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Diffstat (limited to 'third_party/abseil_cpp/absl/hash/internal/hash.h')
| -rw-r--r-- | third_party/abseil_cpp/absl/hash/internal/hash.h | 1003 |
1 files changed, 0 insertions, 1003 deletions
diff --git a/third_party/abseil_cpp/absl/hash/internal/hash.h b/third_party/abseil_cpp/absl/hash/internal/hash.h deleted file mode 100644 index b0132da2069d..000000000000 --- a/third_party/abseil_cpp/absl/hash/internal/hash.h +++ /dev/null @@ -1,1003 +0,0 @@ -// Copyright 2018 The Abseil Authors. -// -// Licensed under the Apache License, Version 2.0 (the "License"); -// you may not use this file except in compliance with the License. -// You may obtain a copy of the License at -// -// https://www.apache.org/licenses/LICENSE-2.0 -// -// Unless required by applicable law or agreed to in writing, software -// distributed under the License is distributed on an "AS IS" BASIS, -// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. -// See the License for the specific language governing permissions and -// limitations under the License. -// -// ----------------------------------------------------------------------------- -// File: hash.h -// ----------------------------------------------------------------------------- -// -#ifndef ABSL_HASH_INTERNAL_HASH_H_ -#define ABSL_HASH_INTERNAL_HASH_H_ - -#include <algorithm> -#include <array> -#include <cmath> -#include <cstring> -#include <deque> -#include <forward_list> -#include <functional> -#include <iterator> -#include <limits> -#include <list> -#include <map> -#include <memory> -#include <set> -#include <string> -#include <tuple> -#include <type_traits> -#include <utility> -#include <vector> - -#include "absl/base/internal/endian.h" -#include "absl/base/port.h" -#include "absl/container/fixed_array.h" -#include "absl/meta/type_traits.h" -#include "absl/numeric/int128.h" -#include "absl/strings/string_view.h" -#include "absl/types/optional.h" -#include "absl/types/variant.h" -#include "absl/utility/utility.h" -#include "absl/hash/internal/city.h" - -namespace absl { -ABSL_NAMESPACE_BEGIN -namespace hash_internal { - -// Internal detail: Large buffers are hashed in smaller chunks. This function -// returns the size of these chunks. -constexpr size_t PiecewiseChunkSize() { return 1024; } - -// PiecewiseCombiner -// -// PiecewiseCombiner is an internal-only helper class for hashing a piecewise -// buffer of `char` or `unsigned char` as though it were contiguous. This class -// provides two methods: -// -// H add_buffer(state, data, size) -// H finalize(state) -// -// `add_buffer` can be called zero or more times, followed by a single call to -// `finalize`. This will produce the same hash expansion as concatenating each -// buffer piece into a single contiguous buffer, and passing this to -// `H::combine_contiguous`. -// -// Example usage: -// PiecewiseCombiner combiner; -// for (const auto& piece : pieces) { -// state = combiner.add_buffer(std::move(state), piece.data, piece.size); -// } -// return combiner.finalize(std::move(state)); -class PiecewiseCombiner { - public: - PiecewiseCombiner() : position_(0) {} - PiecewiseCombiner(const PiecewiseCombiner&) = delete; - PiecewiseCombiner& operator=(const PiecewiseCombiner&) = delete; - - // PiecewiseCombiner::add_buffer() - // - // Appends the given range of bytes to the sequence to be hashed, which may - // modify the provided hash state. - template <typename H> - H add_buffer(H state, const unsigned char* data, size_t size); - template <typename H> - H add_buffer(H state, const char* data, size_t size) { - return add_buffer(std::move(state), - reinterpret_cast<const unsigned char*>(data), size); - } - - // PiecewiseCombiner::finalize() - // - // Finishes combining the hash sequence, which may may modify the provided - // hash state. - // - // Once finalize() is called, add_buffer() may no longer be called. The - // resulting hash state will be the same as if the pieces passed to - // add_buffer() were concatenated into a single flat buffer, and then provided - // to H::combine_contiguous(). - template <typename H> - H finalize(H state); - - private: - unsigned char buf_[PiecewiseChunkSize()]; - size_t position_; -}; - -// HashStateBase -// -// A hash state object represents an intermediate state in the computation -// of an unspecified hash algorithm. `HashStateBase` provides a CRTP style -// base class for hash state implementations. Developers adding type support -// for `absl::Hash` should not rely on any parts of the state object other than -// the following member functions: -// -// * HashStateBase::combine() -// * HashStateBase::combine_contiguous() -// -// A