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Diffstat (limited to 'third_party/abseil_cpp/absl/container/internal/container_memory.h')
| -rw-r--r-- | third_party/abseil_cpp/absl/container/internal/container_memory.h | 445 |
1 files changed, 445 insertions, 0 deletions
diff --git a/third_party/abseil_cpp/absl/container/internal/container_memory.h b/third_party/abseil_cpp/absl/container/internal/container_memory.h new file mode 100644 index 000000000000..536ea398eb10 --- /dev/null +++ b/third_party/abseil_cpp/absl/container/internal/container_memory.h @@ -0,0 +1,445 @@ +// Copyright 2018 The Abseil Authors. +// +// Licensed under the Apache License, Version 2.0 (the "License"); +// you may not use this file except in compliance with the License. +// You may obtain a copy of the License at +// +// https://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, software +// distributed under the License is distributed on an "AS IS" BASIS, +// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +// See the License for the specific language governing permissions and +// limitations under the License. + +#ifndef ABSL_CONTAINER_INTERNAL_CONTAINER_MEMORY_H_ +#define ABSL_CONTAINER_INTERNAL_CONTAINER_MEMORY_H_ + +#ifdef ADDRESS_SANITIZER +#include <sanitizer/asan_interface.h> +#endif + +#ifdef MEMORY_SANITIZER +#include <sanitizer/msan_interface.h> +#endif + +#include <cassert> +#include <cstddef> +#include <memory> +#include <tuple> +#include <type_traits> +#include <utility> + +#include "absl/memory/memory.h" +#include "absl/meta/type_traits.h" +#include "absl/utility/utility.h" + +namespace absl { +ABSL_NAMESPACE_BEGIN +namespace container_internal { + +template <size_t Alignment> +struct alignas(Alignment) AlignedType {}; + +// Allocates at least n bytes aligned to the specified alignment. +// Alignment must be a power of 2. It must be positive. +// +// Note that many allocators don't honor alignment requirements above certain +// threshold (usually either alignof(std::max_align_t) or alignof(void*)). +// Allocate() doesn't apply alignment corrections. If the underlying allocator +// returns insufficiently alignment pointer, that's what you are going to get. +template <size_t Alignment, class Alloc> +void* Allocate(Alloc* alloc, size_t n) { + static_assert(Alignment > 0, ""); + assert(n && "n must be positive"); + using M = AlignedType<Alignment>; + using A = typename absl::allocator_traits<Alloc>::template rebind_alloc<M>; + using AT = typename absl::allocator_traits<Alloc>::template rebind_traits<M>; + A mem_alloc(*alloc); + void* p = AT::allocate(mem_alloc, (n + sizeof(M) - 1) / sizeof(M)); + assert(reinterpret_cast<uintptr_t>(p) % Alignment == 0 && + "allocator does not respect alignment"); + return p; +} + +// The pointer must have been previously obtained by calling +// Allocate<Alignment>(alloc, n). +template <size_t Alignment, class Alloc> +void Deallocate(Alloc* alloc, void* p, size_t n) { + static_assert(Alignment > 0, ""); + assert(n && "n must be positive"); + using M = AlignedType<Alignment>; + using A = typename absl::allocator_traits<Alloc>::template rebind_alloc<M>; + using AT = typename absl::allocator_traits<Alloc>::template rebind_traits<M>; + A mem_alloc(*alloc); + AT::deallocate(mem_alloc, static_cast<M*>(p), + (n + sizeof(M) - 1) / sizeof(M)); +} + +namespace memory_internal { + +// Constructs T into uninitialized storage pointed by `ptr` using the args +// specified in the tuple. +template <class Alloc, class T, class Tuple, size_t... I> +void ConstructFromTupleImpl(Alloc* alloc, T* ptr, Tuple&& t, + absl::index_sequence<I...>) { + absl::allocator_traits<Alloc>::construct( + *alloc, ptr, std::get<I>(std::forward<Tuple>(t))...); +} + +template <class T, class F> +struct WithConstructedImplF { + template <class... Args> + decltype(std::declval<F>()(std::declval<T>())) operator()( + Args&&... args) const { + return std::forward<F>(f)(T(std::forward<Args>(args)...)); + } + F&& f; +}; + +template <class T, class Tuple, size_t... Is, class F> +decltype(std::declval<F>()(std::declval<T>())) WithConstructedImpl( + Tuple&& t, absl::index_sequence<Is...