diff options
Diffstat (limited to 'absl/container/internal/btree.h')
| -rw-r--r-- | absl/container/internal/btree.h | 1090 |
1 files changed, 662 insertions, 428 deletions
diff --git a/absl/container/internal/btree.h b/absl/container/internal/btree.h index 0bb38366..01f4e749 100644 --- a/absl/container/internal/btree.h +++ b/absl/container/internal/btree.h @@ -58,6 +58,7 @@ #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/compressed_tuple.h" @@ -74,12 +75,24 @@ 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 + +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; @@ -88,7 +101,12 @@ struct StringBtreeDefaultLess { // Compatibility constructor. StringBtreeDefaultLess(std::less<std::string>) {} // NOLINT - StringBtreeDefaultLess(std::less<string_view>) {} // 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 { @@ -115,7 +133,12 @@ struct StringBtreeDefaultGreater { StringBtreeDefaultGreater() = default; StringBtreeDefaultGreater(std::greater<std::string>) {} // NOLINT - StringBtreeDefaultGreater(std::greater<string_view>) {} // 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 { @@ -136,49 +159,140 @@ 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; }; @@ -214,19 +328,70 @@ 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> + bool IsMulti, bool IsMap, typename SlotPolicy> struct common_params { + 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; + // 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; + static constexpr bool kEnableGenerations = +#ifdef ABSL_BTREE_ENABLE_GENERATIONS + true; +#else + false; +#endif + // 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; using slot_policy = SlotPolicy; @@ -238,6 +403,12 @@ 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 @@ -248,27 +419,25 @@ struct common_params { // that we know has the same equivalence classes for all lookup types. template <typename LookupKey> constexpr static bool can_have_multiple_equivalent_keys() { - return Multi || - (IsTransparent<key_compare>::value && - !std::is_same<LookupKey, Key>::value && - !std::is_same<key_compare, StringBtreeDefaultLess>::value && - !std::is_same<key_compare, StringBtreeDefaultGreater>::value); + 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 = + 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 @@ -291,116 +460,10 @@ struct common_params { 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); + slot_policy::transfer(alloc, new_slot, old_slot); } }; -// A parameters structure for holding the type parameters for a btree_set. -// Compare and Alloc should be nothrow copy-constructible. -template <typename Key, typename Compare, typename Alloc, int TargetNodeSize, - bool Multi> -struct set_params : common_params<Key, Compare, Alloc, TargetNodeSize, Multi, - set_slot_policy<Key>> { - using value_type = Key; - using slot_type = typename set_params::common_params::slot_type; - using value_compare = typename set_params::common_params::key_compare; - using is_map_container = std::false_type; - - template <typename V> - static const V &key(const V &value) { return value; } - static const Key &key(const slot_type *slot) { return *slot; } - static const Key &key(slot_type *slot) { return *slot; } -}; - // An adapter class that converts a lower-bound compare into an upper-bound // compare. Note: there is no need to make a version of this adapter specialized // for key-compare-to functors because the upper-bound (the first value greater @@ -435,8 +498,8 @@ struct SearchResult { template <typename V> struct SearchResult<V, false> { SearchResult() {} - explicit SearchResult(V value) : value(value) {} - SearchResult(V value, MatchKind /*match*/) : value(value) {} + explicit SearchResult(V v) : value(v) {} + SearchResult(V v, MatchKind /*match*/) : value(v) {} V value; @@ -453,6 +516,7 @@ class btree_node { 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; @@ -474,21 +538,28 @@ class btree_node { // - Otherwise, choose binary. // TODO(ezb): Might make sense to add condition(s) based on node-size. using use_linear_search = std::integral_constant< - bool, - has_linear_node_search_preference<key_compare>::value - ? prefers_linear_node_search<key_compare>::value - : has_linear_node_search_preference<key_type>::value + 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>, key_compare>::value || + (std::is_same<std::less<key_type>, + original_key_compare>::value || std::is_same<std::greater<key_type>, - key_compare>::value)>; + original_key_compare>::value)>; - // This class is organized by gtl::Layout as if it had the following - // structure: + // 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`. @@ -535,23 +606,27 @@ class btree_node { btree_node() = default; private: - using layout_type = absl::container_internal::Layout<btree_node *, field_type, - slot_type, btree_node *>; + 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, - /*position, start, finish, max_count*/ 4, - /*slots*/ n, - /*children*/ 0) + return layout_type( + /*parent*/ 1, + /*generation*/ params_type::kEnableGenerations ? 