private TreeSpan MapSpanDownToChild(TreeSpan span, int childIndex)
{
Debug.Assert(childIndex >= 0 && childIndex < _nodeCount, $"Assertion failed: {nameof(childIndex)} >= 0 && {nameof(childIndex)} < {nameof(_nodeCount)}");
// Offset the input span
TreeSpan mappedFullSpan = span.Offset(-_offsets[childIndex]);
// Return the intersection
return(TreeSpan.Intersect(mappedFullSpan, _nodes[childIndex].Span));
}
internal override void Sort(TreeSpan span, IComparer <T> comparer)
{
Debug.Assert(span.IsSubspanOf(Span), $"Assertion failed: {nameof(span)}.IsSubspanOf({nameof(Span)})");
Debug.Assert(comparer != null, $"Assertion failed: {nameof(comparer)} != null");
int firstPage = FindLowerBound(_offsets, _nodeCount, span.Start);
int lastPage = firstPage;
for (int i = firstPage; i < _nodeCount; i++)
{
TreeSpan mappedSpan = MapSpanDownToChild(span, i);
if (mappedSpan.IsEmpty)
{
break;
}
lastPage = i;
_nodes[i].Sort(mappedSpan, comparer);
}
if (firstPage != lastPage)
{
// Need to merge the results
int pageCount = lastPage - firstPage + 1;
for (int mergeSegmentSize = 1; mergeSegmentSize < pageCount; mergeSegmentSize *= 2)
{
for (int firstSegment = firstPage; firstSegment < lastPage; firstSegment += mergeSegmentSize * 2)
{
int secondSegment = firstSegment + mergeSegmentSize;
if (secondSegment > lastPage)
{
break;
}
TreeSpan firstSpan = GetSegmentSpan(span, firstSegment, mergeSegmentSize);
TreeSpan secondSpan = GetSegmentSpan(span, secondSegment, mergeSegmentSize);
MergeSegments(firstSpan, secondSpan);
}
}
}
// Local functions
TreeSpan GetSegmentSpan(TreeSpan bounds, int firstPageOfSegment, int segmentPageCount)
{
int lastPageOfSegment = Math.Min(_nodeCount - 1, firstPageOfSegment + segmentPageCount - 1);
int startIndex = _offsets[firstPageOfSegment];
int endIndexExclusive = _offsets[lastPageOfSegment] + _nodes[lastPageOfSegment].Count;
return(TreeSpan.Intersect(bounds, TreeSpan.FromBounds(startIndex, endIndexExclusive)));
}
void MergeSegments(TreeSpan first, TreeSpan second)
{
Debug.Assert(first.IsSubspanOf(Span), $"Assertion failed: {nameof(first)}.IsSubspanOf({nameof(Span)})");
Debug.Assert(second.IsSubspanOf(Span), $"Assertion failed: {nameof(second)}.IsSubspanOf({nameof(Span)})");
Debug.Assert(first.EndExclusive == second.Start, $"Assertion failed: first.EndExclusive == second.Start");
// Stop immediately if already ordered
if (comparer.Compare(this[first.EndInclusive], this[second.Start]) <= 0)
{
return;
}
int i = first.Start;
int j = second.Start;
while (true)
{
if (i == first.EndExclusive)
{
break;
}
Debug.Assert(j < second.EndExclusive, $"Assertion failed: j < second.EndExclusive");
int c = comparer.Compare(this[i], this[j]);
if (c == 0)
{
i++;
}
else if (c < 0)
{
i++;
}
else
{
T temp = this[i];
this[i] = this[j];
this[j] = temp;
i++;
while (i < first.EndExclusive && j < second.EndExclusive - 1 && comparer.Compare(temp, this[j + 1]) > 0)
{
j++;
T temp2 = this[i];
this[i] = this[j];
this[j] = temp2;
i++;
}
if (j > 1 && j + 1 < second.EndExclusive)
{
MergeSegments(TreeSpan.FromBounds(second.Start, j + 1), TreeSpan.FromBounds(j + 1, second.EndExclusive));
}
j = second.Start;
}
}
}
}