hash.h

//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//

#ifndef _LIBCPP___FUNCTIONAL_HASH_H
#define _LIBCPP___FUNCTIONAL_HASH_H

#include <__config>
#include <__functional/unary_function.h>
#include <__fwd/functional.h>
#include <__type_traits/conjunction.h>
#include <__type_traits/invoke.h>
#include <__type_traits/is_constructible.h>
#include <__type_traits/is_enum.h>
#include <__type_traits/underlying_type.h>
#include <__utility/pair.h>
#include <__utility/swap.h>
#include <cstddef>
#include <cstdint>
#include <cstring>

#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
#  pragma GCC system_header
#endif

_LIBCPP_BEGIN_NAMESPACE_STD

template <class _Size>
inline _LIBCPP_HIDE_FROM_ABI _Size __loadword(const void* __p) {
  _Size __r;
  std::memcpy(&__r, __p, sizeof(__r));
  return __r;
}

// We use murmur2 when size_t is 32 bits, and cityhash64 when size_t
// is 64 bits.  This is because cityhash64 uses 64bit x 64bit
// multiplication, which can be very slow on 32-bit systems.
template <class _Size, size_t = sizeof(_Size) * __CHAR_BIT__>
struct __murmur2_or_cityhash;

template <class _Size>
struct __murmur2_or_cityhash<_Size, 32> {
  _LIBCPP_HIDE_FROM_ABI _LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK _Size
  operator()(const void* __key, _Size __len) const {
    // murmur2
    const _Size __m             = 0x5bd1e995;
    const _Size __r             = 24;
    _Size __h                   = __len;
    const unsigned char* __data = static_cast<const unsigned char*>(__key);
    for (; __len >= 4; __data += 4, __len -= 4) {
      _Size __k = std::__loadword<_Size>(__data);
      __k *= __m;
      __k ^= __k >> __r;
      __k *= __m;
      __h *= __m;
      __h ^= __k;
    }
    switch (__len) {
    case 3:
      __h ^= static_cast<_Size>(__data[2] << 16);
      _LIBCPP_FALLTHROUGH();
    case 2:
      __h ^= static_cast<_Size>(__data[1] << 8);
      _LIBCPP_FALLTHROUGH();
    case 1:
      __h ^= __data[0];
      __h *= __m;
    }
    __h ^= __h >> 13;
    __h *= __m;
    __h ^= __h >> 15;
    return __h;
  }
};

template <class _Size>
struct __murmur2_or_cityhash<_Size, 64> {
  // cityhash64
  _LIBCPP_HIDE_FROM_ABI _LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK _Size
  operator()(const void* __key, _Size __len) const {
    const char* __s = static_cast<const char*>(__key);
    if (__len <= 32) {
      if (__len <= 16) {
        return __hash_len_0_to_16(__s, __len);
      } else {
        return __hash_len_17_to_32(__s, __len);
      }
    } else if (__len <= 64) {
      return __hash_len_33_to_64(__s, __len);
    }

    // For strings over 64 bytes we hash the end first, and then as we
    // loop we keep 56 bytes of state: v, w, x, y, and z.
    _Size __x = std::__loadword<_Size>(__s + __len - 40);
    _Size __y = std::__loadword<_Size>(__s + __len - 16) + std::__loadword<_Size>(__s + __len - 56);
    _Size __z =
        __hash_len_16(std::__loadword<_Size>(__s + __len - 48) + __len, std::__loadword<_Size>(__s + __len - 24));
    pair<_Size, _Size> __v = __weak_hash_len_32_with_seeds(__s + __len - 64, __len, __z);
    pair<_Size, _Size> __w = __weak_hash_len_32_with_seeds(__s + __len - 32, __y + __k1, __x);
    __x                    = __x * __k1 + std::__loadword<_Size>(__s);

