Abseil Common Libraries (C++) (grcp 依赖)
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2612 lines
91 KiB
2612 lines
91 KiB
// Copyright 2018 The Abseil Authors. |
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// |
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// Licensed under the Apache License, Version 2.0 (the "License"); |
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// you may not use this file except in compliance with the License. |
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// You may obtain a copy of the License at |
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// |
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// https://www.apache.org/licenses/LICENSE-2.0 |
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// |
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// Unless required by applicable law or agreed to in writing, software |
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// distributed under the License is distributed on an "AS IS" BASIS, |
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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// See the License for the specific language governing permissions and |
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// limitations under the License. |
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// A btree implementation of the STL set and map interfaces. A btree is smaller |
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// and generally also faster than STL set/map (refer to the benchmarks below). |
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// The red-black tree implementation of STL set/map has an overhead of 3 |
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// pointers (left, right and parent) plus the node color information for each |
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// stored value. So a set<int32_t> consumes 40 bytes for each value stored in |
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// 64-bit mode. This btree implementation stores multiple values on fixed |
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// size nodes (usually 256 bytes) and doesn't store child pointers for leaf |
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// nodes. The result is that a btree_set<int32_t> may use much less memory per |
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// stored value. For the random insertion benchmark in btree_bench.cc, a |
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// btree_set<int32_t> with node-size of 256 uses 5.1 bytes per stored value. |
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// |
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// The packing of multiple values on to each node of a btree has another effect |
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// besides better space utilization: better cache locality due to fewer cache |
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// lines being accessed. Better cache locality translates into faster |
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// operations. |
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// |
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// CAVEATS |
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// |
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// Insertions and deletions on a btree can cause splitting, merging or |
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// rebalancing of btree nodes. And even without these operations, insertions |
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// and deletions on a btree will move values around within a node. In both |
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// cases, the result is that insertions and deletions can invalidate iterators |
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// pointing to values other than the one being inserted/deleted. Therefore, this |
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// container does not provide pointer stability. This is notably different from |
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// STL set/map which takes care to not invalidate iterators on insert/erase |
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// except, of course, for iterators pointing to the value being erased. A |
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// partial workaround when erasing is available: erase() returns an iterator |
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// pointing to the item just after the one that was erased (or end() if none |
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// exists). |
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#ifndef ABSL_CONTAINER_INTERNAL_BTREE_H_ |
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#define ABSL_CONTAINER_INTERNAL_BTREE_H_ |
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#include <algorithm> |
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#include <cassert> |
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#include <cstddef> |
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#include <cstdint> |
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#include <cstring> |
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#include <functional> |
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#include <iterator> |
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#include <limits> |
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#include <new> |
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#include <string> |
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#include <type_traits> |
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#include <utility> |
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#include "absl/base/macros.h" |
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#include "absl/container/internal/common.h" |
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#include "absl/container/internal/compressed_tuple.h" |
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#include "absl/container/internal/container_memory.h" |
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#include "absl/container/internal/layout.h" |
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#include "absl/memory/memory.h" |
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#include "absl/meta/type_traits.h" |
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#include "absl/strings/string_view.h" |
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#include "absl/types/compare.h" |
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#include "absl/utility/utility.h" |
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namespace absl { |
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namespace container_internal { |
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// A helper class that indicates if the Compare parameter is a key-compare-to |
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// comparator. |
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template <typename Compare, typename T> |
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using btree_is_key_compare_to = |
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std::is_convertible<absl::result_of_t<Compare(const T &, const T &)>, |
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absl::weak_ordering>; |
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struct StringBtreeDefaultLess { |
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using is_transparent = void; |
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StringBtreeDefaultLess() = default; |
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// Compatibility constructor. |
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StringBtreeDefaultLess(std::less<std::string>) {} // NOLINT |
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StringBtreeDefaultLess(std::less<string_view>) {} // NOLINT |
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absl::weak_ordering operator()(absl::string_view lhs, |
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absl::string_view rhs) const { |
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return compare_internal::compare_result_as_ordering(lhs.compare(rhs)); |
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} |
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}; |
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struct StringBtreeDefaultGreater { |
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using is_transparent = void; |
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StringBtreeDefaultGreater() = default; |
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StringBtreeDefaultGreater(std::greater<std::string>) {} // NOLINT |
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StringBtreeDefaultGreater(std::greater<string_view>) {} // NOLINT |
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absl::weak_ordering operator()(absl::string_view lhs, |
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absl::string_view rhs) const { |
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return compare_internal::compare_result_as_ordering(rhs.compare(lhs)); |
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} |
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}; |
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// A helper class to convert a boolean comparison into a three-way "compare-to" |
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// comparison that returns a negative value to indicate less-than, zero to |
