C实现与 uint64_t 相同功能的类

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_ENDIAN
struct maybe_big_endian : std::true_type {};
#elif __BYTE_ORDER == __LITTLE_ENDIAN
struct 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 /*if (n >= 64)*/ {
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 /*if (n >= 64)*/ {
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。

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