// functional_hash.h header -*- C++ -*-
-// Copyright (C) 2007, 2008, 2009, 2010 Free Software Foundation, Inc.
+// Copyright (C) 2007-2020 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library. This library is free
// software; you can redistribute it and/or modify it under the
/** @file bits/functional_hash.h
* This is an internal header file, included by other library headers.
- * You should not attempt to use it directly.
+ * Do not attempt to use it directly. @headername{functional}
*/
#ifndef _FUNCTIONAL_HASH_H
#pragma GCC system_header
-#include <bits/c++config.h>
-#include <bits/stl_function.h>
+#include <bits/hash_bytes.h>
-namespace std
+namespace std _GLIBCXX_VISIBILITY(default)
{
+_GLIBCXX_BEGIN_NAMESPACE_VERSION
+
/** @defgroup hashes Hashes
* @ingroup functors
*
* @{
*/
+ template<typename _Result, typename _Arg>
+ struct __hash_base
+ {
+ typedef _Result result_type _GLIBCXX17_DEPRECATED;
+ typedef _Arg argument_type _GLIBCXX17_DEPRECATED;
+ };
+
/// Primary class template hash.
template<typename _Tp>
- struct hash : public std::unary_function<_Tp, size_t>
+ struct hash;
+
+ template<typename _Tp, typename = void>
+ struct __poison_hash
+ {
+ static constexpr bool __enable_hash_call = false;
+ private:
+ // Private rather than deleted to be non-trivially-copyable.
+ __poison_hash(__poison_hash&&);
+ ~__poison_hash();
+ };
+
+ template<typename _Tp>
+ struct __poison_hash<_Tp, __void_t<decltype(hash<_Tp>()(declval<_Tp>()))>>
+ {
+ static constexpr bool __enable_hash_call = true;
+ };
+
+ // Helper struct for SFINAE-poisoning non-enum types.
+ template<typename _Tp, bool = is_enum<_Tp>::value>
+ struct __hash_enum
+ {
+ private:
+ // Private rather than deleted to be non-trivially-copyable.
+ __hash_enum(__hash_enum&&);
+ ~__hash_enum();
+ };
+
+ // Helper struct for hash with enum types.
+ template<typename _Tp>
+ struct __hash_enum<_Tp, true> : public __hash_base<size_t, _Tp>
{
size_t
- operator()(_Tp __val) const;
+ operator()(_Tp __val) const noexcept
+ {
+ using __type = typename underlying_type<_Tp>::type;
+ return hash<__type>{}(static_cast<__type>(__val));
+ }
};
+ /// Primary class template hash, usable for enum types only.
+ // Use with non-enum types still SFINAES.
+ template<typename _Tp>
+ struct hash : __hash_enum<_Tp>
+ { };
+
/// Partial specializations for pointer types.
template<typename _Tp>
- struct hash<_Tp*> : public std::unary_function<_Tp*, size_t>
+ struct hash<_Tp*> : public __hash_base<size_t, _Tp*>
{
size_t
- operator()(_Tp* __p) const
+ operator()(_Tp* __p) const noexcept
{ return reinterpret_cast<size_t>(__p); }
};
// Explicit specializations for integer types.
#define _Cxx_hashtable_define_trivial_hash(_Tp) \
template<> \
- inline size_t \
- hash<_Tp>::operator()(_Tp __val) const \
- { return static_cast<size_t>(__val); }
+ struct hash<_Tp> : public __hash_base<size_t, _Tp> \
+ { \
+ size_t \
+ operator()(_Tp __val) const noexcept \
+ { return static_cast<size_t>(__val); } \
+ };
/// Explicit specialization for bool.
- _Cxx_hashtable_define_trivial_hash(bool);
+ _Cxx_hashtable_define_trivial_hash(bool)
/// Explicit specialization for char.
- _Cxx_hashtable_define_trivial_hash(char);
+ _Cxx_hashtable_define_trivial_hash(char)
/// Explicit specialization for signed char.
- _Cxx_hashtable_define_trivial_hash(signed char);
+ _Cxx_hashtable_define_trivial_hash(signed char)
/// Explicit specialization for unsigned char.
- _Cxx_hashtable_define_trivial_hash(unsigned char);
+ _Cxx_hashtable_define_trivial_hash(unsigned char)
/// Explicit specialization for wchar_t.
