// 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_

#ifdef __APPLE__

#include <Availability.h>

#include <TargetConditionals.h>

#endif

// We include config.h here to make sure that ABSL_INTERNAL_CPLUSPLUS_LANG is

// defined.

#include "absl/base/config.h"

// GCC15 warns that <ciso646> is deprecated in C++17 and suggests using

// <version> instead, even though <version> is not available in C++17 mode prior

// to GCC9.

#if defined(__has_include)

#if __has_include(<version>)

#define ABSL_INTERNAL_VERSION_HEADER_AVAILABLE 1

#endif

#endif

// For feature testing and determining which headers can be included.

#if ABSL_INTERNAL_CPLUSPLUS_LANG >= 202002L || \

    defined(ABSL_INTERNAL_VERSION_HEADER_AVAILABLE)

#include <version>

#else

#include <ciso646>

#endif

#undef ABSL_INTERNAL_VERSION_HEADER_AVAILABLE

#include <algorithm>

#include <array>

#include <bitset>

#include <cassert>

#include <cmath>

#include <cstddef>

#include <cstdint>

#include <cstring>

#include <deque>

#include <forward_list>

#include <functional>

#include <iterator>

#include <limits>

#include <list>

#include <map>

#include <memory>

#include <set>

#include <string>

#include <string_view>

#include <tuple>

#include <type_traits>

#include <unordered_map>

#include <unordered_set>

#include <utility>

#include <vector>

#include "absl/base/attributes.h"

#include "absl/base/internal/unaligned_access.h"

#include "absl/base/optimization.h"

#include "absl/base/port.h"

#include "absl/container/fixed_array.h"

#include "absl/hash/internal/city.h"

#include "absl/hash/internal/weakly_mixed_integer.h"

#include "absl/meta/type_traits.h"

#include "absl/numeric/bits.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"

#if defined(__cpp_lib_filesystem) && __cpp_lib_filesystem >= 201703L && \

    !defined(__XTENSA__)

#include <filesystem>  // NOLINT

#endif

namespace absl {

ABSL_NAMESPACE_BEGIN

class HashState;

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 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() = default;

  PiecewiseCombiner(const PiecewiseCombiner&) = delete;

  PiecewiseCombiner& operator=(const PiecewiseCombiner&) = delete;

  // 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);

  }

  // 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_ = 0;

  bool added_something_ = false;

};

// 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;

// HashStateBase is an internal implementation detail that contains common

// implementation details for all of the "hash state objects" objects generated

// by Abseil.  This is not a public API; users should not create classes that

// inherit from this.

//

// A hash state object is the template argument `H` passed to `AbslHashValue`.

// It 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()

//   * HashStateBase::combine_unordered()

//

// A derived hash state class of type `H` must provide a public member function

// with a signature similar to the following:

//

//    `static H combine_contiguous(H state, const unsigned char*, size_t)`.

//

// It must also provide a private template method named RunCombineUnordered.

//

// A "consumer" is a 1-arg functor returning void.  Its argument is a reference

// to an inner hash state object, and it may be called multiple times.  When

// called, the functor consumes the entropy from the provided state object,

// and resets that object to its empty state.

//

// A "combiner" is a stateless 2-arg functor returning void.  Its arguments are

// an inner hash state object and an ElementStateConsumer functor.  A combiner

// uses the provided inner hash state object to hash each element of the

// container, passing the inner hash state object to the consumer after hashing

// each element.

//

// Given these definitions, a derived hash state class of type H

// must provide a private template method with a signature similar to the

// following:

//

//    `template <typename CombinerT>`

//    `static H RunCombineUnordered(H outer_state, CombinerT combiner)`

//

// This function is responsible for constructing the inner state object and

// providing a consumer to the combiner.  It uses side effects of the consumer

// and combiner to mix the state of each element in an order-independent manner,

// and uses this to return an updated value of `outer_state`.

//

// This inside-out approach generates efficient object code in the normal case,

// but allows us to use stack storage to implement the absl::HashState type

// erasure mechanism (avoiding heap allocations while hashing).

