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#include "hash-impl.hpp"
// ReSharper disable CppDefaultCaseNotHandledInSwitchStatement
// NOLINTBEGIN(*-multiway-paths-covered, *-switch-missing-default-case)
namespace floormat::FNVHash {
namespace {
template<size_t N = sizeof nullptr * 8> struct fnvhash_params;
template<> struct fnvhash_params<32> { [[maybe_unused]] static constexpr uint32_t a = 0x811c9dc5u, b = 0x01000193u; };
template<> struct fnvhash_params<64> { [[maybe_unused]] static constexpr uint64_t a = 0xcbf29ce484222325u, b = 0x100000001b3u; };
CORRADE_ALWAYS_INLINE size_t fnvhash_uint(uint64_t x)
{
constexpr auto params = fnvhash_params{};
constexpr auto a = params.a, b = params.b;
auto hash = a;
const auto* str = (const uint8_t*)&x;
hash *= b; hash ^= *str++; // 0
hash *= b; hash ^= *str++; // 1
hash *= b; hash ^= *str++; // 2
hash *= b; hash ^= *str++; // 3
hash *= b; hash ^= *str++; // 4
hash *= b; hash ^= *str++; // 5
hash *= b; hash ^= *str++; // 6
hash *= b; hash ^= *str++; // 7
return hash;
}
CORRADE_ALWAYS_INLINE size_t fnvhash_uint(uint32_t x)
{
constexpr auto params = fnvhash_params{};
constexpr auto a = params.a, b = params.b;
auto hash = a;
const auto* str = (const uint8_t*)&x;
hash *= b; hash ^= *str++; // 0
hash *= b; hash ^= *str++; // 1
hash *= b; hash ^= *str++; // 2
hash *= b; hash ^= *str++; // 3
return hash;
}
CORRADE_ALWAYS_INLINE size_t fnvhash_buf(const void* __restrict buf, size_t size) noexcept
{
constexpr auto params = fnvhash_params{};
constexpr auto a = params.a, b = params.b;
size_t full_rounds = size / 8, rest = size % 8;
size_t hash = a;
const auto* str = (const uint8_t*)buf;
while (full_rounds--)
{
hash *= b; hash ^= *str++; // 0
hash *= b; hash ^= *str++; // 1
hash *= b; hash ^= *str++; // 2
hash *= b; hash ^= *str++; // 3
hash *= b; hash ^= *str++; // 4
hash *= b; hash ^= *str++; // 5
hash *= b; hash ^= *str++; // 6
hash *= b; hash ^= *str++; // 7
}
switch (rest)
{
case 7: hash *= b; hash ^= *str++; [[fallthrough]];
case 6: hash *= b; hash ^= *str++; [[fallthrough]];
case 5: hash *= b; hash ^= *str++; [[fallthrough]];
case 4: hash *= b; hash ^= *str++; [[fallthrough]];
case 3: hash *= b; hash ^= *str++; [[fallthrough]];
case 2: hash *= b; hash ^= *str++; [[fallthrough]];
case 1: hash *= b; hash ^= *str++; [[fallthrough]];
case 0: break;
}
return hash;
}
} // namespace
size_t hash_buf(const void* __restrict buf, size_t size) noexcept
{
return fnvhash_buf(buf, size);
}
size_t hash_int(uint32_t x) noexcept
{
return fnvhash_uint(x);
}
size_t hash_int(uint64_t x) noexcept
{
return fnvhash_uint(x);
}
} // namespace floormat::FNVHash
// NOLINTEND(*-multiway-paths-covered, *-switch-missing-default-case)
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