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// indicate equality and a positive value to indicate greater-than. This helper |
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// class is specialized for less<std::string>, greater<std::string>, |
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// less<string_view>, and greater<string_view>. |
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// |
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// key_compare_to_adapter is provided so that btree users |
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// automatically get the more efficient compare-to code when using common |
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// google string types with common comparison functors. |
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// These string-like specializations also turn on heterogeneous lookup by |
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// default. |
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template <typename Compare> |
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struct key_compare_to_adapter { |
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using type = Compare; |
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}; |
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template <> |
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struct key_compare_to_adapter<std::less<std::string>> { |
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using type = StringBtreeDefaultLess; |
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}; |
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template <> |
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struct key_compare_to_adapter<std::greater<std::string>> { |
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using type = StringBtreeDefaultGreater; |
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}; |
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template <> |
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struct key_compare_to_adapter<std::less<absl::string_view>> { |
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using type = StringBtreeDefaultLess; |
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}; |
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template <> |
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struct key_compare_to_adapter<std::greater<absl::string_view>> { |
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using type = StringBtreeDefaultGreater; |
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}; |
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template <typename Key, typename Compare, typename Alloc, int TargetNodeSize, |
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bool Multi, typename SlotPolicy> |
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struct common_params { |
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// If Compare is a common comparator for a std::string-like type, then we adapt it |
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// to use heterogeneous lookup and to be a key-compare-to comparator. |
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using key_compare = typename key_compare_to_adapter<Compare>::type; |
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// A type which indicates if we have a key-compare-to functor or a plain old |
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// key-compare functor. |
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using is_key_compare_to = btree_is_key_compare_to<key_compare, Key>; |
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using allocator_type = Alloc; |
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using key_type = Key; |
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using size_type = std::make_signed<size_t>::type; |
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using difference_type = ptrdiff_t; |
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// True if this is a multiset or multimap. |
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using is_multi_container = std::integral_constant<bool, Multi>; |
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using slot_policy = SlotPolicy; |
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using slot_type = typename slot_policy::slot_type; |
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using value_type = typename slot_policy::value_type; |
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using init_type = typename slot_policy::mutable_value_type; |
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using pointer = value_type *; |
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using const_pointer = const value_type *; |
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using reference = value_type &; |
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using const_reference = const value_type &; |
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enum { |
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kTargetNodeSize = TargetNodeSize, |
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// Upper bound for the available space for values. This is largest for leaf |
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// nodes, which have overhead of at least a pointer + 4 bytes (for storing |
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// 3 field_types and an enum). |
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kNodeValueSpace = |
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TargetNodeSize - /*minimum overhead=*/(sizeof(void *) + 4), |
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}; |
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// This is an integral type large enough to hold as many |
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// ValueSize-values as will fit a node of TargetNodeSize bytes. |
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using node_count_type = |
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absl::conditional_t<(kNodeValueSpace / sizeof(value_type) > |
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(std::numeric_limits<uint8_t>::max)()), |
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uint16_t, uint8_t>; // NOLINT |
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// The following methods are necessary for passing this struct as PolicyTraits |
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// for node_handle and/or are used within btree. |
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static value_type &element(slot_type *slot) { |
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return slot_policy::element(slot); |
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} |
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static const value_type &element(const slot_type *slot) { |
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return slot_policy::element(slot); |
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} |
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template <class... Args> |
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static void construct(Alloc *alloc, slot_type *slot, Args &&... args) { |
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slot_policy::construct(alloc, slot, std::forward<Args>(args)...); |
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} |
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static void construct(Alloc *alloc, slot_type *slot, slot_type *other) { |
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slot_policy::construct(alloc, slot, other); |
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} |
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static void destroy(Alloc *alloc, slot_type *slot) { |
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slot_policy::destroy(alloc, slot); |
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} |
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static void transfer(Alloc *alloc, slot_type *new_slot, slot_type *old_slot) { |
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construct(alloc, new_slot, old_slot); |
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destroy(alloc, old_slot); |
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} |
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static void swap(Alloc *alloc, slot_type *a, slot_type *b) { |
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slot_policy::swap(alloc, a, b); |
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} |
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static void move(Alloc *alloc, slot_type *src, slot_type *dest) { |
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slot_policy::move(alloc, src, dest); |
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} |
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static void move(Alloc *alloc, slot_type *first, slot_type *last, |
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slot_type *result) { |
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slot_policy::move(alloc, first, last, result); |
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} |
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}; |
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// A parameters structure for holding the type parameters for a btree_map. |
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// Compare and Alloc should be nothrow copy-constructible. |
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template <typename Key, typename Data, typename Compare, typename Alloc, |
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int TargetNodeSize, bool Multi> |
