diff options
Diffstat (limited to 'abseil-cpp/absl/container/internal/btree.h')
| -rw-r--r-- | abseil-cpp/absl/container/internal/btree.h | 1970 |
1 files changed, 1202 insertions, 768 deletions
diff --git a/abseil-cpp/absl/container/internal/btree.h b/abseil-cpp/absl/container/internal/btree.h index 002ccc1..569faa0 100644 --- a/abseil-cpp/absl/container/internal/btree.h +++ b/abseil-cpp/absl/container/internal/btree.h @@ -58,8 +58,10 @@ #include <type_traits> #include <utility> +#include "absl/base/internal/raw_logging.h" #include "absl/base/macros.h" #include "absl/container/internal/common.h" +#include "absl/container/internal/common_policy_traits.h" #include "absl/container/internal/compressed_tuple.h" #include "absl/container/internal/container_memory.h" #include "absl/container/internal/layout.h" @@ -74,12 +76,30 @@ namespace absl { ABSL_NAMESPACE_BEGIN namespace container_internal { +#ifdef ABSL_BTREE_ENABLE_GENERATIONS +#error ABSL_BTREE_ENABLE_GENERATIONS cannot be directly set +#elif defined(ABSL_HAVE_ADDRESS_SANITIZER) || \ + defined(ABSL_HAVE_MEMORY_SANITIZER) +// When compiled in sanitizer mode, we add generation integers to the nodes and +// iterators. When iterators are used, we validate that the container has not +// been mutated since the iterator was constructed. +#define ABSL_BTREE_ENABLE_GENERATIONS +#endif + +#ifdef ABSL_BTREE_ENABLE_GENERATIONS +constexpr bool BtreeGenerationsEnabled() { return true; } +#else +constexpr bool BtreeGenerationsEnabled() { return false; } +#endif + +template <typename Compare, typename T, typename U> +using compare_result_t = absl::result_of_t<const Compare(const T &, const U &)>; + // A helper class that indicates if the Compare parameter is a key-compare-to // comparator. template <typename Compare, typename T> using btree_is_key_compare_to = - std::is_convertible<absl::result_of_t<Compare(const T &, const T &)>, - absl::weak_ordering>; + std::is_convertible<compare_result_t<Compare, T, T>, absl::weak_ordering>; struct StringBtreeDefaultLess { using is_transparent = void; @@ -87,8 +107,13 @@ struct StringBtreeDefaultLess { StringBtreeDefaultLess() = default; // Compatibility constructor. - StringBtreeDefaultLess(std::less<std::string>) {} // NOLINT - StringBtreeDefaultLess(std::less<string_view>) {} // NOLINT + StringBtreeDefaultLess(std::less<std::string>) {} // NOLINT + StringBtreeDefaultLess(std::less<absl::string_view>) {} // NOLINT + + // Allow converting to std::less for use in key_comp()/value_comp(). + explicit operator std::less<std::string>() const { return {}; } + explicit operator std::less<absl::string_view>() const { return {}; } + explicit operator std::less<absl::Cord>() const { return {}; } absl::weak_ordering operator()(absl::string_view lhs, absl::string_view rhs) const { @@ -114,8 +139,13 @@ struct StringBtreeDefaultGreater { StringBtreeDefaultGreater() = default; - StringBtreeDefaultGreater(std::greater<std::string>) {} // NOLINT - StringBtreeDefaultGreater(std::greater<string_view>) {} // NOLINT + StringBtreeDefaultGreater(std::greater<std::string>) {} // NOLINT + StringBtreeDefaultGreater(std::greater<absl::string_view>) {} // NOLINT + + // Allow converting to std::greater for use in key_comp()/value_comp(). + explicit operator std::greater<std::string>() const { return {}; } + explicit operator std::greater<absl::string_view>() const { return {}; } + explicit operator std::greater<absl::Cord>() const { return {}; } absl::weak_ordering operator()(absl::string_view lhs, absl::string_view rhs) const { @@ -136,73 +166,234 @@ struct StringBtreeDefaultGreater { } }; -// A helper class to convert a boolean comparison into a three-way "compare-to" -// comparison that returns an `absl::weak_ordering`. This helper -// class is specialized for less<std::string>, greater<std::string>, -// less<string_view>, greater<string_view>, less<absl::Cord>, and -// greater<absl::Cord>. -// -// key_compare_to_adapter is provided so that btree users -// automatically get the more efficient compare-to code when using common -// Abseil string types with common comparison functors. -// These string-like specializations also turn on heterogeneous lookup by -// default. +// See below comments for checked_compare. +template <typename Compare, bool is_class = std::is_class<Compare>::value> +struct checked_compare_base : Compare { + using Compare::Compare; + explicit checked_compare_base(Compare c) : Compare(std::move(c)) {} + const Compare &comp() const { return *this; } +}; template <typename Compare> -struct key_compare_to_adapter { - using type = Compare; +struct checked_compare_base<Compare, false> { + explicit checked_compare_base(Compare c) : compare(std::move(c)) {} + const Compare &comp() const { return compare; } + Compare compare; +}; + +// A mechanism for opting out of checked_compare for use only in btree_test.cc. +struct BtreeTestOnlyCheckedCompareOptOutBase {}; + +// A helper class to adapt the specified comparator for two use cases: +// (1) When using common Abseil string types with common comparison functors, +// convert a boolean comparison into a three-way comparison that returns an +// `absl::weak_ordering`. This helper class is specialized for +// less<std::string>, greater<std::string>, less<string_view>, +// greater<string_view>, less<absl::Cord>, and greater<absl::Cord>. +// (2) Adapt the comparator to diagnose cases of non-strict-weak-ordering (see +// https://en.cppreference.com/w/cpp/named_req/Compare) in debug mode. Whenever +// a comparison is made, we will make assertions to verify that the comparator +// is valid. +template <typename Compare, typename Key> +struct key_compare_adapter { + // Inherit from checked_compare_base to support function pointers and also + // keep empty-base-optimization (EBO) support for classes. + // Note: we can't use CompressedTuple here because that would interfere + // with the EBO for `btree::rightmost_`. `btree::rightmost_` is itself a + // CompressedTuple and nested `CompressedTuple`s don't support EBO. + // TODO(b/214288561): use CompressedTuple instead once it supports EBO for + // nested `CompressedTuple`s. + struct checked_compare : checked_compare_base<Compare> { + private: + using Base = typename checked_compare::checked_compare_base; + using Base::comp; + + // If possible, returns whether `t` is equivalent to itself. We can only do + // this for `Key`s because we can't be sure that it's safe to call + // `comp()(k, k)` otherwise. Even if SFINAE allows it, there could be a + // compilation failure inside the implementation of the comparison operator. + bool is_self_equivalent(const Key &k) const { + // Note: this works for both boolean and three-way comparators. + return comp()(k, k) == 0; + } + // If we can't compare `t` with itself, returns true unconditionally. + template <typename T> + bool is_self_equivalent(const T &) const { + return true; + } + + public: + using Base::Base; + checked_compare(Compare comp) : Base(std::move(comp)) {} // NOLINT + + // Allow converting to Compare for use in key_comp()/value_comp(). + explicit operator Compare() const { return comp(); } + + template <typename T, typename U, + absl::enable_if_t< + std::is_same<bool, compare_result_t<Compare, T, U>>::value, + int> = 0> + bool operator()(const T &lhs, const U &rhs) const { + // NOTE: if any of these assertions fail, then the comparator does not + // establish a strict-weak-ordering (see + // https://en.cppreference.com/w/cpp/named_req/Compare). + assert(is_self_equivalent(lhs)); + assert(is_self_equivalent(rhs)); + const bool lhs_comp_rhs = comp()(lhs, rhs); + assert(!lhs_comp_rhs || !comp()(rhs, lhs)); + return lhs_comp_rhs; + } + + template < + typename T, typename U, + absl::enable_if_t<std::is_convertible<compare_result_t<Compare, T, U>, + absl::weak_ordering>::value, + int> = 0> + absl::weak_ordering operator()(const T &lhs, const U &rhs) const { + // NOTE: if any of these assertions fail, then the comparator does not + // establish a strict-weak-ordering (see + // https://en.cppreference.com/w/cpp/named_req/Compare). + assert(is_self_equivalent(lhs)); + assert(is_self_equivalent(rhs)); + const absl::weak_ordering lhs_comp_rhs = comp()(lhs, rhs); +#ifndef NDEBUG + const absl::weak_ordering rhs_comp_lhs = comp()(rhs, lhs); + if (lhs_comp_rhs > 0) { + assert(rhs_comp_lhs < 0 && "lhs_comp_rhs > 0 -> rhs_comp_lhs < 0"); + } else if (lhs_comp_rhs == 0) { + assert(rhs_comp_lhs == 0 && "lhs_comp_rhs == 0 -> rhs_comp_lhs == 0"); + } else { + assert(rhs_comp_lhs > 0 && "lhs_comp_rhs < 0 -> rhs_comp_lhs > 0"); + } +#endif + return lhs_comp_rhs; + } + }; + using type = absl::conditional_t< + std::is_base_of<BtreeTestOnlyCheckedCompareOptOutBase, Compare>::value, + Compare, checked_compare>; }; template <> -struct key_compare_to_adapter<std::less<std::string>> { +struct key_compare_adapter<std::less<std::string>, std::string> { using type = StringBtreeDefaultLess; }; template <> -struct key_compare_to_adapter<std::greater<std::string>> { +struct key_compare_adapter<std::greater<std::string>, std::string> { using type = StringBtreeDefaultGreater; }; template <> -struct key_compare_to_adapter<std::less<absl::string_view>> { +struct key_compare_adapter<std::less<absl::string_view>, absl::string_view> { using type = StringBtreeDefaultLess; }; template <> -struct key_compare_to_adapter<std::greater<absl::string_view>> { +struct key_compare_adapter<std::greater<absl::string_view>, absl::string_view> { using type = StringBtreeDefaultGreater; }; template <> -struct key_compare_to_adapter<std::less<absl::Cord>> { +struct key_compare_adapter<std::less<absl::Cord>, absl::Cord> { using type = StringBtreeDefaultLess; }; template <> -struct key_compare_to_adapter<std::greater<absl::Cord>> { +struct key_compare_adapter<std::greater<absl::Cord>, absl::Cord> { using type = StringBtreeDefaultGreater; }; +// Detects an 'absl_btree_prefer_linear_node_search' member. This is +// a protocol used as an opt-in or opt-out of linear search. +// +// For example, this would be useful for key types that wrap an integer +// and define their own cheap operator<(). For example: +// +// class K { +// public: +// using absl_btree_prefer_linear_node_search = std::true_type; +// ... +// private: +// friend bool operator<(K a, K b) { return a.k_ < b.k_; } +// int k_; +// }; +// +// btree_map<K, V> m; // Uses linear search +// +// If T has the preference tag, then it has a preference. +// Btree will use the tag's truth value. +template <typename T, typename = void> +struct has_linear_node_search_preference : std::false_type {}; +template <typename T, typename = void> +struct prefers_linear_node_search : std::false_type {}; +template <typename T> +struct has_linear_node_search_preference< + T, absl::void_t<typename T::absl_btree_prefer_linear_node_search>> + : std::true_type {}; +template <typename T> +struct prefers_linear_node_search< + T, absl::void_t<typename T::absl_btree_prefer_linear_node_search>> + : T::absl_btree_prefer_linear_node_search {}; + +template <typename Compare, typename Key> +constexpr bool compare_has_valid_result_type() { + using compare_result_type = compare_result_t<Compare, Key, Key>; + return std::is_same<compare_result_type, bool>::value || + std::is_convertible<compare_result_type, absl::weak_ordering>::value; +} + +template <typename original_key_compare, typename value_type> +class map_value_compare { + template <typename Params> + friend class btree; + + // Note: this `protected` is part of the API of std::map::value_compare. See + // https://en.cppreference.com/w/cpp/container/map/value_compare. + protected: + explicit map_value_compare(original_key_compare c) : comp(std::move(c)) {} + + original_key_compare comp; // NOLINT + + public: + auto operator()(const value_type &lhs, const value_type &rhs) const + -> decltype(comp(lhs.first, rhs.first)) { + return comp(lhs.first, rhs.first); + } +}; + template <typename Key, typename Compare, typename Alloc, int TargetNodeSize, - bool Multi, typename SlotPolicy> -struct common_params { + bool IsMulti, bool IsMap, typename SlotPolicy> +struct common_params : common_policy_traits<SlotPolicy> { + using original_key_compare = Compare; + // If Compare is a common comparator for a string-like type, then we adapt it // to use heterogeneous lookup and to be a key-compare-to comparator. - using key_compare = typename key_compare_to_adapter<Compare>::type; - // True when key_compare has been adapted to StringBtreeDefault{Less,Greater}. - using is_key_compare_adapted = - absl::negation<std::is_same<key_compare, Compare>>; + // We also adapt the comparator to diagnose invalid comparators in debug mode. + // We disable this when `Compare` is invalid in a way that will cause + // adaptation to fail (having invalid return type) so that we can give a + // better compilation failure in static_assert_validation. If we don't do + // this, then there will be cascading compilation failures that are confusing + // for users. + using key_compare = + absl::conditional_t<!compare_has_valid_result_type<Compare, Key>(), + Compare, + typename key_compare_adapter<Compare, Key>::type>; + + static constexpr bool kIsKeyCompareStringAdapted = + std::is_same<key_compare, StringBtreeDefaultLess>::value || + std::is_same<key_compare, StringBtreeDefaultGreater>::value; + static constexpr bool kIsKeyCompareTransparent = + IsTransparent<original_key_compare>::value || kIsKeyCompareStringAdapted; + // A type which indicates if we have a key-compare-to functor or a plain old // key-compare functor. using is_key_compare_to = btree_is_key_compare_to<key_compare, Key>; using allocator_type = Alloc; using key_type = Key; - using size_type = std::make_signed<size_t>::type; + using size_type = size_t; using difference_type = ptrdiff_t; - // True if this is a multiset or multimap. - using is_multi_container = std::integral_constant<bool, Multi>; - using slot_policy = SlotPolicy; using slot_type = typename slot_policy::slot_type; using value_type = typename slot_policy::value_type; @@ -212,150 +403,42 @@ struct common_params { using reference = value_type &; using const_reference = const value_type &; + using value_compare = + absl::conditional_t<IsMap, + map_value_compare<original_key_compare, value_type>, + original_key_compare>; + using is_map_container = std::integral_constant<bool, IsMap>; + + // For the given lookup key type, returns whether we can have multiple + // equivalent keys in the btree. If this is a multi-container, then we can. + // Otherwise, we can have multiple equivalent keys only if all of the + // following conditions are met: + // - The comparator is transparent. + // - The lookup key type is not the same as key_type. + // - The comparator is not a StringBtreeDefault{Less,Greater} comparator + // that we know has the same equivalence classes for all lookup types. + template <typename LookupKey> + constexpr static bool can_have_multiple_equivalent_keys() { + return IsMulti || (IsTransparent<key_compare>::value && + !std::is_same<LookupKey, Key>::value && + !kIsKeyCompareStringAdapted); + } + enum { kTargetNodeSize = TargetNodeSize, - // Upper bound for the available space for values. This is largest for leaf + // Upper bound for the available space for slots. This is largest for leaf // nodes, which have overhead of at least a pointer + 4 bytes (for storing // 3 field_types and an enum). - kNodeValueSpace = - TargetNodeSize - /*minimum overhead=*/(sizeof(void *) + 4), + kNodeSlotSpace = TargetNodeSize - /*minimum overhead=*/(sizeof(void *) + 4), }; - // This is an integral type large enough to hold as many - // ValueSize-values as will fit a node of TargetNodeSize bytes. + // This is an integral type large enough to hold as many slots as will fit a + // node of TargetNodeSize bytes. using node_count_type = - absl::conditional_t<(kNodeValueSpace / sizeof(value_type) > + absl::conditional_t<(kNodeSlotSpace / sizeof(slot_type) > (std::numeric_limits<uint8_t>::max)()), uint16_t, uint8_t>; // NOLINT - - // The following methods are necessary for passing this struct as PolicyTraits - // for node_handle and/or are used within btree. - static value_type &element(slot_type *slot) { - return slot_policy::element(slot); - } - static const value_type &element(const slot_type *slot) { - return slot_policy::element(slot); - } - template <class... Args> - static void construct(Alloc *alloc, slot_type *slot, Args &&... args) { - slot_policy::construct(alloc, slot, std::forward<Args>(args)...); - } - static void construct(Alloc *alloc, slot_type *slot, slot_type *other) { - slot_policy::construct(alloc, slot, other); - } - static void destroy(Alloc *alloc, slot_type *slot) { - slot_policy::destroy(alloc, slot); - } - static void transfer(Alloc *alloc, slot_type *new_slot, slot_type *old_slot) { - construct(alloc, new_slot, old_slot); - destroy(alloc, old_slot); - } - static void swap(Alloc *alloc, slot_type *a, slot_type *b) { - slot_policy::swap(alloc, a, b); - } - static void move(Alloc *alloc, slot_type *src, slot_type *dest) { - slot_policy::move(alloc, src, dest); - } -}; - -// A parameters structure for holding the type parameters for a btree_map. -// Compare and Alloc should be nothrow copy-constructible. -template <typename Key, typename Data, typename Compare, typename Alloc, - int TargetNodeSize, bool Multi> -struct map_params : common_params<Key, Compare, Alloc, TargetNodeSize, Multi, - map_slot_policy<Key, Data>> { - using super_type = typename map_params::common_params; - using mapped_type = Data; - // This type allows us to move keys when it is safe to do so. It is safe - // for maps in which value_type and mutable_value_type are layout compatible. - using slot_policy = typename super_type::slot_policy; - using slot_type = typename super_type::slot_type; - using value_type = typename super_type::value_type; - using init_type = typename super_type::init_type; - - using key_compare = typename super_type::key_compare; - // Inherit from key_compare for empty base class optimization. - struct value_compare : private key_compare { - value_compare() = default; - explicit value_compare(const key_compare &cmp) : key_compare(cmp) {} - - template <typename T, typename U> - auto operator()(const T &left, const U &right) const - -> decltype(std::declval<key_compare>()(left.first, right.first)) { - return key_compare::operator()(left.first, right.first); - } - }; - using is_map_container = std::true_type; - - template <typename V> - static auto key(const V &value) -> decltype(value.first) { - return value.first; - } - static const Key &key(const slot_type *s) { return slot_policy::key(s); } - static const Key &key(slot_type *s) { return slot_policy::key(s); } - // For use in node handle. - static auto mutable_key(slot_type *s) - -> decltype(slot_policy::mutable_key(s)) { - return slot_policy::mutable_key(s); - } - static mapped_type &value(value_type *value) { return value->second; } -}; - -// This type implements the necessary functions from the -// absl::container_internal::slot_type interface. -template <typename Key> -struct set_slot_policy { - using slot_type = Key; - using value_type = Key; - using mutable_value_type = Key; - - static value_type &element(slot_type *slot) { return *slot; } - static const value_type &element(const slot_type *slot) { return *slot; } - - template <typename Alloc, class... Args> - static void construct(Alloc *alloc, slot_type *slot, Args &&... args) { - absl::allocator_traits<Alloc>::construct(*alloc, slot, - std::forward<Args>(args)...); - } - - template <typename Alloc> - static void construct(Alloc *alloc, slot_type *slot, slot_type *other) { - absl::allocator_traits<Alloc>::construct(*alloc, slot, std::move(*other)); - } - - template <typename Alloc> - static void destroy(Alloc *alloc, slot_type *slot) { - absl::allocator_traits<Alloc>::destroy(*alloc, slot); - } - - template <typename Alloc> - static void swap(Alloc * /*alloc*/, slot_type *a, slot_type *b) { - using std::swap; - swap(*a, *b); - } - - template <typename Alloc> - static void move(Alloc * /*alloc*/, slot_type *src, slot_type *dest) { - *dest = std::move(*src); - } -}; - -// A parameters structure for holding the type parameters for a btree_set. -// Compare and Alloc should be nothrow copy-constructible. -template <typename Key, typename Compare, typename Alloc, int TargetNodeSize, - bool Multi> -struct set_params : common_params<Key, Compare, Alloc, TargetNodeSize, Multi, - set_slot_policy<Key>> { - using value_type = Key; - using slot_type = typename set_params::common_params::slot_type; - using value_compare = typename set_params::common_params::key_compare; - using is_map_container = std::false_type; - - template <typename V> - static const V &key(const V &value) { return value; } - static const Key &key(const slot_type *slot) { return *slot; } - static const Key &key(slot_type *slot) { return *slot; } }; // An adapter class that converts a lower-bound compare into an upper-bound @@ -391,6 +474,10 @@ struct SearchResult { // useful information. template <typename V> struct SearchResult<V, false> { + SearchResult() {} + explicit SearchResult(V v) : value(v) {} + SearchResult(V v, MatchKind /*match*/) : value(v) {} + V value; static constexpr bool HasMatch() { return false; } @@ -403,10 +490,10 @@ struct SearchResult<V, false> { template <typename Params> class btree_node { using is_key_compare_to = typename Params::is_key_compare_to; - using is_multi_container = typename Params::is_multi_container; using field_type = typename Params::node_count_type; using allocator_type = typename Params::allocator_type; using slot_type = typename Params::slot_type; + using original_key_compare = typename Params::original_key_compare; public: using params_type = Params; @@ -421,21 +508,35 @@ class btree_node { using difference_type = typename Params::difference_type; // Btree decides whether to use linear node search as follows: + // - If the comparator expresses a preference, use that. + // - If the key expresses a preference, use that. // - If the key is arithmetic and the comparator is std::less or // std::greater, choose linear. // - Otherwise, choose binary. // TODO(ezb): Might make sense to add condition(s) based on node-size. using use_linear_search = std::integral_constant< - bool, - std::is_arithmetic<key_type>::value && - (std::is_same<std::less<key_type>, key_compare>::value || - std::is_same<std::greater<key_type>, key_compare>::value)>; - - // This class is organized by gtl::Layout as if it had the following - // structure: + bool, has_linear_node_search_preference<original_key_compare>::value + ? prefers_linear_node_search<original_key_compare>::value + : has_linear_node_search_preference<key_type>::value + ? prefers_linear_node_search<key_type>::value + : std::is_arithmetic<key_type>::value && + (std::is_same<std::less<key_type>, + original_key_compare>::value || + std::is_same<std::greater<key_type>, + original_key_compare>::value)>; + + // This class is organized by absl::container_internal::Layout as if it had + // the following structure: // // A pointer to the node's parent. // btree_node *parent; // + // // When ABSL_BTREE_ENABLE_GENERATIONS is defined, we also have a + // // generation integer in order to check that when iterators are + // // used, they haven't been invalidated already. Only the generation on + // // the root is used, but we have one on each node because whether a node + // // is root or not can change. + // uint32_t generation; + // // // The position of the node in the node's parent. // field_type position; // // The index of the first populated value in `values`. @@ -446,23 +547,23 @@ class btree_node { // // is the same as the count of values. // field_type finish; // // The maximum number of values the node can hold. This is an integer in - // // [1, kNodeValues] for root leaf nodes, kNodeValues for non-root leaf + // // [1, kNodeSlots] for root leaf nodes, kNodeSlots for non-root leaf // // nodes, and kInternalNodeMaxCount (as a sentinel value) for internal - // // nodes (even though there are still kNodeValues values in the node). + // // nodes (even though there are still kNodeSlots values in the node). // // TODO(ezb): make max_count use only 4 bits and record log2(capacity) // // to free extra bits for is_root, etc. // field_type max_count; // // // The array of values. The capacity is `max_count` for leaf nodes and - // // kNodeValues for internal nodes. Only the values in + // // kNodeSlots for internal nodes. Only the values in // // [start, finish) have been initialized and are valid. // slot_type values[max_count]; // // // The array of child pointers. The keys in children[i] are all less // // than key(i). The keys in children[i + 1] are all greater than key(i). - // // There are 0 children for leaf nodes and kNodeValues + 1 children for + // // There are 0 children for leaf nodes and kNodeSlots + 1 children for // // internal nodes. - // btree_node *children[kNodeValues + 1]; + // btree_node *children[kNodeSlots + 1]; // // This class is only constructed by EmptyNodeType. Normally, pointers to the // layout above are allocated, cast to btree_node*, and de-allocated within @@ -482,59 +583,71 @@ class btree_node { btree_node() = default; private: - using layout_type = absl::container_internal::Layout<btree_node *, field_type, - slot_type, btree_node *>; - constexpr static size_type SizeWithNValues(size_type n) { - return layout_type(/*parent*/ 1, - /*position, start, finish, max_count*/ 4, - /*values*/ n, - /*children*/ 0) + using layout_type = + absl::container_internal::Layout<btree_node *, uint32_t, field_type, + slot_type, btree_node *>; + constexpr static size_type SizeWithNSlots(size_type n) { + return layout_type( + /*parent*/ 1, + /*generation*/ BtreeGenerationsEnabled() ? 1 : 0, + /*position, start, finish, max_count*/ 4, + /*slots*/ n, + /*children*/ 0) .AllocSize(); } - // A lower bound for the overhead of fields other than values in a leaf node. + // A lower bound for the overhead of fields other than slots in a leaf node. constexpr static size_type MinimumOverhead() { - return SizeWithNValues(1) - sizeof(value_type); + return SizeWithNSlots(1) - sizeof(slot_type); } // Compute how many values we can fit onto a leaf node taking into account // padding. - constexpr static size_type NodeTargetValues(const int begin, const int end) { + constexpr static size_type NodeTargetSlots(const size_type begin, + const size_type end) { return begin == end ? begin - : SizeWithNValues((begin + end) / 2 + 1) > - params_type::kTargetNodeSize - ? NodeTargetValues(begin, (begin + end) / 2) - : NodeTargetValues((begin + end) / 2 + 1, end); - } - - enum { - kTargetNodeSize = params_type::kTargetNodeSize, - kNodeTargetValues = NodeTargetValues(0, params_type::kTargetNodeSize), - - // We need a minimum of 3 values per internal node in order to perform - // splitting (1 value for the two nodes involved in the split and 1 value - // propagated to the parent as the delimiter for the split). - kNodeValues = kNodeTargetValues >= 3 ? kNodeTargetValues : 3, - - // The node is internal (i.e. is not a leaf node) if and only if `max_count` - // has this value. - kInternalNodeMaxCount = 0, - }; - - // Leaves can have less than kNodeValues values. - constexpr static layout_type LeafLayout(const int max_values = kNodeValues) { - return layout_type(/*parent*/ 1, - /*position, start, finish, max_count*/ 4, - /*values*/ max_values, - /*children*/ 0); + : SizeWithNSlots((begin + end) / 2 + 1) > + params_type::kTargetNodeSize + ? NodeTargetSlots(begin, (begin + end) / 2) + : NodeTargetSlots((begin + end) / 2 + 1, end); + } + + constexpr static size_type kTargetNodeSize = params_type::kTargetNodeSize; + constexpr static size_type kNodeTargetSlots = + NodeTargetSlots(0, kTargetNodeSize); + + // We need a minimum of 3 slots per internal node in order to perform + // splitting (1 value for the two nodes involved in the split and 1 value + // propagated to the parent as the delimiter for the split). For performance + // reasons, we don't allow 3 slots-per-node due to bad worst case occupancy of + // 1/3 (for a node, not a b-tree). + constexpr static size_type kMinNodeSlots = 4; + + constexpr static size_type kNodeSlots = + kNodeTargetSlots >= kMinNodeSlots ? kNodeTargetSlots : kMinNodeSlots; + + // The node is internal (i.e. is not a leaf node) if and only if `max_count` + // has this value. + constexpr static field_type kInternalNodeMaxCount = 0; + + constexpr static layout_type Layout(const size_type slot_count, + const size_type child_count) { + return layout_type( + /*parent*/ 1, + /*generation*/ BtreeGenerationsEnabled() ? 