// 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 <bitset>

#include <cmath>

#include <cstddef>

#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 <unordered_map>

#include <unordered_set>

#include <utility>

#include <vector>

#include "absl/base/config.h"

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

#include "absl/base/port.h"

#include "absl/container/fixed_array.h"

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

#include "absl/hash/internal/low_level_hash.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"

#ifdef ABSL_HAVE_STD_STRING_VIEW

#include <string_view>

#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

//

// 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_;

};

// 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;

// HashStateBase

//

// 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:

  // 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);

  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

//

// `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));

}

absl::hash_internal::MixingHashState absl::hash_internal::hash_bytes<absl::hash_internal::MixingHashState, unsigned long>(absl::hash_internal::MixingHashState, unsigned long const&)

Line

Count

Source

330

62

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

331

62

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

332

62

  return H::combine_contiguous(std::move(hash_state), start, sizeof(value));

333

62

}

Unexecuted instantiation: absl::hash_internal::MixingHashState absl::hash_internal::hash_bytes<absl::hash_internal::MixingHashState, int>(absl::hash_internal::MixingHashState, int const&)

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

// 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 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 (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);

}

// 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)...);

}

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&, absl::integer_sequence<unsigned long, 0ul>)

Unexecuted instantiation: absl::hash_internal::MixingHashState absl::hash_internal::hash_tuple<absl::hash_internal::MixingHashState, std::__1::tuple<absl::string_view const&, int const&>, 0ul, 1ul>(absl::hash_internal::MixingHashState, std::__1::tuple<absl::string_view const&, int const&> const&, absl::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_15MixingHashStateEJRKNS_11string_viewERKiEEENSt3__19enable_ifIXsr4absl11conjunctionIDpNS0_11is_hashableIT0_EEEE5valueET_E4typeESE_RKNS8_5tupleIJDpSB_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(

      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());

}

#ifdef ABSL_HAVE_STD_STRING_VIEW

// 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(

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

      str.size());

}

#endif  // ABSL_HAVE_STD_STRING_VIEW

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

// 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> 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(H::combine_contiguous(std::move(hash_state), vector.data(),

                                          vector.size()),

                    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)), 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),

                    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), 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 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()),

      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()),

      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()),

      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()),

      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());

}

// 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 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 (int 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

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

// 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);

    }

_ZN4absl13hash_internal10HashSelect24UniquelyRepresentedProbe6InvokeINS0_15MixingHashStateEmEENSt3__19enable_ifIXsr23is_uniquely_representedIT0_EE5valueET_E4typeES8_RKS7_

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        -> absl::enable_if_t<is_uniquely_represented<T>::value, H> {

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      return hash_internal::hash_bytes(std::move(state), value);

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    }

Unexecuted instantiation: _ZN4absl13hash_internal10HashSelect24UniquelyRepresentedProbe6InvokeINS0_15MixingHashStateEiEENSt3__19enable_ifIXsr23is_uniquely_representedIT0_EE5valueET_E4typeES8_RKS7_

  };

  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);

    }

_ZN4absl13hash_internal10HashSelect14HashValueProbe6InvokeINS0_15MixingHashStateENS_11string_viewEEENSt3__19enable_ifIXsr3std7is_sameIT_DTcl13AbslHashValueclsr3stdE4movefp_Efp0_EEEE5valueES8_E4typeES8_RKT0_

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        H> {

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      return AbslHashValue(std::move(state), value);

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    }

Unexecuted instantiation: _ZN4absl13hash_internal10HashSelect14HashValueProbe6InvokeINS0_15MixingHashStateENS_4CordEEENSt3__19enable_ifIXsr3std7is_sameIT_DTcl13AbslHashValueclsr3stdE4movefp_Efp0_EEEE5valueES8_E4typeES8_RKT0_

Unexecuted instantiation: _ZN4absl13hash_internal10HashSelect14HashValueProbe6InvokeINS0_15MixingHashStateENSt3__15tupleIJRKmEEEEENS5_9enable_ifIXsr3std7is_sameIT_DTcl13AbslHashValueclsr3stdE4movefp_Efp0_EEEE5valueESB_E4typeESB_RKT0_