derived hash state class of type `H` must provide a static member function -// with a signature similar to the following: -// -// `static H combine_contiguous(H state, const unsigned char*, size_t)`. -// -// `HashStateBase` will provide a complete implementation for a hash state -// object in terms of this method. -// -// Example: -// -// // Use CRTP to define your derived class. -// struct MyHashState : HashStateBase<MyHashState> { -// static H combine_contiguous(H state, const unsigned char*, size_t); -// using MyHashState::HashStateBase::combine; -// using MyHashState::HashStateBase::combine_contiguous; -// }; -template <typename H> -class HashStateBase { - public: - // HashStateBase::combine() - // - // Combines an arbitrary number of values into a hash state, returning the - // updated state. - // - // Each of the value types `T` must be separately hashable by the Abseil - // hashing framework. - // - // NOTE: - // - // state = H::combine(std::move(state), value1, value2, value3); - // - // is guaranteed to produce the same hash expansion as: - // - // state = H::combine(std::move(state), value1); - // state = H::combine(std::move(state), value2); - // state = H::combine(std::move(state), value3); - template <typename T, typename... Ts> - static H combine(H state, const T& value, const Ts&... values); - static H combine(H state) { return state; } - - // HashStateBase::combine_contiguous() - // - // Combines a contiguous array of `size` elements into a hash state, returning - // the updated state. - // - // NOTE: - // - // state = H::combine_contiguous(std::move(state), data, size); - // - // is NOT guaranteed to produce the same hash expansion as a for-loop (it may - // perform internal optimizations). If you need this guarantee, use the - // for-loop instead. - template <typename T> - static H combine_contiguous(H state, const T* data, size_t size); - - using AbslInternalPiecewiseCombiner = PiecewiseCombiner; -}; - -// is_uniquely_represented -// -// `is_uniquely_represented<T>` is a trait class that indicates whether `T` -// is uniquely represented. -// -// A type is "uniquely represented" if two equal values of that type are -// guaranteed to have the same bytes in their underlying storage. In other -// words, if `a == b`, then `memcmp(&a, &b, sizeof(T))` is guaranteed to be -// zero. This property cannot be detected automatically, so this trait is false -// by default, but can be specialized by types that wish to assert that they are -// uniquely represented. This makes them eligible for certain optimizations. -// -// If you have any doubt whatsoever, do not specialize this template. -// The default is completely safe, and merely disables some optimizations -// that will not matter for most types. Specializing this template, -// on the other hand, can be very hazardous. -// -// To be uniquely represented, a type must not have multiple ways of -// representing the same value; for example, float and double are not -// uniquely represented, because they have distinct representations for -// +0 and -0. Furthermore, the type's byte representation must consist -// solely of user-controlled data, with no padding bits and no compiler- -// controlled data such as vptrs or sanitizer metadata. This is usually -// very difficult to guarantee, because in most cases the compiler can -// insert data and padding bits at its own discretion. -// -// If you specialize this template for a type `T`, you must do so in the file -// that defines that type (or in this file). If you define that specialization -// anywhere else, `is_uniquely_represented<T>` could have different meanings -// in different places. -// -// The Enable parameter is meaningless; it is provided as a convenience, -// to support certain SFINAE techniques when defining specializations. -template <typename T, typename Enable = void> -struct is_uniquely_represented : std::false_type {}; - -// is_uniquely_represented<unsigned char> -// -// unsigned char is a synonym for "byte", so it is guaranteed to be -// uniquely represented. -template <> -struct is_uniquely_represented<unsigned char> : std::true_type {}; - -// is_uniquely_represented for non-standard integral types -// -// Integral types other than bool should be uniquely represented on any -// platform that this will plausibly be ported to. -template <typename Integral> -struct is_uniquely_represented< - Integral, typename std::enable_if<std::is_integral<Integral>::value>::type> - : std::true_type {}; - -// is_uniquely_represented<bool> -// -// -template <> -struct is_uniquely_represented<bool> : std::false_type {}; - -// hash_bytes() -// -// Convenience