misc.hpp

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#undef min
#endif 

inline word32 min(word32 a, word32 b)
{
    return a < b ? a : b;
}


inline word32 ByteReverse(word32 value)
{
#ifdef PPC_INTRINSICS
    // PPC: load reverse indexed instruction
    return (word32)__lwbrx(&value,0);
#elif defined(FAST_ROTATE)
    // 5 instructions with rotate instruction, 9 without
    return (rotrFixed(value, 8U) & 0xff00ff00) |
           (rotlFixed(value, 8U) & 0x00ff00ff);
#else
    // 6 instructions with rotate instruction, 8 without
    value = ((value & 0xFF00FF00) >> 8) | ((value & 0x00FF00FF) << 8);
    return rotlFixed(value, 16U);
#endif
}


template <typename T>
inline void ByteReverse(T* out, const T* in, word32 byteCount)
{
    assert(byteCount % sizeof(T) == 0);
    word32 count = byteCount/sizeof(T);
    for (word32 i=0; i<count; i++)
        out[i] = ByteReverse(in[i]);
}

inline void ByteReverse(byte* out, const byte* in, word32 byteCount)
{
    word32* o       = reinterpret_cast<word32*>(out);
    const word32* i = reinterpret_cast<const word32*>(in);
    ByteReverse(o, i, byteCount);
}


template <class T>
inline T ByteReverseIf(T value, ByteOrder order)
{
    return HostByteOrderIs(order) ? value : ByteReverse(value);
}


template <typename T>
inline void ByteReverseIf(T* out, const T* in, word32 bc, ByteOrder order)
{
    if (!HostByteOrderIs(order)) 
        ByteReverse(out, in, bc);
    else if (out != in)
        memcpy(out, in, bc);
}


template <class T>
inline void GetUserKey(ByteOrder order, T* out, word32 outlen, const byte* in,
                       word32 inlen)
{
    const unsigned int U = sizeof(T);
    assert(inlen <= outlen*U);
    memcpy(out, in, inlen);
    memset((byte *)out+inlen, 0, outlen*U-inlen);
    ByteReverseIf(out, out, RoundUpToMultipleOf(inlen, U), order);
}


#ifdef _MSC_VER
    // disable conversion warning
    #pragma warning(disable:4244)
#endif


inline byte UnalignedGetWordNonTemplate(ByteOrder order, const byte *block,
                                        byte*)
{
    return block[0];
}

inline word16 UnalignedGetWordNonTemplate(ByteOrder order, const byte* block,
                                          word16*)
{
    return (order == BigEndianOrder)
        ? block[1] | (block[0] << 8)
        : block[0] | (block[1] << 8);
}

inline word32 UnalignedGetWordNonTemplate(ByteOrder order, const byte* block,
                                          word32*)
{
    return (order == BigEndianOrder)
        ? word32(block[3]) | (word32(block[2]) << 8) | (word32(block[1]) << 16)
            | (word32(block[0]) << 24)
        : word32(block[0]) | (word32(block[1]) << 8) | (word32(block[2]) << 16)
            | (word32(block[3]) << 24);
}

template <class T>
inline T UnalignedGetWord(ByteOrder order, const byte *block, T* dummy = 0)
{
    return UnalignedGetWordNonTemplate(order, block, dummy);
}

inline void UnalignedPutWord(ByteOrder order, byte *block, byte value,
                             const byte *xorBlock = 0)
{
    block[0] = xorBlock ? (value ^ xorBlock[0]) : value;
}

#define GETBYTE(x, y) (unsigned int)byte((x)>>(8*(y)))

inline void UnalignedPutWord(ByteOrder order, byte *block, word16 value,
                             const byte *xorBlock = 0)
{
    if (order == BigEndianOrder)
    {
        block[0] = GETBYTE(value, 1);
        block[1] = GETBYTE(value, 0);
    }
    else
    {
        block[0] = GETBYTE(value, 0);
        block[1] = GETBYTE(value, 1);
    }

    if (xorBlock)
    {
        block[0] ^= xorBlock[0];
        block[1] ^= xorBlock[1];
    }
}

inline void UnalignedPutWord(ByteOrder order, byte* block, word32 value,
                             const byte* xorBlock = 0)
{
    if (order == BigEndianOrder)
    {
        block[0] = GETBYTE(value, 3);
        block[1] = GETBYTE(value, 2);
        block[2] = GETBYTE(value, 1);
        block[3] = GETBYTE(value, 0);
    }
    else
    {
        block[0] = GETBYTE(value, 0);
        block[1] = GETBYTE(value, 1);
        block[2] = GETBYTE(value, 2);
        block[3] = GETBYTE(value, 3);
    }

    if (xorBlock)
    {
        block[0] ^= xorBlock[0];
        block[1] ^= xorBlock[1];
        block[2] ^= xorBlock[2];
        block[3] ^= xorBlock[3];
    }
}


template <class T>
inline T GetWord(bool assumeAligned, ByteOrder order, const byte *block)
{
    if (assumeAligned)
    {
        assert(IsAligned<T>(block));
        return ByteReverseIf(*reinterpret_cast<const T *>(block), order);
    }
    else
        return UnalignedGetWord<T>(order, block);
}