//

// `HashStateBase` will provide a complete implementation for a hash state

// object in terms of these two methods.

//

// 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;

//       using MyHashState::HashStateBase::combine_unordered;

//     private:

//       template <typename CombinerT>

//       static H RunCombineUnordered(H state, CombinerT combiner);

//   };

template <typename H>

class HashStateBase {

 public:

  // 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; }

  // 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);

  template <typename I>

  static H combine_unordered(H state, I begin, I end);

  using AbslInternalPiecewiseCombiner = PiecewiseCombiner;

  template <typename T>

  using is_hashable = absl::hash_internal::is_hashable<T>;

 private:

  // Common implementation of the iteration step of a "combiner", as described

  // above.

  template <typename I>

  struct CombineUnorderedCallback {

    I begin;

    I end;

    template <typename InnerH, typename ElementStateConsumer>

    void operator()(InnerH inner_state, ElementStateConsumer cb) {

      for (; begin != end; ++begin) {

        inner_state = H::combine(std::move(inner_state), *begin);

        cb(inner_state);

      }

    }

  };

};

// `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 {};

// 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 {};

template <>

struct is_uniquely_represented<bool> : std::false_type {};

#ifdef ABSL_HAVE_INTRINSIC_INT128

// Specialize the trait for GNU extension types.

template <>

struct is_uniquely_represented<__int128> : std::true_type {};

template <>

struct is_uniquely_represented<unsigned __int128> : std::true_type {};

#endif  // ABSL_HAVE_INTRINSIC_INT128

template <typename T>

struct FitsIn64Bits : std::integral_constant<bool, sizeof(T) <= 8> {};

struct CombineRaw {

  template <typename H>

  H operator()(H state, uint64_t value) const {

    return H::combine_raw(std::move(state), value);

  }

};

// For use in `raw_hash_set` to pass a seed to the hash function.

struct HashWithSeed {

  template <typename Hasher, typename T>

  size_t hash(const Hasher& hasher, const T& value, size_t seed) const {

    // NOLINTNEXTLINE(clang-diagnostic-sign-conversion)

    return hasher.hash_with_seed(value, seed);

  }

unsigned long absl::hash_internal::HashWithSeed::hash<absl::container_internal::StringHash, std::__1::basic_string_view<char, std::__1::char_traits<char> > >(absl::container_internal::StringHash const&, std::__1::basic_string_view<char, std::__1::char_traits<char> > const&, unsigned long) const

Line

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Source

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  size_t hash(const Hasher& hasher, const T& value, size_t seed) const {

361

    // NOLINTNEXTLINE(clang-diagnostic-sign-conversion)

362

30

    return hasher.hash_with_seed(value, seed);

363

30

  }

unsigned long absl::hash_internal::HashWithSeed::hash<absl::hash_internal::Hash<std::__1::basic_string_view<char, std::__1::char_traits<char> > >, std::__1::basic_string_view<char, std::__1::char_traits<char> > >(absl::hash_internal::Hash<std::__1::basic_string_view<char, std::__1::char_traits<char> > > const&, std::__1::basic_string_view<char, std::__1::char_traits<char> > const&, unsigned long) const

Line

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Source

360

30

  size_t hash(const Hasher& hasher, const T& value, size_t seed) const {

361

    // NOLINTNEXTLINE(clang-diagnostic-sign-conversion)

362

30

    return hasher.hash_with_seed(value, seed);

363

30

  }

Unexecuted instantiation: unsigned long absl::hash_internal::HashWithSeed::hash<absl::hash_internal::Hash<absl::Cord>, absl::Cord>(absl::hash_internal::Hash<absl::Cord> const&, absl::Cord const&, unsigned long) const

};

// Convenience function that combines `hash_state` with the byte representation

// of `value`.

template <typename H, typename T,

          absl::enable_if_t<FitsIn64Bits<T>::value, int> = 0>

H hash_bytes(H hash_state, const T& value) {

  const unsigned char* start = reinterpret_cast<const unsigned char*>(&value);

  uint64_t v;

  if constexpr (sizeof(T) == 1) {

    v = *start;

