const { - while (s != e) { - const int mid = (s + e) >> 1; - if (comp(key(mid), k)) { - s = mid + 1; - } else { - e = mid; - } - } - return SearchResult<int, false>{s}; - } - - // Returns the position of the first value whose key is not less than k using - // binary search performed using compare-to. - template <typename K, typename CompareTo> - SearchResult<int, true> binary_search_impl( - const K &k, int s, int e, const CompareTo &comp, - std::true_type /* IsCompareTo */) const { - if (is_multi_container::value) { - MatchKind exact_match = MatchKind::kNe; - while (s != e) { - const int mid = (s + e) >> 1; - const absl::weak_ordering c = comp(key(mid), k); - if (c < 0) { - s = mid + 1; - } else { - e = mid; - if (c == 0) { - // Need to return the first value whose key is not less than k, - // which requires continuing the binary search if this is a - // multi-container. - exact_match = MatchKind::kEq; - } - } - } - return {s, exact_match}; - } else { // Not a multi-container. - while (s != e) { - const int mid = (s + e) >> 1; - const absl::weak_ordering c = comp(key(mid), k); - if (c < 0) { - s = mid + 1; - } else if (c > 0) { - e = mid; - } else { - return {mid, MatchKind::kEq}; - } - } - return {s, MatchKind::kNe}; - } - } - - // Emplaces a value at position i, shifting all existing values and - // children at positions >= i to the right by 1. - 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); - - // Rebalances a node with its right sibling. - void rebalance_right_to_left(int to_move, btree_node *right, - allocator_type *alloc); - void rebalance_left_to_right(int to_move, btree_node *right, - allocator_type *alloc); - - // Splits a node, moving a portion of the node's values to its right sibling. - 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. - void merge(btree_node *src, allocator_type *alloc); - - // Node allocation/deletion routines. - void init_leaf(btree_node *parent, int max_count) { - set_parent(parent); - set_position(0); - set_start(0); - set_finish(0); - set_max_count(max_count); - absl::container_internal::SanitizerPoisonMemoryRegion( - start_slot(), max_count * sizeof(slot_type)); - } - void init_internal(btree_node *parent) { - init_leaf(parent, kNodeValues); - // Set `max_count` to a sentinel value to indicate that this node is - // internal. - set_max_count(kInternalNodeMaxCount); - absl::container_internal::SanitizerPoisonMemoryRegion( - &mutable_child(start()), (kNodeValues + 1) * sizeof(btree_node *)); - } - - static void deallocate(const size_type size, btree_node *node, - allocator_type *alloc) { - absl::container_internal::Deallocate<Alignment()>(alloc, node, size); - } - - // Deletes a node and all of its children. - static void clear_and_delete(btree_node *node, allocator_type *alloc); - - private: - template <typename... Args> - void value_init(const field_type i, allocator_type *alloc, Args &&... args) { - absl::container_internal::SanitizerUnpoisonObject(slot(i)); - params_type::construct(alloc, slot(i), std::forward<Args>(args)...); - } - void value_destroy(const field_type i, allocator_type *alloc) { - params_type::destroy(alloc, slot(i)); - absl::container_internal::SanitizerPoisonObject(slot(i)); - } - void value_destroy_n(const field_type i, const field_type n, - allocator_type *alloc) { - for (slot_type *s = slot(i), *end = slot(i + n); s != end; ++s) { - params_type::destroy(alloc, s); - absl::container_internal::SanitizerPoisonObject(s); - } - } - - static void transfer(slot_type *dest, slot_type *src, allocator_type *alloc) { - absl::container_internal::SanitizerUnpoisonObject(dest); - params_type::transfer(alloc, dest, src); - absl::container_internal::SanitizerPoisonObject(src); - } - - // Transfers value from slot `src_i` in `src_node` to slot `dest_i` in `this`. - void transfer(const size_type dest_i, const size_type src_i, - btree_node *src_node, allocator_type *alloc) { - transfer(slot(dest_i), src_node->slot(src_i), alloc); - } - - // Transfers `n` values starting at value `src_i` in `src_node` into the - // values starting at value `dest_i` in `this`. - void transfer_n(const size_type n, const size_type dest_i, - const size_type src_i, btree_node *src_node, - allocator_type *alloc) { - for (slot_type *src = src_node->slot(src_i), *end = src + n, - *dest = slot(dest_i); - src != end; ++src, ++dest) { - transfer(dest, src, alloc); - } - } - - // Same as above, except that we start at the end and work our way to the - // beginning. - void transfer_n_backward(const size_type n, const size_type dest_i, - const size_type src_i, btree_node *src_node, - allocator_type *alloc) { - for (slot_type *src = src_node->slot(src_i + n - 1), *end = src - n, - *dest = slot(dest_i + n - 1); - src != end; --src, --dest) { - transfer(dest, src, alloc); - } - } - - template <typename P> - friend class btree; - template <typename N, typename R, typename P> - friend struct btree_iterator; - friend class BtreeNodePeer; -}; - -template <typename Node, typename Reference, typename Pointer> -struct btree_iterator { - private: - using key_type = typename Node::key_type; - using size_type = typename Node::size_type; - using params_type = typename Node::params_type; - - using node_type = Node; - using normal_node = typename std::remove_const<Node>::type; - using const_node = const Node; - using normal_pointer = typename params_type::pointer; - using normal_reference = typename params_type::reference; - using const_pointer = typename params_type::const_pointer; - using const_reference = typename params_type::const_reference; - using slot_type = typename params_type::slot_type; - - using iterator = - btree_iterator<normal_node, normal_reference, normal_pointer>; - using const_iterator = - btree_iterator<const_node, const_reference, const_pointer>; - - public: - // These aliases are public for std::iterator_traits. - using difference_type = typename Node::difference_type; - using value_type = typename params_type::value_type; - using pointer = Pointer; - using reference = Reference; - using iterator_category = std::bidirectional_iterator_tag; - - btree_iterator() : node(nullptr), position(-1) {} - explicit btree_iterator(Node *n) : node(n), position(n->start()) {} - btree_iterator(Node *n, int p) : node(n), position(p) {} - - // NOTE: this SFINAE allows for implicit conversions from iterator to - // const_iterator, but it specifically avoids defining copy constructors so - // that btree_iterator can be trivially copyable. This is for performance and - // binary size reasons. - template <typename N, typename R, typename P, - absl::enable_if_t< - std::is_same<btree_iterator<N, R, P>, iterator>::value && - std::is_same<btree_iterator, const_iterator>::value, - int> = 0> - btree_iterator(const btree_iterator<N, R, P> &other) // NOLINT - : node(other.node), position(other.position) {} - - private: - // This SFINAE allows explicit conversions from const_iterator to - // iterator, but also avoids defining a copy constructor. - // NOTE: the const_cast is safe because this constructor is only called by - // non-const methods and the container owns the nodes. - template <typename N, typename R, typename P, - absl::enable_if_t< - std::is_same<btree_iterator<N, R, P>, const_iterator>::value && - std::is_same<btree_iterator, iterator>::value, - int> = 0> - explicit btree_iterator(const btree_iterator<N, R, P> &other) - : node(const_cast<node_type *>(other.node)), position(other.position) {} - - // Increment/decrement the iterator. - void increment() { - if (node->leaf() && ++position < node->finish()) { - return; - } - increment_slow(); - } - void increment_slow(); - - void decrement() { - if (node->leaf() && --position >= node->start()) { - return; - } - decrement_slow(); - } - void decrement_slow(); - - public: - bool operator==(const iterator &other) const { - return node == other.node && position == other.position; - } - bool operator==(const const_iterator &other) const { - return node == other.node && position == other.position; - } - bool operator!