1 : 0, + /*position, start, finish, max_count*/ 4, + /*slots*/ slot_count, + /*children*/ child_count); + } + // Leaves can have less than kNodeSlots values. + constexpr static layout_type LeafLayout( + const size_type slot_count = kNodeSlots) { + return Layout(slot_count, 0); } constexpr static layout_type InternalLayout() { - return layout_type(/*parent*/ 1, - /*position, start, finish, max_count*/ 4, - /*values*/ kNodeValues, - /*children*/ kNodeValues + 1); + return Layout(kNodeSlots, kNodeSlots + 1); } - constexpr static size_type LeafSize(const int max_values = kNodeValues) { - return LeafLayout(max_values).AllocSize(); + constexpr static size_type LeafSize(const size_type slot_count = kNodeSlots) { + return LeafLayout(slot_count).AllocSize(); } constexpr static size_type InternalSize() { return InternalLayout().AllocSize(); @@ -545,44 +658,47 @@ class btree_node { template <size_type N> inline typename layout_type::template ElementType<N> *GetField() { // We assert that we don't read from values that aren't there. - assert(N < 3 || !leaf()); + assert(N < 4 || is_internal()); return InternalLayout().template Pointer<N>(reinterpret_cast<char *>(this)); } template <size_type N> inline const typename layout_type::template ElementType<N> *GetField() const { - assert(N < 3 || !leaf()); + assert(N < 4 || is_internal()); return InternalLayout().template Pointer<N>( reinterpret_cast<const char *>(this)); } void set_parent(btree_node *p) { *GetField<0>() = p; } - field_type &mutable_finish() { return GetField<1>()[2]; } - slot_type *slot(int i) { return &GetField<2>()[i]; } + field_type &mutable_finish() { return GetField<2>()[2]; } + slot_type *slot(size_type i) { return &GetField<3>()[i]; } slot_type *start_slot() { return slot(start()); } slot_type *finish_slot() { return slot(finish()); } - const slot_type *slot(int i) const { return &GetField<2>()[i]; } - void set_position(field_type v) { GetField<1>()[0] = v; } - void set_start(field_type v) { GetField<1>()[1] = v; } - void set_finish(field_type v) { GetField<1>()[2] = v; } + const slot_type *slot(size_type i) const { return &GetField<3>()[i]; } + void set_position(field_type v) { GetField<2>()[0] = v; } + void set_start(field_type v) { GetField<2>()[1] = v; } + void set_finish(field_type v) { GetField<2>()[2] = v; } // This method is only called by the node init methods. - void set_max_count(field_type v) { GetField<1>()[3] = v; } + void set_max_count(field_type v) { GetField<2>()[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; } + bool is_leaf() const { return GetField<2>()[3] != kInternalNodeMaxCount; } + // Whether this is an internal node or not. This value doesn't change after + // the node is created. + bool is_internal() const { return !is_leaf(); } // Getter for the position of this node in its parent. - field_type position() const { return GetField<1>()[0]; } + field_type position() const { return GetField<2>()[0]; } // Getter for the offset of the first value in the `values` array. field_type start() const { - // TODO(ezb): when floating storage is implemented, return GetField<1>()[1]; - assert(GetField<1>()[1] == 0); + // TODO(ezb): when floating storage is implemented, return GetField<2>()[1]; + assert(GetField<2>()[1] == 0); return 0; } // Getter for the offset after the last value in the `values` array. - field_type finish() const { return GetField<1>()[2]; } + field_type finish() const { return GetField<2>()[2]; } // Getters for the number of values stored in this node. field_type count() const { @@ -591,10 +707,10 @@ class btree_node { } 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]; + // Leaf nodes have max_count in [1, kNodeSlots]. + const field_type max_count = GetField<2>()[3]; return max_count == field_type{kInternalNodeMaxCount} - ? field_type{kNodeValues} + ? field_type{kNodeSlots} : max_count; } @@ -603,58 +719,86 @@ class btree_node { // 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(); } + bool is_root() const { return parent()->is_leaf(); } void make_root() { assert(parent()->is_root()); + set_generation(parent()->generation()); set_parent(parent()->parent()); } + // Gets the root node's generation integer, which is the one used by the tree. + uint32_t *get_root_generation() const { + assert(BtreeGenerationsEnabled()); + const btree_node *curr = this; + for (; !curr->is_root(); curr = curr->parent()) continue; + return const_cast<uint32_t *>(&curr->GetField<1>()[0]); + } + + // Returns the generation for iterator validation. + uint32_t generation() const { + return BtreeGenerationsEnabled() ? *get_root_generation() : 0; + } + // Updates generation. Should only be called on a root node or during node + // initialization. + void set_generation(uint32_t generation) { + if (BtreeGenerationsEnabled()) GetField<1>()[0] = generation; + } + // Updates the generation. We do this whenever the node is mutated. + void next_generation() { + if (BtreeGenerationsEnabled()) ++*get_root_generation(); + } + // 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)); } + const key_type &key(size_type i) const { return params_type::key(slot(i)); } + reference value(size_type i) { return params_type::element(slot(i)); } + const_reference value(size_type 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 *child(field_type i) const { return GetField<4>()[i]; } btree_node *start_child() const { return child(start()); } - btree_node *&mutable_child(int i) { return GetField<3>()[i]; } - void clear_child(int i) { + btree_node *&mutable_child(field_type i) { return GetField<4>()[i]; } + void clear_child(field_type i) { absl::container_internal::SanitizerPoisonObject(&mutable_child(i)); } - void set_child(int i, btree_node *c) { + void set_child_noupdate_position(field_type i, btree_node *c) { absl::container_internal::SanitizerUnpoisonObject(&mutable_child(i)); mutable_child(i) = c; + } + void set_child(field_type i, btree_node *c) { + set_child_noupdate_position(i, c); c->set_position(i); } - void init_child(int i, btree_node *c) { + void init_child(field_type 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( + SearchResult<size_type, 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 { + size_type 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> + SearchResult<size_type, btree_is_key_compare_to<Compare, key_type>::value> linear_search(const K &k, const Compare &comp) const { return linear_search_impl(k, start(), finish(), comp, btree_is_key_compare_to<Compare, key_type>()); } template <typename K, typename Compare> - SearchResult<int, btree_is_key_compare_to<Compare, key_type>::value> + SearchResult<size_type, btree_is_key_compare_to<Compare, key_type>::value> binary_search(const K &k, const Compare &comp) const { return binary_search_impl(k, start(), finish(), comp, btree_is_key_compare_to<Compare, key_type>()); @@ -663,8 +807,8 @@ class btree_node { // 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, + SearchResult<size_type, false> linear_search_impl( + const K &k, size_type s, const size_type e, const Compare &comp, std::false_type /* IsCompareTo */) const { while (s < e) { if (!comp(key(s), k)) { @@ -672,14 +816,14 @@ class btree_node { } ++s; } - return {s}; + return SearchResult<size_type, false>{s}; } // Returns the position of the first value whose key is not less than k using // linear search performed using compare-to. template <typename K, typename Compare> - SearchResult<int, true> linear_search_impl( - const K &k, int s, const int e, const Compare &comp, + SearchResult<size_type, true> linear_search_impl( + const K &k, size_type s, const size_type e, const Compare &comp, std::true_type /* IsCompareTo */) const { while (s < e) { const absl::weak_ordering c = comp(key(s), k); @@ -696,30 +840,30 @@ class btree_node { // 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, + SearchResult<size_type, false> binary_search_impl( + const K &k, size_type s, size_type e, const Compare &comp, std::false_type /* IsCompareTo */) const { while (s != e) { - const int mid = (s + e) >> 1; + const size_type mid = (s + e) >> 1; if (comp(key(mid), k)) { s = mid + 1; } else { e = mid; } } - return {s}; + return SearchResult<size_type, false>{s}; } // Returns the position of the first value whose key is not less than k using // binary search performed using compare-to. template <typename K, typename CompareTo> - SearchResult<int, true> binary_search_impl( - const K &k, int s, int e, const CompareTo &comp, + SearchResult<size_type, true> binary_search_impl( + const K &k, size_type s, size_type e, const CompareTo &comp, std::true_type /* IsCompareTo */) const { - if (is_multi_container::value) { + if (params_type::template can_have_multiple_equivalent_keys<K>()) { MatchKind exact_match = MatchKind::kNe; while (s != e) { - const int mid = (s + e) >> 1; + const size_type mid = (s + e) >> 1; const absl::weak_ordering c = comp(key(mid), k); if (c < 0) { s = mid + 1; @@ -727,16 +871,16 @@ class btree_node { 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. + // which requires continuing the binary search if there could be + // multiple equivalent keys. exact_match = MatchKind::kEq; } } } return {s, exact_match}; - } else { // Not a multi-container. + } else { // Can't have multiple equivalent keys. while (s != e) { - const int mid = (s + e) >> 1; + const size_type mid = (s + e) >> 1; const absl::weak_ordering c = comp(key(mid), k); if (c < 0) { s = mid + 1; @@ -750,10 +894,42 @@ class btree_node { } } + // Returns whether key i is ordered correctly with respect to the other keys + // in the node. The motivation here is to detect comparators that violate + // transitivity. Note: we only do comparisons of keys on this node rather than + // the whole tree so that this is constant time. + template <typename Compare> + bool is_ordered_correctly(field_type i, const Compare &comp) const { + if (std::is_base_of<BtreeTestOnlyCheckedCompareOptOutBase, + Compare>::value || + params_type::kIsKeyCompareStringAdapted) { + return true; + } + + const auto compare = [&](field_type a, field_type b) { + const absl::weak_ordering cmp = + compare_internal::do_three_way_comparison(comp, key(a), key(b)); + return cmp < 0 ? -1 : cmp > 0 ? 1 : 0; + }; + int cmp = -1; + constexpr bool kCanHaveEquivKeys = + params_type::template can_have_multiple_equivalent_keys<key_type>(); + for (field_type j = start(); j < finish(); ++j) { + if (j == i) { + if (cmp > 0) return false; + continue; + } + int new_cmp = compare(j, i); + if (new_cmp < cmp || (!kCanHaveEquivKeys && new_cmp == 0)) return false; + cmp = new_cmp; + } + return true; + } + // 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); + void emplace_value(field_type i, allocator_type *alloc, Args &&...args); // Removes the values at positions [i, i + to_erase), shifting all existing // values and children after that range to the left by to_erase. Clears all @@ -761,9 +937,9 @@ class btree_node { void remove_values(field_type i, field_type to_erase, allocator_type *alloc); // Rebalances a node with its right sibling. - void rebalance_right_to_left(int to_move, btree_node *right, + void rebalance_right_to_left(field_type to_move, btree_node *right, allocator_type *alloc); - void rebalance_left_to_right(int to_move, btree_node *right, + void rebalance_left_to_right(field_type to_move, btree_node *right, allocator_type *alloc); // Splits a node, moving a portion of the node's values to its right sibling. @@ -774,50 +950,50 @@ class btree_node { void merge(btree_node *src, allocator_type *alloc); // Node allocation/deletion routines. - void init_leaf(btree_node *parent, int max_count) { + void init_leaf(field_type position, field_type max_count, + btree_node *parent) { + set_generation(0); set_parent(parent); - set_position(0); + set_position(position); set_start(0); set_finish(0); set_max_count(max_count); absl::container_internal::SanitizerPoisonMemoryRegion( start_slot(), max_count * sizeof(slot_type)); } - void init_internal(btree_node *parent) { - init_leaf(parent, kNodeValues); + void init_internal(field_type position, btree_node *parent) { + init_leaf(position, kNodeSlots, parent); // Set `max_count` to a sentinel value to indicate that this node is // internal. set_max_count(kInternalNodeMaxCount); absl::container_internal::SanitizerPoisonMemoryRegion( - &mutable_child(start()), (kNodeValues + 1) * sizeof(btree_node *)); + &mutable_child(start()), (kNodeSlots + 1) * sizeof(btree_node *)); } static void deallocate(const size_type size, btree_node *node, allocator_type *alloc) { + absl::container_internal::SanitizerUnpoisonMemoryRegion(node, size); absl::container_internal::Deallocate<Alignment()>(alloc, node, size); } // Deletes a node and all of its children. static void clear_and_delete(btree_node *node, allocator_type *alloc); - 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 field_type i, allocator_type *alloc, Args &&... args) { + void value_init(const field_type i, allocator_type *alloc, Args &&...args) { + next_generation(); absl::container_internal::SanitizerUnpoisonObject(slot(i)); params_type::construct(alloc, slot(i), std::forward<Args>(args)...); } void value_destroy(const field_type i, allocator_type *alloc) { + next_generation(); params_type::destroy(alloc, slot(i)); absl::container_internal::SanitizerPoisonObject(slot(i)); } void value_destroy_n(const field_type i, const field_type n, allocator_type *alloc) { + next_generation(); for (slot_type *s = slot(i), *end = slot(i + n); s != end; ++s) { params_type::destroy(alloc, s); absl::container_internal::SanitizerPoisonObject(s); @@ -833,6 +1009,7 @@ class btree_node { // Transfers value from slot `src_i` in `src_node` to slot `dest_i` in `this`. void transfer(const size_type dest_i, const size_type src_i, btree_node *src_node, allocator_type *alloc) { + next_generation(); transfer(slot(dest_i), src_node->slot(src_i), alloc); } @@ -841,6 +1018,7 @@ class btree_node { void transfer_n(const size_type n, const size_type dest_i, const size_type src_i, btree_node *src_node, allocator_type *alloc) { + next_generation(); for (slot_type *src = src_node->slot(src_i), *end = src + n, *dest = slot(dest_i); src != end; ++src, ++dest) { @@ -853,26 +1031,87 @@ class btree_node { void transfer_n_backward(const size_type n, const size_type dest_i, const size_type src_i, btree_node *src_node, allocator_type *alloc) { - for (slot_type *src = src_node->slot(src_i + n - 1), *end = src - n, - *dest = slot(dest_i + n - 1); + next_generation(); + for (slot_type *src = src_node->slot(src_i + n), *end = src - n, + *dest = slot(dest_i + n); src != end; --src, --dest) { - transfer(dest, src, alloc); + // If we modified the loop index calculations above to avoid the -1s here, + // it would result in UB in the computation of `end` (and possibly `src` + // as well, if n == 0), since slot() is effectively an array index and it + // is UB to compute the address of any out-of-bounds array element except + // for one-past-the-end. + transfer(dest - 1, src - 1, alloc); } } template <typename P> friend class btree; template <typename N, typename R, typename P> - friend struct btree_iterator; + friend class btree_iterator; friend class BtreeNodePeer; + friend struct btree_access; }; -template <typename Node, typename Reference, typename Pointer> -struct btree_iterator { +template <typename Node> +bool AreNodesFromSameContainer(const Node *node_a, const Node *node_b) { + // If either node is null, then give up on checking whether they're from the + // same container. (If exactly one is null, then we'll trigger the + // default-constructed assert in Equals.) + if (node_a == nullptr || node_b == nullptr) return true; + while (!node_a->is_root()) node_a = node_a->parent(); + while (!node_b->is_root()) node_b = node_b->parent(); + return node_a == node_b; +} + +class btree_iterator_generation_info_enabled { + public: + explicit btree_iterator_generation_info_enabled(uint32_t g) + : generation_(g) {} + + // Updates the generation. For use internally right before we return an + // iterator to the user. + template <typename Node> + void update_generation(const Node *node) { + if (node != nullptr) generation_ = node->generation(); + } + uint32_t generation() const { return generation_; } + + template <typename Node> + void assert_valid_generation(const Node *node) const { + if (node != nullptr && node->generation() != generation_) { + ABSL_INTERNAL_LOG( + FATAL, + "Attempting to use an invalidated iterator. The corresponding b-tree " + "container has been mutated since this iterator was constructed."); + } + } + private: + // Used to check that the iterator hasn't been invalidated. + uint32_t generation_; +}; + +class btree_iterator_generation_info_disabled { + public: + explicit btree_iterator_generation_info_disabled(uint32_t) {} + static void update_generation(const void *) {} + static uint32_t generation() { return 0; } + static void assert_valid_generation(const void *) {} +}; + +#ifdef ABSL_BTREE_ENABLE_GENERATIONS +using btree_iterator_generation_info = btree_iterator_generation_info_enabled; +#else +using btree_iterator_generation_info = btree_iterator_generation_info_disabled; +#endif + +template <typename Node, typename Reference, typename Pointer> +class btree_iterator : private btree_iterator_generation_info { + using field_type = typename Node::field_type; using key_type = typename Node::key_type; using size_type = typename Node::size_type; using params_type = typename Node::params_type; + using is_map_container = typename params_type::is_map_container; using node_type = Node; using normal_node = typename std::remove_const<Node>::type; @@ -884,7 +1123,7 @@ struct btree_iterator { using slot_type = typename params_type::slot_type; using iterator = - btree_iterator<normal_node, normal_reference, normal_pointer>; + btree_iterator<normal_node, normal_reference, normal_pointer>; using const_iterator = btree_iterator<const_node, const_reference, const_pointer>; @@ -896,72 +1135,60 @@ struct btree_iterator { using reference = Reference; using iterator_category = std::bidirectional_iterator_tag; - btree_iterator() : node(nullptr), position(-1) {} - explicit btree_iterator(Node *n) : node(n), position(n->start()) {} - btree_iterator(Node *n, int p) : node(n), position(p) {} + btree_iterator() : btree_iterator(nullptr, -1) {} + explicit btree_iterator(Node *n) : btree_iterator(n, n->start()) {} + btree_iterator(Node *n, int p) + : btree_iterator_generation_info(n != nullptr ? n->generation() + : ~uint32_t{}), + 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. + // const_iterator, but it specifically avoids hiding the copy constructor so + // that the trivial one will be used when possible. template <typename N, typename R, typename P, absl::enable_if_t< std::is_same<btree_iterator<N, R, P>, iterator>::value && std::is_same<btree_iterator, const_iterator>::value, int> = 0> - btree_iterator(const btree_iterator<N, R, P> &other) // NOLINT - : node(other.node), position(other.position) {} - - private: - // This SFINAE allows explicit conversions from const_iterator to - // iterator, but also avoids defining a copy constructor. - // NOTE: the const_cast is safe because this constructor is only called by - // non-const methods and the container owns the nodes. - template <typename N, typename R, typename P, - absl::enable_if_t< - std::is_same<btree_iterator<N, R, P>, const_iterator>::value && - std::is_same<btree_iterator, iterator>::value, - int> = 0> - explicit btree_iterator(const btree_iterator<N, R, P> &other) - : node(const_cast<node_type *>(other.node)), position(other.position) {} - - // Increment/decrement the iterator. - void increment() { - if (node->leaf() && ++position < node->finish()) { - return; - } - increment_slow(); - } - void increment_slow(); + btree_iterator(const btree_iterator<N, R, P> other) // NOLINT + : btree_iterator_generation_info(other), + node_(other.node_), + position_(other.position_) {} - void decrement() { - if (node->leaf() && --position >= node->start()) { - return; - } - decrement_slow(); - } - void decrement_slow(); - - public: bool operator==(const iterator &other) const { - return node == other.node && position == other.position; + return Equals(other); } bool operator==(const const_iterator &other) const { - return node == other.node && position == other.position; + return Equals(other); } bool operator!=(const iterator &other) const { - return node != other.node || position != other.position; + return !Equals(other); } bool operator!=(const const_iterator &other) const { - return node != other.node || position != other.position; + return !Equals(other); + } + + // Returns n such that n calls to ++other yields *this. + // Precondition: n exists. + difference_type operator-(const_iterator other) const { + if (node_ == other.node_) { + if (node_->is_leaf()) return position_ - other.position_; + if (position_ == other.position_) return 0; + } + return distance_slow(other); } // Accessors for the key/value the iterator is pointing at. reference operator*() const { - ABSL_HARDENING_ASSERT(node != nullptr); - ABSL_HARDENING_ASSERT(node->start() <= position); - ABSL_HARDENING_ASSERT(node->finish() > position); - return node->value(position); + ABSL_HARDENING_ASSERT(node_ != nullptr); + assert_valid_generation(node_); + ABSL_HARDENING_ASSERT(position_ >= node_->start()); + if (position_ >= node_->finish()) { + ABSL_HARDENING_ASSERT(!IsEndIterator() && "Dereferencing end() iterator"); + ABSL_HARDENING_ASSERT(position_ < node_->finish()); + } + return node_->value(static_cast<field_type>(position_)); } pointer operator->() const { return &operator*(); } @@ -985,6 +1212,8 @@ struct btree_iterator { } private: + friend iterator; + friend const_iterator; template <typename Params> friend class btree; template <typename Tree> @@ -995,36 +1224,106 @@ struct btree_iterator { 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; + friend struct btree_access; - const key_type &key() const { return node->key(position); } - slot_type *slot() { return node->slot(position); } + // This SFINAE allows explicit conversions from const_iterator to + // iterator, but also avoids hiding the copy constructor. + // NOTE: the const_cast is safe because this constructor is only called by + // non-const methods and the container owns the nodes. + template <typename N, typename R, typename P, + absl::enable_if_t< + std::is_same<btree_iterator<N, R, P>, const_iterator>::value && + std::is_same<btree_iterator, iterator>::value, + int> = 0> + explicit btree_iterator(const btree_iterator<N, R, P> other) + : btree_iterator_generation_info(other.generation()), + node_(const_cast<node_type *>(other.node_)), + position_(other.position_) {} + + bool Equals(const const_iterator other) const { + ABSL_HARDENING_ASSERT(((node_ == nullptr && other.node_ == nullptr) || + (node_ != nullptr && other.node_ != nullptr)) && + "Comparing default-constructed iterator with " + "non-default-constructed iterator."); + // Note: we use assert instead of ABSL_HARDENING_ASSERT here because this + // changes the complexity of Equals from O(1) to O(log(N) + log(M)) where + // N/M are sizes of the containers containing node_/other.node_. + assert(AreNodesFromSameContainer(node_, other.node_) && + "Comparing iterators from different containers."); + assert_valid_generation(node_); + other.assert_valid_generation(other.node_); + return node_ == other.node_ && position_ == other.position_; + } + + bool IsEndIterator() const { + if (position_ != node_->finish()) return false; + node_type *node = node_; + while (!node->is_root()) { + if (node->position() != node->parent()->finish()) return false; + node = node->parent(); + } + return true; + } + + // Returns n such that n calls to ++other yields *this. + // Precondition: n exists && (this->node_ != other.node_ || + // !this->node_->is_leaf() || this->position_ != other.position_). + difference_type distance_slow(const_iterator other) const; + + // Increment/decrement the iterator. + void increment() { + assert_valid_generation(node_); + if (node_->is_leaf() && ++position_ < node_->finish()) { + return; + } + increment_slow(); + } + void increment_slow(); + + void decrement() { + assert_valid_generation(node_); + if (node_->is_leaf() && --position_ >= node_->start()) { + return; + } + decrement_slow(); + } + void decrement_slow(); + + const key_type &key() const { + return node_->key(static_cast<size_type>(position_)); + } + decltype(std::declval<Node *>()->slot(0)) slot() { + return node_->slot(static_cast<size_type>(position_)); + } + + void update_generation() { + btree_iterator_generation_info::update_generation(node_); + } // The node in the tree the iterator is pointing at. - Node *node; + Node *node_; // The position within the node of the tree the iterator is pointing at. // NOTE: this is an int rather than a field_type because iterators can point // to invalid positions (such as -1) in certain circumstances. - int position; + int position_; }; template <typename Params> class btree { using node_type = btree_node<Params>; using is_key_compare_to = typename Params::is_key_compare_to; - using init_type = typename Params::init_type; using field_type = typename node_type::field_type; - using is_multi_container = typename Params::is_multi_container; - using is_key_compare_adapted = typename Params::is_key_compare_adapted; // We use a static empty node for the root/leftmost/rightmost of empty btrees // in order to avoid branching in begin()/end(). struct alignas(node_type::Alignment()) EmptyNodeType : node_type { using field_type = typename node_type::field_type; node_type *parent; +#ifdef ABSL_BTREE_ENABLE_GENERATIONS + uint32_t generation = 0; +#endif field_type position = 0; field_type start = 0; field_type finish = 0; @@ -1036,7 +1335,7 @@ class btree { // MSVC has constexpr code generations bugs here. EmptyNodeType() : parent(this) {} #else - constexpr EmptyNodeType(node_type *p) : parent(p) {} + explicit constexpr EmptyNodeType(node_type *p) : parent(p) {} #endif }; @@ -1054,8 +1353,8 @@ class btree { } enum : uint32_t { - kNodeValues = node_type::kNodeValues, - kMinNodeValues = kNodeValues / 2, + kNodeSlots = node_type::kNodeSlots, + kMinNodeValues = kNodeSlots / 2, }; struct node_stats { @@ -1079,13 +1378,15 @@ class btree { using size_type = typename Params::size_type; using difference_type = typename Params::difference_type; using key_compare = typename Params::key_compare; + using original_key_compare = typename Params::original_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 iterator = + typename btree_iterator<node_type, reference, pointer>::iterator; using const_iterator = typename iterator::const_iterator; using reverse_iterator = std::reverse_iterator<iterator>; using const_reverse_iterator = std::reverse_iterator<const_iterator>; @@ -1096,29 +1397,39 @@ class btree { using slot_type = typename Params::slot_type; private: - // For use in copy_or_move_values_in_order. - const value_type &maybe_move_from_iterator(const_iterator it) { return *it; } - value_type &&maybe_move_from_iterator(iterator it) { return std::move(*it); } - // Copies or moves (depending on the template parameter) the values in // other into this btree in their order in other. This btree must be empty // before this method is called. This method is used in copy construction, // copy assignment, and move assignment. template <typename Btree> - void copy_or_move_values_in_order(Btree *other); + void copy_or_move_values_in_order(Btree &other); // Validates