cpp-大小端转换

如果使用 vc 可以使用下面的函数

// For 16 bit numbers:
unsigned short _byteswap_ushort(unsigned short value);
// For 32 bit numbers:
unsigned long _byteswap_ulong(unsigned long value);
// For 64 bit numbers:
unsigned __int64 _byteswap_uint64(unsigned __int64 value);

#include <climits>

template <typename T>
T swap_endian(T u)
{
    static_assert (CHAR_BIT == 8, "CHAR_BIT != 8");

    union
    {
        T u;
        unsigned char u8[sizeof(T)];
    } source, dest;

    source.u = u;

    for (size_t k = 0; k < sizeof(T); k++)
        dest.u8[k] = source.u8[sizeof(T) - k - 1];

    return dest.u;
}

swap_endian<uint32_t>(42);

#ifdef _MSC_VER

#include <stdlib.h>
#define bswap_32(x) _byteswap_ulong(x)
#define bswap_64(x) _byteswap_uint64(x)

#elif defined(__APPLE__)

// Mac OS X / Darwin features
#include <libkern/OSByteOrder.h>
#define bswap_32(x) OSSwapInt32(x)
#define bswap_64(x) OSSwapInt64(x)

#elif defined(__sun) || defined(sun)

#include <sys/byteorder.h>
#define bswap_32(x) BSWAP_32(x)
#define bswap_64(x) BSWAP_64(x)

#elif defined(__FreeBSD__)

#include <sys/endian.h>
#define bswap_32(x) bswap32(x)
#define bswap_64(x) bswap64(x)

#elif defined(__OpenBSD__)

#include <sys/types.h>
#define bswap_32(x) swap32(x)
#define bswap_64(x) swap64(x)

#elif defined(__NetBSD__)

#include <sys/types.h>
#include <machine/bswap.h>
#if defined(__BSWAP_RENAME) && !defined(__bswap_32)
#define bswap_32(x) bswap32(x)
#define bswap_64(x) bswap64(x)
#endif

#else

#include <byteswap.h>

#endif