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struct map_params : common_params<Key, Compare, Alloc, TargetNodeSize, Multi, |
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map_slot_policy<Key, Data>> { |
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using super_type = typename map_params::common_params; |
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using mapped_type = Data; |
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// This type allows us to move keys when it is safe to do so. It is safe |
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// for maps in which value_type and mutable_value_type are layout compatible. |
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using slot_policy = typename super_type::slot_policy; |
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using slot_type = typename super_type::slot_type; |
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using value_type = typename super_type::value_type; |
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using init_type = typename super_type::init_type; |
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using key_compare = typename super_type::key_compare; |
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// Inherit from key_compare for empty base class optimization. |
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struct value_compare : private key_compare { |
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value_compare() = default; |
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explicit value_compare(const key_compare &cmp) : key_compare(cmp) {} |
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template <typename T, typename U> |
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auto operator()(const T &left, const U &right) const |
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-> decltype(std::declval<key_compare>()(left.first, right.first)) { |
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return key_compare::operator()(left.first, right.first); |
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} |
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}; |
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using is_map_container = std::true_type; |
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static const Key &key(const value_type &x) { return x.first; } |
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static const Key &key(const init_type &x) { return x.first; } |
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static const Key &key(const slot_type *x) { return slot_policy::key(x); } |
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static mapped_type &value(value_type *value) { return value->second; } |
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}; |
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// This type implements the necessary functions from the |
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// absl::container_internal::slot_type interface. |
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template <typename Key> |
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struct set_slot_policy { |
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using slot_type = Key; |
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using value_type = Key; |
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using mutable_value_type = Key; |
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static value_type &element(slot_type *slot) { return *slot; } |
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static const value_type &element(const slot_type *slot) { return *slot; } |
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template <typename Alloc, class... Args> |
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static void construct(Alloc *alloc, slot_type *slot, Args &&... args) { |
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absl::allocator_traits<Alloc>::construct(*alloc, slot, |
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std::forward<Args>(args)...); |
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} |
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template <typename Alloc> |
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static void construct(Alloc *alloc, slot_type *slot, slot_type *other) { |
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absl::allocator_traits<Alloc>::construct(*alloc, slot, std::move(*other)); |
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} |
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template <typename Alloc> |
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static void destroy(Alloc *alloc, slot_type *slot) { |
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absl::allocator_traits<Alloc>::destroy(*alloc, slot); |
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} |
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template <typename Alloc> |
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static void swap(Alloc * /*alloc*/, slot_type *a, slot_type *b) { |
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using std::swap; |
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swap(*a, *b); |
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} |
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template <typename Alloc> |
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static void move(Alloc * /*alloc*/, slot_type *src, slot_type *dest) { |
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*dest = std::move(*src); |
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} |
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template <typename Alloc> |
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static void move(Alloc *alloc, slot_type *first, slot_type *last, |
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slot_type *result) { |
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for (slot_type *src = first, *dest = result; src != last; ++src, ++dest) |
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move(alloc, src, dest); |
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} |
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}; |
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// A parameters structure for holding the type parameters for a btree_set. |
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// Compare and Alloc should be nothrow copy-constructible. |
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template <typename Key, typename Compare, typename Alloc, int TargetNodeSize, |
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bool Multi> |
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struct set_params : common_params<Key, Compare, Alloc, TargetNodeSize, Multi, |
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set_slot_policy<Key>> { |
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using value_type = Key; |
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using slot_type = typename set_params::common_params::slot_type; |
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using value_compare = typename set_params::common_params::key_compare; |
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using is_map_container = std::false_type; |
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static const Key &key(const value_type &x) { return x; } |
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static const Key &key(const slot_type *x) { return *x; } |
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}; |
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// An adapter class that converts a lower-bound compare into an upper-bound |
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// compare. Note: there is no need to make a version of this adapter specialized |
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// for key-compare-to functors because the upper-bound (the first value greater |
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// than the input) is never an exact match. |
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template <typename Compare> |
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struct upper_bound_adapter { |
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explicit upper_bound_adapter(const Compare &c) : comp(c) {} |
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template <typename K, typename LK> |
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bool operator()(const K &a, const LK &b) const { |
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// Returns true when a is not greater than b. |
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return !compare_internal::compare_result_as_less_than(comp(b, a)); |
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} |
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private: |
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Compare comp; |
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}; |
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enum class MatchKind : uint8_t { kEq, kNe }; |
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template <typename V, bool IsCompareTo> |
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struct SearchResult { |
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V value; |
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MatchKind match; |
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static constexpr bool HasMatch() { return true; } |
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bool IsEq() const { return match == MatchKind::kEq; } |
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}; |
