// Skip to the next window and return true, if there is one more:
bool PositionWindow::next()
{
// Calculate how many positions we can skip with the
// first element without loosing any window of a size
// within the defined proximity range:
PostingIteratorInterface* itr = m_set.begin()->itr;
std::set<Element>::iterator top = getWinTopElement();
#ifdef STRUS_LOWLEVEL_DEBUG
printf( "top [%s %u] begin [%s %u]\n",
top->itr->featureid(), top->pos,
m_set.begin()->itr->featureid(), m_set.begin()->pos);
#endif
Index posdiff = top->pos - m_set.begin()->pos;
Index skipsize = posdiff > (Index)m_range ? (posdiff - (Index)m_range) : 1;
// Change the position of the first element in the
// sliding window by the calculated size:
Index pos = m_set.begin()->pos;
#ifdef STRUS_LOWLEVEL_DEBUG
printf( "delete %s %u\n", itr->featureid(), pos);
#endif
m_set.erase( m_set.begin());
Index newpos = itr->skipPos( pos + skipsize);
if (newpos)
{
#ifdef STRUS_LOWLEVEL_DEBUG
printf( "insert %s %u\n", itr->featureid(), newpos);
#endif
m_set.insert( Element( itr, newpos));
}
else
{
--m_setsize;
}
// Return, if there is valid window left:
return m_setsize >= m_cardinality;
}
// Constructor that fills the sliding window implemented as set
// with the argument element start positions:
PositionWindow::PositionWindow(
const std::vector<PostingIteratorInterface*>& args,
unsigned int range_,
unsigned int cardinality_,
Index firstpos_)
:m_args(args)
,m_setsize(0)
,m_range(range_)
,m_cardinality(cardinality_>0?cardinality_:args.size())
{
std::vector<PostingIteratorInterface*>::iterator
ai = m_args.begin(), ae = m_args.end();
for (; ai != ae; ++ai)
{
PostingIteratorInterface* itr = *ai;
Index pos = itr->skipPos( firstpos_);
if (pos)
{
m_set.insert( Element( itr, pos));
++m_setsize;
}
}
}
// Skip to the next window and return true, if there is one more:
bool PositionWindow::next()
{
// Calculate how many positions we can skip with the
// first element without loosing any window of a size
// within the defined proximity range:
PostingIteratorInterface* itr = m_set.begin()->itr;
std::set<Element>::iterator top = getWinTopElement();
Index posdiff = top->pos - m_set.begin()->pos;
Index skipsize = posdiff > m_range ? (posdiff - m_range) : 1;
// Change the position of the first element in the
// sliding window by the calculated size:
Index newpos = itr->skipPos( m_set.begin()->pos + skipsize);
if (newpos)
{
m_set.insert( Element( itr, newpos));
}
else
{
--m_setsize;
}
m_set.erase( m_set.begin());
// Return, if there is valid window left:
return m_setsize >= m_cardinality;
}
