1// Copyright 2021-2023 Peter Dimov
2// Distributed under the Boost Software License, Version 1.0.
3// https://www.boost.org/LICENSE_1_0.txt
4
5#ifndef BOOST_HASH_DETAIL_HASH_INTEGRAL_HPP
6#define BOOST_HASH_DETAIL_HASH_INTEGRAL_HPP
7
8#include <boost/container_hash/detail/hash_mix.hpp>
9#include <type_traits>
10#include <cstddef>
11#include <climits>
12
13namespace boost
14{
15namespace hash_detail
16{
17
18// libstdc++ doesn't provide support for __int128 in the standard traits
19
20template<class T> struct is_integral: public std::is_integral<T>
21{
22};
23
24template<class T> struct is_unsigned: public std::is_unsigned<T>
25{
26};
27
28template<class T> struct make_unsigned: public std::make_unsigned<T>
29{
30};
31
32#if defined(__SIZEOF_INT128__)
33
34template<> struct is_integral<__int128_t>: public std::true_type
35{
36};
37
38template<> struct is_integral<__uint128_t>: public std::true_type
39{
40};
41
42template<> struct is_unsigned<__int128_t>: public std::false_type
43{
44};
45
46template<> struct is_unsigned<__uint128_t>: public std::true_type
47{
48};
49
50template<> struct make_unsigned<__int128_t>
51{
52 typedef __uint128_t type;
53};
54
55template<> struct make_unsigned<__uint128_t>
56{
57 typedef __uint128_t type;
58};
59
60#endif
61
62template<class T,
63 bool bigger_than_size_t = (sizeof(T) > sizeof(std::size_t)),
64 bool is_unsigned = is_unsigned<T>::value,
65 std::size_t size_t_bits = sizeof(std::size_t) * CHAR_BIT,
66 std::size_t type_bits = sizeof(T) * CHAR_BIT>
67struct hash_integral_impl;
68
69template<class T, bool is_unsigned, std::size_t size_t_bits, std::size_t type_bits> struct hash_integral_impl<T, false, is_unsigned, size_t_bits, type_bits>
70{
71 static std::size_t fn( T v )
72 {
73 return static_cast<std::size_t>( v );
74 }
75};
76
77template<class T, std::size_t size_t_bits, std::size_t type_bits> struct hash_integral_impl<T, true, false, size_t_bits, type_bits>
78{
79 static std::size_t fn( T v )
80 {
81 typedef typename make_unsigned<T>::type U;
82
83 if( v >= 0 )
84 {
85 return hash_integral_impl<U>::fn( static_cast<U>( v ) );
86 }
87 else
88 {
89 return ~hash_integral_impl<U>::fn( static_cast<U>( ~static_cast<U>( v ) ) );
90 }
91 }
92};
93
94template<class T> struct hash_integral_impl<T, true, true, 32, 64>
95{
96 static std::size_t fn( T v )
97 {
98 std::size_t seed = 0;
99
100 seed = static_cast<std::size_t>( v >> 32 ) + hash_detail::hash_mix( v: seed );
101 seed = static_cast<std::size_t>( v & 0xFFFFFFFF ) + hash_detail::hash_mix( v: seed );
102
103 return seed;
104 }
105};
106
107template<class T> struct hash_integral_impl<T, true, true, 32, 128>
108{
109 static std::size_t fn( T v )
110 {
111 std::size_t seed = 0;
112
113 seed = static_cast<std::size_t>( v >> 96 ) + hash_detail::hash_mix( v: seed );
114 seed = static_cast<std::size_t>( v >> 64 ) + hash_detail::hash_mix( v: seed );
115 seed = static_cast<std::size_t>( v >> 32 ) + hash_detail::hash_mix( v: seed );
116 seed = static_cast<std::size_t>( v ) + hash_detail::hash_mix( v: seed );
117
118 return seed;
119 }
120};
121
122template<class T> struct hash_integral_impl<T, true, true, 64, 128>
123{
124 static std::size_t fn( T v )
125 {
126 std::size_t seed = 0;
127
128 seed = static_cast<std::size_t>( v >> 64 ) + hash_detail::hash_mix( v: seed );
129 seed = static_cast<std::size_t>( v ) + hash_detail::hash_mix( v: seed );
130
131 return seed;
132 }
133};
134
135} // namespace hash_detail
136
137template <typename T>
138typename std::enable_if<hash_detail::is_integral<T>::value, std::size_t>::type
139 hash_value( T v )
140{
141 return hash_detail::hash_integral_impl<T>::fn( v );
142}
143
144} // namespace boost
145
146#endif // #ifndef BOOST_HASH_DETAIL_HASH_INTEGRAL_HPP
147

source code of boost/libs/container_hash/include/boost/container_hash/detail/hash_integral.hpp