function that combines `hash_state` with the byte representation -// of `value`. -template <typename H, typename T> -H hash_bytes(H hash_state, const T& value) { - const unsigned char* start = reinterpret_cast<const unsigned char*>(&value); - return H::combine_contiguous(std::move(hash_state), start, sizeof(value)); -} - -// ----------------------------------------------------------------------------- -// AbslHashValue for Basic Types -// ----------------------------------------------------------------------------- - -// Note: Default `AbslHashValue` implementations live in `hash_internal`. This -// allows us to block lexical scope lookup when doing an unqualified call to -// `AbslHashValue` below. User-defined implementations of `AbslHashValue` can -// only be found via ADL. - -// AbslHashValue() for hashing bool values -// -// We use SFINAE to ensure that this overload only accepts bool, not types that -// are convertible to bool. -template <typename H, typename B> -typename std::enable_if<std::is_same<B, bool>::value, H>::type AbslHashValue( - H hash_state, B value) { - return H::combine(std::move(hash_state), - static_cast<unsigned char>(value ? 1 : 0)); -} - -// AbslHashValue() for hashing enum values -template <typename H, typename Enum> -typename std::enable_if<std::is_enum<Enum>::value, H>::type AbslHashValue( - H hash_state, Enum e) { - // In practice, we could almost certainly just invoke hash_bytes directly, - // but it's possible that a sanitizer might one day want to - // store data in the unused bits of an enum. To avoid that risk, we - // convert to the underlying type before hashing. Hopefully this will get - // optimized away; if not, we can reopen discussion with c-toolchain-team. - return H::combine(std::move(hash_state), - static_cast<typename std::underlying_type<Enum>::type>(e)); -} -// AbslHashValue() for hashing floating-point values -template <typename H, typename Float> -typename std::enable_if<std::is_same<Float, float>::value || - std::is_same<Float, double>::value, - H>::type -AbslHashValue(H hash_state, Float value) { - return hash_internal::hash_bytes(std::move(hash_state), - value == 0 ? 0 : value); -} - -// Long double has the property that it might have extra unused bytes in it. -// For example, in x86 sizeof(long double)==16 but it only really uses 80-bits -// of it. This means we can't use hash_bytes on a long double and have to -// convert it to something else first. -template <typename H, typename LongDouble> -typename std::enable_if<std::is_same<LongDouble, long double>::value, H>::type -AbslHashValue(H hash_state, LongDouble value) { - const int category = std::fpclassify(value); - switch (category) { - case FP_INFINITE: - // Add the sign bit to differentiate between +Inf and -Inf - hash_state = H::combine(std::move(hash_state), std::signbit(value)); - break; - - case FP_NAN: - case FP_ZERO: - default: - // Category is enough for these. - break; - - case FP_NORMAL: - case FP_SUBNORMAL: - // We can't convert `value` directly to double because this would have - // undefined behavior if the value is out of range. - // std::frexp gives us a value in the range (-1, -.5] or [.5, 1) that is - // guaranteed to be in range for `double`. The truncation is - // implementation defined, but that works as long as it is deterministic. - int exp; - auto mantissa = static_cast<double>(std::frexp(value, &exp)); - hash_state = H::combine(std::move(hash_state), mantissa, exp); - } - - return H::combine(std::move(hash_state), category); -} - -// AbslHashValue() for hashing pointers -template <typename H, typename T> -H AbslHashValue(H hash_state, T* ptr) { - auto v = reinterpret_cast<uintptr_t>(ptr); - // Due to alignment, pointers tend to have low bits as zero, and the next few - // bits follow a pattern since they are also multiples of some base value. - // Mixing the pointer twice helps prevent stuck low bits for certain alignment - // values. - return H::combine(std::move(hash_state), v, v); -} - -// AbslHashValue() for hashing nullptr_t -template <typename H> -H AbslHashValue(H hash_state, std::nullptr_t) { - return H::combine(std::move(hash_state), static_cast<void*>(nullptr)); -} - -// ----------------------------------------------------------------------------- -// AbslHashValue for Composite Types -// ----------------------------------------------------------------------------- - -// is_hashable() -// -// Trait class which returns true if T is hashable by the absl::Hash framework. -// Used for the AbslHashValue implementations for composite types below. -template <typename T> -struct is_hashable; - -// AbslHashValue() for hashing pairs -template <typename H, typename T1, typename T2> -typename std::enable_if<is_hashable<T1>::value && is_hashable<T2>::value, - H>::type -AbslHashValue(H hash_state, const std::pair<T1, T2>& p) { - return H::combine(std::move(hash_state), p.first, p.second); -} - -// hash_tuple() -// -// Helper function for hashing a tuple. The third argument should -// be an index_sequence running from 0 to tuple_size<Tuple> - 1. -template <typename H, typename Tuple, size_t... Is> -H hash_tuple(H hash_state, const Tuple& t, absl::index_sequence<Is...