that various assumptions/requirements are true at compile time. constexpr static bool static_assert_validation(); public: - btree(const key_compare &comp, const allocator_type &alloc); + btree(const key_compare &comp, const allocator_type &alloc) + : root_(EmptyNode()), rightmost_(comp, alloc, EmptyNode()), size_(0) {} - btree(const btree &other); + btree(const btree &other) : btree(other, other.allocator()) {} + btree(const btree &other, const allocator_type &alloc) + : btree(other.key_comp(), alloc) { + copy_or_move_values_in_order(other); + } btree(btree &&other) noexcept - : root_(std::move(other.root_)), - rightmost_(absl::exchange(other.rightmost_, EmptyNode())), - size_(absl::exchange(other.size_, 0)) { - other.mutable_root() = EmptyNode(); + : root_(absl::exchange(other.root_, EmptyNode())), + rightmost_(std::move(other.rightmost_)), + size_(absl::exchange(other.size_, 0u)) { + other.mutable_rightmost() = EmptyNode(); + } + btree(btree &&other, const allocator_type &alloc) + : btree(other.key_comp(), alloc) { + if (alloc == other.allocator()) { + swap(other); + } else { + // Move values from `other` one at a time when allocators are different. + copy_or_move_values_in_order(other); + } } ~btree() { @@ -1134,9 +1445,9 @@ class btree { iterator begin() { return iterator(leftmost()); } const_iterator begin() const { return const_iterator(leftmost()); } - iterator end() { return iterator(rightmost_, rightmost_->finish()); } + iterator end() { return iterator(rightmost(), rightmost()->finish()); } const_iterator end() const { - return const_iterator(rightmost_, rightmost_->finish()); + return const_iterator(rightmost(), rightmost()->finish()); } reverse_iterator rbegin() { return reverse_iterator(end()); } const_reverse_iterator rbegin() const { @@ -1147,17 +1458,22 @@ class btree { return const_reverse_iterator(begin()); } - // Finds the first element whose key is not less than key. + // 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)); + return internal_end(internal_lower_bound(key).value); } template <typename K> const_iterator lower_bound(const K &key) const { - return internal_end(internal_lower_bound(key)); + return internal_end(internal_lower_bound(key).value); } - // Finds the first element whose key is greater than key. + // Finds the first element whose key is not less than `key` and also returns + // whether that element is equal to `key`. + template <typename K> + std::pair<iterator, bool> lower_bound_equal(const K &key) const; + + // 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)); @@ -1182,7 +1498,7 @@ class btree { // Requirement: if `key` already exists in the btree, does not consume `args`. // Requirement: `key` is never referenced after consuming `args`. template <typename K, typename... Args> - std::pair<iterator, bool> insert_unique(const K &key, Args &&... args); + std::pair<iterator, bool> insert_unique(const K &key, Args &&...args); // Inserts with hint. Checks to see if the value should be placed immediately // before `position` in the tree. If so, then the insertion will take @@ -1191,9 +1507,8 @@ class btree { // Requirement: if `key` already exists in the btree, does not consume `args`. // Requirement: `key` is never referenced after consuming `args`. template <typename K, typename... Args> - std::pair<iterator, bool> insert_hint_unique(iterator position, - const K &key, - Args &&... args); + std::pair<iterator, bool> insert_hint_unique(iterator position, const K &key, + Args &&...args); // Insert a range of values into the btree. // Note: the first overload avoids constructing a value_type if the key @@ -1227,7 +1542,8 @@ class btree { // Insert a range of values into the btree. template <typename InputIterator> - void insert_iterator_multi(InputIterator b, InputIterator e); + 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 @@ -1239,18 +1555,8 @@ class btree { // to the element after the last erased element. std::pair<size_type, iterator> erase_range(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. + // Finds an element with key equivalent to `key` or returns `end()` if `key` + // is not present. template <typename K> iterator find(const K &key) { return internal_end(internal_find(key)); @@ -1260,23 +1566,6 @@ class btree { 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(); @@ -1284,14 +1573,16 @@ class btree { void swap(btree &other); const key_compare &key_comp() const noexcept { - return root_.template get<0>(); + return rightmost_.template get<0>(); } template <typename K1, typename K2> bool compare_keys(const K1 &a, const K2 &b) const { return compare_internal::compare_result_as_less_than(key_comp()(a, b)); } - value_compare value_comp() const { return value_compare(key_comp()); } + value_compare value_comp() const { + return value_compare(original_key_compare(key_comp())); + } // Verifies the structure of the btree. void verify() const; @@ -1329,6 +1620,7 @@ class btree { } // The total number of bytes used by the btree. + // TODO(b/169338300): update to support node_btree_*. size_type bytes_used() const { node_stats stats = internal_stats(root()); if (stats.leaf_nodes == 1 && stats.internal_nodes == 0) { @@ -1339,12 +1631,13 @@ class btree { } } - // The average number of bytes used per value stored in the btree. + // The average number of bytes used per value stored in the btree assuming + // random insertion order. 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 expected number of values per node with random insertion order is the + // average of the maximum and minimum numbers of values per node. + const double expected_values_per_node = (kNodeSlots + kMinNodeValues) / 2.0; + return node_type::LeafSize() / expected_values_per_node; } // The fullness of the btree. Computed as the number of elements in the btree @@ -1354,7 +1647,7 @@ class btree { // Returns 0 for empty trees. double fullness() const { if (empty()) return 0.0; - return static_cast<double>(size()) / (nodes() * kNodeValues); + return static_cast<double>(size()) / (nodes() * kNodeSlots); } // 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 @@ -1370,11 +1663,20 @@ class btree { allocator_type get_allocator() const { return allocator(); } private: + friend struct btree_access; + // 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>(); } + node_type *root() { return root_; } + const node_type *root() const { return root_; } + node_type *&mutable_root() noexcept { return root_; } + node_type *rightmost() { return rightmost_.template get<2>(); } + const node_type *rightmost() const { return rightmost_.template get<2>(); } + node_type *&mutable_rightmost() noexcept { + return rightmost_.template get<2>(); + } + key_compare *mutable_key_comp() noexcept { + return &rightmost_.template get<0>(); + } // The leftmost node is stored as the parent of the root node. node_type *leftmost() { return root()->parent(); } @@ -1382,34 +1684,34 @@ class btree { // Allocator routines. allocator_type *mutable_allocator() noexcept { - return &root_.template get<1>(); + return &rightmost_.template get<1>(); } const allocator_type &allocator() const noexcept { - return root_.template get<1>(); + return rightmost_.template get<1>(); } // Allocates a correctly aligned node of at least size bytes using the // allocator. - node_type *allocate(const size_type size) { + node_type *allocate(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 *new_internal_node(field_type position, node_type *parent) { node_type *n = allocate(node_type::InternalSize()); - n->init_internal(parent); + n->init_internal(position, parent); return n; } - node_type *new_leaf_node(node_type *parent) { + node_type *new_leaf_node(field_type position, node_type *parent) { node_type *n = allocate(node_type::LeafSize()); - n->init_leaf(parent, kNodeValues); + n->init_leaf(position, kNodeSlots, parent); return n; } - node_type *new_leaf_root_node(const int max_count) { + node_type *new_leaf_root_node(field_type max_count) { node_type *n = allocate(node_type::LeafSize(max_count)); - n->init_leaf(/*parent=*/n, max_count); + n->init_leaf(/*position=*/0, max_count, /*parent=*/n); return n; } @@ -1433,48 +1735,38 @@ class btree { void try_shrink(); iterator internal_end(iterator iter) { - return iter.node != nullptr ? iter : end(); + return iter.node_ != nullptr ? iter : end(); } const_iterator internal_end(const_iterator iter) const { - return iter.node != nullptr ? iter : end(); + 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); + iterator internal_emplace(iterator iter, Args &&...args); // Returns an iterator pointing to the first value >= the value "iter" is // pointing at. Note that "iter" might be pointing to an invalid location such - // as iter.position == iter.node->finish(). This routine simply moves iter up - // in the tree to a valid location. - // Requires: iter.node is non-null. + // as iter.position_ == iter.node_->finish(). This routine simply moves iter + // up in the tree to a valid location. Requires: iter.node_ is non-null. template <typename IterType> static IterType internal_last(IterType iter); // Returns an iterator pointing to the leaf position at which key would - // reside in the tree. 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. + // reside in the tree, unless there is an exact match - in which case, the + // result may not be on a leaf. When there's a three-way comparator, we can + // return whether there was an exact match. This allows the caller to avoid a + // subsequent comparison to determine if an exact match was made, which is + // important for keys with expensive comparison, such as strings. template <typename K> SearchResult<iterator, is_key_compare_to::value> internal_locate( const K &key) const; - 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; + SearchResult<iterator, is_key_compare_to::value> internal_lower_bound( + const K &key) const; // Internal routine which implements upper_bound(). template <typename K> @@ -1485,15 +1777,15 @@ class btree { iterator internal_find(const K &key) const; // Verifies the tree structure of node. - int internal_verify(const node_type *node, const key_type *lo, - const key_type *hi) const; + size_type 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()) { + if (node->is_leaf()) { return node_stats(1, 0); } node_stats res(0, 1); @@ -1503,22 +1795,14 @@ class btree { return res; } - public: - // Exposed only for tests. - static bool testonly_uses_linear_node_search() { - return node_type::testonly_uses_linear_node_search(); - } + node_type *root_; - private: - // We use compressed tuple in order to save space because key_compare and - // allocator_type are usually empty. + // A pointer to the rightmost node. Note that the leftmost node is stored as + // the root's parent. 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_; + rightmost_; // Number of values. size_type size_; @@ -1528,9 +1812,9 @@ class btree { // btree_node methods template <typename P> template <typename... Args> -inline void btree_node<P>::emplace_value(const size_type i, +inline void btree_node<P>::emplace_value(const field_type i, allocator_type *alloc, - Args &&... args) { + Args &&...args) { assert(i >= start()); assert(i <= finish()); // Shift old values to create space for new value and then construct it in @@ -1539,11 +1823,11 @@ inline void btree_node<P>::emplace_value(const size_type i, transfer_n_backward(finish() - i, /*dest_i=*/i + 1, /*src_i=*/i, this, alloc); } - value_init(i, alloc, std::forward<Args>(args)...); + value_init(static_cast<field_type>(i), alloc, std::forward<Args>(args)...); set_finish(finish() + 1); - if (!leaf() && finish() > i + 1) { - for (int j = finish(); j > i + 1; --j) { + if (is_internal() && finish() > i + 1) { + for (field_type j = finish(); j > i + 1; --j) { set_child(j, child(j - 1)); } clear_child(i + 1); @@ -1560,13 +1844,13 @@ inline void btree_node<P>::remove_values(const field_type i, const field_type src_i = i + to_erase; transfer_n(orig_finish - src_i, i, src_i, this, alloc); - if (!leaf()) { + if (is_internal()) { // Delete all children between begin and end. - for (int j = 0; j < to_erase; ++j) { + for (field_type j = 0; j < to_erase; ++j) { clear_and_delete(child(i + j + 1), alloc); } // Rotate children after end into new positions. - for (int j = i + to_erase + 1; j <= orig_finish; ++j) { + for (field_type j = i + to_erase + 1; j <= orig_finish; ++j) { set_child(j - to_erase, child(j)); clear_child(j); } @@ -1575,7 +1859,7 @@ inline void btree_node<P>::remove_values(const field_type i, } template <typename P> -void btree_node<P>::rebalance_right_to_left(const int to_move, +void btree_node<P>::rebalance_right_to_left(field_type to_move, btree_node *right, allocator_type *alloc) { assert(parent() == right->parent()); @@ -1597,12 +1881,12 @@ void btree_node<P>::rebalance_right_to_left(const int to_move, right->transfer_n(right->count() - to_move, right->start(), right->start() + to_move, right, alloc); - if (!leaf()) { + if (is_internal()) { // Move the child pointers from the right to the left node. - for (int i = 0; i < to_move; ++i) { + for (field_type i = 0; i < to_move; ++i) { init_child(finish() + i + 1, right->child(i)); } - for (int i = right->start(); i <= right->finish() - to_move; ++i) { + for (field_type i = right->start(); i <= right->finish() - to_move; ++i) { assert(i + to_move <= right->max_count()); right->init_child(i, right->child(i + to_move)); right->clear_child(i + to_move); @@ -1615,7 +1899,7 @@ void btree_node<P>::rebalance_right_to_left(const int to_move, } template <typename P> -void btree_node<P>::rebalance_left_to_right(const int to_move, +void btree_node<P>::rebalance_left_to_right(field_type to_move, btree_node *right, allocator_type *alloc) { assert(parent() == right->parent()); @@ -1644,13 +1928,13 @@ void btree_node<P>::rebalance_left_to_right(const int to_move, // 4) Move the new delimiting value to the parent from the left node. parent()->transfer(position(), finish() - to_move, this, alloc); - if (!leaf()) { + if (is_internal()) { // Move