ydb/util/system/byteorder.h

#pragma once

#include "defaults.h"

// #define USE_GENERIC_ENDIAN_CVT

#if defined(_linux_) && !defined(USE_GENERIC_ENDIAN_CVT)
    #include <byteswap.h>
#elif defined(_darwin_)
    #if defined(_arm_) || defined(__IOS__)
        #include <architecture/byte_order.h>
    #else
        #include <machine/byte_order.h>
    #endif
#else
    #include <util/generic/utility.h>
#endif

#if defined(_linux_) && !defined(USE_GENERIC_ENDIAN_CVT)
    #define SwapBytes16 bswap_16
    #define SwapBytes32 bswap_32
    #define SwapBytes64 bswap_64
#elif defined(_darwin_)
    #ifdef _arm_
        #define SwapBytes16 _OSSwapInt16
        #define SwapBytes32 _OSSwapInt32
        #define SwapBytes64 _OSSwapInt64
    #else
        #define SwapBytes16 OSSwapInt16
        #define SwapBytes32 OSSwapInt32
        #define SwapBytes64 OSSwapInt64
    #endif
#endif

#ifndef SwapBytes16
inline ui16 SwapBytes16(ui16 val) noexcept {
    #define byte_n(__val, __n) ((((unsigned char*)(&__val))[__n]))
    DoSwap(byte_n(val, 0), byte_n(val, 1));
    return val;
    #undef byte_n
}
#endif

#ifndef SwapBytes32
inline ui32 SwapBytes32(ui32 val) noexcept {
    #define byte_n(__val, __n) ((((unsigned char*)(&__val))[__n]))
    DoSwap(byte_n(val, 0), byte_n(val, 3));
    DoSwap(byte_n(val, 1), byte_n(val, 2));
    return val;
    #undef byte_n
}
#endif

#ifndef SwapBytes64
inline ui64 SwapBytes64(ui64 val) noexcept {
    union {
        ui64 val;
        ui32 p[2];
    } tmp, ret;

    tmp.val = val;
    ret.p[0] = SwapBytes32(tmp.p[1]);
    ret.p[1] = SwapBytes32(tmp.p[0]);

    return ret.val;
}
#endif

// for convenience
static inline ui8 SwapBytes8(ui8 v) noexcept {
    return v;
}

namespace NSwapBytes {
    template <unsigned N>
    struct TSwapBytesHelper {
    };

#define DEF_SB(X)                             \
    template <>                               \
    struct TSwapBytesHelper<X> {              \
        template <class T>                    \
        static inline T Swap(T t) noexcept {  \
            return (T)SwapBytes##X((ui##X)t); \
        }                                     \
    };

    DEF_SB(8)
    DEF_SB(16)
    DEF_SB(32)
    DEF_SB(64)

#undef DEF_SB
} // namespace NSwapBytes

template <class T>
inline T SwapBytes(T val) noexcept {
    return NSwapBytes::TSwapBytesHelper<sizeof(T) * 8>::Swap(val);
}

template <class T>
inline T LittleToBig(T val) noexcept {
    return SwapBytes(val);
}

template <class T>
inline T BigToLittle(T val) noexcept {
    return LittleToBig(val);
}

template <class T>
inline T HostToInet(T val) noexcept {
#if defined(_big_endian_)
    return val;
#elif defined(_little_endian_)
    return LittleToBig(val);
#else
    #error todo
#endif
}

template <class T>
inline T InetToHost(T val) noexcept {
    return HostToInet(val);
}

template <class T>
inline T HostToLittle(T val) noexcept {
#if defined(_big_endian_)
    return BigToLittle(val);
#elif defined(_little_endian_)
    return val;
#else
    #error todo
#endif
}

template <class T>
inline T LittleToHost(T val) noexcept {
    return HostToLittle(val);
}