  } else if constexpr (sizeof(T) == 2) {

    v = absl::base_internal::UnalignedLoad16(start);

  } else if constexpr (sizeof(T) == 4) {

    v = absl::base_internal::UnalignedLoad32(start);

  } else {

    static_assert(sizeof(T) == 8);

    v = absl::base_internal::UnalignedLoad64(start);

  }

  return CombineRaw()(std::move(hash_state), v);

}

Unexecuted instantiation: _ZN4absl13hash_internal10hash_bytesINS0_15MixingHashStateEmTnNSt3__19enable_ifIXsr12FitsIn64BitsIT0_EE5valueEiE4typeELi0EEET_S8_RKS5_

Unexecuted instantiation: _ZN4absl13hash_internal10hash_bytesINS0_15MixingHashStateEiTnNSt3__19enable_ifIXsr12FitsIn64BitsIT0_EE5valueEiE4typeELi0EEET_S8_RKS5_

template <typename H, typename T,

          absl::enable_if_t<!FitsIn64Bits<T>::value, int> = 0>

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));

}

template <typename H>

H hash_weakly_mixed_integer(H hash_state, WeaklyMixedInteger value) {

  return H::combine_weakly_mixed_integer(std::move(hash_state), 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) {

  // We use ~size_t{} instead of 1 so that all bits are different between

  // true/false instead of only 1.

  return H::combine(std::move(hash_state),

                    static_cast<size_t>(value ? ~size_t{} : 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);

}

// Without this overload, an array decays to a pointer and we hash that, which

// is not likely to be what the caller intended.

template <typename H, typename T, size_t N>

H AbslHashValue(H hash_state, T (&)[N]) {

  static_assert(

      sizeof(T) == -1,

      "Hashing C arrays is not allowed. For string literals, wrap the literal "

      "in absl::string_view(). To hash the array contents, use "

      "absl::MakeSpan() or make the array an std::array. To hash the array "

      "address, use &array[0].");

  return hash_state;

}

// AbslHashValue() for hashing pointers

template <typename H, typename T>

std::enable_if_t<std::is_pointer<T>::value, 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.

  // The PointerAlignment test verifies that our mixing is good enough to handle

  // these cases.

  return H::combine(std::move(hash_state), 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 hashing pointers-to-member

template <typename H, typename T, typename C>

H AbslHashValue(H hash_state, T C::*ptr) {

  auto salient_ptm_size = [](std::size_t n) -> std::size_t {

#if defined(_MSC_VER)

    // Pointers-to-member-function on MSVC consist of one pointer plus 0, 1, 2,

    // or 3 ints. In 64-bit mode, they are 8-byte aligned and thus can contain

    // padding (namely when they have 1 or 3 ints). The value below is a lower

    // bound on the number of salient, non-padding bytes that we use for

    // hashing.

    if constexpr (alignof(T C::*) == alignof(int)) {

      // No padding when all subobjects have the same size as the total

      // alignment. This happens in 32-bit mode.

      return n;

    } else {

      // Padding for 1 int (size 16) or 3 ints (size 24).

      // With 2 ints, the size is 16 with no padding, which we pessimize.

      return n == 24 ? 20 : n == 16 ? 12 : n;

    }

#else

  // On other platforms, we assume that pointers-to-members do not have

  // padding.

#ifdef __cpp_lib_has_unique_object_representations

    static_assert(std::has_unique_object_representations<T C::*>::value);

#endif  // __cpp_lib_has_unique_object_representations

    return n;

#endif

  };

  return H::combine_contiguous(std::move(hash_state),

                               reinterpret_cast<unsigned char*>(&ptr),

                               salient_ptm_size(sizeof ptr));

}

// -----------------------------------------------------------------------------

// AbslHashValue for Composite Types

// -----------------------------------------------------------------------------

// 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);

}

// 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)...);

