Документация по криптоалгоритмам / CRYPTO30 / iterhash

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

#include "pch.h"
#include "iterhash.h"

NAMESPACE_BEGIN(CryptoPP)

template <class T> IteratedHash<T>::IteratedHash(unsigned int blockSize, unsigned int digestSize)
	: blockSize(blockSize), data(blockSize/sizeof(T)), digest(digestSize/sizeof(T))
{
}

template <class T> IteratedHash<T>::~IteratedHash()
{
}

template <class T> void IteratedHash<T>::Update(const byte *input, unsigned int len)
{
	word32 tmp = countLo;
	if ((countLo = tmp + ((word32)len << 3)) < tmp)
		countHi++;             // Carry from low to high
	countHi += len >> 29;

	assert((blockSize & (blockSize-1)) == 0);	// blockSize is a power of 2
	unsigned int num = (unsigned int)(tmp >> 3) & (blockSize-1);

	if (num != 0)
	{
		if ((num+len) >= blockSize)
		{
			memcpy((byte *)data.ptr+num, input, blockSize-num);
			HashBlock(data);
			input += (blockSize-num);
			len-=(blockSize - num);
			num=0;
			// drop through and do the rest
		}
		else
		{
			memcpy((byte *)data.ptr+num, input, len);
			return;
		}
	}

	// we now can process the input data in blocks of blockSize
	// chars and save the leftovers to this->data.
	if (len >= blockSize)
	{
		if ((unsigned int)input % sizeof(T))   // test for alignment
			do
			{   // copy input first if it's not aligned correctly
				memcpy(data, input, blockSize);
				HashBlock(data);
				input+=blockSize;
				len-=blockSize;
			} while (len >= blockSize);
		else
			do
			{
				HashBlock((T *)input);
				input+=blockSize;
				len-=blockSize;
			} while (len >= blockSize);
	}

	memcpy(data, input, len);
}

template <class T> void IteratedHash<T>::PadLastBlock(unsigned int lastBlockSize, byte padFirst)
{
	unsigned int num = (unsigned int)(countLo >> 3) & (blockSize-1);
	assert(num < blockSize);
	((byte *)data.ptr)[num++]=padFirst;
	if (num <= lastBlockSize)
		memset((byte *)data.ptr+num, 0, lastBlockSize-num);
	else
	{
		memset((byte *)data.ptr+num, 0, blockSize-num);
		HashBlock(data);
		memset(data, 0, lastBlockSize);
	}
}

// provide empty definitions to avoid instantiation warnings
template <class T> void IteratedHash<T>::Init() {}
template <class T> void IteratedHash<T>::HashBlock(const T *input) {}

#ifdef WORD64_AVAILABLE
template class IteratedHash<word64>;
#endif

template class IteratedHash<word32>;

NAMESPACE_END