=(const iterator &other) const { - return node != other.node || position != other.position; - } - bool operator!=(const const_iterator &other) const { - return node != other.node || position != other.position; - } - - // Accessors for the key/value the iterator is pointing at. - reference operator*() const { - ABSL_HARDENING_ASSERT(node != nullptr); - ABSL_HARDENING_ASSERT(node->start() <= position); - ABSL_HARDENING_ASSERT(node->finish() > position); - return node->value(position); - } - pointer operator->() const { return &operator*(); } - - btree_iterator &operator++() { - increment(); - return *this; - } - btree_iterator &operator--() { - decrement(); - return *this; - } - btree_iterator operator++(int) { - btree_iterator tmp = *this; - ++*this; - return tmp; - } - btree_iterator operator--(int) { - btree_iterator tmp = *this; - --*this; - return tmp; - } - - private: - template <typename Params> - friend class btree; - template <typename Tree> - friend class btree_container; - template <typename Tree> - friend class btree_set_container; - template <typename Tree> - friend class btree_map_container; - template <typename Tree> - friend class btree_multiset_container; - template <typename N, typename R, typename P> - friend struct btree_iterator; - template <typename TreeType, typename CheckerType> - friend class base_checker; - - const key_type &key() const { return node->key(position); } - slot_type *slot() { return node->slot(position); } - - // The node in the tree the iterator is pointing at. - Node *node; - // The position within the node of the tree the iterator is pointing at. - // NOTE: this is an int rather than a field_type because iterators can point - // to invalid positions (such as -1) in certain circumstances. - int position; -}; - -template <typename Params> -class btree { - using node_type = btree_node<Params>; - using is_key_compare_to = typename Params::is_key_compare_to; - using init_type = typename Params::init_type; - using field_type = typename node_type::field_type; - using is_multi_container = typename Params::is_multi_container; - using is_key_compare_adapted = typename Params::is_key_compare_adapted; - - // We use a static empty node for the root/leftmost/rightmost of empty btrees - // in order to avoid branching in begin()/end(). - struct alignas(node_type::Alignment()) EmptyNodeType : node_type { - using field_type = typename node_type::field_type; - node_type *parent; - field_type position = 0; - field_type start = 0; - field_type finish = 0; - // max_count must be != kInternalNodeMaxCount (so that this node is regarded - // as a leaf node). max_count() is never called when the tree is empty. - field_type max_count = node_type::kInternalNodeMaxCount + 1; - -#ifdef _MSC_VER - // MSVC has constexpr code generations bugs here. - EmptyNodeType() : parent(this) {} -#else - constexpr EmptyNodeType(node_type *p) : parent(p) {} -#endif - }; - - static node_type *EmptyNode() { -#ifdef _MSC_VER - static EmptyNodeType *empty_node = new EmptyNodeType; - // This assert fails on some other construction methods. - assert(empty_node->parent == empty_node); - return empty_node; -#else - static constexpr EmptyNodeType empty_node( - const_cast<EmptyNodeType *>(&empty_node)); - return const_cast<EmptyNodeType *>(&empty_node); -#endif - } - - enum : uint32_t { - kNodeValues = node_type::kNodeValues, - kMinNodeValues = kNodeValues / 2, - }; - - struct node_stats { - using size_type = typename Params::size_type; - - node_stats(size_type l, size_type i) : leaf_nodes(l), internal_nodes(i) {} - - node_stats &operator+=(const node_stats &other) { - leaf_nodes += other.leaf_nodes; - internal_nodes += other.internal_nodes; - return *this; - } - - size_type leaf_nodes; - size_type internal_nodes; - }; - - public: - using key_type = typename Params::key_type; - using value_type = typename Params::value_type; - using size_type = typename Params::size_type; - using difference_type = typename Params::difference_type; - using key_compare = typename Params::key_compare; - using value_compare = typename Params::value_compare; - using allocator_type = typename Params::allocator_type; - using reference = typename Params::reference; - using const_reference = typename Params::const_reference; - using pointer = typename Params::pointer; - using const_pointer = typename Params::const_pointer; - using iterator = btree_iterator<node_type, reference, pointer>; - using const_iterator = typename iterator::const_iterator; - using reverse_iterator = std::reverse_iterator<iterator>; - using const_reverse_iterator = std::reverse_iterator<const_iterator>; - using node_handle_type = node_handle<Params, Params, allocator_type>; - - // Internal types made public for use by btree_container types. - using params_type = Params; - using slot_type = typename Params::slot_type; - - private: - // For use in copy_or_move_values_in_order. - const value_type &maybe_move_from_iterator(const_iterator it) { return *it; } - value_type &&maybe_move_from_iterator(iterator it) { return std::move(*it); } - - // Copies or moves (depending on the template parameter) the values in - // other into this btree in their order in other. This btree must be empty - // before this method is called. This method is used in copy construction, - // copy assignment, and move assignment. - template <typename Btree> - void copy_or_move_values_in_order(Btree &other); - - // Validates that various assumptions/requirements are true at compile time. - constexpr static bool static_assert_validation(); - - public: - btree(const key_compare &comp, const allocator_type &alloc) - : root_(comp, alloc, EmptyNode()), rightmost_(EmptyNode()), size_(0) {} - - btree(const btree &other) : btree(other, other.allocator()) {} - btree(const btree &other, const allocator_type &alloc) - : btree(other.key_comp(), alloc) { - copy_or_move_values_in_order(other); - } - btree(btree &&other) noexcept - : root_(std::move(other.root_)), - rightmost_(absl::exchange(other.rightmost_, EmptyNode())), - size_(absl::exchange(other.size_, 0)) { - other.mutable_root() = EmptyNode(); - } - btree(btree &&other, const allocator_type &alloc) - : btree(other.key_comp(), alloc) { - if (alloc == other.allocator()) { - swap(other); - } else { - // Move values from `other` one at a time when allocators are different. - copy_or_move_values_in_order(other); - } - } - - ~btree() { - // Put static_asserts in destructor to avoid triggering them before the type - // is complete. - static_assert(static_assert_validation(), "This call must be elided."); - clear(); - } - - // Assign the contents of other to *this. - btree &operator=(const btree &other); - btree &operator=(btree &&other) noexcept; - - iterator begin() { return iterator(leftmost()); } - const_iterator begin() const { return const_iterator(leftmost()); } - iterator end() { return iterator(rightmost_, rightmost_->finish()); } - const_iterator end() const { - return const_iterator(rightmost_, rightmost_->finish()); - } - reverse_iterator rbegin() { return reverse_iterator(end()); } - const_reverse_iterator rbegin() const { - return const_reverse_iterator(end()); - } - reverse_iterator rend() { return reverse_iterator(begin()); } - const_reverse_iterator rend() const { - return const_reverse_iterator(begin()); - } - - // Finds the first element whose key is not less than key. - template <typename K> - iterator lower_bound(const