Something

#ifdef __linux__
#include <byteswap.h>
#elif defined(__OpenBSD__)
#include <sys/endian.h>
#define bswap_16 __swap16
#define bswap_32 __swap32
#define bswap_64 __swap64
#elif defined(__APPLE__)
#include <libkern/OSByteOrder.h>
#define bswap_16 OSSwapInt16
#define bswap_32 OSSwapInt32
#define bswap_64 OSSwapInt64
#else
#include <sys/endian.h>
#define bswap_16 bswap16
#define bswap_32 bswap32
#define bswap_64 bswap64
#endif