>) { - return H::combine(std::move(hash_state), std::get<Is>(t)...); -} - -// AbslHashValue for hashing tuples -template <typename H, typename... Ts> -#if defined(_MSC_VER) -// This SFINAE gets MSVC confused under some conditions. Let's just disable it -// for now. -H -#else // _MSC_VER -typename std::enable_if<absl::conjunction<is_hashable<Ts>...>::value, H>::type -#endif // _MSC_VER -AbslHashValue(H hash_state, const std::tuple<Ts...>& t) { - return hash_internal::hash_tuple(std::move(hash_state), t, - absl::make_index_sequence<sizeof...(Ts)>()); -} - -// ----------------------------------------------------------------------------- -// AbslHashValue for Pointers -// ----------------------------------------------------------------------------- - -// AbslHashValue for hashing unique_ptr -template <typename H, typename T, typename D> -H AbslHashValue(H hash_state, const std::unique_ptr<T, D>& ptr) { - return H::combine(std::move(hash_state), ptr.get()); -} - -// AbslHashValue for hashing shared_ptr -template <typename H, typename T> -H AbslHashValue(H hash_state, const std::shared_ptr<T>& ptr) { - return H::combine(std::move(hash_state), ptr.get()); -} - -// ----------------------------------------------------------------------------- -// AbslHashValue for String-Like Types -// ----------------------------------------------------------------------------- - -// AbslHashValue for hashing strings -// -// All the string-like types supported here provide the same hash expansion for -// the same character sequence. These types are: -// -// - `absl::Cord` -// - `std::string` (and std::basic_string<char, std::char_traits<char>, A> for -// any allocator A) -// - `absl::string_view` and `std::string_view` -// -// For simplicity, we currently support only `char` strings. This support may -// be broadened, if necessary, but with some caution - this overload would -// misbehave in cases where the traits' `eq()` member isn't equivalent to `==` -// on the underlying character type. -template <typename H> -H AbslHashValue(H hash_state, absl::string_view str) { - return H::combine( - H::combine_contiguous(std::move(hash_state), str.data(), str.size()), - str.size()); -} - -// Support std::wstring, std::u16string and std::u32string. -template <typename Char, typename Alloc, typename H, - typename = absl::enable_if_t<std::is_same<Char, wchar_t>::value || - std::is_same<Char, char16_t>::value || - std::is_same<Char, char32_t>::value>> -H AbslHashValue( - H hash_state, - const std::basic_string<Char, std::char_traits<Char>, Alloc>& str) { - return H::combine( - H::combine_contiguous(std::move(hash_state), str.data(), str.size()), - str.size()); -} - -// ----------------------------------------------------------------------------- -// AbslHashValue for Sequence Containers -// ----------------------------------------------------------------------------- - -// AbslHashValue for hashing std::array -template <typename H, typename T, size_t N> -typename std::enable_if<is_hashable<T>::value, H>::type AbslHashValue( - H hash_state, const std::array<T, N>& array) { - return H::combine_contiguous(std::move(hash_state), array.data(), - array.size()); -} - -// AbslHashValue for hashing std::deque -template <typename H, typename T, typename Allocator> -typename std::enable_if<is_hashable<T>::value, H>::type AbslHashValue( - H hash_state, const std::deque<T, Allocator>& deque) { - // TODO(gromer): investigate a more efficient implementation taking - // advantage of the chunk structure. - for (const auto& t : deque) { - hash_state = H::combine(std::move(hash_state), t); - } - return H::combine(std::move(hash_state), deque.size()); -} - -// AbslHashValue for hashing std::forward_list -template <typename H, typename T, typename Allocator> -typename std::enable_if<is_hashable<T>::value, H>::type AbslHashValue( - H hash_state, const std::forward_list<T, Allocator>& list) { - size_t size = 0; - for (const T& t : list) { - hash_state = H::combine(std::move(hash_state), t); - ++size; - } - return H::combine(std::move(hash_state), size); -} - -// AbslHashValue for hashing std::list -template <typename H, typename T, typename Allocator> -typename std::enable_if<is_hashable<T>::value, H>::type AbslHashValue( - H hash_state, const std::list<T, Allocator>& list) { - for (const auto& t : list) { - hash_state = H::combine(std::move(hash_state), t); - } - return H::combine(std::move(hash_state), list.size()); -} - -// AbslHashValue for hashing std::vector -// -// Do not use this for vector<bool>. It does not have a .data(), and a fallback -// for std::hash<> is most likely faster. -template <typename H, typename T, typename Allocator> -typename std::enable_if<is_hashable<T>::value && !std::is_same<T, bool>::value, - H>::type -AbslHashValue(H hash_state, const std::vector<T, Allocator>& vector) { - return H::combine(H::combine_contiguous(std::move(hash_state), vector.data(), - vector.size()), - vector.size()); -} - -// ----------------------------------------------------------------------------- -// AbslHashValue for Ordered Associative Containers -// ----------------------------------------------------------------------------- - -// AbslHashValue for hashing std::map -template <typename H, typename Key, typename T, typename Compare, - typename Allocator> -typename std::enable_if<is_hashable<Key>::value && is_hashable<T>::value, - H>::type -AbslHashValue(H hash_state, const std::map<Key, T, Compare, Allocator>& map) { - for (const auto& t : map) { - hash_state = H::combine(std::move(hash_state), t); - } - return H::combine(std::move(hash_state), map.size()); -} - -// AbslHashValue for hashing std::multimap -template <typename H, typename Key, typename T, typename Compare, - typename Allocator> -typename std::enable_if<is_hashable<Key>::value && is_hashable<T>::value, - H>::type -AbslHashValue(H hash_state, - const std::multimap<Key, T, Compare, Allocator>& map) { - for (const auto& t : map) { - hash_state = H::combine(std::move(hash_state), t); - } - return H::combine(std::move(hash_state), map.size()); -} - -// AbslHashValue for hashing std::set -template <typename H, typename Key, typename Compare, typename Allocator> -typename std::enable_if<is_hashable<Key>::value, H>::type AbslHashValue( - H hash_state, const std::set<Key, Compare, Allocator>& set) { - for (const auto& t : set) { - hash_state = H::combine(std::move(hash_state), t); - } - return H::combine(std::move(hash_state), set.size()); -} - -// AbslHashValue for hashing std::multiset -template <typename H, typename Key, typename Compare, typename Allocator> -typename std::enable_if<is_hashable<Key>::value, H>::type AbslHashValue( - H hash_state, const std::multiset<Key, Compare, Allocator>& set) { - for (const auto& t : set) { - hash_state = H::combine(std::move(hash_state), t); - } - return H::combine(std::move(hash_state), set.size()); -} - -// ----------------------------------------------------------------------------- -// AbslHashValue for Wrapper Types -// ----------------------------------------------------------------------------- - -// AbslHashValue for hashing std::reference_wrapper -template <typename H, typename T> -typename std::enable_if<is_hashable<T>::value, H>::type AbslHashValue( - H hash_state, std::reference_wrapper<T> opt) { - return H::combine(std::move(hash_state), opt.get()); -} - -// AbslHashValue for hashing absl::optional -template <typename H, typename T> -typename std::enable_if<is_hashable<T>::value, H>::type AbslHashValue( - H hash_state, const absl::optional<T>& opt) { - if (opt) hash_state = H::combine(std::move(hash_state), *opt); - return H::combine(std::move(hash_state), opt.has_value()); -} - -// VariantVisitor -template <typename H> -struct VariantVisitor { - H&& hash_state; - template <typename T> - H operator()(const T& t) const { - return H::combine(std::move(hash_state), t); - } -}; - -// AbslHashValue for hashing absl::variant -template <typename H, typename... T> -typename std::enable_if<conjunction<is_hashable<T>...>::value, H>::type -AbslHashValue(H hash_state, const absl::variant<T...