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 SizeWithNSlots(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 NodeTargetSlots(const int begin, const int end) { + constexpr static size_type NodeTargetSlots(const size_type begin, + const size_type end) { return begin == end ? begin : SizeWithNSlots((begin + end) / 2 + 1) > params_type::kTargetNodeSize @@ -580,16 +655,20 @@ class btree_node { // Leaves can have less than kNodeSlots values. constexpr static layout_type LeafLayout(const int slot_count = kNodeSlots) { - return layout_type(/*parent*/ 1, - /*position, start, finish, max_count*/ 4, - /*slots*/ slot_count, - /*children*/ 0); + return layout_type( + /*parent*/ 1, + /*generation*/ params_type::kEnableGenerations ? 1 : 0, + /*position, start, finish, max_count*/ 4, + /*slots*/ slot_count, + /*children*/ 0); } constexpr static layout_type InternalLayout() { - return layout_type(/*parent*/ 1, - /*position, start, finish, max_count*/ 4, - /*slots*/ kNodeSlots, - /*children*/ kNodeSlots + 1); + return layout_type( + /*parent*/ 1, + /*generation*/ params_type::kEnableGenerations ? 1 : 0, + /*position, start, finish, max_count*/ 4, + /*slots*/ kNodeSlots, + /*children*/ kNodeSlots + 1); } constexpr static size_type LeafSize(const int slot_count = kNodeSlots) { return LeafLayout(slot_count).AllocSize(); @@ -603,44 +682,47 @@ 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(int 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(int 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 { @@ -650,7 +732,7 @@ class btree_node { field_type max_count() const { // Internal nodes have max_count==kInternalNodeMaxCount. // Leaf nodes have max_count in [1, kNodeSlots]. - const field_type max_count = GetField<1>()[3]; + const field_type max_count = GetField<2>()[3]; return max_count == field_type{kInternalNodeMaxCount} ? field_type{kNodeSlots} : max_count; @@ -661,21 +743,44 @@ 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(params_type::kEnableGenerations); + 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 params_type::kEnableGenerations ? *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 (params_type::kEnableGenerations) GetField<1>()[0] = generation; + } + // Updates the generation. We do this whenever the node is mutated. + void next_generation() { + if (params_type::kEnableGenerations) ++*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)); } // Getters/setter for the child at position i in the node. - btree_node *child(int i) const { return GetField<3>()[i]; } + btree_node *child(int i) const { return GetField<4>()[i]; } btree_node *start_child() const { return child(start()); } - btree_node *&mutable_child(int i) { return GetField<3>()[i]; } + btree_node *&mutable_child(int i) { return GetField<4>()[i]; } void clear_child(int i) { absl::container_internal::SanitizerPoisonObject(&mutable_child(i)); } @@ -832,7 +937,8 @@ 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(int max_count, btree_node *parent) { + set_generation(0); set_parent(parent); set_position(0); set_start(0); @@ -842,7 +948,7 @@ class btree_node { start_slot(), max_count * sizeof(slot_type)); } void init_internal(btree_node *parent) { - init_leaf(parent, kNodeSlots); + init_leaf(kNodeSlots, parent); // Set `max_count` to a sentinel value to indicate that this node is // internal. set_max_count(kInternalNodeMaxCount); @@ -861,15 +967,18 @@ class btree_node { private: template <typename... 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); @@ -885,6 +994,7 @@ 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); } @@ -893,6 +1003,7 @@ 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) { @@ -905,6 +1016,7 @@ 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) { + next_generation(); for (slot_type *src = src_node->slot(src_i + n - 1), *end = src - n, *dest = slot(dest_i + n - 1); src != end; --src, --dest) { @@ -915,13 +1027,13 @@ class btree_node { 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 { - private: +class btree_iterator { using key_type = typename Node::key_type; using size_type = typename Node::size_type; using params_type = typename Node::params_type; @@ -949,9 +1061,15 @@ 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) : node_(n), position_(p) { +#ifdef ABSL_BTREE_ENABLE_GENERATIONS + // Use `~uint32_t{}` as a sentinel value for iterator generations so it + // doesn't match the initial value for the actual generation. + generation_ = n != nullptr ? n->generation() : ~uint32_t{}; +#endif + } // NOTE: this SFINAE allows for implicit conversions from iterator to // const_iterator, but it specifically avoids hiding the copy constructor so @@ -962,58 +1080,32 @@ struct btree_iterator { 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 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) - : node(const_cast<node_type *>(other.node)), position(other.position) {} - - // Increment/decrement the iterator. - void increment() { - if (node->leaf() && ++position < node->finish()) { - return; - } - increment_slow(); - } - void increment_slow(); - - void decrement() { - if (node->leaf() && --position >= node->start()) { - return; - } - decrement_slow(); + : node_(other.node_), position_(other.position_) { +#ifdef ABSL_BTREE_ENABLE_GENERATIONS + generation_ = other.generation_; +#endif } - void decrement_slow(); - public: bool operator==(const iterator &other) const { - return node == other.node && position == other.position; + return node_ == other.node_ && position_ == other.position_; } bool operator==(const const_iterator &other) const { - return node == other.node && position == other.position; + return node_ == other.node_ && position_ == other.position_; } bool operator!