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// When we don't use CompareTo, `match` is not present. |
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// This ensures that callers can't use it accidentally when it provides no |
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// useful information. |
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template <typename V> |
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struct SearchResult<V, false> { |
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V value; |
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static constexpr bool HasMatch() { return false; } |
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static constexpr bool IsEq() { return false; } |
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}; |
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// A node in the btree holding. The same node type is used for both internal |
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// and leaf nodes in the btree, though the nodes are allocated in such a way |
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// that the children array is only valid in internal nodes. |
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template <typename Params> |
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class btree_node { |
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using is_key_compare_to = typename Params::is_key_compare_to; |
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using is_multi_container = typename Params::is_multi_container; |
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using field_type = typename Params::node_count_type; |
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using allocator_type = typename Params::allocator_type; |
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using slot_type = typename Params::slot_type; |
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public: |
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using params_type = Params; |
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using key_type = typename Params::key_type; |
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using value_type = typename Params::value_type; |
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using pointer = typename Params::pointer; |
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using const_pointer = typename Params::const_pointer; |
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using reference = typename Params::reference; |
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using const_reference = typename Params::const_reference; |
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using key_compare = typename Params::key_compare; |
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using size_type = typename Params::size_type; |
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using difference_type = typename Params::difference_type; |
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// Btree decides whether to use linear node search as follows: |
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// - If the key is arithmetic and the comparator is std::less or |
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// std::greater, choose linear. |
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// - Otherwise, choose binary. |
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// TODO(ezb): Might make sense to add condition(s) based on node-size. |
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using use_linear_search = std::integral_constant< |
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bool, |
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std::is_arithmetic<key_type>::value && |
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(std::is_same<std::less<key_type>, key_compare>::value || |
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std::is_same<std::greater<key_type>, key_compare>::value)>; |
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// This class is organized by gtl::Layout as if it had the following |
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// structure: |
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// // A pointer to the node's parent. |
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// btree_node *parent; |
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// |
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// // The position of the node in the node's parent. |
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// field_type position; |
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// // The index of the first populated value in `values`. |
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// // TODO(ezb): right now, `start` is always 0. Update insertion/merge |
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// // logic to allow for floating storage within nodes. |
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// field_type start; |
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// // The count of the number of populated values in the node. |
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// field_type count; |
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// // The maximum number of values the node can hold. This is an integer in |
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// // [1, kNodeValues] for root leaf nodes, kNodeValues for non-root leaf |
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// // nodes, and kInternalNodeMaxCount (as a sentinel value) for internal |
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// // nodes (even though there are still kNodeValues values in the node). |
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// // TODO(ezb): make max_count use only 4 bits and record log2(capacity) |
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// // to free extra bits for is_root, etc. |
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// field_type max_count; |
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// |
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// // The array of values. The capacity is `max_count` for leaf nodes and |
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// // kNodeValues for internal nodes. Only the values in |
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// // [start, start + count) have been initialized and are valid. |
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// slot_type values[max_count]; |
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// |
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// // The array of child pointers. The keys in children[i] are all less |
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// // than key(i). The keys in children[i + 1] are all greater than key(i). |
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// // There are 0 children for leaf nodes and kNodeValues + 1 children for |
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// // internal nodes. |
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// btree_node *children[kNodeValues + 1]; |
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// |
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// This class is only constructed by EmptyNodeType. Normally, pointers to the |
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// layout above are allocated, cast to btree_node*, and de-allocated within |
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// the btree implementation. |
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~btree_node() = default; |
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btree_node(btree_node const &) = delete; |
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btree_node &operator=(btree_node const &) = delete; |
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// Public for EmptyNodeType. |
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constexpr static size_type Alignment() { |
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static_assert(LeafLayout(1).Alignment() == InternalLayout().Alignment(), |
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"Alignment of all nodes must be equal."); |
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return InternalLayout().Alignment(); |
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} |
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protected: |
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btree_node() = default; |
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private: |
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using layout_type = absl::container_internal::Layout<btree_node *, field_type, |
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slot_type, btree_node *>; |
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constexpr static size_type SizeWithNValues(size_type n) { |
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return layout_type(/*parent*/ 1, |
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/*position, start, count, max_count*/ 4, |
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/*values*/ n, |
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/*children*/ 0) |
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.AllocSize(); |
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} |
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// A lower bound for the overhead of fields other than values in a leaf node. |
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constexpr static size_type MinimumOverhead() { |
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return SizeWithNValues(1) - sizeof(value_type); |