}

Unexecuted instantiation: absl::hash_internal::MixingHashState absl::hash_internal::hash_tuple<absl::hash_internal::MixingHashState, std::__1::tuple<unsigned long const&>, 0ul>(absl::hash_internal::MixingHashState, std::__1::tuple<unsigned long const&> const&, std::__1::integer_sequence<unsigned long, 0ul>)

Unexecuted instantiation: absl::hash_internal::MixingHashState absl::hash_internal::hash_tuple<absl::hash_internal::MixingHashState, std::__1::tuple<std::__1::basic_string_view<char, std::__1::char_traits<char> > const&, int const&>, 0ul, 1ul>(absl::hash_internal::MixingHashState, std::__1::tuple<std::__1::basic_string_view<char, std::__1::char_traits<char> > const&, int const&> const&, std::__1::integer_sequence<unsigned long, 0ul, 1ul>)

// 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)>());

}

Unexecuted instantiation: _ZN4absl13hash_internal13AbslHashValueINS0_15MixingHashStateEJRKmEEENSt3__19enable_ifIXsr4absl11conjunctionIDpNS0_11is_hashableIT0_EEEE5valueET_E4typeESB_RKNS5_5tupleIJDpS8_EEE

Unexecuted instantiation: _ZN4absl13hash_internal13AbslHashValueINS0_15MixingHashStateEJRKNSt3__117basic_string_viewIcNS3_11char_traitsIcEEEERKiEEENS3_9enable_ifIXsr4absl11conjunctionIDpNS0_11is_hashableIT0_EEEE5valueET_E4typeESH_RKNS3_5tupleIJDpSE_EEE

// -----------------------------------------------------------------------------

// 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<T, std::char_traits<T>, A> for

//      any allocator A and any T in {char, wchar_t, char16_t, char32_t})

//  - `absl::string_view`, `std::string_view`, `std::wstring_view`,

//    `std::u16string_view`, and `std::u32_string_view`.

//

// For simplicity, we currently support only strings built on `char`, `wchar_t`,

// `char16_t`, or `char32_t`. 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_contiguous(std::move(hash_state), str.data(), 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_contiguous(std::move(hash_state), str.data(), str.size());

}

// Support std::wstring_view, std::u16string_view and std::u32string_view.

template <typename Char, 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, std::basic_string_view<Char> str) {

  return H::combine_contiguous(std::move(hash_state), str.data(), str.size());

}

#if defined(__cpp_lib_filesystem) && __cpp_lib_filesystem >= 201703L && \

    (!defined(__ENVIRONMENT_IPHONE_OS_VERSION_MIN_REQUIRED__) ||        \

     __ENVIRONMENT_IPHONE_OS_VERSION_MIN_REQUIRED__ >= 130000) &&       \

    (!defined(__ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__) ||         \

     __ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__ >= 101500) &&        \

    (!defined(__XTENSA__))

#define ABSL_INTERNAL_STD_FILESYSTEM_PATH_HASH_AVAILABLE 1

// Support std::filesystem::path. The SFINAE is required because some string

// types are implicitly convertible to std::filesystem::path.

template <typename Path, typename H,

          typename = absl::enable_if_t<

              std::is_same_v<Path, std::filesystem::path>>>

H AbslHashValue(H hash_state, const Path& path) {

  // This is implemented by deferring to the standard library to compute the

  // hash.  The standard library requires that for two paths, `p1 == p2`, then

  // `hash_value(p1) == hash_value(p2)`. `AbslHashValue` has the same

  // requirement. Since `operator==` does platform specific matching, deferring

  // to the standard library is the simplest approach.

  return H::combine(std::move(hash_state), std::filesystem::hash_value(path));

}

#endif  // ABSL_INTERNAL_STD_FILESYSTEM_PATH_HASH_AVAILABLE

// -----------------------------------------------------------------------------

// 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), WeaklyMixedInteger{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), WeaklyMixedInteger{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), WeaklyMixedInteger{list.size()});

}

// AbslHashValue for hashing std::vector

//

// Do not use this for vector<bool> on platforms that have a working

// implementation of std::hash. 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_contiguous(std::move(hash_state), vector.data(),

                               vector.size());