=(const iterator &other) const { - return node != other.node || position != other.position; + return node_ != other.node_ || position_ != other.position_; } bool operator!=(const const_iterator &other) const { - return node != other.node || position != other.position; + return node_ != other.node_ || position_ != other.position_; } // Accessors for the key/value the iterator is pointing at. reference operator*() const { - ABSL_HARDENING_ASSERT(node != nullptr); - ABSL_HARDENING_ASSERT(node->start() <= position); - ABSL_HARDENING_ASSERT(node->finish() > position); - return node->value(position); + ABSL_HARDENING_ASSERT(node_ != nullptr); + ABSL_HARDENING_ASSERT(node_->start() <= position_); + ABSL_HARDENING_ASSERT(node_->finish() > position_); + assert_valid_generation(); + return node_->value(position_); } pointer operator->() const { return &operator*(); } @@ -1051,23 +1143,84 @@ struct btree_iterator { friend class btree_multiset_container; 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) + : node_(const_cast<node_type *>(other.node_)), + position_(other.position_) { +#ifdef ABSL_BTREE_ENABLE_GENERATIONS + generation_ = other.generation_; +#endif + } + + // Increment/decrement the iterator. + void increment() { + assert_valid_generation(); + if (node_->is_leaf() && ++position_ < node_->finish()) { + return; + } + increment_slow(); + } + void increment_slow(); + + void decrement() { + assert_valid_generation(); + if (node_->is_leaf() && --position_ >= node_->start()) { + return; + } + decrement_slow(); + } + void decrement_slow(); + + // Updates the generation. For use internally right before we return an + // iterator to the user. + void update_generation() { +#ifdef ABSL_BTREE_ENABLE_GENERATIONS + if (node_ != nullptr) generation_ = node_->generation(); +#endif + } + + const key_type &key() const { return node_->key(position_); } + decltype(std::declval<Node *>()->slot(0)) slot() { + return node_->slot(position_); + } + + void assert_valid_generation() const { +#ifdef ABSL_BTREE_ENABLE_GENERATIONS + 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."); + } +#endif + } // 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_; +#ifdef ABSL_BTREE_ENABLE_GENERATIONS + // Used to check that the iterator hasn't been invalidated. + uint32_t generation_; +#endif }; 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; // We use a static empty node for the root/leftmost/rightmost of empty btrees @@ -1075,6 +1228,9 @@ class btree { 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; @@ -1129,6 +1285,7 @@ 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; @@ -1147,14 +1304,6 @@ 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) { - // This is a destructive operation on the other container so it's safe for - // us to const_cast and move from the keys here even if it's a set. - return std::move(const_cast<value_type &>(*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, @@ -1167,7 +1316,7 @@ class btree { public: btree(const key_compare &comp, const allocator_type &alloc) - : root_(comp, alloc, EmptyNode()), rightmost_(EmptyNode()), size_(0) {} + : root_(EmptyNode()), rightmost_(comp, alloc, EmptyNode()), size_(0) {} btree(const btree &other) : btree(other, other.allocator()) {} btree(const btree &other, const allocator_type &alloc) @@ -1175,10 +1324,10 @@ class btree { copy_or_move_values_in_order(other); } btree(btree &&other) noexcept - : root_(std::move(other.root_)), - rightmost_(absl::exchange(other.rightmost_, EmptyNode())), + : root_(absl::exchange(other.root_, EmptyNode())), + rightmost_(std::move(other.rightmost_)), size_(absl::exchange(other.size_, 0)) { - other.mutable_root() = EmptyNode(); + other.mutable_rightmost() = EmptyNode(); } btree(btree &&other, const allocator_type &alloc) : btree(other.key_comp(), alloc) { @@ -1203,9 +1352,9 @@ 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 { @@ -1331,14 +1480,16 @@ 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; @@ -1376,6 +1527,7 @@ 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) { @@ -1419,11 +1571,20 @@ 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(); } @@ -1431,10 +1592,10 @@ 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 @@ -1453,12 +1614,12 @@ class btree { } node_type *new_leaf_node(node_type *parent) { node_type *n = allocate(node_type::LeafSize()); - n->init_leaf(parent, kNodeSlots); + n->init_leaf(kNodeSlots, parent); return n; } node_type *new_leaf_root_node(const int max_count) { node_type *n = allocate(node_type::LeafSize(max_count)); - n->init_leaf(/*parent=*/n, max_count); + n->init_leaf(max_count, /*parent=*/n); return n; } @@ -1482,10 +1643,10 @@ 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 @@ -1495,9 +1656,8 @@ class btree { // 