assimp/include/assimp/ByteSwapper.h

/*
Open Asset Import Library (assimp)
----------------------------------------------------------------------

Copyright (c) 2006-2018, assimp team


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  following disclaimer.

* Redistributions in binary form must reproduce the above
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"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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*/

/** @file Helper class tp perform various byte oder swappings
   (e.g. little to big endian) */
#ifndef AI_BYTESWAPPER_H_INC
#define AI_BYTESWAPPER_H_INC

#include <assimp/ai_assert.h>
#include <assimp/types.h>
#include <stdint.h>

#if _MSC_VER >= 1400
#include <stdlib.h>
#endif

namespace Assimp    {
// --------------------------------------------------------------------------------------
/** Defines some useful byte order swap routines.
 *
 * This is required to read big-endian model formats on little-endian machines,
 * and vice versa. Direct use of this class is DEPRECATED. Use #StreamReader instead. */
// --------------------------------------------------------------------------------------
class ByteSwap {
    ByteSwap() noexcept {}

public:

    // ----------------------------------------------------------------------
    /** Swap two bytes of data
     *  @param[inout] _szOut A void* to save the reintcasts for the caller. */
    static inline void Swap2(void* _szOut)
    {
        ai_assert(_szOut);

#if _MSC_VER >= 1400
        uint16_t* const szOut = reinterpret_cast<uint16_t*>(_szOut);
        *szOut = _byteswap_ushort(*szOut);
#else
        uint8_t* const szOut = reinterpret_cast<uint8_t*>(_szOut);
        std::swap(szOut[0],szOut[1]);
#endif
    }

    // ----------------------------------------------------------------------
    /** Swap four bytes of data
     *  @param[inout] _szOut A void* to save the reintcasts for the caller. */
    static inline void Swap4(void* _szOut)
    {
        ai_assert(_szOut);

#if _MSC_VER >= 1400
        uint32_t* const szOut = reinterpret_cast<uint32_t*>(_szOut);
        *szOut = _byteswap_ulong(*szOut);
#else
        uint8_t* const szOut = reinterpret_cast<uint8_t*>(_szOut);
        std::swap(szOut[0],szOut[3]);
        std::swap(szOut[1],szOut[2]);
#endif
    }

    // ----------------------------------------------------------------------
    /** Swap eight bytes of data
     *  @param[inout] _szOut A void* to save the reintcasts for the caller. */
    static inline void Swap8(void* _szOut)
    {
    ai_assert(_szOut);

#if _MSC_VER >= 1400
        uint64_t* const szOut = reinterpret_cast<uint64_t*>(_szOut);
        *szOut = _byteswap_uint64(*szOut);
#else
        uint8_t* const szOut = reinterpret_cast<uint8_t*>(_szOut);
        std::swap(szOut[0],szOut[7]);
        std::swap(szOut[1],szOut[6]);
        std::swap(szOut[2],szOut[5]);
        std::swap(szOut[3],szOut[4]);
#endif
    }

    // ----------------------------------------------------------------------
    /** ByteSwap a float. Not a joke.
     *  @param[inout] fOut ehm. .. */
    static inline void Swap(float* fOut) {
        Swap4(fOut);
    }

    // ----------------------------------------------------------------------
    /** ByteSwap a double. Not a joke.
     *  @param[inout] fOut ehm. .. */
    static inline void Swap(double* fOut) {
        Swap8(fOut);
    }


    // ----------------------------------------------------------------------
    /** ByteSwap an int16t. Not a joke.
     *  @param[inout] fOut ehm. .. */
    static inline void Swap(int16_t* fOut) {
        Swap2(fOut);
    }

    static inline void Swap(uint16_t* fOut) {
        Swap2(fOut);
    }

    // ----------------------------------------------------------------------
    /** ByteSwap an int32t. Not a joke.
     *  @param[inout] fOut ehm. .. */
    static inline void Swap(int32_t* fOut){
        Swap4(fOut);
    }

    static inline void Swap(uint32_t* fOut){
        Swap4(fOut);
    }

    // ----------------------------------------------------------------------
    /** ByteSwap an int64t. Not a joke.
     *  @param[inout] fOut ehm. .. */
    static inline void Swap(int64_t* fOut) {
        Swap8(fOut);
    }

