private int NextNonExcluded()
{
Debug.Assert(_candidates != null);
Debug.Assert(_exclusions != null);
var candidate = _candidates.Doc;
var excluded = _exclusions.Doc;
do
{
if (candidate < excluded)
{
return(candidate); // candidate before next exclusion
}
if (candidate > excluded)
{
excluded = _exclusions.Advance(candidate);
if (excluded == NoMoreDocs)
{
_exclusions = null; // no more exclusions
return(candidate);
}
if (candidate < excluded)
{
return(candidate); // candidate before next exclusion
}
}
// else: candidate == excluded, try next candidate
}while ((candidate = _candidates.NextDoc()) != NoMoreDocs);
_candidates = null; // no more candidates
return(NoMoreDocs);
}
public override int Advance(int target)
{
if (_candidates == null)
{
return(Doc = NoMoreDocs);
}
if (_exclusions == null)
{
return(Doc = _candidates.Advance(target));
}
if (_candidates.Advance(target) == NoMoreDocs)
{
_candidates = null;
return(Doc = NoMoreDocs);
}
return(Doc = NextNonExcluded());
}
public override int NextDoc()
{
if (_candidates == null)
{
return(Doc = NoMoreDocs);
}
Doc = _candidates.NextDoc();
if (Doc == NoMoreDocs)
{
_candidates = null; // exhausted
return(Doc);
}
if (_exclusions == null)
{
return(Doc); // nothing more to subtract
}
return(Doc = NextNonExcluded());
}
public ButNotIterator(DocSetIterator candidates, DocSetIterator exclusions)
{
_candidates = candidates; // can be null
_exclusions = exclusions; // can be null
}