- _Cxx_hashtable_define_trivial_hash(wchar_t);
+ _Cxx_hashtable_define_trivial_hash(wchar_t)
+
+#ifdef _GLIBCXX_USE_CHAR8_T
+ /// Explicit specialization for char8_t.
+ _Cxx_hashtable_define_trivial_hash(char8_t)
+#endif
/// Explicit specialization for char16_t.
- _Cxx_hashtable_define_trivial_hash(char16_t);
+ _Cxx_hashtable_define_trivial_hash(char16_t)
/// Explicit specialization for char32_t.
- _Cxx_hashtable_define_trivial_hash(char32_t);
+ _Cxx_hashtable_define_trivial_hash(char32_t)
/// Explicit specialization for short.
- _Cxx_hashtable_define_trivial_hash(short);
+ _Cxx_hashtable_define_trivial_hash(short)
/// Explicit specialization for int.
- _Cxx_hashtable_define_trivial_hash(int);
+ _Cxx_hashtable_define_trivial_hash(int)
/// Explicit specialization for long.
- _Cxx_hashtable_define_trivial_hash(long);
+ _Cxx_hashtable_define_trivial_hash(long)
/// Explicit specialization for long long.
- _Cxx_hashtable_define_trivial_hash(long long);
+ _Cxx_hashtable_define_trivial_hash(long long)
/// Explicit specialization for unsigned short.
- _Cxx_hashtable_define_trivial_hash(unsigned short);
+ _Cxx_hashtable_define_trivial_hash(unsigned short)
/// Explicit specialization for unsigned int.
- _Cxx_hashtable_define_trivial_hash(unsigned int);
+ _Cxx_hashtable_define_trivial_hash(unsigned int)
/// Explicit specialization for unsigned long.
- _Cxx_hashtable_define_trivial_hash(unsigned long);
+ _Cxx_hashtable_define_trivial_hash(unsigned long)
/// Explicit specialization for unsigned long long.
- _Cxx_hashtable_define_trivial_hash(unsigned long long);
+ _Cxx_hashtable_define_trivial_hash(unsigned long long)
+
+#ifdef __GLIBCXX_TYPE_INT_N_0
+ _Cxx_hashtable_define_trivial_hash(__GLIBCXX_TYPE_INT_N_0)
+ _Cxx_hashtable_define_trivial_hash(__GLIBCXX_TYPE_INT_N_0 unsigned)
+#endif
+#ifdef __GLIBCXX_TYPE_INT_N_1
+ _Cxx_hashtable_define_trivial_hash(__GLIBCXX_TYPE_INT_N_1)
+ _Cxx_hashtable_define_trivial_hash(__GLIBCXX_TYPE_INT_N_1 unsigned)
+#endif
+#ifdef __GLIBCXX_TYPE_INT_N_2
+ _Cxx_hashtable_define_trivial_hash(__GLIBCXX_TYPE_INT_N_2)
+ _Cxx_hashtable_define_trivial_hash(__GLIBCXX_TYPE_INT_N_2 unsigned)
+#endif
+#ifdef __GLIBCXX_TYPE_INT_N_3
+ _Cxx_hashtable_define_trivial_hash(__GLIBCXX_TYPE_INT_N_3)
+ _Cxx_hashtable_define_trivial_hash(__GLIBCXX_TYPE_INT_N_3 unsigned)
+#endif
#undef _Cxx_hashtable_define_trivial_hash
- // Fowler / Noll / Vo (FNV) Hash (type FNV-1a)
+ struct _Hash_impl
+ {
+ static size_t
+ hash(const void* __ptr, size_t __clength,
+ size_t __seed = static_cast<size_t>(0xc70f6907UL))
+ { return _Hash_bytes(__ptr, __clength, __seed); }
+
+ template<typename _Tp>
+ static size_t
+ hash(const _Tp& __val)
+ { return hash(&__val, sizeof(__val)); }
+
+ template<typename _Tp>
+ static size_t
+ __hash_combine(const _Tp& __val, size_t __hash)
+ { return hash(&__val, sizeof(__val), __hash); }
+ };
+
+ // A hash function similar to FNV-1a (see PR59406 for how it differs).
+ struct _Fnv_hash_impl
+ {
+ static size_t
+ hash(const void* __ptr, size_t __clength,
+ size_t __seed = static_cast<size_t>(2166136261UL))
+ { return _Fnv_hash_bytes(__ptr, __clength, __seed); }
+
+ template<typename _Tp>
+ static size_t
+ hash(const _Tp& __val)
+ { return hash(&__val, sizeof(__val)); }
+
+ template<typename _Tp>
+ static size_t
+ __hash_combine(const _Tp& __val, size_t __hash)
+ { return hash(&__val, sizeof(__val), __hash); }
+ };
- // Dummy generic implementation (for sizeof(size_t) != 4, 8).
