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Simplify and generalize hash_integral_impl

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Glen Fernandes
2022-06-27 13:25:02 -04:00
parent c28d0b813b
commit f86cdfe502
1 changed files with 18 additions and 23 deletions
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41
include/boost/container_hash/hash.hpp
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@@ -1,5 +1,6 @@
// Copyright 2005-2014 Daniel James. // Copyright 2005-2014 Daniel James.
// Copyright 2021 Peter Dimov. // Copyright 2021 Peter Dimov.
// Copyright 2022 Glen Joseph Fernandes (glenjofe@gmail.com)
// Distributed under the Boost Software License, Version 1.0. // Distributed under the Boost Software License, Version 1.0.
// https://www.boost.org/LICENSE_1_0.txt // https://www.boost.org/LICENSE_1_0.txt
@@ -78,11 +79,10 @@ namespace boost
template<class T, template<class T,
bool bigger_than_size_t = (sizeof(T) > sizeof(std::size_t)), bool bigger_than_size_t = (sizeof(T) > sizeof(std::size_t)),
bool is_unsigned = boost::is_unsigned<T>::value, bool is_unsigned = boost::is_unsigned<T>::value,
std::size_t size_t_bits = sizeof(std::size_t) * CHAR_BIT, std::size_t blocks = sizeof(T) / sizeof(std::size_t)>
std::size_t type_bits = sizeof(T) * CHAR_BIT>
struct hash_integral_impl; struct hash_integral_impl;
template<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> template<class T, bool is_unsigned, std::size_t blocks> struct hash_integral_impl<T, false, is_unsigned, blocks>
{ {
static std::size_t fn( T v ) static std::size_t fn( T v )
{ {
@@ -90,7 +90,7 @@ namespace boost
} }
}; };
template<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> template<class T, std::size_t blocks> struct hash_integral_impl<T, true, false, blocks>
{ {
static std::size_t fn( T v ) static std::size_t fn( T v )
{ {
@@ -107,41 +107,36 @@ namespace boost
} }
}; };
template<class T> struct hash_integral_impl<T, true, true, 32, 64> template<class T> struct hash_integral_impl<T, true, true, 2>
{ {
static std::size_t fn( T v ) static std::size_t fn( T v )
{ {
enum {
M = sizeof(std::size_t) * CHAR_BIT
};
std::size_t seed = 0; std::size_t seed = 0;
seed ^= static_cast<std::size_t>( v >> 32 ) + ( seed << 6 ) + ( seed >> 2 ); seed ^= static_cast<std::size_t>( v >> M ) + ( seed << 6 ) + ( seed >> 2 );
seed ^= static_cast<std::size_t>( v ) + ( seed << 6 ) + ( seed >> 2 ); seed ^= static_cast<std::size_t>( v ) + ( seed << 6 ) + ( seed >> 2 );
return seed; return seed;
} }
}; };
template<class T> struct hash_integral_impl<T, true, true, 32, 128> template<class T> struct hash_integral_impl<T, true, true, 4>
{ {
static std::size_t fn( T v ) static std::size_t fn( T v )
{ {
enum {
M1 = sizeof(std::size_t) * CHAR_BIT,
M2 = M1 + M1,
M3 = M2 + M1
};
std::size_t seed = 0; std::size_t seed = 0;
seed ^= static_cast<std::size_t>( v >> 96 ) + ( seed << 6 ) + ( seed >> 2 ); seed ^= static_cast<std::size_t>( v >> M3 ) + ( seed << 6 ) + ( seed >> 2 );
seed ^= static_cast<std::size_t>( v >> 64 ) + ( seed << 6 ) + ( seed >> 2 ); seed ^= static_cast<std::size_t>( v >> M2 ) + ( seed << 6 ) + ( seed >> 2 );
seed ^= static_cast<std::size_t>( v >> 32 ) + ( seed << 6 ) + ( seed >> 2 ); seed ^= static_cast<std::size_t>( v >> M1 ) + ( seed << 6 ) + ( seed >> 2 );
seed ^= static_cast<std::size_t>( v ) + ( seed << 6 ) + ( seed >> 2 );
return seed;
}
};
template<class T> struct hash_integral_impl<T, true, true, 64, 128>
{
static std::size_t fn( T v )
{
std::size_t seed = 0;
seed ^= static_cast<std::size_t>( v >> 64 ) + ( seed << 6 ) + ( seed >> 2 );
seed ^= static_cast<std::size_t>( v ) + ( seed << 6 ) + ( seed >> 2 ); seed ^= static_cast<std::size_t>( v ) + ( seed << 6 ) + ( seed >> 2 );
return seed; return seed;