    // Decrease len to the nearest multiple of 64, and operate on 64-byte chunks.
    __len = (__len - 1) & ~static_cast<_Size>(63);
    do {
      __x = __rotate(__x + __y + __v.first + std::__loadword<_Size>(__s + 8), 37) * __k1;
      __y = __rotate(__y + __v.second + std::__loadword<_Size>(__s + 48), 42) * __k1;
      __x ^= __w.second;
      __y += __v.first + std::__loadword<_Size>(__s + 40);
      __z = __rotate(__z + __w.first, 33) * __k1;
      __v = __weak_hash_len_32_with_seeds(__s, __v.second * __k1, __x + __w.first);
      __w = __weak_hash_len_32_with_seeds(__s + 32, __z + __w.second, __y + std::__loadword<_Size>(__s + 16));
      std::swap(__z, __x);
      __s += 64;
      __len -= 64;
    } while (__len != 0);
    return __hash_len_16(__hash_len_16(__v.first, __w.first) + __shift_mix(__y) * __k1 + __z,
                         __hash_len_16(__v.second, __w.second) + __x);
  }

private:
  // Some primes between 2^63 and 2^64.
  static const _Size __k0 = 0xc3a5c85c97cb3127ULL;
  static const _Size __k1 = 0xb492b66fbe98f273ULL;
  static const _Size __k2 = 0x9ae16a3b2f90404fULL;
  static const _Size __k3 = 0xc949d7c7509e6557ULL;

  _LIBCPP_HIDE_FROM_ABI static _Size __rotate(_Size __val, int __shift) {
    return __shift == 0 ? __val : ((__val >> __shift) | (__val << (64 - __shift)));
  }

  _LIBCPP_HIDE_FROM_ABI static _Size __rotate_by_at_least_1(_Size __val, int __shift) {
    return (__val >> __shift) | (__val << (64 - __shift));
  }

  _LIBCPP_HIDE_FROM_ABI static _Size __shift_mix(_Size __val) { return __val ^ (__val >> 47); }

  _LIBCPP_HIDE_FROM_ABI _LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK static _Size __hash_len_16(_Size __u, _Size __v) {
    const _Size __mul = 0x9ddfea08eb382d69ULL;
    _Size __a         = (__u ^ __v) * __mul;
    __a ^= (__a >> 47);
    _Size __b = (__v ^ __a) * __mul;
    __b ^= (__b >> 47);
    __b *= __mul;
    return __b;
  }

  _LIBCPP_HIDE_FROM_ABI _LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK static _Size
  __hash_len_0_to_16(const char* __s, _Size __len) {
    if (__len > 8) {
      const _Size __a = std::__loadword<_Size>(__s);
      const _Size __b = std::__loadword<_Size>(__s + __len - 8);
      return __hash_len_16(__a, __rotate_by_at_least_1(__b + __len, __len)) ^ __b;
    }
    if (__len >= 4) {
      const uint32_t __a = std::__loadword<uint32_t>(__s);
      const uint32_t __b = std::__loadword<uint32_t>(__s + __len - 4);
#ifdef _LIBCPP_ABI_FIX_CITYHASH_IMPLEMENTATION
      return __hash_len_16(__len + (static_cast<_Size>(__a) << 3), __b);
#else
      return __hash_len_16(__len + (__a << 3), __b);
#endif
    }
    if (__len > 0) {
      const unsigned char __a = static_cast<unsigned char>(__s[0]);
      const unsigned char __b = static_cast<unsigned char>(__s[__len >> 1]);
      const unsigned char __c = static_cast<unsigned char>(__s[__len - 1]);
      const uint32_t __y      = static_cast<uint32_t>(__a) + (static_cast<uint32_t>(__b) << 8);
      const uint32_t __z      = __len + (static_cast<uint32_t>(__c) << 2);
      return __shift_mix(__y * __k2 ^ __z * __k3) * __k2;
    }
    return __k2;
  }