template <class T>
inline void GetWord(bool assumeAligned, ByteOrder order, T &result,
                    const byte *block)
{
    result = GetWord<T>(assumeAligned, order, block);
}

template <class T>
inline void PutWord(bool assumeAligned, ByteOrder order, byte* block, T value,
                    const byte *xorBlock = 0)
{
    if (assumeAligned)
    {
        assert(IsAligned<T>(block));
        if (xorBlock)
            *reinterpret_cast<T *>(block) = ByteReverseIf(value, order) 
                ^ *reinterpret_cast<const T *>(xorBlock);
        else
            *reinterpret_cast<T *>(block) = ByteReverseIf(value, order);
    }
    else
        UnalignedPutWord(order, block, value, xorBlock);
}

template <class T, class B, bool A=true>
class GetBlock
{
public:
    GetBlock(const void *block)
        : m_block((const byte *)block) {}

    template <class U>
    inline GetBlock<T, B, A> & operator()(U &x)
    {
        TAOCRYPT_COMPILE_ASSERT(sizeof(U) >= sizeof(T));
        x = GetWord<T>(A, B::ToEnum(), m_block);
        m_block += sizeof(T);
        return *this;
    }

private:
    const byte *m_block;
};

template <class T, class B, bool A = true>
class PutBlock
{
public:
    PutBlock(const void *xorBlock, void *block)
        : m_xorBlock((const byte *)xorBlock), m_block((byte *)block) {}

    template <class U>
    inline PutBlock<T, B, A> & operator()(U x)
    {
        PutWord(A, B::ToEnum(), m_block, (T)x, m_xorBlock);
        m_block += sizeof(T);
        if (m_xorBlock)
            m_xorBlock += sizeof(T);
        return *this;
    }

private:
    const byte *m_xorBlock;
    byte *m_block;
};

template <class T, class B, bool A=true>
struct BlockGetAndPut
{
    // function needed because of C++ grammatical ambiguity between
    // expression-statements and declarations
    static inline GetBlock<T, B, A> Get(const void *block) 
        {return GetBlock<T, B, A>(block);}
    typedef PutBlock<T, B, A> Put;
};



template <bool overflow> struct SafeShifter;

template<> struct SafeShifter<true>
{
    template <class T>
    static inline T RightShift(T value, unsigned int bits)
    {
        return 0;
    }

    template <class T>
    static inline T LeftShift(T value, unsigned int bits)
    {
        return 0;
    }
};

template<> struct SafeShifter<false>
{
    template <class T>
    static inline T RightShift(T value, unsigned int bits)
    {
        return value >> bits;
    }

    template <class T>
    static inline T LeftShift(T value, unsigned int bits)
    {
        return value << bits;
    }
};

template <unsigned int bits, class T>
inline T SafeRightShift(T value)
{
    return SafeShifter<(bits>=(8*sizeof(T)))>::RightShift(value, bits);
}

template <unsigned int bits, class T>
inline T SafeLeftShift(T value)
{
    return SafeShifter<(bits>=(8*sizeof(T)))>::LeftShift(value, bits);
}


inline
word ShiftWordsLeftByBits(word* r, unsigned int n, unsigned int shiftBits)
{
    assert (shiftBits<WORD_BITS);
    word u, carry=0;
    if (shiftBits)
        for (unsigned int i=0; i<n; i++)
        {
            u = r[i];
            r[i] = (u << shiftBits) | carry;
            carry = u >> (WORD_BITS-shiftBits);
        }
    return carry;
}


inline
word ShiftWordsRightByBits(word* r, unsigned int n, unsigned int shiftBits)
{
    assert (shiftBits<WORD_BITS);
    word u, carry=0;
    if (shiftBits)
        for (int i=n-1; i>=0; i--)
        {
            u = r[i];
            r[i] = (u >> shiftBits) | carry;
            carry = u << (WORD_BITS-shiftBits);
        }
    return carry;
}


inline
void ShiftWordsLeftByWords(word* r, unsigned int n, unsigned int shiftWords)
{
    shiftWords = min(shiftWords, n);
    if (shiftWords)
    {
        for (unsigned int i=n-1; i>=shiftWords; i--)
            r[i] = r[i-shiftWords];
        SetWords(r, 0, shiftWords);
    }
}


inline
void ShiftWordsRightByWords(word* r, unsigned int n, unsigned int shiftWords)
{
    shiftWords = min(shiftWords, n);
    if (shiftWords)
    {
        for (unsigned int i=0; i+shiftWords<n; i++)
            r[i] = r[i+shiftWords];
        SetWords(r+n-shiftWords, 0, shiftWords);
    }
}


template <class T1, class T2>
inline T1 SaturatingSubtract(T1 a, T2 b)
{
    TAOCRYPT_COMPILE_ASSERT_INSTANCE(T1(-1)>0, 0);  // T1 is unsigned type
    TAOCRYPT_COMPILE_ASSERT_INSTANCE(T2(-1)>0, 1);  // T2 is unsigned type
    return T1((a > b) ? (a - b) : 0);
}


// declares
unsigned int  BytePrecision(unsigned long value);
unsigned int  BitPrecision(unsigned long);
unsigned long Crop(unsigned long value, unsigned int size);



} // namespace

#endif // TAO_CRYPT_MISC_HPP