}

// AbslHashValue special cases for hashing std::vector<bool>

#if defined(ABSL_IS_BIG_ENDIAN) && \

    (defined(__GLIBCXX__) || defined(__GLIBCPP__))

// std::hash in libstdc++ does not work correctly with vector<bool> on Big

// Endian platforms therefore we need to implement a custom AbslHashValue for

// it. More details on the bug:

// https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102531

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) {

  typename H::AbslInternalPiecewiseCombiner combiner;

  for (const auto& i : vector) {

    unsigned char c = static_cast<unsigned char>(i);

    hash_state = combiner.add_buffer(std::move(hash_state), &c, sizeof(c));

  }

  return H::combine(combiner.finalize(std::move(hash_state)),

                    WeaklyMixedInteger{vector.size()});

}

#else

// When not working around the libstdc++ bug above, we still have to contend

// with the fact that std::hash<vector<bool>> is often poor quality, hashing

// directly on the internal words and on no other state.  On these platforms,

// vector<bool>{1, 1} and vector<bool>{1, 1, 0} hash to the same value.

//

// Mixing in the size (as we do in our other vector<> implementations) on top

// of the library-provided hash implementation avoids this QOI issue.

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(std::move(hash_state),

                    std::hash<std::vector<T, Allocator>>{}(vector),

                    WeaklyMixedInteger{vector.size()});

}

#endif

// -----------------------------------------------------------------------------

// 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), WeaklyMixedInteger{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), WeaklyMixedInteger{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), WeaklyMixedInteger{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), WeaklyMixedInteger{set.size()});

}

// -----------------------------------------------------------------------------

// AbslHashValue for Unordered Associative Containers

// -----------------------------------------------------------------------------

// AbslHashValue for hashing std::unordered_set

template <typename H, typename Key, typename Hash, typename KeyEqual,

          typename Alloc>

typename std::enable_if<is_hashable<Key>::value, H>::type AbslHashValue(

    H hash_state, const std::unordered_set<Key, Hash, KeyEqual, Alloc>& s) {

  return H::combine(

      H::combine_unordered(std::move(hash_state), s.begin(), s.end()),

      WeaklyMixedInteger{s.size()});

}

// AbslHashValue for hashing std::unordered_multiset

template <typename H, typename Key, typename Hash, typename KeyEqual,

          typename Alloc>

typename std::enable_if<is_hashable<Key>::value, H>::type AbslHashValue(

    H hash_state,

    const std::unordered_multiset<Key, Hash, KeyEqual, Alloc>& s) {

  return H::combine(

      H::combine_unordered(std::move(hash_state), s.begin(), s.end()),

      WeaklyMixedInteger{s.size()});

}

// AbslHashValue for hashing std::unordered_set

template <typename H, typename Key, typename T, typename Hash,

          typename KeyEqual, typename Alloc>

typename std::enable_if<is_hashable<Key>::value && is_hashable<T>::value,

                        H>::type

AbslHashValue(H hash_state,

              const std::unordered_map<Key, T, Hash, KeyEqual, Alloc>& s) {

  return H::combine(

      H::combine_unordered(std::move(hash_state), s.begin(), s.end()),

      WeaklyMixedInteger{s.size()});

}

// AbslHashValue for hashing std::unordered_multiset

template <typename H, typename Key, typename T, typename Hash,

          typename KeyEqual, typename Alloc>

typename std::enable_if<is_hashable<Key>::value && is_hashable<T>::value,

                        H>::type

AbslHashValue(H hash_state,

              const std::unordered_multimap<Key, T, Hash, KeyEqual, Alloc>& s) {

  return H::combine(

      H::combine_unordered(std::move(hash_state), s.begin(), s.end()),

      WeaklyMixedInteger{s.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());

}

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 on Little Endian

// platforms, 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.