  _LIBCPP_HIDE_FROM_ABI _LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK static _Size
  __hash_len_17_to_32(const char* __s, _Size __len) {
    const _Size __a = std::__loadword<_Size>(__s) * __k1;
    const _Size __b = std::__loadword<_Size>(__s + 8);
    const _Size __c = std::__loadword<_Size>(__s + __len - 8) * __k2;
    const _Size __d = std::__loadword<_Size>(__s + __len - 16) * __k0;
    return __hash_len_16(
        __rotate(__a - __b, 43) + __rotate(__c, 30) + __d, __a + __rotate(__b ^ __k3, 20) - __c + __len);
  }

  // Return a 16-byte hash for 48 bytes.  Quick and dirty.
  // Callers do best to use "random-looking" values for a and b.
  _LIBCPP_HIDE_FROM_ABI _LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK static pair<_Size, _Size>
  __weak_hash_len_32_with_seeds(_Size __w, _Size __x, _Size __y, _Size __z, _Size __a, _Size __b) {
    __a += __w;
    __b             = __rotate(__b + __a + __z, 21);
    const _Size __c = __a;
    __a += __x;
    __a += __y;
    __b += __rotate(__a, 44);
    return pair<_Size, _Size>(__a + __z, __b + __c);
  }

  // Return a 16-byte hash for s[0] ... s[31], a, and b.  Quick and dirty.
  _LIBCPP_HIDE_FROM_ABI _LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK static pair<_Size, _Size>
  __weak_hash_len_32_with_seeds(const char* __s, _Size __a, _Size __b) {
    return __weak_hash_len_32_with_seeds(
        std::__loadword<_Size>(__s),
        std::__loadword<_Size>(__s + 8),
        std::__loadword<_Size>(__s + 16),
        std::__loadword<_Size>(__s + 24),
        __a,
        __b);
  }

  // Return an 8-byte hash for 33 to 64 bytes.
  _LIBCPP_HIDE_FROM_ABI _LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK static _Size
  __hash_len_33_to_64(const char* __s, size_t __len) {
    _Size __z = std::__loadword<_Size>(__s + 24);
    _Size __a = std::__loadword<_Size>(__s) + (__len + std::__loadword<_Size>(__s + __len - 16)) * __k0;
    _Size __b = __rotate(__a + __z, 52);
    _Size __c = __rotate(__a, 37);
    __a += std::__loadword<_Size>(__s + 8);
    __c += __rotate(__a, 7);
    __a += std::__loadword<_Size>(__s + 16);
    _Size __vf = __a + __z;
    _Size __vs = __b + __rotate(__a, 31) + __c;
    __a        = std::__loadword<_Size>(__s + 16) + std::__loadword<_Size>(__s + __len - 32);
    __z += std::__loadword<_Size>(__s + __len - 8);
    __b = __rotate(__a + __z, 52);
    __c = __rotate(__a, 37);
    __a += std::__loadword<_Size>(__s + __len - 24);
    __c += __rotate(__a, 7);
    __a += std::__loadword<_Size>(__s + __len - 16);
    _Size __wf = __a + __z;
    _Size __ws = __b + __rotate(__a, 31) + __c;
    _Size __r  = __shift_mix((__vf + __ws) * __k2 + (__wf + __vs) * __k0);
    return __shift_mix(__r * __k0 + __vs) * __k2;
  }
};

template <class _Tp, size_t = sizeof(_Tp) / sizeof(size_t)>
struct __scalar_hash;

template <class _Tp>
struct __scalar_hash<_Tp, 0> : public __unary_function<_Tp, size_t> {
  _LIBCPP_HIDE_FROM_ABI size_t operator()(_Tp __v) const _NOEXCEPT {
    union {
      _Tp __t;
      size_t __a;
    } __u;
    __u.__a = 0;
    __u.__t = __v;
    return __u.__a;
  }
};

template <class _Tp>
struct __scalar_hash<_Tp, 1> : public __unary_function<_Tp, size_t> {
  _LIBCPP_HIDE_FROM_ABI size_t operator()(_Tp __v) const _NOEXCEPT {
    union {
      _Tp __t;
      size_t __a;
    } __u;
    __u.__t = __v;
    return __u.__a;
  }
};

