thin-provisioning-tools/base/rolling_hash.cc

#include "base/rolling_hash.h"

using namespace base;
using namespace boost;
using namespace hash_detail;
using namespace std;

//----------------------------------------------------------------

rolling_hash::rolling_hash(unsigned window_size)
	: a_(MULTIPLIER),
	  a_to_k_minus_1_(a_),
	  window_size_(window_size),
	  buffer_(window_size) {

	for (unsigned i = 1; i < window_size_ - 1; i++)
		a_to_k_minus_1_ *= a_;

	reset();
}

void
rolling_hash::reset()
{
	// prime with zeroes
	buffer_.clear();

	hash_ = 0;
	for (unsigned i = 0; i < window_size_; i++) {
		hash_ = (hash_ * a_) + SEED;
		buffer_.push_back(0);
	}
}

//--------------------------------

content_based_hash::content_based_hash(unsigned window_size)
	: rhash_(window_size),

	  // FIXME: hard coded values
	  backup_div_((window_size / 4) - 1),
	  div_((window_size / 2) - 1),
	  min_len_(window_size / 8),
	  max_len_(window_size),
	  len_(0)
{
}

void
content_based_hash::reset()
{
	len_ = 0;
	backup_break_.reset();
	rhash_.reset();
}

//----------------------------------------------------------------