/** @see <a href="http://en.wikipedia.org/wiki/Sweep_line_algorithm">Sweep line algorithm</a> */
private void sweepCleanColumns(CTCols cols, CTCol[] flattenedColsArray, CTCol overrideColumn) {
List<CTCol> flattenedCols = new ArrayList<CTCol>(Arrays.asList(flattenedColsArray));
TreeSet<CTCol> currentElements = new TreeSet<CTCol>(CTColComparator.BY_MAX);
ListIterator<CTCol> flIter = flattenedCols.listIterator();
CTCol haveOverrideColumn = null;
long lastMaxIndex = 0;
long currentMax = 0;
while (flIter.hasNext()) {
CTCol col = flIter.next();
long currentIndex = col.getMin();
long colMax = col.getMax();
long nextIndex = (colMax > currentMax) ? colMax : currentMax;
if (flIter.hasNext()) {
nextIndex = flIter.next().getMin();
flIter.previous();
}
Iterator<CTCol> iter = currentElements.iterator();
while (iter.hasNext()) {
CTCol elem = iter.next();
if (currentIndex <= elem.getMax()) break; // all passed elements have been purged
iter.remove();
}
if (!currentElements.isEmpty() && lastMaxIndex < currentIndex) {
// we need to process previous elements first
insertCol(
cols,
lastMaxIndex,
currentIndex - 1,
currentElements.toArray(new CTCol[currentElements.size()]),
true,
haveOverrideColumn);
}
currentElements.add(col);
if (colMax > currentMax) currentMax = colMax;
if (col.equals(overrideColumn)) haveOverrideColumn = overrideColumn;
while (currentIndex <= nextIndex && !currentElements.isEmpty()) {
Set<CTCol> currentIndexElements = new HashSet<CTCol>();
long currentElemIndex;
{
// narrow scope of currentElem
CTCol currentElem = currentElements.first();
currentElemIndex = currentElem.getMax();
currentIndexElements.add(currentElem);
while (true) {
CTCol higherElem = currentElements.higher(currentElem);
if (higherElem == null || higherElem.getMax() != currentElemIndex) break;
currentElem = higherElem;
currentIndexElements.add(currentElem);
if (colMax > currentMax) currentMax = colMax;
if (col.equals(overrideColumn)) haveOverrideColumn = overrideColumn;
}
}
if (currentElemIndex < nextIndex || !flIter.hasNext()) {
insertCol(
cols,
currentIndex,
currentElemIndex,
currentElements.toArray(new CTCol[currentElements.size()]),
true,
haveOverrideColumn);
if (flIter.hasNext()) {
if (nextIndex > currentElemIndex) {
currentElements.removeAll(currentIndexElements);
if (currentIndexElements.contains(overrideColumn)) haveOverrideColumn = null;
}
} else {
currentElements.removeAll(currentIndexElements);
if (currentIndexElements.contains(overrideColumn)) haveOverrideColumn = null;
}
lastMaxIndex = currentIndex = currentElemIndex + 1;
} else {
lastMaxIndex = currentIndex;
currentIndex = nextIndex + 1;
}
}
}
sortColumns(cols);
}