K &key) { - return internal_end(internal_lower_bound(key).value); - } - template <typename K> - const_iterator lower_bound(const K &key) const { - return internal_end(internal_lower_bound(key).value); - } - - // Finds the first element whose key is greater than key. - template <typename K> - iterator upper_bound(const K &key) { - return internal_end(internal_upper_bound(key)); - } - template <typename K> - const_iterator upper_bound(const K &key) const { - return internal_end(internal_upper_bound(key)); - } - - // Finds the range of values which compare equal to key. The first member of - // the returned pair is equal to lower_bound(key). The second member of the - // pair is equal to upper_bound(key). - template <typename K> - std::pair<iterator, iterator> equal_range(const K &key); - template <typename K> - std::pair<const_iterator, const_iterator> equal_range(const K &key) const { - return const_cast<btree *>(this)->equal_range(key); - } - - // Inserts a value into the btree only if it does not already exist. The - // boolean return value indicates whether insertion succeeded or failed. - // Requirement: if `key` already exists in the btree, does not consume `args`. - // Requirement: `key` is never referenced after consuming `args`. - template <typename K, typename... Args> - std::pair<iterator, bool> insert_unique(const K &key, Args &&... args); - - // Inserts with hint. Checks to see if the value should be placed immediately - // before `position` in the tree. If so, then the insertion will take - // amortized constant time. If not, the insertion will take amortized - // logarithmic time as if a call to insert_unique() were made. - // Requirement: if `key` already exists in the btree, does not consume `args`. - // Requirement: `key` is never referenced after consuming `args`. - template <typename K, typename... Args> - std::pair<iterator, bool> insert_hint_unique(iterator position, - const K &key, - Args &&... args); - - // Insert a range of values into the btree. - // Note: the first overload avoids constructing a value_type if the key - // already exists in the btree. - template <typename InputIterator, - typename = decltype(std::declval<const key_compare &>()( - params_type::key(*std::declval<InputIterator>()), - std::declval<const key_type &>()))> - void insert_iterator_unique(InputIterator b, InputIterator e, int); - // We need the second overload for cases in which we need to construct a - // value_type in order to compare it with the keys already in the btree. - template <typename InputIterator> - void insert_iterator_unique(InputIterator b, InputIterator e, char); - - // Inserts a value into the btree. - template <typename ValueType> - iterator insert_multi(const key_type &key, ValueType &&v); - - // Inserts a value into the btree. - template <typename ValueType> - iterator insert_multi(ValueType &&v) { - return insert_multi(params_type::key(v), std::forward<ValueType>(v)); - } - - // Insert with hint. Check to see if the value should be placed immediately - // before position in the tree. If it does, then the insertion will take - // amortized constant time. If not, the insertion will take amortized - // logarithmic time as if a call to insert_multi(v) were made. - template <typename ValueType> - iterator insert_hint_multi(iterator position, ValueType &&v); - - // Insert a range of values into the btree. - template <typename InputIterator> - void insert_iterator_multi(InputIterator b, InputIterator e); - - // Erase the specified iterator from the btree. The iterator must be valid - // (i.e. not equal to end()). Return an iterator pointing to the node after - // the one that was erased (or end() if none exists). - // Requirement: does not read the value at `*iter`. - iterator erase(iterator iter); - - // Erases range. Returns the number of keys erased and an iterator pointing - // to the element after the last erased element. - std::pair<size_type, iterator> erase_range(iterator begin, iterator end); - - // Finds the iterator corresponding to a key or returns end() if the key is - // not present. - template <typename K> - iterator find(const K &key) { - return internal_end(internal_find(key)); - } - template <typename K> - const_iterator find(const K &key) const { - return internal_end(internal_find(key)); - } - - // Clear the btree, deleting all of the values it contains. - void clear(); - - // Swaps the contents of `this` and `other`. - void swap(btree &other); - - const key_compare &key_comp() const noexcept { - return root_.template get<0>(); - } - template <typename K1, typename K2> - bool compare_keys(const K1 &a, const K2 &b) const { - return compare_internal::compare_result_as_less_than(key_comp()(a, b)); - } - - value_compare value_comp() const { return value_compare(key_comp()); } - - // Verifies the structure of the btree. - void verify() const; - - // Size routines. - size_type size() const { return size_; } - size_type max_size() const { return (std::numeric_limits<size_type>::max)(); } - bool empty() const { return size_ == 0; } - - // The height of the btree. An empty tree will have height 0. - size_type height() const { - size_type h = 0; - if (!empty()) { - // Count the length of the chain from the leftmost node up to the - // root. We actually count from the root back around to the level below - // the root, but the calculation is the same because of the circularity - // of that traversal. - const node_type *n = root(); - do { - ++h; - n = n->parent(); - } while (n != root()); - } - return h; - } - - // The number of internal, leaf and total nodes used by the btree. - size_type leaf_nodes() const { return internal_stats(root()).leaf_nodes; } - size_type internal_nodes() const { - return internal_stats(root()).internal_nodes; - } - size_type nodes() const { - node_stats stats = internal_stats(root()); - return stats.leaf_nodes + stats.internal_nodes; - } - - // The total number of bytes used by the btree. - size_type bytes_used() const { - node_stats stats = internal_stats(root()); - if (stats.leaf_nodes == 1 && stats.internal_nodes == 0) { - return sizeof(*this) + node_type::LeafSize(root()->max_count()); - } else { - return sizeof(*this) + stats.leaf_nodes * node_type::LeafSize() + - stats.internal_nodes * node_type::InternalSize(); - } - } - - // The average number of bytes used per value stored in the btree. - static double average_bytes_per_value() { - // Returns the number of bytes per value on a leaf node that is 75% - // full. Experimentally, this matches up nicely with the computed number of - // bytes per value in trees that had their values inserted in random order. - return node_type::LeafSize() / (kNodeValues * 0.75); - } - - // The fullness of the btree. Computed as the number of elements in the btree - // divided by the maximum number of elements a tree with the current number - // of nodes could hold. A value of 1 indicates perfect space - // utilization. Smaller values indicate space wastage. - // Returns 0 for empty trees. - double fullness() const { - if (empty()) return 0.0; - return static_cast<double>(size()) / (nodes() * kNodeValues); - } - // The overhead of the btree structure in bytes per node. Computed as the - // total number of bytes used by the btree minus the number of bytes used for - // storing elements divided by the number of elements. - // Returns 0 for empty trees. - double overhead() const { - if (empty()) return 0.0; - return (bytes_used() - size() * sizeof(value_type)) / - static_cast<double>(size()); - } - - // The allocator used by the btree. - allocator_type get_allocator() const { return allocator(); } - - private: - // Internal accessor routines. - node_type *root() { return root_.template