Unexecuted instantiation: _ZN4absl13hash_internal10HashSelect14HashValueProbe6InvokeINS0_15MixingHashStateENSt3__15tupleIJRKNS_11string_viewERKiEEEEENS5_9enable_ifIXsr3std7is_sameIT_DTcl13AbslHashValueclsr3stdE4movefp_Efp0_EEEE5valueESE_E4typeESE_RKT0_

  };

  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> {};

// MixingHashState

class ABSL_DLL MixingHashState : public HashStateBase<MixingHashState> {

  // 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

  MixingHashState(MixingHashState&&) = default;

  MixingHashState& operator=(MixingHashState&&) = default;

  // MixingHashState::combine_contiguous()

  //

  // Fundamental base case for hash recursion: mixes the given range of bytes

  // into the hash state.

  static MixingHashState combine_contiguous(MixingHashState hash_state,

                                            const unsigned char* first,

                                            size_t size) {

    return MixingHashState(

        CombineContiguousImpl(hash_state.state_, first, size,

                              std::integral_constant<int, sizeof(size_t)>{}));

  }

  using MixingHashState::HashStateBase::combine_contiguous;

  // MixingHashState::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<std::make_unsigned_t<T>>(value)));

  }

  // Overload of MixingHashState::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(MixingHashState{}, value).state_);

  }

unsigned long absl::hash_internal::MixingHashState::hash<absl::string_view, 0>(absl::string_view const&)

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  static size_t hash(const T& value) {

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    return static_cast<size_t>(combine(MixingHashState{}, value).state_);

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  }

Unexecuted instantiation: unsigned long absl::hash_internal::MixingHashState::hash<absl::Cord, 0>(absl::Cord const&)

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

Unexecuted instantiation: unsigned long absl::hash_internal::MixingHashState::hash<std::__1::tuple<absl::string_view const&, int const&>, 0>(std::__1::tuple<absl::string_view const&, int const&> const&)

 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.

  MixingHashState() : state_(Seed()) {}

  friend class MixingHashState::HashStateBase;

  template <typename CombinerT>

  static MixingHashState RunCombineUnordered(MixingHashState state,

                                             CombinerT combiner) {

    uint64_t unordered_state = 0;

    combiner(MixingHashState{}, [&](MixingHashState& inner_state) {

      // Add the hash state of the element to the running total, but mix the

      // carry bit back into the low bit.  This in intended to avoid losing

      // entropy to overflow, especially when unordered_multisets contain

      // multiple copies of the same value.

      auto element_state = inner_state.state_;

      unordered_state += element_state;

      if (unordered_state < element_state) {

        ++unordered_state;

      }

      inner_state = MixingHashState{};

    });

    return MixingHashState::combine(std::move(state), unordered_state);

  }

  // Allow the HashState type-erasure implementation to invoke

  // RunCombinedUnordered() directly.

  friend class absl::HashState;

  // 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.

  MixingHashState(const MixingHashState&) = default;

  explicit MixingHashState(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 least significant 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 low_mem = absl::base_internal::UnalignedLoad64(p);

    uint64_t high_mem = absl::base_internal::UnalignedLoad64(p + len - 8);

#ifdef ABSL_IS_LITTLE_ENDIAN

    uint64_t most_significant = high_mem;

    uint64_t least_significant = low_mem;

#else

    uint64_t most_significant = low_mem;

    uint64_t least_significant = high_mem;

#endif

    return {least_significant, most_significant};

  }

  // Reads 4 to 8 bytes from p. Zero pads to fill uint64_t.

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

    uint32_t low_mem = absl::base_internal::UnalignedLoad32(p);

    uint32_t high_mem = absl::base_internal::UnalignedLoad32(p + len - 4);

#ifdef ABSL_IS_LITTLE_ENDIAN

    uint32_t most_significant = high_mem;

    uint32_t least_significant = low_mem;

#else

    uint32_t most_significant = low_mem;

    uint32_t least_significant = high_mem;

#endif

    return (static_cast<uint64_t>(most_significant) << (len - 4) * 8) |

           least_significant;

  }

  // Reads 1 to 3 bytes from p. Zero pads to fill uint32_t.

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

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

    unsigned char mem0 = p[0];

    unsigned char mem1 = p[len / 2];

    unsigned char mem2 = p[len - 1];