- template<size_t>
- struct _Fnv_hash_base
+ /// Specialization for float.
+ template<>
+ struct hash<float> : public __hash_base<size_t, float>
{
- template<typename _Tp>
- static size_t
- hash(const _Tp* __ptr, size_t __clength, size_t __hash = 0)
- {
- const char* __cptr = reinterpret_cast<const char*>(__ptr);
- for (; __clength; --__clength)
- __hash = (__hash * 131) + *__cptr++;
- return __hash;
- }
+ size_t
+ operator()(float __val) const noexcept
+ {
+ // 0 and -0 both hash to zero.
+ return __val != 0.0f ? std::_Hash_impl::hash(__val) : 0;
+ }
};
+ /// Specialization for double.
template<>
- struct _Fnv_hash_base<4>
+ struct hash<double> : public __hash_base<size_t, double>
{
- template<typename _Tp>
- static size_t
- hash(const _Tp* __ptr, size_t __clength,
- size_t __hash = static_cast<size_t>(2166136261UL))
- {
- const char* __cptr = reinterpret_cast<const char*>(__ptr);
- for (; __clength; --__clength)
- {
- __hash ^= static_cast<size_t>(*__cptr++);
- __hash *= static_cast<size_t>(16777619UL);
- }
- return __hash;
- }
+ size_t
+ operator()(double __val) const noexcept
+ {
+ // 0 and -0 both hash to zero.
+ return __val != 0.0 ? std::_Hash_impl::hash(__val) : 0;
+ }
};
-
+
+ /// Specialization for long double.
template<>
- struct _Fnv_hash_base<8>
+ struct hash<long double>
+ : public __hash_base<size_t, long double>
{
- template<typename _Tp>
- static size_t
- hash(const _Tp* __ptr, size_t __clength,
- size_t __hash = static_cast<size_t>(14695981039346656037ULL))
- {
- const char* __cptr = reinterpret_cast<const char*>(__ptr);
- for (; __clength; --__clength)
- {
- __hash ^= static_cast<size_t>(*__cptr++);
- __hash *= static_cast<size_t>(1099511628211ULL);
- }
- return __hash;
- }
+ _GLIBCXX_PURE size_t
+ operator()(long double __val) const noexcept;
};
- struct _Fnv_hash
- : public _Fnv_hash_base<sizeof(size_t)>
+#if __cplusplus >= 201703L
+ template<>
+ struct hash<nullptr_t> : public __hash_base<size_t, nullptr_t>
{
- using _Fnv_hash_base<sizeof(size_t)>::hash;
-
- template<typename _Tp>
- static size_t
- hash(const _Tp& __val)
- { return hash(&__val, sizeof(__val)); }
-
- template<typename _Tp>
- static size_t
- __hash_combine(const _Tp& __val, size_t __hash)
- { return hash(&__val, sizeof(__val), __hash); }
+ size_t
+ operator()(nullptr_t) const noexcept
+ { return 0; }
};
+#endif
- /// Specialization for float.
- template<>
- inline size_t
- hash<float>::operator()(float __val) const
- {
- // 0 and -0 both hash to zero.
- return __val != 0.0f ? std::_Fnv_hash::hash(__val) : 0;
- }
+ // @} group hashes
- /// Specialization for double.
- template<>
- inline size_t
- hash<double>::operator()(double __val) const
- {
- // 0 and -0 both hash to zero.
- return __val != 0.0 ? std::_Fnv_hash::hash(__val) : 0;
- }
+ // Hint about performance of hash functor. If not fast the hash-based
+ // containers will cache the hash code.
+ // Default behavior is to consider that hashers are fast unless specified
+ // otherwise.
+ template<typename _Hash>
+ struct __is_fast_hash : public std::true_type
+ { };
- /// Specialization for long double.
template<>
- _GLIBCXX_PURE size_t
- hash<long double>::operator()(long double __val) const;
+ struct __is_fast_hash<hash<long double>> : public std::false_type
+ { };
- // @} group hashes
-}
+_GLIBCXX_END_NAMESPACE_VERSION
+} // namespace
#endif // _FUNCTIONAL_HASH_H
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