template <class _Tp>
struct __scalar_hash<_Tp, 2> : public __unary_function<_Tp, size_t> {
  _LIBCPP_HIDE_FROM_ABI size_t operator()(_Tp __v) const _NOEXCEPT {
    union {
      _Tp __t;
      struct {
        size_t __a;
        size_t __b;
      } __s;
    } __u;
    __u.__t = __v;
    return __murmur2_or_cityhash<size_t>()(&__u, sizeof(__u));
  }
};

template <class _Tp>
struct __scalar_hash<_Tp, 3> : public __unary_function<_Tp, size_t> {
  _LIBCPP_HIDE_FROM_ABI size_t operator()(_Tp __v) const _NOEXCEPT {
    union {
      _Tp __t;
      struct {
        size_t __a;
        size_t __b;
        size_t __c;
      } __s;
    } __u;
    __u.__t = __v;
    return __murmur2_or_cityhash<size_t>()(&__u, sizeof(__u));
  }
};

template <class _Tp>
struct __scalar_hash<_Tp, 4> : public __unary_function<_Tp, size_t> {
  _LIBCPP_HIDE_FROM_ABI size_t operator()(_Tp __v) const _NOEXCEPT {
    union {
      _Tp __t;
      struct {
        size_t __a;
        size_t __b;
        size_t __c;
        size_t __d;
      } __s;
    } __u;
    __u.__t = __v;
    return __murmur2_or_cityhash<size_t>()(&__u, sizeof(__u));
  }
};

struct _PairT {
  size_t first;
  size_t second;
};

_LIBCPP_HIDE_FROM_ABI inline size_t __hash_combine(size_t __lhs, size_t __rhs) _NOEXCEPT {
  typedef __scalar_hash<_PairT> _HashT;
  const _PairT __p = {__lhs, __rhs};
  return _HashT()(__p);
}

template <class _Tp>
struct _LIBCPP_TEMPLATE_VIS hash<_Tp*> : public __unary_function<_Tp*, size_t> {
  _LIBCPP_HIDE_FROM_ABI size_t operator()(_Tp* __v) const _NOEXCEPT {
    union {
      _Tp* __t;
      size_t __a;
    } __u;
    __u.__t = __v;
    return __murmur2_or_cityhash<size_t>()(&__u, sizeof(__u));
  }
};

template <>
struct _LIBCPP_TEMPLATE_VIS hash<bool> : public __unary_function<bool, size_t> {
  _LIBCPP_HIDE_FROM_ABI size_t operator()(bool __v) const _NOEXCEPT { return static_cast<size_t>(__v); }
};

template <>
struct _LIBCPP_TEMPLATE_VIS hash<char> : public __unary_function<char, size_t> {
  _LIBCPP_HIDE_FROM_ABI size_t operator()(char __v) const _NOEXCEPT { return static_cast<size_t>(__v); }
};

template <>
struct _LIBCPP_TEMPLATE_VIS hash<signed char> : public __unary_function<signed char, size_t> {
  _LIBCPP_HIDE_FROM_ABI size_t operator()(signed char __v) const _NOEXCEPT { return static_cast<size_t>(__v); }
};

template <>
struct _LIBCPP_TEMPLATE_VIS hash<unsigned char> : public __unary_function<unsigned char, size_t> {
  _LIBCPP_HIDE_FROM_ABI size_t operator()(unsigned char __v) const _NOEXCEPT { return static_cast<size_t>(__v); }
};