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} |
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// Compute how many values we can fit onto a leaf node taking into account |
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// padding. |
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constexpr static size_type NodeTargetValues(const int begin, const int end) { |
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return begin == end ? begin |
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: SizeWithNValues((begin + end) / 2 + 1) > |
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params_type::kTargetNodeSize |
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? NodeTargetValues(begin, (begin + end) / 2) |
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: NodeTargetValues((begin + end) / 2 + 1, end); |
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} |
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enum { |
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kTargetNodeSize = params_type::kTargetNodeSize, |
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kNodeTargetValues = NodeTargetValues(0, params_type::kTargetNodeSize), |
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// We need a minimum of 3 values per internal node in order to perform |
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// splitting (1 value for the two nodes involved in the split and 1 value |
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// propagated to the parent as the delimiter for the split). |
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kNodeValues = kNodeTargetValues >= 3 ? kNodeTargetValues : 3, |
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// The node is internal (i.e. is not a leaf node) if and only if `max_count` |
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// has this value. |
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kInternalNodeMaxCount = 0, |
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}; |
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// Leaves can have less than kNodeValues values. |
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constexpr static layout_type LeafLayout(const int max_values = kNodeValues) { |
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return layout_type(/*parent*/ 1, |
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/*position, start, count, max_count*/ 4, |
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/*values*/ max_values, |
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/*children*/ 0); |
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} |
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constexpr static layout_type InternalLayout() { |
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return layout_type(/*parent*/ 1, |
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/*position, start, count, max_count*/ 4, |
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/*values*/ kNodeValues, |
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/*children*/ kNodeValues + 1); |
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} |
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constexpr static size_type LeafSize(const int max_values = kNodeValues) { |
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return LeafLayout(max_values).AllocSize(); |
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} |
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constexpr static size_type InternalSize() { |
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return InternalLayout().AllocSize(); |
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} |
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// N is the index of the type in the Layout definition. |
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// ElementType<N> is the Nth type in the Layout definition. |
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template <size_type N> |
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inline typename layout_type::template ElementType<N> *GetField() { |
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// We assert that we don't read from values that aren't there. |
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assert(N < 3 || !leaf()); |
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return InternalLayout().template Pointer<N>(reinterpret_cast<char *>(this)); |
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} |
|
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_count() { return GetField<1>()[2]; } |
|
slot_type *slot(int i) { return &GetField<2>()[i]; } |
|
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_count(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 { return GetField<1>()[1]; } |
|
|
|
// Getters for the number of values stored in this node. |
|
field_type count() const { return GetField<1>()[2]; } |
|
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 *&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, 0, count(), 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, 0, count(), 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 {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 {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 value at position i, shifting all existing values and children |
|
// at positions > i to the left by 1. |
|
void remove_value(int i, allocator_type *alloc); |
|
|
|
// Removes the values at positions [i, i + to_erase), shifting all values |
|
// after that range to the left by to_erase. Does not change children at all. |
|
void remove_values_ignore_children(int i, int to_erase, |
|
allocator_type *alloc); |
|
|
|
// Rebalances a node with its right sibling. |
|
void rebalance_right_to_left(int to_move, btree_node *right, |
|
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. |
|
void merge(btree_node *sibling, allocator_type *alloc); |
|
|
|
// Swap the contents of "this" and "src". |
|
void swap(btree_node *src, allocator_type *alloc); |
|
|
|
// Node allocation/deletion routines. |
|
static btree_node *init_leaf(btree_node *n, btree_node *parent, |
|
int max_count) { |
|
n->set_parent(parent); |
|
n->set_position(0); |
|
n->set_start(0); |
|
n->set_count(0); |
|
n->set_max_count(max_count); |
|
absl::container_internal::SanitizerPoisonMemoryRegion( |
|
n->slot(0), max_count * sizeof(slot_type)); |
|
return n; |
|
} |
|
static btree_node *init_internal(btree_node *n, btree_node *parent) { |
|
init_leaf(n, parent, kNodeValues); |
|
// Set `max_count` to a sentinel value to indicate that this node is |
|
// internal. |
|
n->set_max_count(kInternalNodeMaxCount); |
|
absl::container_internal::SanitizerPoisonMemoryRegion( |
|
&n->mutable_child(0), (kNodeValues + 1) * sizeof(btree_node *)); |
|
return n; |
|
} |
|
void destroy(allocator_type *alloc) { |
|
for (int i = 0; i < count(); ++i) { |
|
value_destroy(i, alloc); |
|
} |
|
} |
|
|
|
public: |
|
// Exposed only for tests. |
|
static bool testonly_uses_linear_node_search() { |
|
return use_linear_search::value; |
|
} |
|
|
|
private: |
|
template <typename... Args> |
|
void value_init(const size_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 size_type i, allocator_type *alloc) { |
|
params_type::destroy(alloc, slot(i)); |
|
absl::container_internal::SanitizerPoisonObject(slot(i)); |
|
} |
|
|
|
// Move n values starting at value i in this node into the values starting at |
|
// value j in node x. |
|
void uninitialized_move_n(const size_type n, const size_type i, |
|
const size_type j, btree_node *x, |
|
allocator_type *alloc) { |
|
absl::container_internal::SanitizerUnpoisonMemoryRegion( |
|
x->slot(j), n * sizeof(slot_type)); |
|
for (slot_type *src = slot(i), *end = src + n, *dest = x->slot(j); |
|
src != end; ++src, ++dest) { |
|
params_type::construct(alloc, dest, src); |
|
} |
|
} |
|
|
|
// Destroys a range of n values, starting at index i. |
|
void value_destroy_n(const size_type i, const size_type n, |
|
allocator_type *alloc) { |
|
for (int j = 0; j < n; ++j) { |
|
value_destroy(i + j, 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) {} |
|
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> &x) // NOLINT |
|
: node(x.node), position(x.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> &x) |
|
: node(const_cast<node_type *>(x.node)), position(x.position) {} |
|
|
|
// Increment/decrement the iterator. |
|
void increment() { |
|
if (node->leaf() && ++position < node->count()) { |
|
return; |
|
} |
|
increment_slow(); |
|
} |
|
void increment_slow(); |
|
|
|
void decrement() { |
|
if (node->leaf() && --position >= 0) { |
|
return; |
|
} |
|
decrement_slow(); |
|
} |
|
void decrement_slow(); |
|
|
|
public: |
|
bool operator==(const const_iterator &x) const { |
|
return node == x.node && position == x.position; |
|
} |
|
bool operator!=(const const_iterator &x) const { |
|
return node != x.node || position != x.position; |
|
} |
|
|
|
// Accessors for the key/value the iterator is pointing at. |
|
reference operator*() const { |
|
return node->value(position); |
|
} |
|
pointer operator->() const { |
|
return &node->value(position); |
|
} |
|
|
|
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. |
|
// TODO(ezb): make this a field_type |
|
int position; |
|
}; |
|
|
|
template <typename Params> |
|
class btree { |
|
using node_type = btree_node<Params>; |
|
using is_key_compare_to = typename Params::is_key_compare_to; |
|
|
|
// 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 count = 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 { |
|
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 &x) { |
|
leaf_nodes += x.leaf_nodes; |
