public SectionsIterator(FixedSizeTree.IFixedSizeIterator iterator)
{
this._iterator = iterator;
this._index = 0;
this._isDone = false;
this.Current = -1;
}
private static bool TryMoveNextCyclic(FixedSizeTree.IFixedSizeIterator it, long startPage)
{
if (it.MoveNext())
{
if (it.CurrentKey == startPage)
{
return(false); // we went full circle
}
return(true);
}
// we run out space to move forward, let us go to the start and search from there
return(it.Seek(0) && it.CurrentKey != startPage);
}
private TableValueReader GetTableValueReader(FixedSizeTree.IFixedSizeIterator it)
{
long id;
it.Value.CopyTo((byte *)&id);
int size;
var ptr = DirectRead(id, out size);
return(new TableValueReader(ptr, size)
{
Id = id
});
}
private long?TryFindLargeValue(LowLevelTransaction tx, FixedSizeTree freeSpaceTree, FixedSizeTree.IFixedSizeIterator it, int num)
{
int numberOfNeededFullSections = num / NumberOfPagesInSection;
int numberOfExtraBitsNeeded = num % NumberOfPagesInSection;
var info = new FoundSectionsInfo();
do
{
var stream = it.CreateReaderForCurrent();
{
var current = new StreamBitArray(stream);
var currentSectionId = it.CurrentKey;
//need to find full free pages
if (current.SetCount < NumberOfPagesInSection)
{
info.Clear();
continue;
}
//those sections are not following each other in the memory
if (info.StartSectionId != null && currentSectionId != info.StartSectionId + info.Sections.Count)
{
info.Clear();
}
//set the first section of the sequence
if (info.StartSection == -1)
{
info.StartSection = it.CurrentKey;
info.StartSectionId = currentSectionId;
}
info.Sections.Add(it.CurrentKey);
if (info.Sections.Count != numberOfNeededFullSections)
{
continue;
}
//we found enough full sections now we need just a bit more
if (numberOfExtraBitsNeeded == 0)
{
foreach (var section in info.Sections)
{
freeSpaceTree.Delete(section);
}
return(info.StartSectionId * NumberOfPagesInSection);
}
StreamBitArray next;
var nextSectionId = currentSectionId + 1;
Slice read;
using (freeSpaceTree.Read(nextSectionId, out read))
{
if (!read.HasValue)
{
//not a following next section
info.Clear();
continue;
}
next = new StreamBitArray(read.CreateReader());
}
if (next.HasStartRangeCount(numberOfExtraBitsNeeded) == false)
{
//not enough start range count
info.Clear();
continue;
}
//mark selected bits to false
if (next.SetCount == numberOfExtraBitsNeeded)
{
freeSpaceTree.Delete(nextSectionId);
}
else
{
for (int i = 0; i < numberOfExtraBitsNeeded; i++)
{
next.Set(i, false);
}
Slice val;
using (next.ToSlice(tx.Allocator, out val))
freeSpaceTree.Add(nextSectionId, val);
}
foreach (var section in info.Sections)
{
freeSpaceTree.Delete(section);
}
return(info.StartSectionId * NumberOfPagesInSection);
}
} while (it.MoveNext());
return(null);
}
private bool TryFindContinuousRange(LowLevelTransaction tx, FixedSizeTree freeSpaceTree, FixedSizeTree.IFixedSizeIterator it, int num,
StreamBitArray current, long currentSectionId, out long?page)
{
page = -1;
var start = -1;
var count = 0;
for (int i = 0; i < NumberOfPagesInSection; i++)
{
if (current.Get(i))
{
if (start == -1)
{
start = i;
}
count++;
if (count == num)
{
page = currentSectionId * NumberOfPagesInSection + start;
break;
}
}
else
{
start = -1;
count = 0;
}
}
if (count != num)
{
return(false);
}
if (current.SetCount == num)
{
freeSpaceTree.Delete(it.CurrentKey);
}
else
{
for (int i = 0; i < num; i++)
{
current.Set(i + start, false);
}
Slice val;
using (current.ToSlice(tx.Allocator, out val))
freeSpaceTree.Add(it.CurrentKey, val);
}
return(true);
}
private long?TryFindSmallValue(LowLevelTransaction tx, FixedSizeTree freeSpaceTree, FixedSizeTree.IFixedSizeIterator it, int num)
{
do
{
var current = new StreamBitArray(it.CreateReaderForCurrent());
long?page;
if (current.SetCount < num)
{
if (TryFindSmallValueMergingTwoSections(tx, freeSpaceTree, it.CurrentKey, num, current, out page))
{
return(page);
}
continue;
}
if (TryFindContinuousRange(tx, freeSpaceTree, it, num, current, it.CurrentKey, out page))
{
return(page);
}
//could not find a continuous so trying to merge
if (TryFindSmallValueMergingTwoSections(tx, freeSpaceTree, it.CurrentKey, num, current, out page))
{
return(page);
}
}while (it.MoveNext());
return(null);
}