the child pointers from the left to the right node. - for (int i = right->finish(); i >= right->start(); --i) { - right->init_child(i + to_move, right->child(i)); - right->clear_child(i); + for (field_type i = right->finish() + 1; i > right->start(); --i) { + right->init_child(i - 1 + to_move, right->child(i - 1)); + right->clear_child(i - 1); } - for (int i = 1; i <= to_move; ++i) { + for (field_type i = 1; i <= to_move; ++i) { right->init_child(i - 1, child(finish() - to_move + i)); clear_child(finish() - to_move + i); } @@ -1665,7 +1949,9 @@ 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); + assert(max_count() == kNodeSlots); + assert(position() + 1 == dest->position()); + assert(parent() == dest->parent()); // 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 @@ -1673,7 +1959,7 @@ void btree_node<P>::split(const int insert_position, btree_node *dest, // right node then bias the split to put more values on the left node. if (insert_position == start()) { dest->set_finish(dest->start() + finish() - 1); - } else if (insert_position == kNodeValues) { + } else if (insert_position == kNodeSlots) { dest->set_finish(dest->start()); } else { dest->set_finish(dest->start() + count() / 2); @@ -1688,10 +1974,10 @@ void btree_node<P>::split(const int insert_position, btree_node *dest, --mutable_finish(); parent()->emplace_value(position(), alloc, finish_slot()); value_destroy(finish(), alloc); - parent()->init_child(position() + 1, dest); + parent()->set_child_noupdate_position(position() + 1, dest); - if (!leaf()) { - for (int i = dest->start(), j = finish() + 1; i <= dest->finish(); + if (is_internal()) { + for (field_type i = dest->start(), j = finish() + 1; i <= dest->finish(); ++i, ++j) { assert(child(j) != nullptr); dest->init_child(i, child(j)); @@ -1711,9 +1997,10 @@ void btree_node<P>::merge(btree_node *src, allocator_type *alloc) { // Move the values from the right to the left node. transfer_n(src->count(), finish() + 1, src->start(), src, alloc); - if (!leaf()) { + if (is_internal()) { // Move the child pointers from the right to the left node. - for (int i = src->start(), j = finish() + 1; i <= src->finish(); ++i, ++j) { + for (field_type i = src->start(), j = finish() + 1; i <= src->finish(); + ++i, ++j) { init_child(j, src->child(i)); src->clear_child(i); } @@ -1729,7 +2016,7 @@ void btree_node<P>::merge(btree_node *src, allocator_type *alloc) { template <typename P> void btree_node<P>::clear_and_delete(btree_node *node, allocator_type *alloc) { - if (node->leaf()) { + if (node->is_leaf()) { node->value_destroy_n(node->start(), node->count(), alloc); deallocate(LeafSize(node->max_count()), node, alloc); return; @@ -1743,24 +2030,35 @@ void btree_node<P>::clear_and_delete(btree_node *node, allocator_type *alloc) { btree_node *delete_root_parent = node->parent(); // Navigate to the leftmost leaf under node, and then delete upwards. - while (!node->leaf()) node = node->start_child(); - // Use `int` because `pos` needs to be able to hold `kNodeValues+1`, which - // isn't guaranteed to be a valid `field_type`. - int pos = node->position(); + while (node->is_internal()) node = node->start_child(); +#ifdef ABSL_BTREE_ENABLE_GENERATIONS + // When generations are enabled, we delete the leftmost leaf last in case it's + // the parent of the root and we need to check whether it's a leaf before we + // can update the root's generation. + // TODO(ezb): if we change btree_node::is_root to check a bool inside the node + // instead of checking whether the parent is a leaf, we can remove this logic. + btree_node *leftmost_leaf = node; +#endif + // Use `size_type` because `pos` needs to be able to hold `kNodeSlots+1`, + // which isn't guaranteed to be a valid `field_type`. + size_type pos = node->position(); btree_node *parent = node->parent(); for (;;) { // In each iteration of the next loop, we delete one leaf node and go right. assert(pos <= parent->finish()); do { - node = parent->child(pos); - if (!node->leaf()) { + node = parent->child(static_cast<field_type>(pos)); + if (node->is_internal()) { // Navigate to the leftmost leaf under node. - while (!node->leaf()) node = node->start_child(); + while (node->is_internal()) node = node->start_child(); pos = node->position(); parent = node->parent(); } node->value_destroy_n(node->start(), node->count(), alloc); - deallocate(LeafSize(node->max_count()), node, alloc); +#ifdef ABSL_BTREE_ENABLE_GENERATIONS + if (leftmost_leaf != node) +#endif + deallocate(LeafSize(node->max_count()), node, alloc); ++pos; } while (pos <= parent->finish()); @@ -1772,7 +2070,12 @@ void btree_node<P>::clear_and_delete(btree_node *node, allocator_type *alloc) { parent = node->parent(); node->value_destroy_n(node->start(), node->count(), alloc); deallocate(InternalSize(), node, alloc); - if (parent == delete_root_parent) return; + if (parent == delete_root_parent) { +#ifdef ABSL_BTREE_ENABLE_GENERATIONS + deallocate(LeafSize(leftmost_leaf->max_count()), leftmost_leaf, alloc); +#endif + return; + } ++pos; } while (pos > parent->finish()); } @@ -1780,51 +2083,109 @@ void btree_node<P>::clear_and_delete(btree_node *node, allocator_type *alloc) { //// // btree_iterator methods + +// Note: the implementation here is based on btree_node::clear_and_delete. +template <typename N, typename R, typename P> +auto btree_iterator<N, R, P>::distance_slow(const_iterator other) const + -> difference_type { + const_iterator begin = other; + const_iterator end = *this; + assert(begin.node_ != end.node_ || !begin.node_->is_leaf() || + begin.position_ != end.position_); + + const node_type *node = begin.node_; + // We need to compensate for double counting if begin.node_ is a leaf node. + difference_type count = node->is_leaf() ? -begin.position_ : 0; + + // First navigate to the leftmost leaf node past begin. + if (node->is_internal()) { + ++count; + node = node->child(begin.position_ + 1); + } + while (node->is_internal()) node = node->start_child(); + + // Use `size_type` because `pos` needs to be able to hold `kNodeSlots+1`, + // which isn't guaranteed to be a valid `field_type`. + size_type pos = node->position(); + const node_type *parent = node->parent(); + for (;;) { + // In each iteration of the next loop, we count one leaf node and go right. + assert(pos <= parent->finish()); + do { + node = parent->child(static_cast<field_type>(pos)); + if (node->is_internal()) { + // Navigate to the leftmost leaf under node. + while (node->is_internal()) node = node->start_child(); + pos = node->position(); + parent = node->parent(); + } + if (node == end.node_) return count + end.position_; + if (parent == end.node_ && pos == static_cast<size_type>(end.position_)) + return count + node->count(); + // +1 is for the next internal node value. + count += node->count() + 1; + ++pos; + } while (pos <= parent->finish()); + + // Once we've counted all children of parent, go up/right. + assert(pos > parent->finish()); + do { + node = parent; + pos = node->position(); + parent = node->parent(); + // -1 because we counted the value at end and shouldn't. + if (parent == end.node_ && pos == static_cast<size_type>(end.position_)) + return count - 1; + ++pos; + } while (pos > parent->finish()); + } +} + template <typename N, typename R, typename P> void btree_iterator<N, R, P>::increment_slow() { - if (node->leaf()) { - assert(position >= node->finish()); + if (node_->is_leaf()) { + assert(position_ >= node_->finish()); btree_iterator save(*this); - while (position == node->finish() && !node->is_root()) { - assert(node->parent()->child(node->position()) == node); - position = node->position(); - node = node->parent(); + while (position_ == node_->finish() && !node_->is_root()) { + assert(node_->parent()->child(node_->position()) == node_); + position_ = node_->position(); + node_ = node_->parent(); } // TODO(ezb): assert we aren't incrementing end() instead of handling. - if (position == node->finish()) { + if (position_ == node_->finish()) { *this = save; } } else { - assert(position < node->finish()); - node = node->child(position + 1); - while (!node->leaf()) { - node = node->start_child(); + assert(position_ < node_->finish()); + node_ = node_->child(static_cast<field_type>(position_ + 1)); + while (node_->is_internal()) { + node_ = node_->start_child(); } - position = node->start(); + position_ = node_->start(); } } template <typename N, typename R, typename P> void btree_iterator<N, R, P>::decrement_slow() { - if (node->leaf()) { - assert(position <= -1); + if (node_->is_leaf()) { + assert(position_ <= -1); btree_iterator save(*this); - while (position < node->start() && !node->is_root()) { - assert(node->parent()->child(node->position()) == node); - position = node->position() - 1; - node = node->parent(); + while (position_ < node_->start() && !node_->is_root()) { + assert(node_->parent()->child(node_->position()) == node_); + position_ = node_->position() - 1; + node_ = node_->parent(); } // TODO(ezb): assert we aren't decrementing begin() instead of handling. - if (position < node->start()) { + if (position_ < node_->start()) { *this = save; } } else { - assert(position >= node->start()); - node = node->child(position); - while (!node->leaf()) { - node = node->child(node->finish()); + assert(position_ >= node_->start()); + node_ = node_->child(static_cast<field_type>(position_)); + while (node_->is_internal()) { + node_ = node_->child(node_->finish()); } - position = node->finish() - 1; + position_ = node_->finish() - 1; } } @@ -1832,7 +2193,7 @@ void btree_iterator<N, R, P>::decrement_slow() { // btree methods template <typename P> template <typename Btree> -void btree<P>::copy_or_move_values_in_order(Btree *other) { +void btree<P>::copy_or_move_values_in_order(Btree &other) { static_assert(std::is_same<btree, Btree>::value || std::is_same<const btree, Btree>::value, "Btree type must be same or const."); @@ -1840,14 +2201,14 @@ void btree<P>::copy_or_move_values_in_order(Btree *other) { // We can avoid key comparisons because we know the order of the // values is the same order we'll store them in. - auto iter = other->begin(); - if (iter == other->end()) return; - insert_multi(maybe_move_from_iterator(iter)); + auto iter = other.begin(); + if (iter == other.end()) return; + insert_multi(iter.slot()); ++iter; - for (; iter != other->end(); ++iter) { + for (; iter != other.end(); ++iter) { // If the btree is not empty, we can just insert the new value at the end // of the tree. - internal_emplace(end(), maybe_move_from_iterator(iter)); + internal_emplace(end(), iter.slot()); } } @@ -1857,25 +2218,22 @@ constexpr bool btree<P>::static_assert_validation() { "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, + static_assert(std::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))), + kNodeSlots < (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, + compare_has_valid_result_type<key_compare, key_type>(), "key comparison function must return absl::{weak,strong}_ordering or " "bool."); - // Test the assumption made in setting kNodeValueSpace. + // Test the assumption made in setting kNodeSlotSpace. static_assert(node_type::MinimumOverhead() >= sizeof(void *) + 4, "node space assumption incorrect"); @@ -1883,31 +2241,29 @@ constexpr bool btree<P>::static_assert_validation() { } 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 &other) - : btree(other.key_comp(), other.allocator()) { - copy_or_move_values_in_order(&other); +template <typename K> +auto btree<P>::lower_bound_equal(const K &key) const + -> std::pair<iterator, bool> { + const SearchResult<iterator, is_key_compare_to::value> res = + internal_lower_bound(key); + const iterator lower = iterator(internal_end(res.value)); + const bool equal = res.HasMatch() + ? res.IsEq() + : lower != end() && !compare_keys(key, lower.key()); + return {lower, equal}; } template <typename P> template <typename K> auto btree<P>::equal_range(const K &key) -> std::pair<iterator, iterator> { - const iterator lower = lower_bound(key); - // TODO(ezb): we should be able to avoid this comparison when there's a - // three-way comparator. - if (lower == end() || compare_keys(key, lower.key())) return {lower, lower}; + const std::pair<iterator, bool> lower_and_equal = lower_bound_equal(key); + const iterator lower = lower_and_equal.first; + if (!lower_and_equal.second) { + return {lower, lower}; + } const iterator next = std::next(lower); - // When the comparator is heterogeneous, we can't assume that comparison with - // non-`key_type` will be equivalent to `key_type` comparisons so there - // could be multiple equivalent keys even in a unique-container. But for - // heterogeneous comparisons from the default string adapted comparators, we - // don't need to worry about this. - if (!is_multi_container::value && - (std::is_same<K, key_type>::value || is_key_compare_adapted::value)) { + if (!params_type::template can_have_multiple_equivalent_keys<K>()) { // The next iterator after lower must point to a key greater than `key`. // Note: if this assert fails, then it may indicate that the comparator does // not meet the equivalence requirements for Compare @@ -1918,7 +2274,7 @@ auto btree<P>::equal_range(const K &key) -> std::pair<iterator, iterator> { // Try once more to avoid the call to upper_bound() if there's only one // equivalent key. This should prevent all calls to upper_bound() in cases of // unique-containers with heterogeneous comparators in which all comparison - // operators are equivalent. + // operators have the same equivalence classes. if (next == end() || compare_keys(key, next.key())) return {lower, next}; // In this case, we need to call upper_bound() to avoid worst case O(N) @@ -1928,14 +2284,14 @@ auto btree<P>::equal_range(const K &key) -> std::pair<iterator, iterator> { template <typename P> template <typename K, typename... Args> -auto btree<P>::insert_unique(const K &key, Args &&... args) +auto btree<P>::insert_unique(const K &key, Args &&...args) -> std::pair<iterator, bool> { if (empty()) { - mutable_root() = rightmost_ = new_leaf_root_node(1); + mutable_root() = mutable_rightmost() = new_leaf_root_node(1); } - auto res = internal_locate(key); - iterator &iter = res.value; + SearchResult<iterator, is_key_compare_to::value> res = internal_locate(key); + iterator iter = res.value; if (res.HasMatch()) { if (res.IsEq()) { @@ -1944,7 +2300,7 @@ auto btree<P>::insert_unique(const K &key, Args &&... args) } } else { iterator last = internal_last(iter); - if (last.node && !compare_keys(key, last.key())) { + if (last.node_ && !compare_keys(key, last.key())) { // The key already exists in the tree, do nothing. return {last, false}; } @@ -1955,7 +2311,7 @@ auto btree<P>::insert_unique(const K &key, Args &&... args) template <typename P> template <typename K, typename... Args> inline auto btree<P>::insert_hint_unique(iterator position, const K &key, - Args &&... args) + Args &&...args) -> std::pair<iterator, bool> { if (!empty()) { if (position == end() || compare_keys(key, position.key())) { @@ -1989,8 +2345,11 @@ template <typename P> template <typename InputIterator> void btree<P>::insert_iterator_unique(InputIterator b, InputIterator e, char) { for (; b != e; ++b) { - init_type value(*b); - insert_hint_unique(end(), params_type::key(value), std::move(value)); + // Use a node handle to manage a temp slot. + auto node_handle = + CommonAccess::Construct<node_handle_type>(get_allocator(), *b); + slot_type *slot = CommonAccess::GetSlot(node_handle); + insert_hint_unique(end(), params_type::key(slot), slot); } } @@ -1998,11 +2357,11 @@ 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); + mutable_root() = mutable_rightmost() = new_leaf_root_node(1); } iterator iter = internal_upper_bound(key); - if (iter.node == nullptr) { + if (iter.node_ == nullptr) { iter = end(); } return internal_emplace(iter, std::forward<ValueType>(v)); @@ -2049,7 +2408,7 @@ auto btree<P>::operator=(const btree &other) -> btree & { *mutable_allocator() = other.allocator(); } - copy_or_move_values_in_order(&other); + copy_or_move_values_in_order(other); } return *this; } @@ -2062,15 +2421,15 @@ auto btree<P>::operator=(btree &&other) noexcept -> btree & { using std::swap; if (absl::allocator_traits< allocator_type>::propagate_on_container_copy_assignment::value) { - // Note: `root_` also contains the allocator and the key comparator. swap(root_, other.root_); + // Note: `rightmost_` also contains the allocator and the key comparator. swap(rightmost_, other.rightmost_); swap(size_, other.size_); } else { if (allocator() == other.allocator()) { swap(mutable_root(), other.mutable_root()); swap(*mutable_key_comp(), *other.mutable_key_comp()); - swap(rightmost_, other.rightmost_); + swap(mutable_rightmost(), other.mutable_rightmost()); swap(size_, other.size_); } else { // We aren't allowed to propagate the allocator and the allocator is @@ -2079,7 +2438,7 @@ auto btree<P>::operator=(btree &&other) noexcept -> btree & { // comparator while moving the values so we can't swap the key // comparators. *mutable_key_comp() = other.key_comp(); - copy_or_move_values_in_order(&other); + copy_or_move_values_in_order(other); } } } @@ -2088,22 +2447,34 @@ auto btree<P>::operator=(btree &&other) noexcept -> btree & { template <typename P> auto btree<P>::erase(iterator iter) -> iterator { - bool internal_delete = false; - if (!iter.node->leaf()) { - // Deletion of a value on an internal node. First, move the largest value - // from our left child here, then delete that position (in remove_values() - // below). We can get to the largest value from our left child by - // decrementing iter. + iter.node_->value_destroy(static_cast<field_type>(iter.position_), + mutable_allocator()); + iter.update_generation(); + + const bool internal_delete = iter.node_->is_internal(); + if (internal_delete) { + // Deletion of a value on an internal node. First, transfer the largest + // value from our left child here, then erase/rebalance from that position. + // We can get to the largest value from our left child by decrementing iter. iterator internal_iter(iter); --iter; - assert(iter.node->leaf()); - params_type::move(mutable_allocator(), iter.node->slot(iter.position), - internal_iter.node->slot(internal_iter.position)); - internal_delete = true; - } - - // Delete the key from the leaf. - iter.node->remove_values(iter.position, /*to_erase=*/1, mutable_allocator()); + assert(iter.node_->is_leaf()); + internal_iter.node_->transfer( + static_cast<size_type>(internal_iter.position_), + static_cast<size_type>(iter.position_), iter.node_, + mutable_allocator()); + } else { + // Shift values after erased position in leaf. In the internal case, we + // don't need to do this because the leaf position is the end of the node. + const field_type transfer_from = + static_cast<field_type>(iter.position_ + 1); + const field_type num_to_transfer = iter.node_->finish() - transfer_from; + iter.node_->transfer_n(num_to_transfer, + static_cast<size_type>(iter.position_), + transfer_from, iter.node_, mutable_allocator()); + } + // Update node finish and container size. + iter.node_->set_finish(iter.node_->finish() - 1); --size_; // We want to return the next value after the one we just erased. If we @@ -2111,7 +2482,7 @@ auto btree<P>::erase(iterator iter) -> iterator { // 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. + // (iter.node_) when rebalancing is performed at the leaf level. iterator res = rebalance_after_delete(iter); @@ -2128,14 +2499,14 @@ auto btree<P>::rebalance_after_delete(iterator iter) -> iterator { iterator res(iter); bool first_iteration = true; for (;;) { - if (iter.node == root()) { + if (iter.node_ == root()) { try_shrink(); if (empty()) { return end(); } break; } - if (iter.node->count() >= kMinNodeValues) { + if (iter.node_->count() >= kMinNodeValues) { break; } bool merged = try_merge_or_rebalance(&iter); @@ -2148,14 +2519,15 @@ auto btree<P>::rebalance_after_delete(iterator iter) -> iterator { if (!merged) { break; } - iter.position = iter.node->position(); - iter.node = iter.node->parent(); + iter.position_ = iter.node_->position(); + iter.node_ = iter.node_->parent(); } + res.update_generation(); // Adjust our return value. If we're pointing at the end of a node, advance // the iterator. - if (res.position == res.node->finish()) { - res.position = res.node->finish() - 1; + if (res.position_ == res.node_->finish()) { + res.position_ = res.node_->finish() - 1; ++res; } @@ -2165,75 +2537,54 @@ auto btree<P>::rebalance_after_delete(iterator iter) -> iterator { template <typename P> auto btree<P>::erase_range(iterator begin, iterator end) -> std::pair<size_type, iterator> { - difference_type count = std::distance(begin, end); + size_type count = static_cast<size_type>(end - begin); assert(count >= 0); if (count == 0) { return {0, begin}; } - if (count == size_) { + if (static_cast<size_type>(count) == size_) { clear(); return {count, this->end()}; } - if (begin.node == end.node) { - assert(end.position > begin.position); - begin.node->remove_values(begin.position, end.position - begin.position, - mutable_allocator()); + if (begin.node_ == end.node_) { + assert(end.position_ > begin.position_); + begin.node_->remove_values( + static_cast<field_type>(begin.position_), + static_cast<field_type>(end.position_ - begin.position_), + mutable_allocator()); size_ -= count; return {count, rebalance_after_delete(begin)}; } const size_type target_size = size_ - count; while (size_ > target_size) { - if (begin.node->leaf()) { + if (begin.node_->is_leaf()) { const size_type remaining_to_erase = size_ - target_size; - const size_type remaining_in_node = begin.node->finish() - begin.position; - const size_type to_erase = - (std::min)(remaining_to_erase, remaining_in_node); - begin.node->remove_values(begin.position, to_erase, mutable_allocator()); + const size_type remaining_in_node = + static_cast<size_type>(begin.node_->finish() - begin.position_); + const field_type to_erase = static_cast<field_type>( + (std::min)(remaining_to_erase, remaining_in_node)); + begin.node_->remove_values(static_cast<field_type>(begin.position_), + to_erase, mutable_allocator()); size_ -= to_erase; begin = rebalance_after_delete(begin); } else { begin = erase(begin); } } + begin.update_generation(); return {count, 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_range(begin, end).first; -} - -template <typename P> void btree<P>::clear() { if (!empty()) { node_type::clear_and_delete(root(), mutable_allocator()); } - mutable_root() = EmptyNode(); - rightmost_ = EmptyNode(); + mutable_root() = mutable_rightmost() = EmptyNode(); size_ = 0; } @@ -2242,15 +2593,15 @@ void btree<P>::swap(btree &other) { using std::swap; if (absl::allocator_traits< allocator_type>::propagate_on_container_swap::value) { - // Note: `root_` also contains the allocator and the key comparator. - swap(root_, other.root_); + // Note: `rightmost_` also contains the allocator and the key comparator. + swap(rightmost_, other.rightmost_); } else { // It's undefined behavior if the allocators are unequal here. assert(allocator() == other.allocator()); - swap(mutable_root(), other.mutable_root()); + swap(mutable_rightmost(), other.mutable_rightmost()); swap(*mutable_key_comp(), *other.mutable_key_comp()); } - swap(rightmost_, other.rightmost_); + swap(mutable_root(), other.mutable_root()); swap(size_, other.size_); } @@ -2258,20 +2609,20 @@ template <typename P> void btree<P>::verify() const { assert(root() != nullptr); assert(leftmost() != nullptr); - assert(rightmost_ != nullptr); + assert(rightmost() != nullptr); assert(empty() || size() == internal_verify(root(), nullptr, nullptr)); - assert(leftmost() == (++const_iterator(root(), -1)).node); - assert(rightmost_ == (--const_iterator(root(), root()->finish())).node); - assert(leftmost()->leaf()); - assert(rightmost_->leaf()); + assert(leftmost() == (++const_iterator(root(), -1)).node_); + assert(rightmost() == (--const_iterator(root(), root()->finish())).node_); + assert(leftmost()->is_leaf()); + assert(rightmost()->is_leaf()); } template <typename P> void btree<P>::rebalance_or_split(iterator *iter) { - node_type *&node = iter->node; - int &insert_position = iter->position; + node_type *&node = iter->node_; + int &insert_position = iter->position_; assert(node->count() == node->max_count()); - assert(kNodeValues == node->max_count()); + assert(kNodeSlots == node->max_count()); // First try to make room on the node by rebalancing. node_type *parent = node->parent(); @@ -2279,21 +2630,24 @@ void btree<P>::rebalance_or_split(iterator *iter) { if (node->position() > parent->start()) { // Try rebalancing with our left sibling. node_type *left = parent->child(node->position() - 1); - assert(left->max_count() == kNodeValues); - if (left->count() < kNodeValues) { + assert(left->max_count() == kNodeSlots); + if (left->count() < kNodeSlots) { // 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 >= node->start() || - left->count() + to_move < kNodeValues) { + field_type to_move = + (kNodeSlots - left->count()) / + (1 + (static_cast<field_type>(insert_position) < kNodeSlots)); + to_move = (std::max)(field_type{1}, to_move); + + if (static_cast<field_type>(insert_position) - to_move >= + node->start() || + left->count() + to_move < kNodeSlots) { left->rebalance_right_to_left(to_move, node, mutable_allocator()); assert(node->max_count() - node->count() == to_move); - insert_position = insert_position - to_move; + insert_position = static_cast<int>( + static_cast<field_type>(insert_position) - to_move); if (insert_position < node->start()) { insert_position = insert_position + left->count() + 1; node = left; @@ -2308,17 +2662,18 @@ void btree<P>::rebalance_or_split(iterator *iter) { if (node->position() < parent->finish()) { // Try rebalancing with our right sibling. node_type *right = parent->child(node->position() + 1); - assert(right->max_count() == kNodeValues); - if (right->count() < kNodeValues) { + assert(right->max_count() == kNodeSlots); + if (right->count() < kNodeSlots) { // 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 > node->start())); - to_move = (std::max)(1, to_move); + field_type to_move = (kNodeSlots - right->count()) / + (1 + (insert_position > node->start())); + to_move = (std::max)(field_type{1}, to_move); - if (insert_position <= node->finish() - to_move || - right->count() + to_move < kNodeValues) { + if (static_cast<field_type>(insert_position) <= + node->finish() - to_move || + right->count() + to_move < kNodeSlots) { node->rebalance_left_to_right(to_move, right, mutable_allocator()); if (insert_position > node->finish()) { @@ -2334,31 +2689,33 @@ void btree<P>::rebalance_or_split(iterator *iter) { // 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()); + assert(parent->max_count() == kNodeSlots); + if (parent->count() == kNodeSlots) { + iterator parent_iter(parent, node->position()); rebalance_or_split(&parent_iter); + parent = node->parent(); } } else { // Rebalancing not possible because this is the root node. // Create a new root node and set the current root node as the child of the // new root. - parent = new_internal_node(parent); - parent->init_child(parent->start(), root()); + parent = new_internal_node(/*position=*/0, parent); + parent->set_generation(root()->generation()); + parent->init_child(parent->start(), node); mutable_root() = parent; // If the former root was a leaf node, then it's now the rightmost node. - assert(!parent->start_child()->leaf() || - parent->start_child() == rightmost_); + assert(parent->start_child()->is_internal() || + parent->start_child() == rightmost()); } // Split the node. node_type *split_node; - if (node->leaf()) { - split_node = new_leaf_node(parent); + if (node->is_leaf()) { + split_node = new_leaf_node(node->position() + 1, parent); node->split(insert_position, split_node, mutable_allocator()); - if (rightmost_ == node) rightmost_ = split_node; + if (rightmost() == node) mutable_rightmost() = split_node; } else { - split_node = new_internal_node(parent); + split_node = new_internal_node(node->position() + 