#ifndef _LIBCPP_HAS_NO_CHAR8_T
template <>
struct _LIBCPP_TEMPLATE_VIS hash<char8_t> : public __unary_function<char8_t, size_t> {
  _LIBCPP_HIDE_FROM_ABI size_t operator()(char8_t __v) const _NOEXCEPT { return static_cast<size_t>(__v); }
};
#endif // !_LIBCPP_HAS_NO_CHAR8_T

template <>
struct _LIBCPP_TEMPLATE_VIS hash<char16_t> : public __unary_function<char16_t, size_t> {
  _LIBCPP_HIDE_FROM_ABI size_t operator()(char16_t __v) const _NOEXCEPT { return static_cast<size_t>(__v); }
};

template <>
struct _LIBCPP_TEMPLATE_VIS hash<char32_t> : public __unary_function<char32_t, size_t> {
  _LIBCPP_HIDE_FROM_ABI size_t operator()(char32_t __v) const _NOEXCEPT { return static_cast<size_t>(__v); }
};

#ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
template <>
struct _LIBCPP_TEMPLATE_VIS hash<wchar_t> : public __unary_function<wchar_t, size_t> {
  _LIBCPP_HIDE_FROM_ABI size_t operator()(wchar_t __v) const _NOEXCEPT { return static_cast<size_t>(__v); }
};
#endif // _LIBCPP_HAS_NO_WIDE_CHARACTERS

template <>
struct _LIBCPP_TEMPLATE_VIS hash<short> : public __unary_function<short, size_t> {
  _LIBCPP_HIDE_FROM_ABI size_t operator()(short __v) const _NOEXCEPT { return static_cast<size_t>(__v); }
};

template <>
struct _LIBCPP_TEMPLATE_VIS hash<unsigned short> : public __unary_function<unsigned short, size_t> {
  _LIBCPP_HIDE_FROM_ABI size_t operator()(unsigned short __v) const _NOEXCEPT { return static_cast<size_t>(__v); }
};

template <>
struct _LIBCPP_TEMPLATE_VIS hash<int> : public __unary_function<int, size_t> {
  _LIBCPP_HIDE_FROM_ABI size_t operator()(int __v) const _NOEXCEPT { return static_cast<size_t>(__v); }
};

template <>
struct _LIBCPP_TEMPLATE_VIS hash<unsigned int> : public __unary_function<unsigned int, size_t> {
  _LIBCPP_HIDE_FROM_ABI size_t operator()(unsigned int __v) const _NOEXCEPT { return static_cast<size_t>(__v); }
};

template <>
struct _LIBCPP_TEMPLATE_VIS hash<long> : public __unary_function<long, size_t> {
  _LIBCPP_HIDE_FROM_ABI size_t operator()(long __v) const _NOEXCEPT { return static_cast<size_t>(__v); }
};

template <>
struct _LIBCPP_TEMPLATE_VIS hash<unsigned long> : public __unary_function<unsigned long, size_t> {
  _LIBCPP_HIDE_FROM_ABI size_t operator()(unsigned long __v) const _NOEXCEPT { return static_cast<size_t>(__v); }
};

template <>
struct _LIBCPP_TEMPLATE_VIS hash<long long> : public __scalar_hash<long long> {};

template <>
struct _LIBCPP_TEMPLATE_VIS hash<unsigned long long> : public __scalar_hash<unsigned long long> {};

#ifndef _LIBCPP_HAS_NO_INT128

template <>
struct _LIBCPP_TEMPLATE_VIS hash<__int128_t> : public __scalar_hash<__int128_t> {};

template <>
struct _LIBCPP_TEMPLATE_VIS hash<__uint128_t> : public __scalar_hash<__uint128_t> {};

#endif

template <>
struct _LIBCPP_TEMPLATE_VIS hash<float> : public __scalar_hash<float> {
  _LIBCPP_HIDE_FROM_ABI size_t operator()(float __v) const _NOEXCEPT {
    // -0.0 and 0.0 should return same hash
    if (__v == 0.0f)
      return 0;
    return __scalar_hash<float>::operator()(__v);
  }
};

template <>
struct _LIBCPP_TEMPLATE_VIS hash<double> : public __scalar_hash<double> {
  _LIBCPP_HIDE_FROM_ABI size_t operator()(double __v) const _NOEXCEPT {
    // -0.0 and 0.0 should return same hash
    if (__v == 0.0)
      return 0;
    return __scalar_hash<double>::operator()(__v);
  }
};