>, F&& f) { + return WithConstructedImplF<T, F>{std::forward<F>(f)}( + std::get<Is>(std::forward<Tuple>(t))...); +} + +template <class T, size_t... Is> +auto TupleRefImpl(T&& t, absl::index_sequence<Is...>) + -> decltype(std::forward_as_tuple(std::get<Is>(std::forward<T>(t))...)) { + return std::forward_as_tuple(std::get<Is>(std::forward<T>(t))...); +} + +// Returns a tuple of references to the elements of the input tuple. T must be a +// tuple. +template <class T> +auto TupleRef(T&& t) -> decltype( + TupleRefImpl(std::forward<T>(t), + absl::make_index_sequence< + std::tuple_size<typename std::decay<T>::type>::value>())) { + return TupleRefImpl( + std::forward<T>(t), + absl::make_index_sequence< + std::tuple_size<typename std::decay<T>::type>::value>()); +} + +template <class F, class K, class V> +decltype(std::declval<F>()(std::declval<const K&>(), std::piecewise_construct, + std::declval<std::tuple<K>>(), std::declval<V>())) +DecomposePairImpl(F&& f, std::pair<std::tuple<K>, V> p) { + const auto& key = std::get<0>(p.first); + return std::forward<F>(f)(key, std::piecewise_construct, std::move(p.first), + std::move(p.second)); +} + +} // namespace memory_internal + +// Constructs T into uninitialized storage pointed by `ptr` using the args +// specified in the tuple. +template <class Alloc, class T, class Tuple> +void ConstructFromTuple(Alloc* alloc, T* ptr, Tuple&& t) { + memory_internal::ConstructFromTupleImpl( + alloc, ptr, std::forward<Tuple>(t), + absl::make_index_sequence< + std::tuple_size<typename std::decay<Tuple>::type>::value>()); +} + +// Constructs T using the args specified in the tuple and calls F with the +// constructed value. +template <class T, class Tuple, class F> +decltype(std::declval<F>()(std::declval<T>())) WithConstructed( + Tuple&& t, F&& f) { + return memory_internal::WithConstructedImpl<T>( + std::forward<Tuple>(t), + absl::make_index_sequence< + std::tuple_size<typename std::decay<Tuple>::type>::value>(), + std::forward<F>(f)); +} + +// Given arguments of an std::pair's consructor, PairArgs() returns a pair of +// tuples with references to the passed arguments. The tuples contain +// constructor arguments for the first and the second elements of the pair. +// +// The following two snippets are equivalent. +// +// 1. std::pair<F, S> p(args...); +// +// 2. auto a = PairArgs(args...); +// std::pair<F, S> p(std::piecewise_construct, +// std::move(p.first), std::move(p.second)); +inline std::pair<std::tuple<>, std::tuple<>> PairArgs() { return {}; } +template <class F, class S> +std::pair<std::tuple<F&&>, std::tuple<S&&>> PairArgs(F&& f, S&& s) { + return {std::piecewise_construct, std::forward_as_tuple(std::forward<F>(f)), + std::forward_as_tuple(std::forward<S>(s))}; +} +template <class F, class S> +std::pair<std::tuple<const F&>, std::tuple<const S&>> PairArgs( + const std::pair<F, S>& p) { + return PairArgs(p.first, p.second); +} +template <class F, class S> +std::pair<std::tuple<F&&>, std::tuple<S&&>> PairArgs(std::pair<F, S>&& p) { + return PairArgs(std::forward<F>(p.first), std::forward<S>(p.second)); +} +template <class F, class S> +auto PairArgs(std::piecewise_construct_t, F&& f, S&& s) + -> decltype(std::make_pair(memory_internal::TupleRef(std::forward<F>(f)), + memory_internal::TupleRef(std::forward<S>(s)))) { + return std::make_pair(memory_internal::TupleRef(std::forward<F>(f)), + memory_internal::TupleRef(std::forward<S>(s))); +} + +// A helper function for implementing apply() in map policies. +template <class F, class... Args> +auto DecomposePair(F&& f, Args&&... args) + -> decltype(memory_internal::DecomposePairImpl( + std::forward<F>(f), PairArgs(std::forward<Args>(args)...))) { + return memory_internal::DecomposePairImpl( + std::forward<F>(f), PairArgs(std::forward<Args>(args)...)); +} + +// A helper function for implementing apply() in set policies. +template <class F, class Arg> +decltype(std::declval<F>()(std::declval<const