|
internal_nodes += x.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 x) { return *x; } |
|
value_type &&maybe_move_from_iterator(iterator x) { return std::move(*x); } |
|
|
|
// Copies or moves (depending on the template parameter) the values in |
|
// x into this btree in their order in x. 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 *x); |
|
|
|
// 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); |
|
|
|
btree(const btree &x); |
|
btree(btree &&x) noexcept |
|
: root_(std::move(x.root_)), |
|
rightmost_(absl::exchange(x.rightmost_, EmptyNode())), |
|
size_(absl::exchange(x.size_, 0)) { |
|
x.mutable_root() = EmptyNode(); |
|
} |
|
|
|
~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 x to *this. |
|
btree &operator=(const btree &x); |
|
btree &operator=(btree &&x) noexcept; |
|
|
|
iterator begin() { |
|
return iterator(leftmost(), 0); |
|
} |
|
const_iterator begin() const { |
|
return const_iterator(leftmost(), 0); |
|
} |
|
iterator end() { return iterator(rightmost_, rightmost_->count()); } |
|
const_iterator end() const { |
|
return const_iterator(rightmost_, rightmost_->count()); |
|
} |
|
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)); |
|
} |
|
template <typename K> |
|
const_iterator lower_bound(const K &key) const { |
|
return internal_end(internal_lower_bound(key)); |
|
} |
|
|
|
// 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 pair of |
|
// the pair is equal to upper_bound(key). |
|
template <typename K> |
|
std::pair<iterator, iterator> equal_range(const K &key) { |
|
return {lower_bound(key), upper_bound(key)}; |
|
} |
|
template <typename K> |
|
std::pair<const_iterator, const_iterator> equal_range(const K &key) const { |
|
return {lower_bound(key), upper_bound(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... Args> |
|
std::pair<iterator, bool> insert_unique(const key_type &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... Args> |
|
std::pair<iterator, bool> insert_hint_unique(iterator position, |
|
const key_type &key, |
|
Args &&... args); |
|
|
|
// Insert a range of values into the btree. |
|
template <typename InputIterator> |
|
void insert_iterator_unique(InputIterator b, InputIterator e); |
|
|
|
// 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(iterator begin, iterator end); |
|
|
|
// Erases the specified key from the btree. Returns 1 if an element was |
|
// erased and 0 otherwise. |
|
template <typename K> |
|
size_type erase_unique(const K &key); |
|
|
|
// Erases all of the entries matching the specified key from the |
|
// btree. Returns the number of elements erased. |
|
template <typename K> |
|
size_type erase_multi(const K &key); |
|
|
|
// 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)); |
|
} |
|
|
|
// Returns a count of the number of times the key appears in the btree. |
|
template <typename K> |
|
size_type count_unique(const K &key) const { |
|
const iterator begin = internal_find(key); |
|
if (begin.node == nullptr) { |
|
// The key doesn't exist in the tree. |
|
return 0; |
|
} |
|
return 1; |
|
} |
|
// Returns a count of the number of times the key appears in the btree. |
|
template <typename K> |
|
size_type count_multi(const K &key) const { |
|
const auto range = equal_range(key); |
|
return std::distance(range.first, range.second); |
|
} |
|
|
|
// Clear the btree, deleting all of the values it contains. |
|
void clear(); |
|
|
|
// Swap the contents of *this and x. |
|
void swap(btree &x); |
|
|
|
const key_compare &key_comp() const noexcept { |
|
return root_.template get<0>(); |
|
} |
|
template <typename K, typename LK> |
|
bool compare_keys(const K &x, const LK &y) const { |
|
return compare_internal::compare_result_as_less_than(key_comp()(x, y)); |
|
} |
|
|
|
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 *p = allocate(node_type::InternalSize()); |
|
return node_type::init_internal(p, parent); |
|
} |
|
node_type* new_leaf_node(node_type *parent) { |
|
node_type *p = allocate(node_type::LeafSize()); |
|
return node_type::init_leaf(p, parent, kNodeValues); |
|
} |
|
node_type *new_leaf_root_node(const int max_count) { |
|
node_type *p = allocate(node_type::LeafSize(max_count)); |
|
return node_type::init_leaf(p, p, max_count); |
|
} |
|
|
|
// Deletion helper routines. |
|
void erase_same_node(iterator begin, iterator end); |
|
iterator erase_from_leaf_node(iterator begin, size_type to_erase); |
|
iterator rebalance_after_delete(iterator iter); |
|
|
|
// Deallocates a node of a certain size in bytes using the allocator. |
|
void deallocate(const size_type size, node_type *node) { |
|
absl::container_internal::Deallocate<node_type::Alignment()>( |
|
mutable_allocator(), node, size); |
|
} |
|
|
|
void delete_internal_node(node_type *node) { |
|
node->destroy(mutable_allocator()); |
|
deallocate(node_type::InternalSize(), node); |
|
} |
|
void delete_leaf_node(node_type *node) { |
|
node->destroy(mutable_allocator()); |
|
deallocate(node_type::LeafSize(node->max_count()), node); |
|
} |
|
|
|
// Rebalances or splits the node iter points to. |
|
void rebalance_or_split(iterator *iter); |
|
|
|
// 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 as |
|
// iter.position == iter.node->count(). 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. We provide 2 versions of internal_locate. The first |
|
// version uses a less-than comparator and is incapable of distinguishing when |
|
// there is an exact match. The second version is for the key-compare-to |
|
// specialization and distinguishes exact matches. The key-compare-to |
|
// specialization 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; |
|
|
|
template <typename K> |
|
SearchResult<iterator, false> internal_locate_impl( |
|
const K &key, std::false_type /* IsCompareTo */) const; |
|
|
|
template <typename K> |
|
SearchResult<iterator, true> internal_locate_impl( |
|
const K &key, std::true_type /* IsCompareTo */) const; |
|
|
|
// Internal routine which implements lower_bound(). |
|
template <typename K> |
|
iterator 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; |
|
|
|
// Deletes a node and all of its children. |
|
void internal_clear(node_type *node); |
|
|
|
// Verifies the tree structure of node. |
|
int internal_verify(const node_type *node, |
|
const key_type *lo, const key_type *hi) const; |
|
|
|
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 = 0; i <= node->count(); ++i) { |
|
res += internal_stats(node->child(i)); |
|
} |
|
return res; |
|
} |
|
|
|
public: |
|
// Exposed only for tests. |
|
static bool testonly_uses_linear_node_search() { |
|
return node_type::testonly_uses_linear_node_search(); |
|
} |
|
|
|
private: |
|
// 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 <= count()); |
|
// Shift old values to create space for new value and then construct it in |
|
// place. |
|
if (i < count()) { |
|
value_init(count(), alloc, slot(count() - 1)); |
|
for (size_type j = count() - 1; j > i; --j) |
|
params_type::move(alloc, slot(j - 1), slot(j)); |
|
value_destroy(i, alloc); |
|
} |
|
value_init(i, alloc, std::forward<Args>(args)...); |
|
set_count(count() + 1); |
|
|
|
if (!leaf() && count() > i + 1) { |
|
for (int j = count(); j > i + 1; --j) { |
|
set_child(j, child(j - 1)); |
|
} |
|
clear_child(i + 1); |
|
} |
|
} |
|
|
|
template <typename P> |
|
inline void btree_node<P>::remove_value(const int i, allocator_type *alloc) { |
|
if (!leaf() && count() > i + 1) { |
|
assert(child(i + 1)->count() == 0); |
|
for (size_type j = i + 1; j < count(); ++j) { |
|
set_child(j, child(j + 1)); |
|
} |
|
clear_child(count()); |
|
} |
|
|
|
remove_values_ignore_children(i, /*to_erase=*/1, alloc); |
|
} |
|
|
|
template <typename P> |
|
inline void btree_node<P>::remove_values_ignore_children( |
|
const int i, const int to_erase, allocator_type *alloc) { |
|
params_type::move(alloc, slot(i + to_erase), slot(count()), slot(i)); |
|
value_destroy_n(count() - to_erase, to_erase, alloc); |
|
set_count(count() - 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. |
|
value_init(count(), alloc, parent()->slot(position())); |
|
|
|
// 2) Move the (to_move - 1) values from the right node to the left node. |
|
right->uninitialized_move_n(to_move - 1, 0, count() + 1, this, alloc); |
|
|
|
// 3) Move the new delimiting value to the parent from the right node. |
|
params_type::move(alloc, right->slot(to_move - 1), |
|
parent()->slot(position())); |
|
|
|
// 4) Shift the values in the right node to their correct position. |
|
params_type::move(alloc, right->slot(to_move), right->slot(right->count()), |
|
right->slot(0)); |
|
|
|
// 5) Destroy the now-empty to_move entries in the right node. |
|
right->value_destroy_n(right->count() - to_move, to_move, alloc); |
|
|
|
if (!leaf()) { |
|
// Move the child pointers from the right to the left node. |
|
for (int i = 0; i < to_move; ++i) { |
|
init_child(count() + i + 1, right->child(i)); |
|
} |
|
for (int i = 0; i <= right->count() - 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 the counts on the left and right nodes. |
|
set_count(count() + to_move); |
|
right->set_count(right->count() - 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. |
|
|
|
if (right->count() >= to_move) { |
|
// The original location of the right->count() values are sufficient to hold |
|
// the new to_move entries from the parent and left node. |
|
|
|
// 1) Shift existing values in the right node to their correct positions. |
|
right->uninitialized_move_n(to_move, right->count() - to_move, |
|
right->count(), right, alloc); |
|
for (slot_type *src = right->slot(right->count() - to_move - 1), |
|
*dest = right->slot(right->count() - 1), |
|
*end = right->slot(0); |
|
src >= end; --src, --dest) { |
|