#if defined(ABSL_IS_BIG_ENDIAN) && \

    (defined(__GLIBCXX__) || defined(__GLIBCPP__))

// AbslHashValue for hashing std::bitset

//

// std::hash in libstdc++ does not work correctly with std::bitset on Big Endian

// platforms therefore we need to implement a custom AbslHashValue for it. More

// details on the bug: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102531

template <typename H, size_t N>

H AbslHashValue(H hash_state, const std::bitset<N>& set) {

  typename H::AbslInternalPiecewiseCombiner combiner;

  for (size_t i = 0; i < N; i++) {

    unsigned char c = static_cast<unsigned char>(set[i]);

    hash_state = combiner.add_buffer(std::move(hash_state), &c, sizeof(c));

  }

  return H::combine(combiner.finalize(std::move(hash_state)), N);

}

#endif

// -----------------------------------------------------------------------------

// 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);

}

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 H::combine(std::move(hash_state),

                    hash_internal::WeaklyMixedInteger{size});

}

inline constexpr uint64_t kMul = uint64_t{0x79d5f9e0de1e8cf5};

// Random data taken from the hexadecimal digits of Pi's fractional component.

// https://en.wikipedia.org/wiki/Nothing-up-my-sleeve_number

ABSL_CACHELINE_ALIGNED inline constexpr uint64_t kStaticRandomData[] = {

    0x243f'6a88'85a3'08d3, 0x1319'8a2e'0370'7344, 0xa409'3822'299f'31d0,

    0x082e'fa98'ec4e'6c89, 0x4528'21e6'38d0'1377,

};

// Extremely weak mixture of length that is mixed into the state before

// combining the data. It is used only for small strings. This also ensures that

// we have high entropy in all bits of the state.

inline uint64_t PrecombineLengthMix(uint64_t state, size_t len) {

  ABSL_ASSUME(len + sizeof(uint64_t) <= sizeof(kStaticRandomData));

  uint64_t data = absl::base_internal::UnalignedLoad64(

      reinterpret_cast<const unsigned char*>(&kStaticRandomData[0]) + len);

  return state ^ data;

}

ABSL_ATTRIBUTE_ALWAYS_INLINE inline uint64_t Mix(uint64_t lhs, uint64_t rhs) {

  // Though the 128-bit product needs multiple instructions on non-x86-64

  // platforms, it is still a good balance between speed and hash quality.

  absl::uint128 m = lhs;

  m *= rhs;

  return Uint128High64(m) ^ Uint128Low64(m);

}

// Reads 8 bytes from p.

inline uint64_t Read8(const unsigned char* p) {

// Suppress erroneous array bounds errors on GCC.

#if defined(__GNUC__) && !defined(__clang__)

#pragma GCC diagnostic push

#pragma GCC diagnostic ignored "-Warray-bounds"

#endif

  return absl::base_internal::UnalignedLoad64(p);

#if defined(__GNUC__) && !defined(__clang__)

#pragma GCC diagnostic pop

#endif

}

// Reads 9 to 16 bytes from p.

// The first 8 bytes are in .first, and the rest of the bytes are in .second

// along with duplicated bytes from .first if len<16.

inline std::pair<uint64_t, uint64_t> Read9To16(const unsigned char* p,

                                               size_t len) {

  return {Read8(p), Read8(p + len - 8)};

}

// Reads 4 to 8 bytes from p.

// Bytes are permuted and some input bytes may be duplicated in output.

inline uint64_t Read4To8(const unsigned char* p, size_t len) {

  // If `len < 8`, we duplicate bytes. We always put low memory at the end.

  // E.g., on little endian platforms:

  // `ABCD` will be read as `ABCDABCD`.

  // `ABCDE` will be read as `BCDEABCD`.

  // `ABCDEF` will be read as `CDEFABCD`.

  // `ABCDEFG` will be read as `DEFGABCD`.

  // `ABCDEFGH` will be read as `EFGHABCD`.

  // We also do not care about endianness. On big-endian platforms, bytes will

  // be permuted differently. We always shift low memory by 32, because that

  // can be pipelined earlier. Reading high memory requires computing

  // `p + len - 4`.

  uint64_t most_significant =

      static_cast<uint64_t>(absl::base_internal::UnalignedLoad32(p)) << 32;

  uint64_t least_significant =

      absl::base_internal::UnalignedLoad32(p + len - 4);

  return most_significant | least_significant;

}

// Reads 1 to 3 bytes from p. Some input bytes may be duplicated in output.

inline uint32_t Read1To3(const unsigned char* p, size_t len) {

  // The trick used by this implementation is to avoid branches.