    static inline void Swap(uint64_t* fOut) {
        Swap8(fOut);
    }

    // ----------------------------------------------------------------------
    //! Templatized ByteSwap
    //! \returns param tOut as swapped
    template<typename Type>
    static inline Type Swapped(Type tOut)
    {
        return _swapper<Type,sizeof(Type)>()(tOut);
    }

private:

    template <typename T, size_t size> struct _swapper;
};

template <typename T> struct ByteSwap::_swapper<T,2> {
    T operator() (T tOut) {
        Swap2(&tOut);
        return tOut;
    }
};

template <typename T> struct ByteSwap::_swapper<T,4> {
    T operator() (T tOut) {
        Swap4(&tOut);
        return tOut;
    }
};

template <typename T> struct ByteSwap::_swapper<T,8> {
    T operator() (T tOut) {
        Swap8(&tOut);
        return tOut;
    }
};


// --------------------------------------------------------------------------------------
// ByteSwap macros for BigEndian/LittleEndian support
// --------------------------------------------------------------------------------------
#if (defined AI_BUILD_BIG_ENDIAN)
#   define AI_LE(t) (t)
#   define AI_BE(t) ByteSwap::Swapped(t)
#   define AI_LSWAP2(p)
#   define AI_LSWAP4(p)
#   define AI_LSWAP8(p)
#   define AI_LSWAP2P(p)
#   define AI_LSWAP4P(p)
#   define AI_LSWAP8P(p)
#   define LE_NCONST const
#   define AI_SWAP2(p) ByteSwap::Swap2(&(p))
#   define AI_SWAP4(p) ByteSwap::Swap4(&(p))
#   define AI_SWAP8(p) ByteSwap::Swap8(&(p))
#   define AI_SWAP2P(p) ByteSwap::Swap2((p))
#   define AI_SWAP4P(p) ByteSwap::Swap4((p))
#   define AI_SWAP8P(p) ByteSwap::Swap8((p))
#   define BE_NCONST
#else
#   define AI_BE(t) (t)
#   define AI_LE(t) ByteSwap::Swapped(t)
#   define AI_SWAP2(p)
#   define AI_SWAP4(p)
#   define AI_SWAP8(p)
#   define AI_SWAP2P(p)
#   define AI_SWAP4P(p)
#   define AI_SWAP8P(p)
#   define BE_NCONST const
#   define AI_LSWAP2(p)     ByteSwap::Swap2(&(p))
#   define AI_LSWAP4(p)     ByteSwap::Swap4(&(p))
#   define AI_LSWAP8(p)     ByteSwap::Swap8(&(p))
#   define AI_LSWAP2P(p)    ByteSwap::Swap2((p))
#   define AI_LSWAP4P(p)    ByteSwap::Swap4((p))
#   define AI_LSWAP8P(p)    ByteSwap::Swap8((p))
#   define LE_NCONST
#endif


namespace Intern {

// --------------------------------------------------------------------------------------------
template <typename T, bool doit>
struct ByteSwapper  {
    void operator() (T* inout) {
        ByteSwap::Swap(inout);
    }
};

template <typename T>
struct ByteSwapper<T,false> {
    void operator() (T*) {
    }
};

// --------------------------------------------------------------------------------------------
template <bool SwapEndianess, typename T, bool RuntimeSwitch>
struct Getter {
    void operator() (T* inout, bool le) {
#ifdef AI_BUILD_BIG_ENDIAN
        le =  le;
#else
        le =  !le;
#endif
        if (le) {
            ByteSwapper<T,(sizeof(T)>1?true:false)> () (inout);
        }
        else ByteSwapper<T,false> () (inout);
    }
};

template <bool SwapEndianess, typename T>
struct Getter<SwapEndianess,T,false> {

    void operator() (T* inout, bool /*le*/) {
        // static branch
        ByteSwapper<T,(SwapEndianess && sizeof(T)>1)> () (inout);
    }
};
} // end Intern
} // end Assimp

#endif //!! AI_BYTESWAPPER_H_INC