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); @@ -1533,7 +1693,7 @@ class btree { 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); @@ -1543,15 +1703,14 @@ class btree { return res; } - // We use compressed tuple in order to save space because key_compare and - // allocator_type are usually empty. - absl::container_internal::CompressedTuple<key_compare, allocator_type, - node_type *> - root_; + node_type *root_; // A pointer to the rightmost node. Note that the leftmost node is stored as - // the root's parent. - node_type *rightmost_; + // 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 *> + rightmost_; // Number of values. size_type size_; @@ -1575,8 +1734,8 @@ inline void btree_node<P>::emplace_value(const size_type i, value_init(i, alloc, std::forward<Args>(args)...); set_finish(finish() + 1); - if (!leaf() && finish() > i + 1) { - for (int j = finish(); j > i + 1; --j) { + 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); @@ -1593,7 +1752,7 @@ 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) { clear_and_delete(child(i + j + 1), alloc); @@ -1630,7 +1789,7 @@ 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) { init_child(finish() + i + 1, right->child(i)); @@ -1677,7 +1836,7 @@ 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)); @@ -1723,7 +1882,7 @@ void btree_node<P>::split(const int insert_position, btree_node *dest, value_destroy(finish(), alloc); parent()->init_child(position() + 1, dest); - if (!leaf()) { + if (is_internal()) { for (int i = dest->start(), j = finish() + 1; i <= dest->finish(); ++i, ++j) { assert(child(j) != nullptr); @@ -1744,7 +1903,7 @@ 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) { init_child(j, src->child(i)); @@ -1762,7 +1921,7 @@ 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; @@ -1776,7 +1935,15 @@ 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(); + 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 `int` because `pos` needs to be able to hold `kNodeSlots+1`, which // isn't guaranteed to be a valid `field_type`. int pos = node->position(); @@ -1786,14 +1953,17 @@ void btree_node<P>::clear_and_delete(btree_node *node, allocator_type *alloc) { assert(pos <= parent->finish()); do { node = parent->child(pos); - if (!node->leaf()) { + 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()); @@ -1805,7 +1975,12 @@ 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()); } @@ -1815,49 +1990,49 @@ void btree_node<P>::clear_and_delete(btree_node *node, allocator_type *alloc) { // btree_iterator methods template <typename N, typename R, typename P> void btree_iterator<N, R, P>::increment_slow() { - if (node->leaf()) { - assert(position >= node->finish()); + 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(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(position_); + while (node_->is_internal()) { + node_ = node_->child(node_->finish()); } - position = node->finish() - 1; + position_ = node_->finish() - 1; } } @@ -1875,12 +2050,12 @@ void btree<P>::copy_or_move_values_in_order(Btree &other) { // 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)); + insert_multi(iter.slot()); ++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()); } } @@ -1900,15 +2075,12 @@ constexpr bool btree<P>::static_assert_validation() { "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"); @@ -1962,7 +2134,7 @@ template <typename K, typename... Args> auto btree<P>::insert_unique(const K &key, Args &&... args) -> std::pair<iterator, bool> { if (empty()) { - mutable_root() = rightmost_ = new_leaf_root_node(1); + mutable_root() = mutable_rightmost() = new_leaf_root_node(1); } SearchResult<iterator, is_key_compare_to::value> res = internal_locate(key); @@ -1975,7 +2147,7 @@ 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}; } @@ -2020,8 +2192,11 @@ 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); } } @@ -2029,11 +2204,11 @@ 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)); @@ -2093,15 +2268,15 @@ 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 @@ -2119,22 +2294,29 @@ 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(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(internal_iter.position_, 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 = iter.position_ + 1; + const field_type num_to_transfer = iter.node_->finish() - transfer_from; + iter.node_->transfer_n(num_to_transfer, 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 @@ -2142,7 +2324,7 @@ 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); @@ -2159,14 +2341,14 @@ 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); @@ -2179,14 +2361,15 @@ 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; } @@ -2203,33 +2386,36 @@ auto btree<P>::erase_range(iterator begin, iterator end) 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(begin.position_, end.position_ - begin.position_, + mutable_allocator()); size_ -= count; return {count, rebalance_after_delete(begin)}; } const size_type target_size = size_ - count; while (size_ > target_size) { - if (begin.node->leaf()) { + 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 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()); + begin.node_->remove_values(begin.position_, to_erase, + mutable_allocator()); size_ -= to_erase; begin = rebalance_after_delete(begin); } else { begin = erase(begin); } } + begin.update_generation(); return {count, begin}; } @@ -2238,8 +2424,7 @@ 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; } @@ -2248,15 +2433,15 @@ 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_); } @@ -2264,18 +2449,18 @@ 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(kNodeSlots == node->max_count()); @@ -2350,19 +2535,20 @@ void btree<P>::rebalance_or_split(iterator *iter) { // Create a new root node and set the current root node as the child of the // new root. parent = new_internal_node(parent); + parent->set_generation(root()->generation()); parent->init_child(parent->start(), root()); mutable_root() = parent; // If the former root was a leaf node, then it's now the rightmost node. - assert(!parent->start_child()->leaf() || - parent->start_child() == rightmost_); + assert(parent->start_child()->is_internal() || + parent->start_child() == rightmost()); } // Split the node. node_type *split_node; - if (node->leaf()) { + if (node->is_leaf()) { split_node = new_leaf_node(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); node->split(insert_position, split_node, mutable_allocator()); @@ -2377,55 +2563,56 @@ 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); + 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; + 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); + 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); + 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; + (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_->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; + (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; + left->rebalance_left_to_right(to_move, iter->node_, mutable_allocator()); + iter->position_ += to_move; return false; } } @@ -2439,9 +2626,9 @@ 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(); @@ -2453,15 +2640,16 @@ 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; } @@ -2469,37 +2657,39 @@ template <typename P> template <typename... 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) { + if (iter.node_->count() == max_count) { // Make room in the leaf for the new item. 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 = + assert(iter.node_ == root()); + iter.node_ = new_leaf_root_node((std::min<int>)(kNodeSlots, 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; + 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()); + new_root->set_generation(old_root->generation()); node_type::clear_and_delete(old_root, alloc); - mutable_root() = rightmost_ = new_root; + mutable_root() = mutable_rightmost() = new_root; } else { rebalance_or_split(&iter); } } - iter.node->emplace_value(iter.position, alloc, std::forward<Args>(args)...); + iter.node_->emplace_value(iter.position_, alloc, std::forward<Args>(args)...); ++size_; + iter.update_generation(); return iter; } @@ -2510,8 +2700,8 @@ inline auto btree<P>::internal_locate(const K &key) const iterator iter(const_cast<node_type *>(root())); for (;;) { SearchResult<int, is_key_compare_to::value> res = - iter.node->lower_bound(key, key_comp()); - iter.position = res.value; + iter.node_->lower_bound(key, key_comp()); + iter.position_ = res.value; if (res.IsEq()) { return {iter, MatchKind::kEq}; } @@ -2519,10 +2709,10 @@ inline auto btree<P>::internal_locate(const K &key) const // 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()) { + if (iter.node_->is_leaf()) { break; } - iter.node = iter.node->child(iter.position); + iter.node_ = iter.node_->child(iter.position_); } // Note: in the non-key-compare-to case, the key may actually be equivalent // here (and the MatchKind::kNe is ignored). @@ -2542,13 +2732,13 @@ auto btree<P>::internal_lower_bound(const K &key) const SearchResult<int, is_key_compare_to::value> res; bool seen_eq = false; for (;;) { - res = iter.node->lower_bound(key, key_comp()); - iter.position = res.value; - if (iter.node->leaf()) { + res = iter.node_->lower_bound(key, key_comp()); + iter.position_ = res.value; + if (iter.node_->is_leaf()) { break; } seen_eq = seen_eq || res.IsEq(); - iter.node = iter.node->child(iter.position); + iter.node_ = iter.node_->child(iter.position_); } if (res.IsEq()) return {iter, MatchKind::kEq}; return {internal_last(iter), seen_eq ? MatchKind::kEq : MatchKind::kNe}; @@ -2559,11 +2749,11 @@ 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_ = 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(iter.position_); } return internal_last(iter); } @@ -2578,7 +2768,7 @@ auto btree<P>::internal_find(const K &key) const -> iterator { } } 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; } } @@ -2600,7 +2790,7 @@ int btree<P>::internal_verify(const node_type *node, const key_type *lo, assert(!compare_keys(node->key(i), node->key(i - 1))); } int count = node->count(); - if (!node->leaf()) { + if (node->is_internal()) { for (int i = node->start(); i <= node->finish(); ++i) { assert(node->child(i) != nullptr); assert(node->child(i)->parent() == node); @@ -2613,6 +2803,50 @@ 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 |