//These methods require a lock on SyncRoot. They will not block regular per segment accessors (for long)
/// <summary>
/// Enumerates all segments in _CurrentRange and locking them before yielding them and resleasing the lock afterwards
/// The order in which the segments are returned is undefined.
/// Lock SyncRoot before using this enumerable.
/// </summary>
/// <returns></returns>
internal IEnumerable <Segment <TStored, TSearch> > EnumerateAmorphLockedSegments(bool forReading)
{
//if segments are locked a queue will be created to try them later
//this is so that we can continue with other not locked segments.
Queue <Segment <TStored, TSearch> > lockedSegmentIxs = null;
for (int i = 0, end = _CurrentRange.Count; i != end; ++i)
{
var segment = _CurrentRange.GetSegmentByIndex(i);
if (segment.Lock(forReading))
{
try { yield return(segment); }
finally { segment.Release(forReading); }
}
else
{
if (lockedSegmentIxs == null)
{
lockedSegmentIxs = new Queue <Segment <TStored, TSearch> >();
}
lockedSegmentIxs.Enqueue(segment);
}
}
if (lockedSegmentIxs != null)
{
var ctr = lockedSegmentIxs.Count;
while (lockedSegmentIxs.Count != 0)
{
//once we retried them all and we are still not done.. wait a bit.
if (ctr-- == 0)
{
new System.Threading.ManualResetEvent(false).WaitOne(0);
ctr = lockedSegmentIxs.Count;
}
var segment = lockedSegmentIxs.Dequeue();
if (segment.Lock(forReading))
{
try { yield return(segment); }
finally { segment.Release(forReading); }
}
else
{
lockedSegmentIxs.Enqueue(segment);
}
}
}
}
/// <summary>
/// Adjusts the segmentation to the new segment count
/// </summary>
/// <param name="newSegmentCount">The new number of segments to use. This must be a power of 2.</param>
/// <param name="segmentSize">The number of item slots to reserve in each segment.</param>
void SetSegmentation(Int32 newSegmentCount, Int32 segmentSize)
{
//Variables to detect a bad hash.
var totalNewSegmentSize = 0;
var largestSegmentSize = 0;
//Segment<TStored,TSearch> largestSegment = null;
lock (SyncRoot)
{
#if DEBUG
//<<<<<<<<<<<<<<<<<<<< debug <<<<<<<<<<<<<<<<<<<<<<<<
//{
// int minSize = _CurrentRange.GetSegmentByIndex(0)._List.Length;
// int maxSize = minSize;
// for (int i = 1, end = _CurrentRange.Count; i < end; ++i)
// {
// int currentSize = _CurrentRange.GetSegmentByIndex(i)._List.Length;
// if (currentSize < minSize)
// minSize = currentSize;
// if (currentSize > maxSize)
// maxSize = currentSize;
// }
// System.Diagnostics.Debug.Assert(maxSize <= 8 * minSize, "Probably a bad hash");
//}
//>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
#endif
unchecked
{
//create the new range
Segmentrange <TStored, TSearch> newRange = CreateSegmentRange(newSegmentCount, segmentSize);
//increase total allocated space now. We can do this safely
//because at this point _AssessSegmentationPending flag will be true,
//preventing an immediate reassesment.
Interlocked.Increment(ref _AllocatedSpace);
//lock all new segments
//we are going to release these locks while we migrate the items from the
//old (current) range to the new range.
for (int i = 0, end = newRange.Count; i != end; ++i)
{
newRange.GetSegmentByIndex(i).LockForWriting();
}
//set new (completely locked) range
Interlocked.Exchange(ref _NewRange, newRange);
//calculate the step sizes for our switch points
var currentSwitchPointStep = (UInt32)(1 << _CurrentRange.Shift);
var newSwitchPointStep = (UInt32)(1 << newRange.Shift);
//position in new range up from where the new segments are locked
var newLockedPoint = (UInt32)0;
//At this moment _SwitchPoint should be 0
var switchPoint = (UInt32)_SwitchPoint;
do
{
Segment <TStored, TSearch> currentSegment;
do
{
//aquire segment to migrate
currentSegment = _CurrentRange.GetSegment(switchPoint);
//lock segment
currentSegment.LockForWriting();
if (currentSegment.IsAlive)
{
break;
}
currentSegment.ReleaseForWriting();
}while (true);
//migrate all items in the segment to the new range
TStored currentKey;
int it = -1;
while ((it = currentSegment.GetNextItem(it, out currentKey, this)) >= 0)
{
var currentKeyHash = this.GetItemHashCode(ref currentKey);
//get the new segment. this is already locked.
var newSegment = _NewRange.GetSegment(currentKeyHash);
TStored dummyKey;
newSegment.InsertItem(ref currentKey, out dummyKey, this);
}
//substract allocated space from allocated space count and trash segment.
currentSegment.Bye(this);
currentSegment.ReleaseForWriting();
if (switchPoint == 0 - currentSwitchPointStep)
{
//we are about to wrap _SwitchPoint arround.
//We have migrated all items from the entire table to the
//new range.
//replace current with new before advancing, otherwise
//we would create a completely blocked table.
Interlocked.Exchange(ref _CurrentRange, newRange);
}
//advance _SwitchPoint
switchPoint = (UInt32)Interlocked.Increment(ref _SwitchPoint);
//release lock of new segments upto the point where we can still add new items
//during this migration.
while (true)
{
var nextNewLockedPoint = newLockedPoint + newSwitchPointStep;
if (nextNewLockedPoint > switchPoint || nextNewLockedPoint == 0)
{
break;
}
var newSegment = newRange.GetSegment(newLockedPoint);
newSegment.Trim(this);
var newSegmentSize = newSegment._Count;
totalNewSegmentSize += newSegmentSize;
if (newSegmentSize > largestSegmentSize)
{
largestSegmentSize = newSegmentSize;
//largestSegment = newSegment;
}
newSegment.ReleaseForWriting();
newLockedPoint = nextNewLockedPoint;
}
}while (switchPoint != 0);
//unlock any remaining new segments
while (newLockedPoint != 0)
{
var newSegment = newRange.GetSegment(newLockedPoint);
newSegment.Trim(this);
var newSegmentSize = newSegment._Count;
totalNewSegmentSize += newSegmentSize;
if (newSegmentSize > largestSegmentSize)
{
largestSegmentSize = newSegmentSize;
//largestSegment = newSegment;
}
newSegment.ReleaseForWriting();
newLockedPoint += newSwitchPointStep;
}
}
}
}