实现与 uint64_t 相同的类，如果平台不支持 uint64_t 的话，可以代替之。
目前只完成部分功能，其他功能敬请期待。

uint64.hpp

#include <endian.h>#include <cstdint>#include <type_traits>#include <array> #define MC_BEGIN_NAMESPACE namespace mc {#define MC_END_NAMESPACE } MC_BEGIN_NAMESPACE #if __BYTE_ORDER == __BIG_ENDIANstruct maybe_big_endian : std::true_type {};#elif __BYTE_ORDER == __LITTLE_ENDIANstruct maybe_big_endian : std::false_type {};#else#error "Endianness not defined!"#endif template<typename Array, bool>struct uint64_data : public Array{protected: uint32_t& first() { return (*this)[0]; } uint32_t& second() { return (*this)[1]; } uint32_t first() const { return (*this)[0]; } uint32_t second() const { return (*this)[1]; }}; template<typename Array>struct uint64_data<Array, true> : public Array{protected: uint32_t& first() { return (*this)[1]; } uint32_t& second() { return (*this)[0]; } uint32_t first() const { return (*this)[1]; } uint32_t second() const { return (*this)[0]; }}; class uint64 : public uint64_data<std::array<uint32_t, 2>, maybe_big_endian::value>{public: uint64() = default; //explicit uint64(uint32_t v); uint64(const uint64& o); ~uint64() = default; uint64& operator+=(const uint64& v) noexcept; uint64& operator<<=(unsigned int n) noexcept; uint64& operator>>=(unsigned int n) noexcept; operator uint32_t() { return first(); } friend void swap(uint64& l, uint64& r);}; inline uint64 operator+(const uint64& l, const uint64& r){ auto tmp = l; return tmp += r; } inline uint64 operator>>(const uint64& l, unsigned int n){ auto tmp = l; return tmp >>= n; } inline uint64 operator<<(const uint64& l, unsigned int n){ auto tmp = l; return tmp <<= n; } MC_END_NAMESPACE

uint64.cpp

#include "uint64.hpp" MC_BEGIN_NAMESPACE uint64::uint64(uint32_t v){ first() = v; second() = 0u;} uint64::uint64(const uint64& o){ *this = o;} uint64& uint64::operator+=(const uint64& o) noexcept{ second() += o.second(); // 先计算 second，预防 (this == &o) 的情况 uint32_t old = first(); if ((first() += o.first()) < old) { ++second(); } return *this;} uint64& uint64::operator<<=(unsigned int n) noexcept{ if (n < 32) { second() = (second() << n) | (first() >> (32 - n)); first() <<= n; } else if (n < 64) { second() = first() << (n - 32); first() = 0u; } else { second() = first() = 0u; } return *this;} uint64& uint64::operator>>=(unsigned int n) noexcept{ if (n < 32) { first() = (first() >> n) | (second() << (32 - n)); second() >>= n; } else if (n < 64) { first() = second() >> (n - 32); second() = 0u; } else { second() = first() = 0u; } return *this;} void swap(uint64& l, uint64& r){ if (&l != &r) { auto tmp = l.first(); l.first() = r.first(); r.first() = tmp; tmp = l.second(); l.second() = r.second(); r.second() = tmp; }} MC_END_NAMESPACE

test.cpp

#include <cstdint>#include <cstdio>#include "uint64.hpp" #if 1 typedef mc::uint64 U64; inline void ptype() {std::printf("使用 mc::uint64\n");}#else typedef std::uint64_t U64; inline void ptype() {std::printf("使用 std::uint64_t\n");}#endif void frm(const char* str) { std::printf("%20s", str);} void data_hex(const U64& v) { const uint8_t* p = (const uint8_t*)&v; for (int i = 0; i < 8; ++i) { if (i == 4) std::printf(" "); std::printf("%02x", p[i]); } std::printf("\n");} void test() { uint32_t v = 0xffffffff; U64 a = v; frm("(a = 0xffffffff) => "); data_hex(a); frm("(a >>= 1) => "); data_hex(a >>= 1); a = v; frm("(a <<= 1) => "); data_hex(a <<= 1); a = v; frm("(a += a) => "); data_hex(a += a);} int main() { ptype(); if (mc::maybe_big_endian::value) { std::printf("主机字节序是 big-endian\n"); } else { std::printf("主机字节序是 little-endian\n"); } for (int i = 0; i < 20; ++i) std::printf(" "); if (mc::maybe_big_endian::value) std::printf("H <<<< L H <<<< L\n"); else std::printf("L >>>> H L >>>> H\n"); test(); return 0;}

功能还在逐步完善中，小伙伴们记得关注。