一、背景介绍： 函数指针始终不太灵活，它只能指向全局或静态函数，对于类成员函数、lambda表达式或其他可...
hashcode=hashcode*seed+((*p)>>((sizeof(uint64_t)-tail)<<3));// 大端模式#else#error unexpected ccomplier(msc/gcc)#endifreturn(result_type)hashcode;}};/* SFINAE 判断T有没有std::hash<T>特例实现 */template<typenameU>staticstd::hash<U>test(decltype(declval<std::hash<U>>().operator()...
FNV-1a代码实现(C++) usingByte =uint8_t;constexpruint64_tc_offsetBasis =14695981039346656037;constexpruint64_tc_FNVPrime =1099511628211;uint64_tfnv1a(Byte* bs,size_tlen){uint64_th = c_offsetBasis;for(size_ti =0; i < len; ++i) { h = h ^ bs[i]; h = h * c_FNVPrime; }r...
表示散列值的 std::size_t。 异常散列函数不应抛异常。 示例下列代码演示如何为自定义类特化 std::hash 模板。此散列函数使用 Fowler–Noll–Vo 散列算法。 运行此代码 #include <cstdint> #include <functional> #include <iostream> #include <string> struct Employee { std::string name; std::uint64_t ...
接下来,我为 32 位和 64 位版本提供别名。参数取自 Landon Curt Noll 的网站。 using fnv1a_32 = basic_fnv1a<std::uint32_t, UINT32_C(2166136261), UINT32_C(16777619)>; using fnv1a_64 = basic_fnv1a<std::uint64_t, UINT64_C(14695981039346656037), UINT64_C(1099511628211)>; 最后...
size_t _Len> +inline TEST_ALWAYS_INLINE std::size_t hash_len_0_to_8(const char* __s) { + static_assert(_Len == 4 || _Len == 8, ""); + const uint64_t __a = loadword<uint32_t>(__s); + const uint64_t __b = loadword<uint32_t>(__s + _Len - 4); + ...
size_t size, uint64_t scaling_factor_inverse, bool is_signed = true, typename = typename std::enable_if_t<is_base_2(scaling_factor_inverse)>, typename UnderlyingIntegerType = typename std::conditional_t<(size == 16) && is_signed, std::int16_t, typename std::conditional_t<(size =...
{ public: std::uint64_t operator()(const Employee& employee) const { // computes the hash of an employee using a variant // of the Fowler-Noll-Vo hash function constexpr std::uint64_t prime{0x100000001B3}; std::uint64_t result{0xcbf29ce484222325}; for (std::uint64_t i{}, ie...