  // We always read three bytes by duplicating.

  // E.g.,

  // `A` is read as `AAA`.

  // `AB` is read as `ABB`.

  // `ABC` is read as `ABC`.

  // We always shift `p[0]` so that it can be pipelined better.

  // Other bytes require extra computation to find indices.

  uint32_t mem0 = (static_cast<uint32_t>(p[0]) << 16) | p[len - 1];

  uint32_t mem1 = static_cast<uint32_t>(p[len / 2]) << 8;

  return mem0 | mem1;

}

ABSL_ATTRIBUTE_ALWAYS_INLINE inline uint64_t CombineRawImpl(uint64_t state,

                                                            uint64_t value) {

  return Mix(state ^ value, kMul);

}

// Slow dispatch path for calls to CombineContiguousImpl with a size argument

// larger than inlined size. Has the same effect as calling

// CombineContiguousImpl() repeatedly with the chunk stride size.

uint64_t CombineLargeContiguousImplOn32BitLengthGt8(const unsigned char* first,

                                                    size_t len, uint64_t state);

uint64_t CombineLargeContiguousImplOn64BitLengthGt32(const unsigned char* first,

                                                     size_t len,

                                                     uint64_t state);

ABSL_ATTRIBUTE_ALWAYS_INLINE inline uint64_t CombineSmallContiguousImpl(

    uint64_t state, const unsigned char* first, size_t len) {

  ABSL_ASSUME(len <= 8);

  uint64_t v;

  if (len >= 4) {

    v = Read4To8(first, len);

  } else if (len > 0) {

    v = Read1To3(first, len);

  } else {

    // Empty string must modify the state.

    v = 0x57;

  }

  return CombineRawImpl(state, v);

}

ABSL_ATTRIBUTE_ALWAYS_INLINE inline uint64_t CombineContiguousImpl9to16(

    uint64_t state, const unsigned char* first, size_t len) {

  ABSL_ASSUME(len >= 9);

  ABSL_ASSUME(len <= 16);

  // Note: any time one half of the mix function becomes zero it will fail to

  // incorporate any bits from the other half. However, there is exactly 1 in

  // 2^64 values for each side that achieve this, and only when the size is

  // exactly 16 -- for smaller sizes there is an overlapping byte that makes

  // this impossible unless the seed is *also* incredibly unlucky.

  auto p = Read9To16(first, len);

  return Mix(state ^ p.first, kMul ^ p.second);

}

ABSL_ATTRIBUTE_ALWAYS_INLINE inline uint64_t CombineContiguousImpl17to32(

    uint64_t state, const unsigned char* first, size_t len) {

  ABSL_ASSUME(len >= 17);

  ABSL_ASSUME(len <= 32);

  // Do two mixes of overlapping 16-byte ranges in parallel to minimize

  // latency.

  const uint64_t m0 =

      Mix(Read8(first) ^ kStaticRandomData[1], Read8(first + 8) ^ state);

  const unsigned char* tail_16b_ptr = first + (len - 16);

  const uint64_t m1 = Mix(Read8(tail_16b_ptr) ^ kStaticRandomData[3],

                          Read8(tail_16b_ptr + 8) ^ state);

  return m0 ^ m1;

}

// Implementation of the base case for combine_contiguous where we actually

// mix the bytes into the state.

// Dispatch to different implementations of combine_contiguous depending

// on the value of `sizeof(size_t)`.

inline uint64_t 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 use custom low latency

  // hash.

  if (len <= 8) {

    return CombineSmallContiguousImpl(PrecombineLengthMix(state, len), first,

                                      len);

  }

  return CombineLargeContiguousImplOn32BitLengthGt8(first, len, state);

}

inline uint64_t CombineContiguousImpl(

    uint64_t state, const unsigned char* first, size_t len,