words.h

#ifndef CRYPTOPP_WORDS_H
#define CRYPTOPP_WORDS_H

#include "misc.h"

NAMESPACE_BEGIN(CryptoPP)

inline size_t CountWords(const word *X, size_t N)
{
        while (N && X[N-1]==0)
                N--;
        return N;
}

inline void SetWords(word *r, word a, size_t n)
{
        for (size_t i=0; i<n; i++)
                r[i] = a;
}

inline void CopyWords(word *r, const word *a, size_t n)
{
        for (size_t i=0; i<n; i++)
                r[i] = a[i];
}

inline void XorWords(word *r, const word *a, const word *b, size_t n)
{
        for (size_t i=0; i<n; i++)
                r[i] = a[i] ^ b[i];
}

inline void XorWords(word *r, const word *a, size_t n)
{
        for (size_t i=0; i<n; i++)
                r[i] ^= a[i];
}

inline void AndWords(word *r, const word *a, const word *b, size_t n)
{
        for (size_t i=0; i<n; i++)
                r[i] = a[i] & b[i];
}

inline void AndWords(word *r, const word *a, size_t n)
{
        for (size_t i=0; i<n; i++)
                r[i] &= a[i];
}

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

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

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

NAMESPACE_END

#endif

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