Arg&>(), std::declval<Arg>())) +DecomposeValue(F&& f, Arg&& arg) { + const auto& key = arg; + return std::forward<F>(f)(key, std::forward<Arg>(arg)); +} + +// Helper functions for asan and msan. +inline void SanitizerPoisonMemoryRegion(const void* m, size_t s) { +#ifdef ADDRESS_SANITIZER + ASAN_POISON_MEMORY_REGION(m, s); +#endif +#ifdef MEMORY_SANITIZER + __msan_poison(m, s); +#endif + (void)m; + (void)s; +} + +inline void SanitizerUnpoisonMemoryRegion(const void* m, size_t s) { +#ifdef ADDRESS_SANITIZER + ASAN_UNPOISON_MEMORY_REGION(m, s); +#endif +#ifdef MEMORY_SANITIZER + __msan_unpoison(m, s); +#endif + (void)m; + (void)s; +} + +template <typename T> +inline void SanitizerPoisonObject(const T* object) { + SanitizerPoisonMemoryRegion(object, sizeof(T)); +} + +template <typename T> +inline void SanitizerUnpoisonObject(const T* object) { + SanitizerUnpoisonMemoryRegion(object, sizeof(T)); +} + +namespace memory_internal { + +// If Pair is a standard-layout type, OffsetOf<Pair>::kFirst and +// OffsetOf<Pair>::kSecond are equivalent to offsetof(Pair, first) and +// offsetof(Pair, second) respectively. Otherwise they are -1. +// +// The purpose of OffsetOf is to avoid calling offsetof() on non-standard-layout +// type, which is non-portable. +template <class Pair, class = std::true_type> +struct OffsetOf { + static constexpr size_t kFirst = static_cast<size_t>(-1); + static constexpr size_t kSecond = static_cast<size_t>(-1); +}; + +template <class Pair> +struct OffsetOf<Pair, typename std::is_standard_layout<Pair>::type> { + static constexpr size_t kFirst = offsetof(Pair, first); + static constexpr size_t kSecond = offsetof(Pair, second); +}; + +template <class K, class V> +struct IsLayoutCompatible { + private: + struct Pair { + K first; + V second; + }; + + // Is P layout-compatible with Pair? + template <class P> + static constexpr bool LayoutCompatible() { + return std::is_standard_layout<P>() && sizeof(P) == sizeof(Pair) && + alignof(P) == alignof(Pair) && + memory_internal::OffsetOf<P>::kFirst == + memory_internal::OffsetOf<Pair>::kFirst && + memory_internal::OffsetOf<P>::kSecond == + memory_internal::OffsetOf<Pair>::kSecond; + } + + public: + // Whether pair<const K, V> and pair<K, V> are layout-compatible. If they are, + // then it is safe to store them in a union and read from either. + static constexpr bool value = std::is_standard_layout<K>() && + std::is_standard_layout<Pair>() && + memory_internal::OffsetOf<Pair>::kFirst == 0 && + LayoutCompatible<std::pair<K, V>>() && + LayoutCompatible<std::pair<const K, V>>(); +}; + +} // namespace memory_internal + +// The internal storage type for key-value containers like flat_hash_map. +// +// It is convenient for the value_type of a flat_hash_map<K, V> to be +// pair<const K, V>; the "const K" prevents accidental modification of the key +// when dealing with the reference returned from find() and similar methods. +// However, this creates other problems; we want to be able to emplace(K, V) +// efficiently with move operations, and similarly be able to move a +// pair<K, V> in insert(). +// +// The solution is this union, which aliases the const and non-const versions +// of the pair. This also allows flat_hash_map<const K, V> to work, even though +// that has the same efficiency issues with move in emplace() and insert() - +// but people do it anyway. +// +// If kMutableKeys is false, only the value member can be accessed. +// +// If kMutableKeys is true, key can be accessed through all slots while value +// and mutable_value must be accessed only via INITIALIZED slots. Slots are +// created and destroyed via mutable_value so that the key can be moved later. +// +// Accessing one of the union fields while the other is active is safe as +// long as they are layout-compatible, which is guaranteed by the definition of +// kMutableKeys. For C++11, the relevant section of the standard is +// https://timsong-cpp.github.io/cppwp/n3337/class.mem#19 (9.2.19) +template <class K, class V> +union map_slot_type { + map_slot_type() {} + ~map_slot_type() = delete; + using