template <>
struct _LIBCPP_TEMPLATE_VIS hash<long double> : public __scalar_hash<long double> {
  _LIBCPP_HIDE_FROM_ABI size_t operator()(long double __v) const _NOEXCEPT {
    // -0.0 and 0.0 should return same hash
    if (__v == 0.0L)
      return 0;
#if defined(__i386__) || (defined(__x86_64__) && defined(__ILP32__))
    // Zero out padding bits
    union {
      long double __t;
      struct {
        size_t __a;
        size_t __b;
        size_t __c;
        size_t __d;
      } __s;
    } __u;
    __u.__s.__a = 0;
    __u.__s.__b = 0;
    __u.__s.__c = 0;
    __u.__s.__d = 0;
    __u.__t     = __v;
    return __u.__s.__a ^ __u.__s.__b ^ __u.__s.__c ^ __u.__s.__d;
#elif defined(__x86_64__)
    // Zero out padding bits
    union {
      long double __t;
      struct {
        size_t __a;
        size_t __b;
      } __s;
    } __u;
    __u.__s.__a = 0;
    __u.__s.__b = 0;
    __u.__t     = __v;
    return __u.__s.__a ^ __u.__s.__b;
#else
    return __scalar_hash<long double>::operator()(__v);
#endif
  }
};

template <class _Tp, bool = is_enum<_Tp>::value>
struct _LIBCPP_TEMPLATE_VIS __enum_hash : public __unary_function<_Tp, size_t> {
  _LIBCPP_HIDE_FROM_ABI size_t operator()(_Tp __v) const _NOEXCEPT {
    typedef typename underlying_type<_Tp>::type type;
    return hash<type>()(static_cast<type>(__v));
  }
};
template <class _Tp>
struct _LIBCPP_TEMPLATE_VIS __enum_hash<_Tp, false> {
  __enum_hash()                              = delete;
  __enum_hash(__enum_hash const&)            = delete;
  __enum_hash& operator=(__enum_hash const&) = delete;
};

template <class _Tp>
struct _LIBCPP_TEMPLATE_VIS hash : public __enum_hash<_Tp> {};

#if _LIBCPP_STD_VER >= 17

template <>
struct _LIBCPP_TEMPLATE_VIS hash<nullptr_t> : public __unary_function<nullptr_t, size_t> {
  _LIBCPP_HIDE_FROM_ABI size_t operator()(nullptr_t) const _NOEXCEPT { return 662607004ull; }
};
#endif

#ifndef _LIBCPP_CXX03_LANG
template <class _Key, class _Hash>
using __check_hash_requirements _LIBCPP_NODEBUG =
    integral_constant<bool,
                      is_copy_constructible<_Hash>::value && is_move_constructible<_Hash>::value &&
                          __invokable_r<size_t, _Hash, _Key const&>::value >;

template <class _Key, class _Hash = hash<_Key> >
using __has_enabled_hash _LIBCPP_NODEBUG =
    integral_constant<bool, __check_hash_requirements<_Key, _Hash>::value && is_default_constructible<_Hash>::value >;

#  if _LIBCPP_STD_VER >= 17
template <class _Type, class>
using __enable_hash_helper_imp _LIBCPP_NODEBUG = _Type;

template <class _Type, class... _Keys>
using __enable_hash_helper _LIBCPP_NODEBUG =
    __enable_hash_helper_imp<_Type, __enable_if_t<__all<__has_enabled_hash<_Keys>::value...>::value> >;
#  else
template <class _Type, class...>
using __enable_hash_helper _LIBCPP_NODEBUG = _Type;
#  endif

#endif // !_LIBCPP_CXX03_LANG

_LIBCPP_END_NAMESPACE_STD

#endif // _LIBCPP___FUNCTIONAL_HASH_H