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select hash implementation with macros based on word size

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fixes #46
This commit is contained in:
Krystian Stasiowski
2023-05-29 11:12:13 -04:00
parent 6275cd7fe3
commit 175f467a03
2 changed files with 31 additions and 29 deletions
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11
include/boost/static_string/config.hpp
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@ -14,6 +14,17 @@
// Are we dependent on Boost?
// #define BOOST_STATIC_STRING_STANDALONE
#include <cstdint>
// detect 32/64 bit
#if UINTPTR_MAX == UINT64_MAX
#define BOOST_STATIC_STRING_ARCH 64
#elif UINTPTR_MAX == UINT32_MAX
#define BOOST_STATIC_STRING_ARCH 32
#else
#error Unknown or unsupported architecture, please open an issue
#endif
// Can we have deduction guides?
#if __cpp_deduction_guides >= 201703L
#define BOOST_STATIC_STRING_USE_DEDUCT

49
include/boost/static_string/static_string.hpp
View File

@ -6376,39 +6376,30 @@ struct hash<
return std::hash<view_type>()(view_type(str.data(), str.size()));
#else
std::size_t seed = 0;
for (CharT const& c : str) {
mix_impl(std::integral_constant<bool, sizeof(std::size_t) >= 8>{}, seed, c);
for (CharT const& c : str)
{
#if BOOST_STATIC_STRING_ARCH == 64
seed += 0x9e3779b9 + std::hash<CharT>()( c );
std::size_t const m = (std::size_t(0xe9846af) << 32) + 0x9b1a615d;
seed ^= seed >> 32;
seed *= m;
seed ^= seed >> 32;
seed *= m;
seed ^= seed >> 28;
#elif BOOST_STATIC_STRING_ARCH == 32
seed += 0x9e3779b9 + std::hash<CharT>()( c );
std::size_t const m1 = 0x21f0aaad;
std::size_t const m2 = 0x735a2d97;
seed ^= seed >> 16;
seed *= m1;
seed ^= seed >> 15;
seed *= m2;
seed ^= seed >> 15;
#endif
}
return seed;
#endif
}
static
void
mix_impl(std::true_type, std::size_t& seed, CharT c)
{
seed += 0x9e3779b9 + std::hash<CharT>()( c );
std::size_t const m = (std::size_t(0xe9846af) << 32) + 0x9b1a615d;
seed ^= seed >> 32;
seed *= m;
seed ^= seed >> 32;
seed *= m;
seed ^= seed >> 28;
}
static
void
mix_impl(std::false_type, std::size_t& seed, CharT c)
{
seed += 0x9e3779b9 + std::hash<CharT>()( c );
std::size_t const m1 = 0x21f0aaad;
std::size_t const m2 = 0x735a2d97;
seed ^= seed >> 16;
seed *= m1;
seed ^= seed >> 15;
seed *= m2;
seed ^= seed >> 15;
}
};
} // std