1, parent); node->split(insert_position, split_node, mutable_allocator()); } @@ -2371,55 +2728,57 @@ void btree<P>::rebalance_or_split(iterator *iter) { template <typename P> void btree<P>::merge_nodes(node_type *left, node_type *right) { left->merge(right, mutable_allocator()); - if (rightmost_ == right) rightmost_ = left; + if (rightmost() == right) mutable_rightmost() = left; } template <typename P> bool btree<P>::try_merge_or_rebalance(iterator *iter) { - node_type *parent = iter->node->parent(); - if (iter->node->position() > parent->start()) { + node_type *parent = iter->node_->parent(); + if (iter->node_->position() > parent->start()) { // Try merging with our left sibling. - node_type *left = parent->child(iter->node->position() - 1); - assert(left->max_count() == kNodeValues); - if (1 + left->count() + iter->node->count() <= kNodeValues) { - iter->position += 1 + left->count(); - merge_nodes(left, iter->node); - iter->node = left; + node_type *left = parent->child(iter->node_->position() - 1); + assert(left->max_count() == kNodeSlots); + if (1U + left->count() + iter->node_->count() <= kNodeSlots) { + iter->position_ += 1 + left->count(); + merge_nodes(left, iter->node_); + iter->node_ = left; return true; } } - if (iter->node->position() < parent->finish()) { + if (iter->node_->position() < parent->finish()) { // Try merging with our right sibling. - node_type *right = parent->child(iter->node->position() + 1); - assert(right->max_count() == kNodeValues); - if (1 + iter->node->count() + right->count() <= kNodeValues) { - merge_nodes(iter->node, right); + node_type *right = parent->child(iter->node_->position() + 1); + assert(right->max_count() == kNodeSlots); + if (1U + iter->node_->count() + right->count() <= kNodeSlots) { + 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 + // we deleted the first element from iter->node_ and the node is not // empty. This is a small optimization for the common pattern of deleting // from the front of the tree. if (right->count() > kMinNodeValues && - (iter->node->count() == 0 || iter->position > iter->node->start())) { - int to_move = (right->count() - iter->node->count()) / 2; - to_move = (std::min)(to_move, right->count() - 1); - iter->node->rebalance_right_to_left(to_move, right, mutable_allocator()); + (iter->node_->count() == 0 || iter->position_ > iter->node_->start())) { + field_type to_move = (right->count() - iter->node_->count()) / 2; + to_move = + (std::min)(to_move, static_cast<field_type>(right->count() - 1)); + iter->node_->rebalance_right_to_left(to_move, right, mutable_allocator()); return false; } } - if (iter->node->position() > parent->start()) { + if (iter->node_->position() > parent->start()) { // Try rebalancing with our left sibling. We don't perform rebalancing if - // we deleted the last element from iter->node and the node is not + // 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); + node_type *left = parent->child(iter->node_->position() - 1); if (left->count() > kMinNodeValues && - (iter->node->count() == 0 || iter->position < iter->node->finish())) { - int to_move = (left->count() - iter->node->count()) / 2; - to_move = (std::min)(to_move, left->count() - 1); - left->rebalance_left_to_right(to_move, iter->node, mutable_allocator()); - iter->position += to_move; + (iter->node_->count() == 0 || + iter->position_ < iter->node_->finish())) { + field_type to_move = (left->count() - iter->node_->count()) / 2; + to_move = (std::min)(to_move, static_cast<field_type>(left->count() - 1)); + left->rebalance_left_to_right(to_move, iter->node_, mutable_allocator()); + iter->position_ += to_move; return false; } } @@ -2433,9 +2792,9 @@ void btree<P>::try_shrink() { return; } // Deleted the last item on the root node, shrink the height of the tree. - if (orig_root->leaf()) { + if (orig_root->is_leaf()) { assert(size() == 0); - mutable_root() = rightmost_ = EmptyNode(); + mutable_root() = mutable_rightmost() = EmptyNode(); } else { node_type *child = orig_root->start_child(); child->make_root(); @@ -2447,53 +2806,94 @@ void btree<P>::try_shrink() { template <typename P> template <typename IterType> inline IterType btree<P>::internal_last(IterType iter) { - assert(iter.node != nullptr); - while (iter.position == iter.node->finish()) { - iter.position = iter.node->position(); - iter.node = iter.node->parent(); - if (iter.node->leaf()) { - iter.node = nullptr; + assert(iter.node_ != nullptr); + while (iter.position_ == iter.node_->finish()) { + iter.position_ = iter.node_->position(); + iter.node_ = iter.node_->parent(); + if (iter.node_->is_leaf()) { + iter.node_ = nullptr; break; } } + iter.update_generation(); return iter; } template <typename P> template <typename... Args> -inline auto btree<P>::internal_emplace(iterator iter, Args &&... args) +inline auto btree<P>::internal_emplace(iterator iter, Args &&...args) -> iterator { - if (!iter.node->leaf()) { + if (iter.node_->is_internal()) { // 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; + ++iter.position_; } - const field_type max_count = iter.node->max_count(); + const field_type max_count = iter.node_->max_count(); allocator_type *alloc = mutable_allocator(); - if (iter.node->count() == max_count) { + + const auto transfer_and_delete = [&](node_type *old_node, + node_type *new_node) { + new_node->transfer_n(old_node->count(), new_node->start(), + old_node->start(), old_node, alloc); + new_node->set_finish(old_node->finish()); + old_node->set_finish(old_node->start()); + new_node->set_generation(old_node->generation()); + node_type::clear_and_delete(old_node, alloc); + }; + const auto replace_leaf_root_node = [&](field_type new_node_size) { + assert(iter.node_ == root()); + node_type *old_root = iter.node_; + node_type *new_root = iter.node_ = new_leaf_root_node(new_node_size); + transfer_and_delete(old_root, new_root); + mutable_root() = mutable_rightmost() = new_root; + }; + + bool replaced_node = false; + if (iter.node_->count() == max_count) { // Make room in the leaf for the new item. - if (max_count < kNodeValues) { + if (max_count < kNodeSlots) { // Insertion into the root where the root is smaller than the full node // size. Simply grow the size of the root node. - assert(iter.node == root()); - iter.node = - new_leaf_root_node((std::min<int>)(kNodeValues, 2 * max_count)); - // Transfer the values from the old root to the new root. - node_type *old_root = root(); - node_type *new_root = iter.node; - new_root->transfer_n(old_root->count(), new_root->start(), - old_root->start(), old_root, alloc); - new_root->set_finish(old_root->finish()); - old_root->set_finish(old_root->start()); - node_type::clear_and_delete(old_root, alloc); - mutable_root() = rightmost_ = new_root; + replace_leaf_root_node(static_cast<field_type>( + (std::min)(static_cast<int>(kNodeSlots), 2 * max_count))); + replaced_node = true; } else { rebalance_or_split(&iter); } } - iter.node->emplace_value(iter.position, alloc, std::forward<Args>(args)...); + (void)replaced_node; +#ifdef ABSL_HAVE_ADDRESS_SANITIZER + if (!replaced_node) { + assert(iter.node_->is_leaf()); + if (iter.node_->is_root()) { + replace_leaf_root_node(max_count); + } else { + node_type *old_node = iter.node_; + const bool was_rightmost = rightmost() == old_node; + const bool was_leftmost = leftmost() == old_node; + node_type *parent = old_node->parent(); + const field_type position = old_node->position(); + node_type *new_node = iter.node_ = new_leaf_node(position, parent); + parent->set_child_noupdate_position(position, new_node); + transfer_and_delete(old_node, new_node); + if (was_rightmost) mutable_rightmost() = new_node; + // The leftmost node is stored as the parent of the root node. + if (was_leftmost) root()->set_parent(new_node); + } + } +#endif + iter.node_->emplace_value(static_cast<field_type>(iter.position_), alloc, + std::forward<Args>(args)...); + assert( + iter.node_->is_ordered_correctly(static_cast<field_type>(iter.position_), + original_key_compare(key_comp())) && + "If this assert fails, then either (1) the comparator may violate " + "transitivity, i.e. comp(a,b) && comp(b,c) -> comp(a,c) (see " + "https://en.cppreference.com/w/cpp/named_req/Compare), or (2) a " + "key may have been mutated after it was inserted into the tree."); ++size_; + iter.update_generation(); return iter; } @@ -2501,61 +2901,51 @@ 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())); - 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())); for (;;) { - SearchResult<int, true> res = iter.node->lower_bound(key, key_comp()); - iter.position = res.value; - if (res.match == MatchKind::kEq) { + SearchResult<size_type, is_key_compare_to::value> res = + iter.node_->lower_bound(key, key_comp()); + iter.position_ = static_cast<int>(res.value); + if (res.IsEq()) { return {iter, MatchKind::kEq}; } - if (iter.node->leaf()) { + // Note: in the non-key-compare-to case, we don't need to walk all the way + // down the tree if the keys are equal, but determining equality would + // require doing an extra comparison on each node on the way down, and we + // will need to go all the way to the leaf node in the expected case. + if (iter.node_->is_leaf()) { break; } - iter.node = iter.node->child(iter.position); + iter.node_ = iter.node_->child(static_cast<field_type>(iter.position_)); } + // Note: in the non-key-compare-to case, the key may actually be equivalent + // here (and the MatchKind::kNe is ignored). return {iter, MatchKind::kNe}; } template <typename P> template <typename K> -auto btree<P>::internal_lower_bound(const K &key) const -> iterator { +auto btree<P>::internal_lower_bound(const K &key) const + -> SearchResult<iterator, is_key_compare_to::value> { + if (!params_type::template can_have_multiple_equivalent_keys<K>()) { + SearchResult<iterator, is_key_compare_to::value> ret = internal_locate(key); + ret.value = internal_last(ret.value); + return ret; + } iterator iter(const_cast<node_type *>(root())); + SearchResult<size_type, is_key_compare_to::value> res; + bool seen_eq = false; for (;;) { - iter.position = iter.node->lower_bound(key, key_comp()).value; - if (iter.node->leaf()) { + res = iter.node_->lower_bound(key, key_comp()); + iter.position_ = static_cast<int>(res.value); + if (iter.node_->is_leaf()) { break; } - iter.node = iter.node->child(iter.position); + seen_eq = seen_eq || res.IsEq(); + iter.node_ = iter.node_->child(static_cast<field_type>(iter.position_)); } - return internal_last(iter); + if (res.IsEq()) return {iter, MatchKind::kEq}; + return {internal_last(iter), seen_eq ? MatchKind::kEq : MatchKind::kNe}; } template <typename P> @@ -2563,11 +2953,11 @@ template <typename K> auto btree<P>::internal_upper_bound(const K &key) const -> iterator { iterator iter(const_cast<node_type *>(root())); for (;;) { - iter.position = iter.node->upper_bound(key, key_comp()); - if (iter.node->leaf()) { + iter.position_ = static_cast<int>(iter.node_->upper_bound(key, key_comp())); + if (iter.node_->is_leaf()) { break; } - iter.node = iter.node->child(iter.position); + iter.node_ = iter.node_->child(static_cast<field_type>(iter.position_)); } return internal_last(iter); } @@ -2575,14 +2965,14 @@ auto btree<P>::internal_upper_bound(const K &key) const -> iterator { template <typename P> template <typename K> auto btree<P>::internal_find(const K &key) const -> iterator { - auto res = internal_locate(key); + SearchResult<iterator, is_key_compare_to::value> res = internal_locate(key); if (res.HasMatch()) { if (res.IsEq()) { return res.value; } } else { const iterator iter = internal_last(res.value); - if (iter.node != nullptr && !compare_keys(key, iter.key())) { + if (iter.node_ != nullptr && !compare_keys(key, iter.key())) { return iter; } } @@ -2590,8 +2980,8 @@ auto btree<P>::internal_find(const K &key) const -> iterator { } template <typename P> -int btree<P>::internal_verify(const node_type *node, const key_type *lo, - const key_type *hi) const { +typename btree<P>::size_type 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) { @@ -2603,9 +2993,9 @@ int btree<P>::internal_verify(const node_type *node, const key_type *lo, for (int i = node->start() + 1; i < node->finish(); ++i) { assert(!compare_keys(node->key(i), node->key(i - 1))); } - int count = node->count(); - if (!node->leaf()) { - for (int i = node->start(); i <= node->finish(); ++i) { + size_type count = node->count(); + if (node->is_internal()) { + for (field_type i = node->start(); i <= node->finish(); ++i) { assert(node->child(i) != nullptr); assert(node->child(i)->parent() == node); assert(node->child(i)->position() == i); @@ -2617,6 +3007,50 @@ int btree<P>::internal_verify(const node_type *node, const key_type *lo, return count; } +struct btree_access { + template <typename BtreeContainer, typename Pred> + static auto erase_if(BtreeContainer &container, Pred pred) -> + typename BtreeContainer::size_type { + const auto initial_size = container.size(); + auto &tree = container.tree_; + auto *alloc = tree.mutable_allocator(); + for (auto it = container.begin(); it != container.end();) { + if (!pred(*it)) { + ++it; + continue; + } + auto *node = it.node_; + if (node->is_internal()) { + // Handle internal nodes normally. + it = container.erase(it); + continue; + } + // If this is a leaf node, then we do all the erases from this node + // at once before doing rebalancing. + + // The current position to transfer slots to. + int to_pos = it.position_; + node->value_destroy(it.position_, alloc); + while (++it.position_ < node->finish()) { + it.update_generation(); + if (pred(*it)) { + node->value_destroy(it.position_, alloc); + } else { + node->transfer(node->slot(to_pos++), node->slot(it.position_), alloc); + } + } + const int num_deleted = node->finish() - to_pos; + tree.size_ -= num_deleted; + node->set_finish(to_pos); + it.position_ = to_pos; + it = tree.rebalance_after_delete(it); + } + return initial_size - container.size(); + } +}; + +#undef ABSL_BTREE_ENABLE_GENERATIONS + } // namespace container_internal ABSL_NAMESPACE_END } // namespace absl |