get<2>(); } - const node_type *root() const { return root_.template get<2>(); } - node_type *&mutable_root() noexcept { return root_.template get<2>(); } - key_compare *mutable_key_comp() noexcept { return &root_.template get<0>(); } - - // The leftmost node is stored as the parent of the root node. - node_type *leftmost() { return root()->parent(); } - const node_type *leftmost() const { return root()->parent(); } - - // Allocator routines. - allocator_type *mutable_allocator() noexcept { - return &root_.template get<1>(); - } - const allocator_type &allocator() const noexcept { - return root_.template get<1>(); - } - - // Allocates a correctly aligned node of at least size bytes using the - // allocator. - node_type *allocate(const size_type size) { - return reinterpret_cast<node_type *>( - absl::container_internal::Allocate<node_type::Alignment()>( - mutable_allocator(), size)); - } - - // Node creation/deletion routines. - node_type *new_internal_node(node_type *parent) { - node_type *n = allocate(node_type::InternalSize()); - n->init_internal(parent); - return n; - } - node_type *new_leaf_node(node_type *parent) { - node_type *n = allocate(node_type::LeafSize()); - n->init_leaf(parent, kNodeValues); - return n; - } - node_type *new_leaf_root_node(const int max_count) { - node_type *n = allocate(node_type::LeafSize(max_count)); - n->init_leaf(/*parent=*/n, max_count); - return n; - } - - // Deletion helper routines. - iterator rebalance_after_delete(iterator iter); - - // Rebalances or splits the node iter points to. - void rebalance_or_split(iterator *iter); - - // Merges the values of left, right and the delimiting key on their parent - // onto left, removing the delimiting key and deleting right. - void merge_nodes(node_type *left, node_type *right); - - // Tries to merge node with its left or right sibling, and failing that, - // rebalance with its left or right sibling. Returns true if a merge - // occurred, at which point it is no longer valid to access node. Returns - // false if no merging took place. - bool try_merge_or_rebalance(iterator *iter); - - // Tries to shrink the height of the tree by 1. - void try_shrink(); - - iterator internal_end(iterator iter) { - return iter.node != nullptr ? iter : end(); - } - const_iterator internal_end(const_iterator iter) const { - return iter.node != nullptr ? iter : end(); - } - - // Emplaces a value into the btree immediately before iter. Requires that - // key(v) <= iter.key() and (--iter).key() <= key(v). - template <typename... Args> - iterator internal_emplace(iterator iter, Args &&... args); - - // Returns an iterator pointing to the first value >= the value "iter" is - // pointing at. Note that "iter" might be pointing to an invalid location such - // as iter.position == iter.node->finish(). This routine simply moves iter up - // in the tree to a valid location. - // Requires: iter.node is non-null. - template <typename IterType> - static IterType internal_last(IterType iter); - - // Returns an iterator pointing to the leaf position at which key would - // reside in the tree, unless there is an exact match - in which case, the - // result may not be on a leaf. When there's a three-way comparator, we can - // return whether there was an exact match. This allows the caller to avoid a - // subsequent comparison to determine if an exact match was made, which is - // important for keys with expensive comparison, such as strings. - template <typename K> - SearchResult<iterator, is_key_compare_to::value> internal_locate( - const K &key) const; - - // Internal routine which implements lower_bound(). - template <typename K> - SearchResult<iterator, is_key_compare_to::value> internal_lower_bound( - const K &key) const; - - // Internal routine which implements upper_bound(). - template <typename K> - iterator internal_upper_bound(const K &key) const; - - // Internal routine which implements find(). - template <typename K> - iterator internal_find(const K &key) const; - - // Verifies the tree structure of node. - int internal_verify(const node_type *node, const key_type *lo, - const key_type *hi) const; - - node_stats internal_stats(const node_type *node) const { - // The root can be a static empty node. - if (node == nullptr || (node == root() && empty())) { - return node_stats(0, 0); - } - if (node->leaf()) { - return node_stats(1, 0); - } - node_stats res(0, 1); - for (int i = node->start(); i <= node->finish(); ++i) { - res += internal_stats(node->child(i)); - } - return res; - } - - // We use compressed tuple in order to save space because key_compare and - // allocator_type are usually empty. - absl::container_internal::CompressedTuple<key_compare, allocator_type, - node_type *> - root_; - - // A pointer to the rightmost node. Note that the leftmost node is stored as - // the root's parent. - node_type *rightmost_; - - // Number of values. - size_type size_; -}; - -//// -// btree_node methods -template <typename P> -template <typename... Args> -inline void btree_node<P>::emplace_value(const size_type i, - allocator_type *alloc, - Args &&... args) { - assert(i >= start()); - assert(i <= finish()); - // Shift old values to create space for new value and then construct it in - // place. - if (i < finish()) { - transfer_n_backward(finish() - i, /*dest_i=*/i + 1, /*src_i=*/i, this, - alloc); - } - value_init(i, alloc, std::forward<Args>(args)...); - set_finish(finish() + 1); - - if (!leaf() && finish() > i + 1) { - for (int j = finish(); j > i + 1; --j) { - set_child(j, child(j - 1)); - } - clear_child(i + 1); - } -} - -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. - value_destroy_n(i, to_erase, alloc); - const field_type orig_finish = finish(); - const field_type src_i = i + to_erase; - transfer_n(orig_finish - src_i, i, src_i, this, alloc); - - if (!leaf()) { - // Delete all children between begin and end. - for (int j = 0; j < to_erase; ++j) { - clear_and_delete(child(i + j + 1), alloc); - } - // Rotate children after end into new positions. - for (int j = i + to_erase + 1; j <= orig_finish; ++j) { - set_child(j - to_erase, child(j)); - clear_child(j); - } - } - set_finish(orig_finish - to_erase); -} - -template <typename P> -void btree_node<P>::rebalance_right_to_left(const int to_move, - btree_node *right, - allocator_type *alloc) { - assert(parent() == right->parent()); - assert(position() + 1 == right->position()); - assert(right->count() >= count()); - assert(to_move >= 1); - assert(to_move <= right->count()); - - // 1) Move the delimiting value in the parent to the left node. - transfer(finish(), position(), parent(), alloc); - - // 2) Move the (to_move - 1) values from the right node to the left node. - transfer_n(to_move - 1, finish() + 1, right->start(), right, alloc); - - // 3) Move the new delimiting value to the parent from the right node. - parent()->transfer(position(), right->start() + to_move - 1, right, alloc); - - // 4) Shift the values in the right node to their correct positions. - right->transfer_n(right->count() - to_move, right->start(), - right->start() + to_move, right, alloc); - - if (!leaf()) { - // Move the child pointers from the right to the left node. - for (int i = 0; i < to_move; ++i) { - init_child(finish() + i + 1, right->child(i)); - } - for (int i = right->start(); i <= right->finish() - to_move; ++i) { - assert(i + to_move <= right->max_count()); - right->init_child(i, right->child(i + to_move)); - right->clear_child(i + to_move); - } - } - - // Fixup `finish` on the left and right nodes. - set_finish(finish() + to_move); - right->set_finish(right->finish() - to_move); -} - -template <typename P> -void btree_node<P>::rebalance_left_to_right(const int to_move, - btree_node *right, - allocator_type *alloc) { - assert(parent() == right->parent()); - assert(position() + 1 == right->position()); - assert(count() >= right->count()); - assert(to_move >= 1); - assert(to_move <= count()); - - // Values in the right node are shifted to the right to make room for the - // new to_move values. Then, the delimiting value in the parent and the - // other (to_move - 1) values in the left node are moved into the right node. - // Lastly, a new delimiting value is moved from the left node into the - // parent, and the remaining empty left node entries are destroyed. - - // 1) Shift existing values in the right node to their correct positions. - right->transfer_n_backward(right->count(), right->start() + to_move, - right->start(), right, alloc); - - // 2) Move the delimiting value in the parent to the right node. - right->transfer(right->start() + to_move - 1, position(), parent(), alloc); - - // 3) Move the (to_move - 1) values from the left node to the right node. - right->transfer_n(to_move - 1, right->start(), finish() - (to_move - 1), this, - alloc); - - // 4) Move the new delimiting value to the parent from the left node. - parent()->transfer(position(), finish() - to_move, this, alloc); - - if (!leaf()) { - // Move the child pointers from the left to the right node. - for (int i = right->finish(); i >= right->start(); --i) { - right->init_child(i + to_move, right->child(i)); - right->clear_child(i); - } - for (int i = 1; i <= to_move; ++i) { - right->init_child(i - 1, child(finish() - to_move + i)); - clear_child(finish() - to_move + i); - } - } - - // Fixup the counts on the left and right nodes. - set_finish(finish() - to_move); - right->set_finish(right->finish() + to_move); -} - -template <typename P> -void btree_node<P>::split(const int insert_position, btree_node *dest, - allocator_type *alloc) { - assert(dest->count() == 0); - assert(max_count() == kNodeValues); - - // We bias the split based on the position being inserted. If we're - // inserting at the beginning of the left node then bias the split to put - // more values on the right node. If we're inserting at the end of the - // right node then bias the split to put more values on the left node. - if (insert_position == start()) { - dest->set_finish(dest->start() + finish() - 1); - } else if (insert_position == kNodeValues) { - dest->set_finish(dest->start()); - } else { - dest->set_finish(dest->start() + count() / 2); - } - set_finish(finish() - dest->count()); - assert(count() >= 1); - - // Move values from the left sibling to the right sibling. - dest->transfer_n(dest->count(), dest->start(), finish(), this, alloc); - - // The split key is the largest value in the left sibling. - --mutable_finish(); - parent()->emplace_value(position(), alloc, finish_slot()); - value_destroy(finish(), alloc); - parent()->init_child(position() + 1, dest); - - if (!leaf()) { - for (int i = dest->start(), j = finish() + 1; i <= dest->finish(); - ++i, ++j) { - assert(child(j) != nullptr); - dest->init_child(i, child(j)); - clear_child(j); - } - } -} - -template <typename P> -void btree_node<P>::merge(btree_node *src, allocator_type *alloc) { - assert(parent() == src->parent()); - assert(position() + 1 == src->position()); - - // Move the delimiting value to the left node. - value_init(finish(), alloc, parent()->slot(position())); - - // Move the values from the right to the left node. - transfer_n(src->count(), finish() + 1, src->start(), src, alloc); - - if (!leaf()) { - // Move the child pointers from the right to the left node. - for (int i = src->start(), j = finish() + 1; i <= src->finish(); ++i, ++j) { - init_child(j, src->child(i)); - src->clear_child(i); - } - } - - // Fixup `finish` on the src and dest nodes. - 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); -} - -template <typename P> -void btree_node<P>::clear_and_delete(btree_node *node, allocator_type *alloc) { - if (node->leaf()) { - node->value_destroy_n(node->start(), node->count(), alloc); - deallocate(LeafSize(node->max_count()), node, alloc); - return; - } - if (node->count() == 0) { - deallocate(InternalSize(), node, alloc); - return; - } - - // The parent of the root of the subtree we are deleting. - btree_node *delete_root_parent = node->parent(); - - // Navigate to the leftmost leaf under node, and then delete upwards. - while (!node->leaf()) node = node->start_child(); - // Use `int` because `pos` needs to be able to hold `kNodeValues+1`, which - // isn't guaranteed to be a valid `field_type`. - int pos = node->position(); - btree_node *parent = node->parent(); - for (;;) { - // In each iteration of the next loop, we delete one leaf node and go right. - assert(pos <= parent->finish()); - do { - node = parent->child(pos); - if (!node->leaf()) { - // Navigate to the leftmost leaf under node. - while (!node->leaf()) node = node->start_child(); - pos = node->position(); - parent = node->parent(); - } - node->value_destroy_n(node->start(), node->count(), alloc); - deallocate(LeafSize(node->max_count()), node, alloc); - ++pos; - } while (pos <= parent->finish()); - - // Once we've deleted all children of parent, delete parent and go up/right. - assert(pos > parent->finish()); - do { - node = parent; - pos = node->position(); - parent = node->parent(); - node->value_destroy_n(node->start(), node->count(), alloc); - deallocate(InternalSize(), node, alloc); - if (parent == delete_root_parent) return; - ++pos; - } while (pos > parent->finish()); - } -} - -//// -// btree_iterator methods -template <typename N, typename R, typename P> -void btree_iterator<N, R, P>::increment_slow() { - if (node->leaf()) { - assert(position >= node->finish()); - btree_iterator save(*this); - while (position == node->finish() && !node->is_root()) { - assert(node->parent()->child(node->position()) == node); - position = node->position(); - node = node->parent(); - } - // TODO(ezb): assert we aren't incrementing end() instead of handling. - if (position == node->finish()) { - *this = save; - } - } else { - assert(position < node->finish()); - node = node->child(position + 1); - while (!node->leaf()) { - node = node->start_child(); - } - position = node->start(); - } -} - -template <typename N, typename R, typename P> -void btree_iterator<N, R, P>::decrement_slow() { - if (node->leaf()) { - assert(position <= -1); - btree_iterator save(*this); - while (position < node->start() && !node->is_root()) { - assert(node->parent()->child(node->position()) == node); - position = node->position() - 1; - node = node->parent(); - } - // TODO(ezb): assert we aren't decrementing begin() instead of handling. - if (position < node->start()) { - *this = save; - } - } else { - assert(position >= node->start()); - node = node->child(position); - while (!node->leaf()) { - node = node->child(node->finish()); - } - position = node->finish() - 1; - } -} - -//// -// btree methods -template <typename P> -template <typename Btree> -void btree<P>::copy_or_move_values_in_order(Btree &other) { - static_assert(std::is_same<btree, Btree>::value || - std::is_same<const btree, Btree>::value, - "Btree type must be same or const."); - assert(empty()); - - // We can avoid key comparisons because we know the order of the - // values is the same order we'll store them in. - auto iter = other.begin(); - if (iter == other.end()) return; - insert_multi(maybe_move_from_iterator(iter)); - ++iter; - for (; iter != other.end(); ++iter) { - // If the btree is not empty, we can just insert the new value at the end - // of the tree. - internal_emplace(end(), maybe_move_from_iterator(iter)); - } -} - -template <typename P> -constexpr bool btree<P>::static_assert_validation() { - static_assert(std::is_nothrow_copy_constructible<key_compare>::value, - "Key