>& v) { - if (!v.valueless_by_exception()) { - hash_state = absl::visit(VariantVisitor<H>{std::move(hash_state)}, v); - } - return H::combine(std::move(hash_state), v.index()); -} - -// ----------------------------------------------------------------------------- -// AbslHashValue for Other Types -// ----------------------------------------------------------------------------- - -// AbslHashValue for hashing std::bitset is not defined, for the same reason as -// for vector<bool> (see std::vector above): It does not expose the raw bytes, -// and a fallback to std::hash<> is most likely faster. - -// ----------------------------------------------------------------------------- - -// hash_range_or_bytes() -// -// Mixes all values in the range [data, data+size) into the hash state. -// This overload accepts only uniquely-represented types, and hashes them by -// hashing the entire range of bytes. -template <typename H, typename T> -typename std::enable_if<is_uniquely_represented<T>::value, H>::type -hash_range_or_bytes(H hash_state, const T* data, size_t size) { - const auto* bytes = reinterpret_cast<const unsigned char*>(data); - return H::combine_contiguous(std::move(hash_state), bytes, sizeof(T) * size); -} - -// hash_range_or_bytes() -template <typename H, typename T> -typename std::enable_if<!is_uniquely_represented<T>::value, H>::type -hash_range_or_bytes(H hash_state, const T* data, size_t size) { - for (const auto end = data + size; data < end; ++data) { - hash_state = H::combine(std::move(hash_state), *data); - } - return hash_state; -} - -#if defined(ABSL_INTERNAL_LEGACY_HASH_NAMESPACE) && \ - ABSL_META_INTERNAL_STD_HASH_SFINAE_FRIENDLY_ -#define ABSL_HASH_INTERNAL_SUPPORT_LEGACY_HASH_ 1 -#else -#define ABSL_HASH_INTERNAL_SUPPORT_LEGACY_HASH_ 0 -#endif - -// HashSelect -// -// Type trait to select the appropriate hash implementation to use. -// HashSelect::type<T> will give the proper hash implementation, to be invoked -// as: -// HashSelect::type<T>::Invoke(state, value) -// Also, HashSelect::type<T>::value is a boolean equal to `true` if there is a -// valid `Invoke` function. Types that are not hashable will have a ::value of -// `false`. -struct HashSelect { - private: - struct State : HashStateBase<State> { - static State combine_contiguous(State hash_state, const unsigned char*, - size_t); - using State::HashStateBase::combine_contiguous; - }; - - struct UniquelyRepresentedProbe { - template <typename H, typename T> - static auto Invoke(H state, const T& value) - -> absl::enable_if_t<is_uniquely_represented<T>::value, H> { - return hash_internal::hash_bytes(std::move(state), value); - } - }; - - struct HashValueProbe { - template <typename H, typename T> - static auto Invoke(H state, const T& value) -> absl::enable_if_t< - std::is_same<H, - decltype(AbslHashValue(std::move(state), value))>::value, - H> { - return AbslHashValue(std::move(state), value); - } - }; - - struct LegacyHashProbe { -#if ABSL_HASH_INTERNAL_SUPPORT_LEGACY_HASH_ - template <typename H, typename T> - static auto Invoke(H state, const T& value) -> absl::enable_if_t< - std::is_convertible< - decltype(ABSL_INTERNAL_LEGACY_HASH_NAMESPACE::hash<T>()(value)), - size_t>::value, - H> { - return hash_internal::hash_bytes( - std::move(state), - ABSL_INTERNAL_LEGACY_HASH_NAMESPACE::hash<T>{}(value)); - } -#endif // ABSL_HASH_INTERNAL_SUPPORT_LEGACY_HASH_ - }; - - struct StdHashProbe { - template <typename H, typename T> - static auto Invoke(H state, const T& value) - -> absl::enable_if_t<type_traits_internal::IsHashable<T>::value, H> { - return hash_internal::hash_bytes(std::move(state), std::hash<T>{}(value)); - } - }; - - template <typename Hash, typename T> - struct Probe : Hash { - private: - template <typename H, typename = decltype(H::Invoke( - std::declval<State>(), std::declval<const T&>()))> - static std::true_type Test(int); - template <typename U> - static std::false_type Test(char); - - public: - static constexpr bool value = decltype(Test<Hash>(0))::value; - }; - - public: - // Probe each implementation in order. - // disjunction provides short circuiting wrt instantiation. - template <typename T> - using Apply = absl::disjunction< // - Probe<UniquelyRepresentedProbe, T>, // - Probe<HashValueProbe, T>, // - Probe<LegacyHashProbe, T>, // - Probe<StdHashProbe, T>, // - std::false_type>; -}; - -template <typename T> -struct is_hashable - : std::integral_constant<bool, HashSelect::template Apply<T>::value> {}; - -// CityHashState -class ABSL_DLL CityHashState - : public HashStateBase<CityHashState> { - // absl::uint128 is not an alias or a thin wrapper around the intrinsic. - // We use the intrinsic when available to improve performance. -#ifdef ABSL_HAVE_INTRINSIC_INT128 - using uint128 = __uint128_t; -#else // ABSL_HAVE_INTRINSIC_INT128 - using uint128 = absl::uint128; -#endif // ABSL_HAVE_INTRINSIC_INT128 - - static constexpr uint64_t kMul = - sizeof(size_t) == 4 ? uint64_t{0xcc9e2d51} - : uint64_t{0x9ddfea08eb382d69}; - - template <typename T> - using IntegralFastPath = - conjunction<std::is_integral<T>, is_uniquely_represented<T>>; - - public: - // Move only - CityHashState(CityHashState&&) = default; - CityHashState& operator=(CityHashState&&) = default; - - // CityHashState::combine_contiguous() - // - // Fundamental base case for hash recursion: mixes the