value_type = std::pair<const K, V>; + using mutable_value_type = + std::pair<absl::remove_const_t<K>, absl::remove_const_t<V>>; + + value_type value; + mutable_value_type mutable_value; + absl::remove_const_t<K> key; +}; + +template <class K, class V> +struct map_slot_policy { + using slot_type = map_slot_type<K, V>; + using value_type = std::pair<const K, V>; + using mutable_value_type = std::pair<K, V>; + + private: + static void emplace(slot_type* slot) { + // The construction of union doesn't do anything at runtime but it allows us + // to access its members without violating aliasing rules. + new (slot) slot_type; + } + // If pair<const K, V> and pair<K, V> are layout-compatible, we can accept one + // or the other via slot_type. We are also free to access the key via + // slot_type::key in this case. + using kMutableKeys = memory_internal::IsLayoutCompatible<K, V>; + + public: + static value_type& element(slot_type* slot) { return slot->value; } + static const value_type& element(const slot_type* slot) { + return slot->value; + } + + static const K& key(const slot_type* slot) { + return kMutableKeys::value ? slot->key : slot->value.first; + } + + template <class Allocator, class... Args> + static void construct(Allocator* alloc, slot_type* slot, Args&&... args) { + emplace(slot); + if (kMutableKeys::value) { + absl::allocator_traits<Allocator>::construct(*alloc, &slot->mutable_value, + std::forward<Args>(args)...); + } else { + absl::allocator_traits<Allocator>::construct(*alloc, &slot->value, + std::forward<Args>(args)...); + } + } + + // Construct this slot by moving from another slot. + template <class Allocator> + static void construct(Allocator* alloc, slot_type* slot, slot_type* other) { + emplace(slot); + if (kMutableKeys::value) { + absl::allocator_traits<Allocator>::construct( + *alloc, &slot->mutable_value, std::move(other->mutable_value)); + } else { + absl::allocator_traits<Allocator>::construct(*alloc, &slot->value, + std::move(other->value)); + } + } + + template <class Allocator> + static void destroy(Allocator* alloc, slot_type* slot) { + if (kMutableKeys::value) { + absl::allocator_traits<Allocator>::destroy(*alloc, &slot->mutable_value); + } else { + absl::allocator_traits<Allocator>::destroy(*alloc, &slot->value); + } + } + + template <class Allocator> + static void transfer(Allocator* alloc, slot_type* new_slot, + slot_type* old_slot) { + emplace(new_slot); + if (kMutableKeys::value) { + absl::allocator_traits<Allocator>::construct( + *alloc, &new_slot->mutable_value, std::move(old_slot->mutable_value)); + } else { + absl::allocator_traits<Allocator>::construct(*alloc, &new_slot->value, + std::move(old_slot->value)); + } + destroy(alloc, old_slot); + } + + template <class Allocator> + static void swap(Allocator* alloc, slot_type* a, slot_type* b) { + if (kMutableKeys::value) { + using std::swap; + swap(a->mutable_value, b->mutable_value); + } else { + value_type tmp = std::move(a->value); + absl::allocator_traits<Allocator>::destroy(*alloc, &a->value); + absl::allocator_traits<Allocator>::construct(*alloc, &a->value, + std::move(b->value)); + absl::allocator_traits<Allocator>::destroy(*alloc, &b->value); + absl::allocator_traits<Allocator>::construct(*alloc, &b->value, + std::move(tmp)); + } + } + + template <class Allocator> + static void move(Allocator* alloc, slot_type* src, slot_type* dest) { + if (kMutableKeys::value) { + dest->mutable_value = std::move(src->mutable_value); + } else { + absl::allocator_traits<Allocator>::destroy(*alloc, &dest->value); + absl::allocator_traits<Allocator>::construct(*alloc, &dest->value, + std::move(src->value)); + } + } + + template <class Allocator> + static void move(Allocator* alloc, slot_type* first, slot_type* last, + slot_type* result) { + for (slot_type *src = first, *dest = result; src != last; ++src, ++dest) + move(alloc, src, dest); + } +}; + +} // namespace container_internal +ABSL_NAMESPACE_END +} // namespace absl + +#endif // ABSL_CONTAINER_INTERNAL_CONTAINER_MEMORY_H_ |