comparison must be nothrow copy constructible"); - static_assert(std::is_nothrow_copy_constructible<allocator_type>::value, - "Allocator must be nothrow copy constructible"); - static_assert(type_traits_internal::is_trivially_copyable<iterator>::value, - "iterator not trivially copyable."); - - // Note: We assert that kTargetValues, which is computed from - // Params::kTargetNodeSize, must fit the node_type::field_type. - static_assert( - kNodeValues < (1 << (8 * sizeof(typename node_type::field_type))), - "target node size too large"); - - // Verify that key_compare returns an absl::{weak,strong}_ordering or bool. - using compare_result_type = - absl::result_of_t<key_compare(key_type, key_type)>; - static_assert( - std::is_same<compare_result_type, bool>::value || - std::is_convertible<compare_result_type, absl::weak_ordering>::value, - "key comparison function must return absl::{weak,strong}_ordering or " - "bool."); - - // Test the assumption made in setting kNodeValueSpace. - static_assert(node_type::MinimumOverhead() >= sizeof(void *) + 4, - "node space assumption incorrect"); - - return true; -} - -template <typename P> -template <typename K> -auto btree<P>::equal_range(const K &key) -> std::pair<iterator, iterator> { - const SearchResult<iterator, is_key_compare_to::value> res = - internal_lower_bound(key); - const iterator lower = internal_end(res.value); - if (res.HasMatch() ? !res.IsEq() - : lower == end() || compare_keys(key, lower.key())) { - return {lower, lower}; - } - - const iterator next = std::next(lower); - // When the comparator is heterogeneous, we can't assume that comparison with - // non-`key_type` will be equivalent to `key_type` comparisons so there - // could be multiple equivalent keys even in a unique-container. But for - // heterogeneous comparisons from the default string adapted comparators, we - // don't need to worry about this. - if (!is_multi_container::value && - (std::is_same<K, key_type>::value || is_key_compare_adapted::value)) { - // The next iterator after lower must point to a key greater than `key`. - // Note: if this assert fails, then it may indicate that the comparator does - // not meet the equivalence requirements for Compare - // (see https://en.cppreference.com/w/cpp/named_req/Compare). - assert(next == end() || compare_keys(key, next.key())); - return {lower, next}; - } - // Try once more to avoid the call to upper_bound() if there's only one - // equivalent key. This should prevent all calls to upper_bound() in cases of - // unique-containers with heterogeneous comparators in which all comparison - // operators have the same equivalence classes. - if (next == end() || compare_keys(key, next.key())) return {lower, next}; - - // In this case, we need to call upper_bound() to avoid worst case O(N) - // behavior if we were to iterate over equal keys. - return {lower, upper_bound(key)}; -} - -template <typename P> -template <typename K, typename... Args> -auto btree<P>::insert_unique(const K &key, Args &&... args) - -> std::pair<iterator, bool> { - if (empty()) { - mutable_root() = rightmost_ = new_leaf_root_node(1); - } - - SearchResult<iterator, is_key_compare_to::value> res = internal_locate(key); - iterator iter = res.value; - - if (res.HasMatch()) { - if (res.IsEq()) { - // The key already exists in the tree, do nothing. - return {iter, false}; - } - } else { - iterator last = internal_last(iter); - if (last.node && !compare_keys(key, last.key())) { - // The key already exists in the tree, do nothing. - return {last, false}; - } - } - return {internal_emplace(iter, std::forward<Args>(args)...), true}; -} - -template <typename P> -template <typename K, typename... Args> -inline auto btree<P>::insert_hint_unique(iterator position, const K &key, - Args &&... args) - -> std::pair<iterator, bool> { - if (!empty()) { - if (position == end() || compare_keys(key, position.key())) { - if (position == begin() || compare_keys(std::prev(position).key(), key)) { - // prev.key() < key < position.key() - return {internal_emplace(position, std::forward<Args>(args)...), true}; - } - } else if (compare_keys(position.key(), key)) { - ++position; - if (position == end() || compare_keys(key, position.key())) { - // {original `position`}.key() < key < {current `position`}.key() - return {internal_emplace(position, std::forward<Args>(args)...), true}; - } - } else { - // position.key() == key - return {position, false}; - } - } - return insert_unique(key, std::forward<Args>(args)...); -} - -template <typename P> -template <typename InputIterator, typename> -void btree<P>::insert_iterator_unique(InputIterator b, InputIterator e, int) { - for (; b != e; ++b) { - insert_hint_unique(end(), params_type::key(*b), *b); - } -} - -template <typename P> -template <typename InputIterator> -void btree<P>::insert_iterator_unique(InputIterator b, InputIterator e, char) { - for (; b != e; ++b) { - init_type value(*b); - insert_hint_unique(end(), params_type::key(value), std::move(value)); - } -} - -template <typename P> -template <typename ValueType> -auto btree<P>::insert_multi(const key_type &key, ValueType &&v) -> iterator { - if (empty()) { - mutable_root() = rightmost_ = new_leaf_root_node(1); - } - - iterator iter = internal_upper_bound(key); - if (iter.node == nullptr) { - iter = end(); - } - return internal_emplace(iter, std::forward<ValueType>(v)); -} - -template <typename P> -template <typename ValueType> -auto btree<P>::insert_hint_multi(iterator position, ValueType &&v) -> iterator { - if (!empty()) { - const key_type &key = params_type::key(v); - if (position == end() || !compare_keys(position.key(), key)) { - if (position == begin() || - !compare_keys(key, std::prev(position).key())) { - // prev.key() <= key <= position.key() - return internal_emplace(position, std::forward<ValueType>(v)); - } - } else { - ++position; - if (position == end() || !compare_keys(position.key(), key)) { - // {original `position`}.key() < key < {current `position`}.key() - return internal_emplace(position, std::forward<ValueType>(v)); - } - } - } - return insert_multi(std::forward<ValueType>(v)); -} - -template <typename P> -template <typename InputIterator> -void btree<P>::insert_iterator_multi(InputIterator b, InputIterator e) { - for (; b != e; ++b) { - insert_hint_multi(end(), *b); - } -} - -template <typename P> -auto btree<P>::operator=(const btree &other) -> btree & { - if (this != &other) { - clear(); - - *mutable_key_comp() = other.key_comp(); - if (absl::allocator_traits< - allocator_type>::propagate_on_container_copy_assignment::value) { - *mutable_allocator() = other.allocator(); - } - - copy_or_move_values_in_order(other); - } - return *this; -} - -template <typename P> -auto btree<P>::operator=(btree &&other) noexcept -> btree & { - if (this != &other) { - clear(); - - using std::swap; - if (absl::allocator_traits< - allocator_type>::propagate_on_container_copy_assignment::value) { - // Note: `root_` also contains the allocator and the key comparator. - swap(root_, other.root_); - swap(rightmost_, other.rightmost_); - swap(size_, other.size_); - } else { - if (allocator() == other.allocator()) { - swap(mutable_root(), other.mutable_root()); - swap(*mutable_key_comp(), *other.mutable_key_comp()); - swap(rightmost_, other.rightmost_); - swap(size_, other.size_); - } else { - // We aren't allowed to propagate the allocator and the allocator is - // different so we can't take over its memory. We must move each element - // individually. We need both `other` and `this` to have `other`s key - // comparator while moving the values so we can't swap the key - // comparators. - *mutable_key_comp() = other.key_comp(); - copy_or_move_values_in_order(other); - } - } - } - return *this; -} - -template <typename P> -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() - // below). We can get to the largest value from our left child by - // decrementing iter. - iterator internal_iter(iter); - --iter; - assert(iter.node->leaf()); - params_type::move(mutable_allocator(), iter.node->slot(iter.position), - internal_iter.node->slot(internal_iter.position)); - internal_delete = true; - } - - // Delete the key from the leaf. - iter.node->remove_values(iter.position, /*to_erase=*/1, mutable_allocator()); - --size_; - - // We want to return the next value after the one we just erased. If we - // erased from an internal node (internal_delete == true), then the next - // value is ++(++iter). If we erased from a leaf node (internal_delete == - // false) then the next value is ++iter. Note that ++iter may point to an - // internal node and the value in the internal node may move to a leaf node - // (iter.node) when rebalancing is performed at the leaf level. - - iterator res = rebalance_after_delete(iter); - - // If we erased from an internal node, advance the iterator. - if (internal_delete) { - ++res; - } - return res; -} - -template <typename P> -auto btree<P>::rebalance_after_delete(iterator iter) -> iterator { - // Merge/rebalance as we walk back up the tree. - iterator res(iter); - bool first_iteration = true; - for (;;) { - if (iter.node == root()) { - try_shrink(); - if (empty()) { - return end(); - } - break; - } - if (iter.node->count() >= kMinNodeValues) { - break; - } - bool merged = try_merge_or_rebalance(&iter); - // On the first iteration, we should update `res` with `iter` because `res` - // may have been invalidated. - if (first_iteration) { - res = iter; - first_iteration = false; - } - if (!merged) { - break; - } - iter.position = iter.node->position(); - iter.node = iter.node->parent(); - } - - // Adjust our return value. If we're pointing at the end of a node, advance - // the iterator. - if (res.position == res.node->finish()) { - res.position = res.node->finish() - 1; - ++res; - } - - return res; -} - -template <typename P> -auto btree<P>::erase_range(iterator begin, iterator end) - -> std::pair<size_type, iterator> { - difference_type count = std::distance(begin, end); - assert(count >= 0); - - if (count == 0) { - return {0, begin}; - } - - if (count == size_) { - clear(); - return {count, this->end()}; - } - - if (begin.node == end.node) { - assert(end.position > begin.position); - begin.node->remove_values(begin.position, end.position - begin.position, - mutable_allocator()); - size_ -= count; - return {count, rebalance_after_delete(begin)}; - } - - const size_type target_size = size_ - count; - while (size_ > target_size) { - 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); - } else { - begin = erase(begin); - } - } - return {count, begin}; -} - -template <typename P> -void btree<P>::clear() { - if (!empty()) { - node_type::clear_and_delete(root(), mutable_allocator()); - } - mutable_root() = EmptyNode(); - rightmost_ = EmptyNode(); - size_ = 0; -} - -template <typename P> -void btree<P>::swap(btree &other) { - using std::swap; - if (absl::allocator_traits< - allocator_type>::propagate_on_container_swap::value) { - // Note: `root_` also contains the allocator and the key comparator. - swap(root_, other.root_); - } else { - // It's undefined behavior if the allocators are unequal here. - assert(allocator() == other.allocator()); - swap(mutable_root(), other.mutable_root()); - swap(*mutable_key_comp(), *other.mutable_key_comp()); - } - swap(rightmost_, other.rightmost_); - swap(size_, other.size_); -} - -template <typename P> -void btree<P>::verify() const { - assert(root() != nullptr); - assert(leftmost() != nullptr); - assert(rightmost_ != nullptr); - assert(empty() || size() == internal_verify(root(), nullptr, nullptr)); - assert(leftmost() == (++const_iterator(root(), -1)).node); - assert(rightmost_ == (--const_iterator(root(), root()->finish())).node); - assert(leftmost()->leaf()); - assert(rightmost_->leaf()); -} - -template <typename P> -void btree<P>::rebalance_or_split(iterator *iter) { - node_type *&node = iter->node; - int &insert_position = iter->position; - assert(node->count() == node->max_count()); - assert(kNodeValues == node->max_count()); - - // First try to make room on the node by rebalancing. - node_type *parent = node->parent(); - if (node != root()) { - if (node->position() > parent->start()) { - // Try rebalancing with our left sibling. - node_type *left = parent->child(node->position() - 1); - assert(left->max_count() == kNodeValues); - if (left->count() < kNodeValues) { - // We bias rebalancing based on the position being inserted. If we're - // inserting at the end of the right node then we bias rebalancing to - // fill up the left node. - int to_move = (kNodeValues - left->count()) / - (1 + (insert_position < static_cast<int>(kNodeValues))); - to_move = (std::max)(1, to_move); - - if (insert_position - to_move >= node->start() || - left->count() + to_move < static_cast<int>(kNodeValues)) { - left->rebalance_right_to_left(to_move, node, mutable_allocator()); - - assert(node->max_count() - node->count() == to_move); - insert_position = insert_position - to_move; - if (insert_position < node->start()) { - insert_position = insert_position + left->count() + 1; - node = left; - } - - assert(node->count() < node->max_count()); - return; - } - } - } - - if (node->position() < parent->finish()) { - // Try rebalancing with our right sibling. - node_type *right = parent->child(node->position() + 1); - assert(right->max_count() == kNodeValues); - if (right->count() < kNodeValues) { - // We bias rebalancing based on the position being inserted. If we're - // inserting at the beginning of the left node then we bias rebalancing - // to fill up the right node. - int to_move = (static_cast<int>(kNodeValues) - right->count()) / - (1 + (insert_position > node->start())); - to_move = (std::max)(1, to_move); - - if (insert_position <= node->finish() - to_move || - right->count() + to_move < static_cast<int>(kNodeValues)) { - node->rebalance_left_to_right(to_move, right, mutable_allocator()); - - if (insert_position > node->finish()) { - insert_position = insert_position - node->count() - 1; - node = right; - } - - assert(node->count() < node->max_count()); - return; - } - } - } - - // Rebalancing failed, make sure there is room on the parent node for a new - // value. - assert(parent->max_count() == kNodeValues); - if (parent->count() == kNodeValues) { - iterator parent_iter(node->parent(), node->position()); - rebalance_or_split(&parent_iter); - } - } else { - // Rebalancing not possible because this is the root node. - // Create a new root node and set the current root node as the child of the - // new root. - parent = new_internal_node(parent); - parent->init_child(parent->start(), root()); - mutable_root() = parent; - // If the former root was a leaf node, then it's now the rightmost node. - assert(!parent->start_child()->leaf() || - parent->start_child() == rightmost_); - } - - // Split the node. - node_type *split_node; - if (node->leaf()) { - split_node = new_leaf_node(parent); - node->split(insert_position, split_node, mutable_allocator()); - if (rightmost_ == node) rightmost_ = split_node; - } else { - split_node = new_internal_node(parent); - node->split(insert_position, split_node, mutable_allocator()); - } - - if (insert_position > node->finish()) { - insert_position = insert_position - node->count() - 1; - node = split_node; - } -} - -template <typename P> -void btree<P>::merge_nodes(node_type *left, node_type *right) { - left->merge(right, mutable_allocator()); - if (rightmost_ == right) rightmost_ = left; -} - -template <typename P> -bool btree<P>::try_merge_or_rebalance(iterator *iter) { - node_type *parent = iter->node->parent(); - if (iter->node->position() > parent->start()) { - // Try merging with our left sibling. - node_type *left = parent->child(iter->node->position() - 1); - assert(left->max_count() == kNodeValues); - if (1U + left->count() + iter->node->count() <= kNodeValues) { - iter->position += 1 + left->count(); - merge_nodes(left, iter->node); - iter->node = left; - return true; - } - } - if (iter->node->position() < parent->finish()) { - // Try merging with our right sibling. - node_type *right = parent->child(iter->node->position() + 1); - assert(right->max_count() == kNodeValues); - if (1U + iter->node->count() + right->count() <= kNodeValues) { - merge_nodes(iter->node, right); - return true; - } - // Try rebalancing with our right sibling. We don't perform rebalancing if - // we deleted the first element from iter->node and the node is not - // empty. This is a small optimization for the common pattern of deleting - // from the front of the tree. - if (right->count() > kMinNodeValues && - (iter->node->count() == 0 || iter->position > iter->node->start())) { - int to_move = (right->count() - iter->node->count()) / 2; - to_move = (std::min)(to_move, right->count() - 1); - iter->node->rebalance_right_to_left(to_move, right, mutable_allocator()); - return false; - } - } - if (iter->node->position() > parent->start()) { - // Try rebalancing with our left sibling. We don't perform rebalancing if - // we deleted the last element from iter->node and the node is not - // empty. This is a small optimization for the common pattern of deleting - // from the back of the tree. - node_type *left = parent->child(iter->node->position() - 1); - if (left->count() > kMinNodeValues && - (iter->node->count() == 0 || iter->position < iter->node->finish())) { - int to_move = (left->count() - iter->node->count()) / 2; - to_move = (std::min)(to_move, left->count() - 1); - left->rebalance_left_to_right(to_move, iter->node, mutable_allocator()); - iter->position += to_move; - return false; - } - } - return false; -} - -template <typename P> -void btree<P>::try_shrink() { - node_type *orig_root = root(); - if (orig_root->count() > 0) { - return; - } - // Deleted the last item on the root node, shrink the height of the tree. - if (orig_root->leaf()) { - assert(size() == 0); - mutable_root() = rightmost_ = EmptyNode(); - } else { - node_type *child = orig_root->start_child(); - child->make_root(); - mutable_root() = child; - } - node_type::clear_and_delete(orig_root, mutable_allocator()); -} - -template <typename P> -template <typename IterType> -inline IterType btree<P>::internal_last(IterType iter) { - assert(iter.node != nullptr); - while (iter.position == iter.node->finish()) { - iter.position = iter.node->position(); - iter.node = iter.node->parent(); - if (iter.node->leaf()) { - iter.node = nullptr; - break; - } - } - return iter; -} - -template <typename P> -template <typename... Args> -inline auto btree<P>::internal_emplace(iterator iter, Args &&... args) - -> iterator { - if (!iter.node->leaf()) { - // We can't insert on an internal node. Instead, we'll insert after the - // previous value which is guaranteed to be on a leaf node. - --iter; - ++iter.position; - } - const field_type max_count = iter.node->max_count(); - allocator_type *alloc = mutable_allocator(); - if (iter.node->count() == max_count) { - // Make room in the leaf for the new item. - if (max_count < kNodeValues) { - // Insertion into the root where the root is smaller than the full node - // size. Simply grow the size of the root node. - assert(iter.node == root()); - iter.node = - new_leaf_root_node((std::min<int>)(kNodeValues, 2 * max_count)); - // Transfer the values from the old root to the new root. - node_type *old_root = root(); - node_type *new_root = iter.node; - new_root->transfer_n(old_root->count(), new_root->start(), - 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); - mutable_root() = rightmost_ = new_root; - } else { - rebalance_or_split(&iter); - } - } - iter.node->emplace_value(iter.position, alloc, std::forward<Args>(args)...); - ++size_; - return iter; -} - -template <typename P> -template <typename K> -inline auto btree<P>::internal_locate(const K &key) const - -> SearchResult<iterator, is_key_compare_to::value> { - iterator iter(const_cast<node_type *>(root())); - for (;;) { - SearchResult<int, is_key_compare_to::value> res = - iter.node->lower_bound(key, key_comp()); - iter.position = res.value; - if (res.IsEq()) { - return {iter, MatchKind::kEq}; - } - // Note: in the non-key-compare-to case, we don't need to walk all the way - // down the tree if the keys are equal, but determining equality would - // require doing an extra comparison on each node on the way down, and we - // will need to go all the way to the leaf node in the expected case. - if (iter.node->leaf()) { - break; - } - iter.node = iter.node->child(iter.position); - } - // Note: in the non-key-compare-to case, the key may actually be equivalent - // here (and the MatchKind::kNe is ignored). - return {iter, MatchKind::kNe}; -} - -template <typename P> -template <typename K> -auto btree<P>::internal_lower_bound(const K &key) const - -> SearchResult<iterator, is_key_compare_to::value> { - iterator iter(const_cast<node_type *>(root())); - SearchResult<int, is_key_compare_to::value> res; - bool seen_eq = false; - for (;;) { - res = iter.node->lower_bound(key, key_comp()); - iter.position = res.value; - // TODO(ezb): we should be able to terminate early on IsEq() if there can't - // be multiple equivalent keys in container for this lookup type. - if (iter.node->leaf()) { - break; - } - seen_eq = seen_eq || res.IsEq(); - iter.node = iter.node->child(iter.position); - } - if (res.IsEq()) return {iter, MatchKind::kEq}; - return {internal_last(iter), seen_eq ? MatchKind::kEq : MatchKind::kNe}; -} - -template <typename P> -template <typename K> -auto btree<P>::internal_upper_bound(const K &key) const -> iterator { - iterator iter(const_cast<node_type *>(root())); - for (;;) { - iter.position = iter.node->upper_bound(key, key_comp()); - if (iter.node->leaf()) { - break; - } - iter.node = iter.node->child(iter.position); - } - return internal_last(iter); -} - -template <typename P> -template <typename K> -auto btree<P>::internal_find(const K &key) const -> iterator { - SearchResult<iterator, is_key_compare_to::value> res = internal_locate(key); - if (res.HasMatch()) { - if (res.IsEq()) { - return res.value; - } - } else { - const iterator iter = internal_last(res.value); - if (iter.node != nullptr && !compare_keys(key, iter.key())) { - return iter; - } - } - return {nullptr, 0}; -} - -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); - assert(node->count() <= node->max_count()); - if (lo) { - assert(!compare_keys(node->key(node->start()), *lo)); - } - if (hi) { - assert(!compare_keys(*hi, node->key(node->finish() - 1))); - } - for (int i = node->start() + 1; i < node->finish(); ++i) { - assert(!compare_keys(node->key(i), node->key(i - 1))); - } - int count = node->count(); - if (!node->leaf()) { - for (int i = node->start(); i <= node->finish(); ++i) { - assert(node->child(i) != nullptr); - assert(node->child(i)->parent() == node); - assert(node->child(i)->position() == i); - count += internal_verify(node->child(i), - i == node->start() ? lo : &node->key(i - 1), - i == node->finish() ? hi : &node->key(i)); - } - } - return count; -} - -} // namespace container_internal -ABSL_NAMESPACE_END -} // namespace absl - -#endif // ABSL_CONTAINER_INTERNAL_BTREE_H_ |