params_type::move(alloc, src, dest); |
|
} |
|
|
|
// 2) Move the delimiting value in the parent to the right node. |
|
params_type::move(alloc, parent()->slot(position()), |
|
right->slot(to_move - 1)); |
|
|
|
// 3) Move the (to_move - 1) values from the left node to the right node. |
|
params_type::move(alloc, slot(count() - (to_move - 1)), slot(count()), |
|
right->slot(0)); |
|
} else { |
|
// The right node does not have enough initialized space to hold the new |
|
// to_move entries, so part of them will move to uninitialized space. |
|
|
|
// 1) Shift existing values in the right node to their correct positions. |
|
right->uninitialized_move_n(right->count(), 0, to_move, right, alloc); |
|
|
|
// 2) Move the delimiting value in the parent to the right node. |
|
right->value_init(to_move - 1, alloc, parent()->slot(position())); |
|
|
|
// 3) Move the (to_move - 1) values from the left node to the right node. |
|
const size_type uninitialized_remaining = to_move - right->count() - 1; |
|
uninitialized_move_n(uninitialized_remaining, |
|
count() - uninitialized_remaining, right->count(), |
|
right, alloc); |
|
params_type::move(alloc, slot(count() - (to_move - 1)), |
|
slot(count() - uninitialized_remaining), right->slot(0)); |
|
} |
|
|
|
// 4) Move the new delimiting value to the parent from the left node. |
|
params_type::move(alloc, slot(count() - to_move), parent()->slot(position())); |
|
|
|
// 5) Destroy the now-empty to_move entries in the left node. |
|
value_destroy_n(count() - to_move, to_move, alloc); |
|
|
|
if (!leaf()) { |
|
// Move the child pointers from the left to the right node. |
|
for (int i = right->count(); i >= 0; --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(count() - to_move + i)); |
|
clear_child(count() - to_move + i); |
|
} |
|
} |
|
|
|
// Fixup the counts on the left and right nodes. |
|
set_count(count() - to_move); |
|
right->set_count(right->count() + 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 == 0) { |
|
dest->set_count(count() - 1); |
|
} else if (insert_position == kNodeValues) { |
|
dest->set_count(0); |
|
} else { |
|
dest->set_count(count() / 2); |
|
} |
|
set_count(count() - dest->count()); |
|
assert(count() >= 1); |
|
|
|
// Move values from the left sibling to the right sibling. |
|
uninitialized_move_n(dest->count(), count(), 0, dest, alloc); |
|
|
|
// Destroy the now-empty entries in the left node. |
|
value_destroy_n(count(), dest->count(), alloc); |
|
|
|
// The split key is the largest value in the left sibling. |
|
set_count(count() - 1); |
|
parent()->emplace_value(position(), alloc, slot(count())); |
|
value_destroy(count(), alloc); |
|
parent()->init_child(position() + 1, dest); |
|
|
|
if (!leaf()) { |
|
for (int i = 0; i <= dest->count(); ++i) { |
|
assert(child(count() + i + 1) != nullptr); |
|
dest->init_child(i, child(count() + i + 1)); |
|
clear_child(count() + i + 1); |
|
} |
|
} |
|
} |
|
|
|
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(count(), alloc, parent()->slot(position())); |
|
|
|
// Move the values from the right to the left node. |
|
src->uninitialized_move_n(src->count(), 0, count() + 1, this, alloc); |
|
|
|
// Destroy the now-empty entries in the right node. |
|
src->value_destroy_n(0, src->count(), alloc); |
|
|
|
if (!leaf()) { |
|
// Move the child pointers from the right to the left node. |
|
for (int i = 0; i <= src->count(); ++i) { |
|
init_child(count() + i + 1, src->child(i)); |
|
src->clear_child(i); |
|
} |
|
} |
|
|
|
// Fixup the counts on the src and dest nodes. |
|
set_count(1 + count() + src->count()); |
|
src->set_count(0); |
|
|
|
// Remove the value on the parent node. |
|
parent()->remove_value(position(), alloc); |
|
} |
|
|
|
template <typename P> |
|
void btree_node<P>::swap(btree_node *x, allocator_type *alloc) { |
|
using std::swap; |
|
assert(leaf() == x->leaf()); |
|
|
|
// Determine which is the smaller/larger node. |
|
btree_node *smaller = this, *larger = x; |
|
if (smaller->count() > larger->count()) { |
|
swap(smaller, larger); |
|
} |
|
|
|
// Swap the values. |
|
for (slot_type *a = smaller->slot(0), *b = larger->slot(0), |
|
*end = a + smaller->count(); |
|
a != end; ++a, ++b) { |
|
params_type::swap(alloc, a, b); |
|
} |
|
|
|
// Move values that can't be swapped. |
|
const size_type to_move = larger->count() - smaller->count(); |
|
larger->uninitialized_move_n(to_move, smaller->count(), smaller->count(), |
|
smaller, alloc); |
|
larger->value_destroy_n(smaller->count(), to_move, alloc); |
|
|
|
if (!leaf()) { |
|
// Swap the child pointers. |
|
std::swap_ranges(&smaller->mutable_child(0), |
|
&smaller->mutable_child(smaller->count() + 1), |
|
&larger->mutable_child(0)); |
|
// Update swapped children's parent pointers. |
|
int i = 0; |
|
for (; i <= smaller->count(); ++i) { |
|
smaller->child(i)->set_parent(smaller); |
|
larger->child(i)->set_parent(larger); |
|
} |
|
// Move the child pointers that couldn't be swapped. |
|
for (; i <= larger->count(); ++i) { |
|
smaller->init_child(i, larger->child(i)); |
|
larger->clear_child(i); |
|
} |
|
} |
|
|
|
// Swap the counts. |
|
swap(mutable_count(), x->mutable_count()); |
|
} |
|
|
|
//// |
|
// btree_iterator methods |
|
template <typename N, typename R, typename P> |
|
void btree_iterator<N, R, P>::increment_slow() { |
|
if (node->leaf()) { |
|
assert(position >= node->count()); |
|
btree_iterator save(*this); |
|
while (position == node->count() && !node->is_root()) { |
|
assert(node->parent()->child(node->position()) == node); |
|
position = node->position(); |
|
node = node->parent(); |
|
} |
|
if (position == node->count()) { |
|
*this = save; |
|
} |
|
} else { |
|
assert(position < node->count()); |
|
node = node->child(position + 1); |
|
while (!node->leaf()) { |
|
node = node->child(0); |
|
} |
|
position = 0; |
|
} |
|
} |
|
|
|
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 < 0 && !node->is_root()) { |
|
assert(node->parent()->child(node->position()) == node); |
|
position = node->position() - 1; |
|
node = node->parent(); |
|
} |
|
if (position < 0) { |
|
*this = save; |
|
} |
|
} else { |
|
assert(position >= 0); |
|
node = node->child(position); |
|
while (!node->leaf()) { |
|
node = node->child(node->count()); |
|
} |
|
position = node->count() - 1; |
|
} |
|
} |
|
|
|
//// |
|
// btree methods |
|
template <typename P> |
|
template <typename Btree> |
|
void btree<P>::copy_or_move_values_in_order(Btree *x) { |
|
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 = x->begin(); |
|
if (iter == x->end()) return; |
|
insert_multi(maybe_move_from_iterator(iter)); |
|
++iter; |
|
for (; iter != x->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> |
|
btree<P>::btree(const key_compare &comp, const allocator_type &alloc) |
|
: root_(comp, alloc, EmptyNode()), rightmost_(EmptyNode()), size_(0) {} |
|
|
|
template <typename P> |
|
btree<P>::btree(const btree &x) : btree(x.key_comp(), x.allocator()) { |
|
copy_or_move_values_in_order(&x); |
|
} |
|
|
|
template <typename P> |
|
template <typename... Args> |
|
auto btree<P>::insert_unique(const key_type &key, Args &&... args) |
|
-> std::pair<iterator, bool> { |
|
if (empty()) { |
|
mutable_root() = rightmost_ = new_leaf_root_node(1); |
|
} |
|
|
|
auto 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... Args> |
|
inline auto btree<P>::insert_hint_unique(iterator position, const key_type &key, |
|
Args &&... args) |
|
-> std::pair<iterator, bool> { |
|
if (!empty()) { |
|
if (position == end() || compare_keys(key, position.key())) { |
|
iterator prev = position; |
|
if (position == begin() || compare_keys((--prev).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> |
|
void btree<P>::insert_iterator_unique(InputIterator b, InputIterator e) { |
|
for (; b != e; ++b) { |
|
insert_hint_unique(end(), params_type::key(*b), *b); |
|
} |
|
} |
|
|
|
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)) { |
|
iterator prev = position; |
|
if (position == begin() || !compare_keys(key, (--prev).key())) { |
|
// prev.key() <= key <= position.key() |
|
return internal_emplace(position, std::forward<ValueType>(v)); |
|
} |
|
} else { |
|
iterator next = position; |
|
++next; |
|
if (next == end() || !compare_keys(next.key(), key)) { |
|
// position.key() < key <= next.key() |
|
return internal_emplace(next, 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 &x) -> btree & { |
|
if (this != &x) { |
|
clear(); |
|
|
|
*mutable_key_comp() = x.key_comp(); |
|
if (absl::allocator_traits< |
|
allocator_type>::propagate_on_container_copy_assignment::value) { |
|
*mutable_allocator() = x.allocator(); |
|
} |
|
|
|
copy_or_move_values_in_order(&x); |
|
} |
|
return *this; |
|
} |
|
|
|
template <typename P> |
|
auto btree<P>::operator=(btree &&x) noexcept -> btree & { |
|
if (this != &x) { |
|
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_, x.root_); |
|
swap(rightmost_, x.rightmost_); |
|
swap(size_, x.size_); |
|
} else { |
|
if (allocator() == x.allocator()) { |
|
swap(mutable_root(), x.mutable_root()); |
|
swap(*mutable_key_comp(), *x.mutable_key_comp()); |
|
swap(rightmost_, x.rightmost_); |
|
swap(size_, x.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 `x` and `this` to have `x`s key comparator |
|
// while moving the values so we can't swap the key comparators. |
|
*mutable_key_comp() = x.key_comp(); |
|
copy_or_move_values_in_order(&x); |
|
} |
|
} |
|
} |
|
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_value() |
|
// below). We can get to the largest value from our left child by |
|
// decrementing iter. |
|
iterator internal_iter(iter); |
|
--iter; |
|
assert(iter.node->leaf()); |
|
assert(!compare_keys(internal_iter.key(), iter.key())); |
|