given range of bytes - // into the hash state. - static CityHashState combine_contiguous(CityHashState hash_state, - const unsigned char* first, - size_t size) { - return CityHashState( - CombineContiguousImpl(hash_state.state_, first, size, - std::integral_constant<int, sizeof(size_t)>{})); - } - using CityHashState::HashStateBase::combine_contiguous; - - // CityHashState::hash() - // - // For performance reasons in non-opt mode, we specialize this for - // integral types. - // Otherwise we would be instantiating and calling dozens of functions for - // something that is just one multiplication and a couple xor's. - // The result should be the same as running the whole algorithm, but faster. - template <typename T, absl::enable_if_t<IntegralFastPath<T>::value, int> = 0> - static size_t hash(T value) { - return static_cast<size_t>(Mix(Seed(), static_cast<uint64_t>(value))); - } - - // Overload of CityHashState::hash() - template <typename T, absl::enable_if_t<!IntegralFastPath<T>::value, int> = 0> - static size_t hash(const T& value) { - return static_cast<size_t>(combine(CityHashState{}, value).state_); - } - - private: - // Invoked only once for a given argument; that plus the fact that this is - // move-only ensures that there is only one non-moved-from object. - CityHashState() : state_(Seed()) {} - - // Workaround for MSVC bug. - // We make the type copyable to fix the calling convention, even though we - // never actually copy it. Keep it private to not affect the public API of the - // type. - CityHashState(const CityHashState&) = default; - - explicit CityHashState(uint64_t state) : state_(state) {} - - // Implementation of the base case for combine_contiguous where we actually - // mix the bytes into the state. - // Dispatch to different implementations of the combine_contiguous depending - // on the value of `sizeof(size_t)`. - static uint64_t CombineContiguousImpl(uint64_t state, - const unsigned char* first, size_t len, - std::integral_constant<int, 4> - /* sizeof_size_t */); - static uint64_t CombineContiguousImpl(uint64_t state, - const unsigned char* first, size_t len, - std::integral_constant<int, 8> - /* sizeof_size_t*/); - - // Slow dispatch path for calls to CombineContiguousImpl with a size argument - // larger than PiecewiseChunkSize(). Has the same effect as calling - // CombineContiguousImpl() repeatedly with the chunk stride size. - static uint64_t CombineLargeContiguousImpl32(uint64_t state, - const unsigned char* first, - size_t len); - static uint64_t CombineLargeContiguousImpl64(uint64_t state, - const unsigned char* first, - size_t len); - - // Reads 9 to 16 bytes from p. - // The first 8 bytes are in .first, the rest (zero padded) bytes are in - // .second. - static std::pair<uint64_t, uint64_t> Read9To16(const unsigned char* p, - size_t len) { - uint64_t high = little_endian::Load64(p + len - 8); - return {little_endian::Load64(p), high >> (128 - len * 8)}; - } - - // Reads 4 to 8 bytes from p. Zero pads to fill uint64_t. - static uint64_t Read4To8(const unsigned char* p, size_t len) { - return (static_cast<uint64_t>(little_endian::Load32(p + len - 4)) - << (len - 4) * 8) | - little_endian::Load32(p); - } - - // Reads 1 to 3 bytes from p. Zero pads to fill uint32_t. - static uint32_t Read1To3(const unsigned char* p, size_t len) { - return static_cast<uint32_t>((p[0]) | // - (p[len / 2] << (len / 2 * 8)) | // - (p[len - 1] << ((len - 1) * 8))); - } - - ABSL_ATTRIBUTE_ALWAYS_INLINE static uint64_t Mix(uint64_t state, uint64_t v) { - using MultType = - absl::conditional_t<sizeof(size_t) == 4, uint64_t, uint128>; - // We do the addition in 64-bit space to make sure the 128-bit - // multiplication is fast. If we were to do it as MultType the compiler has - // to assume that the high word is non-zero and needs to perform 2 - // multiplications instead of one. - MultType m = state + v; - m *= kMul; - return static_cast<uint64_t>(m ^ (m >> (sizeof(m) * 8 / 2))); - } - - // Seed() - // - // A non-deterministic seed. - // - // The current purpose of this seed is to generate non-deterministic results - // and prevent having users depend on the particular hash values. - // It is not meant as a security feature right now, but it leaves the door - // open to upgrade it to a true per-process random seed. A true random seed - // costs more and we don't need to pay for that right now. - // - // On platforms with ASLR, we take advantage of it to make a per-process - // random value. - // See https://en.wikipedia.org/wiki/Address_space_layout_randomization - // - // On other platforms this is still going to be non-deterministic but most - // probably per-build