source: git/src-cryptopp/iterhash.cpp

// iterhash.cpp - written and placed in the public domain by Wei Dai

#ifndef __GNUC__
#define CRYPTOPP_MANUALLY_INSTANTIATE_TEMPLATES
#endif

#include "iterhash.h"
#include "misc.h"

NAMESPACE_BEGIN(CryptoPP)

template <class T, class BASE> void IteratedHashBase<T, BASE>::Update(const byte *input, size_t len)
{
        HashWordType oldCountLo = m_countLo, oldCountHi = m_countHi;
        if ((m_countLo = oldCountLo + HashWordType(len)) < oldCountLo)
                m_countHi++;             // carry from low to high
        m_countHi += (HashWordType)SafeRightShift<8*sizeof(HashWordType)>(len);
        if (m_countHi < oldCountHi || SafeRightShift<2*8*sizeof(HashWordType)>(len) != 0)
                throw HashInputTooLong(this->AlgorithmName());

        const unsigned int blockSize = this->BlockSize();
        unsigned int num = ModPowerOf2(oldCountLo, blockSize);

        T* dataBuf = this->DataBuf();
        byte* data = (byte *)dataBuf;
        CRYPTOPP_ASSERT(dataBuf && data);

        if (num != 0)   // process left over data
        {
                if (num+len >= blockSize)
                {
                        if (data && input) {memcpy(data+num, input, blockSize-num);}
                        HashBlock(dataBuf);
                        input += (blockSize-num);
                        len -= (blockSize-num);
                        num = 0;
                        // drop through and do the rest
                }
                else
                {
                        if (data && input && len) {memcpy(data+num, input, len);}
                        return;
                }
        }

        // now process the input data in blocks of blockSize bytes and save the leftovers to m_data
        if (len >= blockSize)
        {
                if (input == data)
                {
                        CRYPTOPP_ASSERT(len == blockSize);
                        HashBlock(dataBuf);
                        return;
                }
                else if (IsAligned<T>(input))
                {
                        size_t leftOver = HashMultipleBlocks((T *)(void*)input, len);
                        input += (len - leftOver);
                        len = leftOver;
                }
                else
                        do
                        {   // copy input first if it's not aligned correctly
                                if (data && input) memcpy(data, input, blockSize);
                                HashBlock(dataBuf);
                                input+=blockSize;
                                len-=blockSize;
                        } while (len >= blockSize);
        }

        if (data && input && len && data != input)
                memcpy(data, input, len);
}

template <class T, class BASE> byte * IteratedHashBase<T, BASE>::CreateUpdateSpace(size_t &size)
{
        unsigned int blockSize = this->BlockSize();
        unsigned int num = ModPowerOf2(m_countLo, blockSize);
        size = blockSize - num;
        return (byte *)DataBuf() + num;
}

template <class T, class BASE> size_t IteratedHashBase<T, BASE>::HashMultipleBlocks(const T *input, size_t length)
{
        unsigned int blockSize = this->BlockSize();
        bool noReverse = NativeByteOrderIs(this->GetByteOrder());
        T* dataBuf = this->DataBuf();
        do
        {
                if (noReverse)
                        this->HashEndianCorrectedBlock(input);
                else
                {
                        ByteReverse(dataBuf, input, this->BlockSize());
                        this->HashEndianCorrectedBlock(dataBuf);
                }

                input += blockSize/sizeof(T);
                length -= blockSize;
        }
        while (length >= blockSize);
        return length;
}

template <class T, class BASE> void IteratedHashBase<T, BASE>::PadLastBlock(unsigned int lastBlockSize, byte padFirst)
{
        unsigned int blockSize = this->BlockSize();
        unsigned int num = ModPowerOf2(m_countLo, blockSize);
        T* dataBuf = this->DataBuf();
        byte* data = (byte *)dataBuf;
        data[num++] = padFirst;
        if (num <= lastBlockSize)
                memset(data+num, 0, lastBlockSize-num);
        else
        {
                memset(data+num, 0, blockSize-num);
                HashBlock(dataBuf);
                memset(data, 0, lastBlockSize);
        }
}

template <class T, class BASE> void IteratedHashBase<T, BASE>::Restart()
{
        m_countLo = m_countHi = 0;
        Init();
}

template <class T, class BASE> void IteratedHashBase<T, BASE>::TruncatedFinal(byte *digest, size_t size)
{
        this->ThrowIfInvalidTruncatedSize(size);

        T* dataBuf = this->DataBuf();
        T* stateBuf = this->StateBuf();
        unsigned int blockSize = this->BlockSize();
        ByteOrder order = this->GetByteOrder();

        PadLastBlock(blockSize - 2*sizeof(HashWordType));
        dataBuf[blockSize/sizeof(T)-2+order] = ConditionalByteReverse(order, this->GetBitCountLo());
        dataBuf[blockSize/sizeof(T)-1-order] = ConditionalByteReverse(order, this->GetBitCountHi());

        HashBlock(dataBuf);

        if (IsAligned<HashWordType>(digest) && size%sizeof(HashWordType)==0)
                ConditionalByteReverse<HashWordType>(order, (HashWordType *)(void*)digest, stateBuf, size);
        else
        {
                ConditionalByteReverse<HashWordType>(order, stateBuf, stateBuf, this->DigestSize());
                memcpy(digest, stateBuf, size);
        }

        this->Restart();                // reinit for next use
}

#ifdef __GNUC__
        template class IteratedHashBase<word64, HashTransformation>;
        template class IteratedHashBase<word64, MessageAuthenticationCode>;

        template class IteratedHashBase<word32, HashTransformation>;
        template class IteratedHashBase<word32, MessageAuthenticationCode>;
#endif

NAMESPACE_END