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_value(iter.position, 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->count()) { |
|
res.position = res.node->count() - 1; |
|
++res; |
|
} |
|
|
|
return res; |
|
} |
|
|
|
template <typename P> |
|
auto btree<P>::erase(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) { |
|
erase_same_node(begin, end); |
|
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->count() - begin.position; |
|
begin = erase_from_leaf_node( |
|
begin, (std::min)(remaining_to_erase, remaining_in_node)); |
|
} else { |
|
begin = erase(begin); |
|
} |
|
} |
|
return {count, begin}; |
|
} |
|
|
|
template <typename P> |
|
void btree<P>::erase_same_node(iterator begin, iterator end) { |
|
assert(begin.node == end.node); |
|
assert(end.position > begin.position); |
|
|
|
node_type *node = begin.node; |
|
size_type to_erase = end.position - begin.position; |
|
if (!node->leaf()) { |
|
// Delete all children between begin and end. |
|
for (size_type i = 0; i < to_erase; ++i) { |
|
internal_clear(node->child(begin.position + i + 1)); |
|
} |
|
// Rotate children after end into new positions. |
|
for (size_type i = begin.position + to_erase + 1; i <= node->count(); ++i) { |
|
node->set_child(i - to_erase, node->child(i)); |
|
node->clear_child(i); |
|
} |
|
} |
|
node->remove_values_ignore_children(begin.position, to_erase, |
|
mutable_allocator()); |
|
|
|
// Do not need to update rightmost_, because |
|
// * either end == this->end(), and therefore node == rightmost_, and still |
|
// exists |
|
// * or end != this->end(), and therefore rightmost_ hasn't been erased, since |
|
// it wasn't covered in [begin, end) |
|
} |
|
|
|
template <typename P> |
|
auto btree<P>::erase_from_leaf_node(iterator begin, size_type to_erase) |
|
-> iterator { |
|
node_type *node = begin.node; |
|
assert(node->leaf()); |
|
assert(node->count() > begin.position); |
|
assert(begin.position + to_erase <= node->count()); |
|
|
|
node->remove_values_ignore_children(begin.position, to_erase, |
|
mutable_allocator()); |
|
|
|
size_ -= to_erase; |
|
|
|
return rebalance_after_delete(begin); |
|
} |
|
|
|
template <typename P> |
|
template <typename K> |
|
auto btree<P>::erase_unique(const K &key) -> size_type { |
|
const iterator iter = internal_find(key); |
|
if (iter.node == nullptr) { |
|
// The key doesn't exist in the tree, return nothing done. |
|
return 0; |
|
} |
|
erase(iter); |
|
return 1; |
|
} |
|
|
|
template <typename P> |
|
template <typename K> |
|
auto btree<P>::erase_multi(const K &key) -> size_type { |
|
const iterator begin = internal_lower_bound(key); |
|
if (begin.node == nullptr) { |
|
// The key doesn't exist in the tree, return nothing done. |
|
return 0; |
|
} |
|
// Delete all of the keys between begin and upper_bound(key). |
|
const iterator end = internal_end(internal_upper_bound(key)); |
|
return erase(begin, end).first; |
|
} |
|
|
|
template <typename P> |
|
void btree<P>::clear() { |
|
if (!empty()) { |
|
internal_clear(root()); |
|
} |
|
mutable_root() = EmptyNode(); |
|
rightmost_ = EmptyNode(); |
|
size_ = 0; |
|
} |
|
|
|
template <typename P> |
|
void btree<P>::swap(btree &x) { |
|
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_, x.root_); |
|
} else { |
|
// It's undefined behavior if the allocators are unequal here. |
|
assert(allocator() == x.allocator()); |
|
swap(mutable_root(), x.mutable_root()); |
|
swap(*mutable_key_comp(), *x.mutable_key_comp()); |
|
} |
|
swap(rightmost_, x.rightmost_); |
|
swap(size_, x.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()->count())).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() > 0) { |
|
// 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 < kNodeValues)); |
|
to_move = (std::max)(1, to_move); |
|
|
|
if (((insert_position - to_move) >= 0) || |
|
((left->count() + to_move) < 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 < 0) { |
|
insert_position = insert_position + left->count() + 1; |
|
node = left; |
|
} |
|
|
|
assert(node->count() < node->max_count()); |
|
return; |
|
} |
|
} |
|
} |
|
|
|
if (node->position() < parent->count()) { |
|
// 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 = |
|
(kNodeValues - right->count()) / (1 + (insert_position > 0)); |
|
to_move = (std::max)(1, to_move); |
|
|
|
if ((insert_position <= (node->count() - to_move)) || |
|
((right->count() + to_move) < kNodeValues)) { |
|
node->rebalance_left_to_right(to_move, right, mutable_allocator()); |
|
|
|
if (insert_position > node->count()) { |
|
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(0, root()); |
|
mutable_root() = parent; |
|
// If the former root was a leaf node, then it's now the rightmost node. |
|
assert(!parent->child(0)->leaf() || parent->child(0) == 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->count()) { |
|
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 (right->leaf()) { |
|
if (rightmost_ == right) rightmost_ = left; |
|
delete_leaf_node(right); |
|
} else { |
|
delete_internal_node(right); |
|
} |
|
} |
|
|
|
template <typename P> |
|
bool btree<P>::try_merge_or_rebalance(iterator *iter) { |
|
node_type *parent = iter->node->parent(); |
|
if (iter->node->position() > 0) { |
|
// Try merging with our left sibling. |
|
node_type *left = parent->child(iter->node->position() - 1); |
|
assert(left->max_count() == kNodeValues); |
|
if ((1 + 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->count()) { |
|
// Try merging with our right sibling. |
|
node_type *right = parent->child(iter->node->position() + 1); |
|
assert(right->max_count() == kNodeValues); |
|
if ((1 + 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 > 0))) { |
|
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() > 0) { |
|
// 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->count()))) { |
|
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() { |
|
if (root()->count() > 0) { |
|
return; |
|
} |
|
// Deleted the last item on the root node, shrink the height of the tree. |
|
if (root()->leaf()) { |
|
assert(size() == 0); |
|
delete_leaf_node(root()); |
|
mutable_root() = EmptyNode(); |
|
rightmost_ = EmptyNode(); |
|
} else { |
|
node_type *child = root()->child(0); |
|
child->make_root(); |
|
delete_internal_node(root()); |
|
mutable_root() = child; |
|
} |
|
} |
|
|
|
template <typename P> |
|
template <typename IterType> |
|
inline IterType btree<P>::internal_last(IterType iter) { |
|
assert(iter.node != nullptr); |
|
while (iter.position == iter.node->count()) { |
|
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 int max_count = iter.node->max_count(); |
|
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)); |
|
iter.node->swap(root(), mutable_allocator()); |
|
delete_leaf_node(root()); |
|
mutable_root() = iter.node; |
|
rightmost_ = iter.node; |
|
} else { |
|
rebalance_or_split(&iter); |
|
} |
|
} |
|
iter.node->emplace_value(iter.position, mutable_allocator(), |
|
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> { |
|
return internal_locate_impl(key, is_key_compare_to()); |
|
} |
|
|
|
template <typename P> |
|
template <typename K> |
|
inline auto btree<P>::internal_locate_impl( |
|
const K &key, std::false_type /* IsCompareTo */) const |
|
-> SearchResult<iterator, false> { |
|
iterator iter(const_cast<node_type *>(root()), 0); |
|
for (;;) { |
|
iter.position = iter.node->lower_bound(key, key_comp()).value; |
|
// NOTE: 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); |
|
} |
|
return {iter}; |
|
} |
|
|
|
template <typename P> |
|
template <typename K> |
|
inline auto btree<P>::internal_locate_impl( |
|
const K &key, std::true_type /* IsCompareTo */) const |
|
-> SearchResult<iterator, true> { |
|
iterator iter(const_cast<node_type *>(root()), 0); |
|
for (;;) { |
|
SearchResult<int, true> res = iter.node->lower_bound(key, key_comp()); |
|
iter.position = res.value; |
|
if (res.match == MatchKind::kEq) { |
|
return {iter, MatchKind::kEq}; |
|
} |
|
if (iter.node->leaf()) { |
|
break; |
|
} |
|
iter.node = iter.node->child(iter.position); |
|
} |
|
return {iter, MatchKind::kNe}; |
|
} |
|
|
|
template <typename P> |
|
template <typename K> |
|
auto btree<P>::internal_lower_bound(const K &key) const -> iterator { |
|
iterator iter(const_cast<node_type *>(root()), 0); |
|
for (;;) { |
|
iter.position = iter.node->lower_bound(key, key_comp()).value; |
|
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_upper_bound(const K &key) const -> iterator { |
|
iterator iter(const_cast<node_type *>(root()), 0); |
|
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 { |
|
auto 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> |
|
void btree<P>::internal_clear(node_type *node) { |
|
if (!node->leaf()) { |
|
for (int i = 0; i <= node->count(); ++i) { |
|
internal_clear(node->child(i)); |
|
} |
|
delete_internal_node(node); |
|
} else { |
|
delete_leaf_node(node); |
|
} |
|
} |
|
|
|
template <typename P> |
|
int btree<P>::internal_verify( |
|
const node_type *node, const key_type *lo, const key_type *hi) const { |
|
assert(node->count() > 0); |
|
assert(node->count() <= node->max_count()); |
|
if (lo) { |
|
assert(!compare_keys(node->key(0), *lo)); |
|
} |
|
if (hi) { |
|
assert(!compare_keys(*hi, node->key(node->count() - 1))); |
|
} |
|
for (int i = 1; i < node->count(); ++i) { |
|
assert(!compare_keys(node->key(i), node->key(i - 1))); |
|
} |
|
int count = node->count(); |
|
if (!node->leaf()) { |
|
for (int i = 0; i <= node->count(); ++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 == 0) ? lo : &node->key(i - 1), |
|
(i == node->count()) ? hi : &node->key(i)); |
|
} |
|
} |
|
return count; |
|
} |
|
|
|
} // namespace container_internal |
|
} // namespace absl |
|
|
|
#endif // ABSL_CONTAINER_INTERNAL_BTREE_H_
|
|
|