and not per-process. - ABSL_ATTRIBUTE_ALWAYS_INLINE static uint64_t Seed() { -#if (!defined(__clang__) || __clang_major__ > 11) && \ - !defined(__apple_build_version__) - return static_cast<uint64_t>(reinterpret_cast<uintptr_t>(&kSeed)); -#else - // Workaround the absence of - // https://github.com/llvm/llvm-project/commit/bc15bf66dcca76cc06fe71fca35b74dc4d521021. - return static_cast<uint64_t>(reinterpret_cast<uintptr_t>(kSeed)); -#endif - } - static const void* const kSeed; - - uint64_t state_; -}; - -// CityHashState::CombineContiguousImpl() -inline uint64_t CityHashState::CombineContiguousImpl( - uint64_t state, const unsigned char* first, size_t len, - std::integral_constant<int, 4> /* sizeof_size_t */) { - // For large values we use CityHash, for small ones we just use a - // multiplicative hash. - uint64_t v; - if (len > 8) { - if (ABSL_PREDICT_FALSE(len > PiecewiseChunkSize())) { - return CombineLargeContiguousImpl32(state, first, len); - } - v = absl::hash_internal::CityHash32(reinterpret_cast<const char*>(first), len); - } else if (len >= 4) { - v = Read4To8(first, len); - } else if (len > 0) { - v = Read1To3(first, len); - } else { - // Empty ranges have no effect. - return state; - } - return Mix(state, v); -} - -// Overload of CityHashState::CombineContiguousImpl() -inline uint64_t CityHashState::CombineContiguousImpl( - uint64_t state, const unsigned char* first, size_t len, - std::integral_constant<int, 8> /* sizeof_size_t */) { - // For large values we use CityHash, for small ones we just use a - // multiplicative hash. - uint64_t v; - if (len > 16) { - if (ABSL_PREDICT_FALSE(len > PiecewiseChunkSize())) { - return CombineLargeContiguousImpl64(state, first, len); - } - v = absl::hash_internal::CityHash64(reinterpret_cast<const char*>(first), len); - } else if (len > 8) { - auto p = Read9To16(first, len); - state = Mix(state, p.first); - v = p.second; - } else if (len >= 4) { - v = Read4To8(first, len); - } else if (len > 0) { - v = Read1To3(first, len); - } else { - // Empty ranges have no effect. - return state; - } - return Mix(state, v); -} - -struct AggregateBarrier {}; - -// HashImpl - -// Add a private base class to make sure this type is not an aggregate. -// Aggregates can be aggregate initialized even if the default constructor is -// deleted. -struct PoisonedHash : private AggregateBarrier { - PoisonedHash() = delete; - PoisonedHash(const PoisonedHash&) = delete; - PoisonedHash& operator=(const PoisonedHash&) = delete; -}; - -template <typename T> -struct HashImpl { - size_t operator()(const T& value) const { return CityHashState::hash(value); } -}; - -template <typename T> -struct Hash - : absl::conditional_t<is_hashable<T>::value, HashImpl<T>, PoisonedHash> {}; - -template <typename H> -template <typename T, typename... Ts> -H HashStateBase<H>::combine(H state, const T& value, const Ts&... values) { - return H::combine(hash_internal::HashSelect::template Apply<T>::Invoke( - std::move(state), value), - values...); -} - -// HashStateBase::combine_contiguous() -template <typename H> -template <typename T> -H HashStateBase<H>::combine_contiguous(H state, const T* data, size_t size) { - return hash_internal::hash_range_or_bytes(std::move(state), data, size); -} - -// HashStateBase::PiecewiseCombiner::add_buffer() -template <typename H> -H PiecewiseCombiner::add_buffer(H state, const unsigned char* data, - size_t size) { - if (position_ + size < PiecewiseChunkSize()) { - // This partial chunk does not fill our existing buffer - memcpy(buf_ + position_, data, size); - position_ += size; - return state; - } - - // If the buffer is partially filled we need to complete the buffer - // and hash it. - if (position_ != 0) { - const size_t bytes_needed = PiecewiseChunkSize() - position_; - memcpy(buf_ + position_, data, bytes_needed); - state = H::combine_contiguous(std::move(state), buf_, PiecewiseChunkSize()); - data += bytes_needed; - size -= bytes_needed; - } - - // Hash whatever chunks we can without copying - while (size >= PiecewiseChunkSize()) { - state = H::combine_contiguous(std::move(state), data, PiecewiseChunkSize()); - data += PiecewiseChunkSize(); - size -= PiecewiseChunkSize(); - } - // Fill the buffer with the remainder - memcpy(buf_, data, size); - position_ = size; - return state; -} - -// HashStateBase::PiecewiseCombiner::finalize() -template <typename H> -H PiecewiseCombiner::finalize(H state) { - // Hash the remainder left in the buffer, which may be empty - return H::combine_contiguous(std::move(state), buf_, position_); -} - -} // namespace hash_internal -ABSL_NAMESPACE_END -} // namespace absl - -#endif // ABSL_HASH_INTERNAL_HASH_H_ |