private static IEnumerable <ITagSpan <TTag> > GetTags(NormalizedSnapshotSpanCollection requestedSpans, ITagSpanIntervalTree <TTag> tags)
{
// Special case the case where there is only one requested span. In that case, we don't
// need to allocate any intermediate collections
return(requestedSpans.Count == 1
? tags.GetIntersectingSpans(requestedSpans[0])
: requestedSpans.Count < MaxNumberOfRequestedSpans
? GetTagsForSmallNumberOfSpans(requestedSpans, tags)
: GetTagsForLargeNumberOfSpans(requestedSpans, tags));
}
private static IEnumerable <ITagSpan <TTag> > GetTagsForSmallNumberOfSpans(
NormalizedSnapshotSpanCollection requestedSpans,
ITagSpanIntervalTree <TTag> tags)
{
var result = new List <ITagSpan <TTag> >();
foreach (var s in requestedSpans)
{
result.AddRange(tags.GetIntersectingSpans(s));
}
return(result);
}
private static IEnumerable <ITagSpan <TTag> > GetTagsForLargeNumberOfSpans(
NormalizedSnapshotSpanCollection requestedSpans,
ITagSpanIntervalTree <TTag> tags)
{
// we are asked with bunch of spans. rather than asking same question again and again, ask once with big span
// which will return superset of what we want. and then filter them out in O(m+n) cost.
// m == number of requested spans, n = number of returned spans
var mergedSpan = new SnapshotSpan(requestedSpans[0].Start, requestedSpans[requestedSpans.Count - 1].End);
var result = tags.GetIntersectingSpans(mergedSpan);
int requestIndex = 0;
var enumerator = result.GetEnumerator();
try
{
if (!enumerator.MoveNext())
{
return(SpecializedCollections.EmptyEnumerable <ITagSpan <TTag> >());
}
var hashSet = new HashSet <ITagSpan <TTag> >();
while (true)
{
var currentTag = enumerator.Current;
var currentRequestSpan = requestedSpans[requestIndex];
var currentTagSpan = currentTag.Span;
if (currentRequestSpan.Start > currentTagSpan.End)
{
if (!enumerator.MoveNext())
{
break;
}
}
else if (currentTagSpan.Start > currentRequestSpan.End)
{
requestIndex++;
if (requestIndex >= requestedSpans.Count)
{
break;
}
}
else
{
if (currentTagSpan.Length > 0)
{
hashSet.Add(currentTag);
}
if (!enumerator.MoveNext())
{
break;
}
}
}
return(hashSet);
}
finally
{
enumerator.Dispose();
}
}