/// <summary>
/// Constructor
/// </summary>
/// <param name="beginAddress"></param>
/// <param name="endAddress"></param>
/// <param name="scanBufferingMode"></param>
/// <param name="epoch"></param>
/// <param name="logPageSizeBits"></param>
/// <param name="initForReads"></param>
public unsafe ScanIteratorBase(long beginAddress, long endAddress, ScanBufferingMode scanBufferingMode, LightEpoch epoch, int logPageSizeBits, bool initForReads = true)
{
// If we are protected when creating the iterator, we do not need per-GetNext protection
if (epoch != null && !epoch.ThisInstanceProtected())
{
this.epoch = epoch;
}
this.beginAddress = beginAddress;
this.endAddress = endAddress;
this.logPageSizeBits = logPageSizeBits;
currentAddress = -1;
nextAddress = beginAddress;
if (scanBufferingMode == ScanBufferingMode.SinglePageBuffering)
{
frameSize = 1;
}
else if (scanBufferingMode == ScanBufferingMode.DoublePageBuffering)
{
frameSize = 2;
}
else if (scanBufferingMode == ScanBufferingMode.NoBuffering)
{
frameSize = 0;
return;
}
if (initForReads)
{
InitializeForReads();
}
}
/// <summary>
/// Attempts to advance the version to the target version, executing the given action in a critical section
/// where no batches are being processed before entering the next version. Each version will be advanced to
/// exactly once. This method may fail and return false if given target version is not larger than the
/// current version (possibly due to concurrent invocations to advance to the same version).
/// After the method returns, subsequent calls to Version() and Enter() will return at least the value of
/// targetVersion.
/// </summary>
/// <param name="criticalSection"> The logic to execute in a critical section </param>
/// <param name="targetVersion"> The version to advance to, or -1 for the immediate next version</param>
/// <returns> Whether the advance was successful </returns>
public bool TryAdvanceVersion(Action <long, long> criticalSection, long targetVersion = -1)
{
var ev = new ManualResetEventSlim();
// Compare and exchange to install our advance
while (Interlocked.CompareExchange(ref versionChanged, ev, null) != null)
{
}
if (targetVersion != -1 && targetVersion <= version)
{
versionChanged.Set();
versionChanged = null;
return(false);
}
// Any thread that sees ev will be in v + 1, because the bump happens only after ev is set.
var original = Interlocked.Read(ref version);
epoch.BumpCurrentEpoch(() =>
{
version = targetVersion == -1 ? original + 1 : targetVersion;
criticalSection(original, version);
versionChanged.Set();
versionChanged = null;
});
// Make sure that even if we are the only thread, we are able to make progress
if (!epoch.ThisInstanceProtected())
{
epoch.Resume();
epoch.Suspend();
}
return(true);
}
/// <summary>
/// Constructor
/// </summary>
/// <param name="hlog"></param>
/// <param name="beginAddress"></param>
/// <param name="endAddress"></param>
/// <param name="scanBufferingMode"></param>
/// <param name="epoch"></param>
public unsafe GenericScanIterator(GenericAllocator <Key, Value> hlog, long beginAddress, long endAddress, ScanBufferingMode scanBufferingMode, LightEpoch epoch)
{
this.hlog = hlog;
// If we are protected when creating the iterator, we do not need per-GetNext protection
if (!epoch.ThisInstanceProtected())
{
this.epoch = epoch;
}
if (beginAddress == 0)
{
beginAddress = hlog.GetFirstValidLogicalAddress(0);
}
this.endAddress = endAddress;
recordSize = hlog.GetRecordSize(0).Item2;
currentAddress = -1;
nextAddress = beginAddress;
if (scanBufferingMode == ScanBufferingMode.SinglePageBuffering)
{
frameSize = 1;
}
else if (scanBufferingMode == ScanBufferingMode.DoublePageBuffering)
{
frameSize = 2;
}
else if (scanBufferingMode == ScanBufferingMode.NoBuffering)
{
frameSize = 0;
return;
}
frame = new GenericFrame <Key, Value>(frameSize, hlog.PageSize);
loaded = new CountdownEvent[frameSize];
// Only load addresses flushed to disk
if (nextAddress < hlog.HeadAddress)
{
var frameNumber = (nextAddress >> hlog.LogPageSizeBits) % frameSize;
hlog.AsyncReadPagesFromDeviceToFrame
(nextAddress >> hlog.LogPageSizeBits,
1, endAddress, AsyncReadPagesCallback, Empty.Default,
frame, out loaded[frameNumber]);
}
}
/// <summary>
/// Constructor
/// </summary>
/// <param name="beginAddress"></param>
/// <param name="endAddress"></param>
/// <param name="scanBufferingMode"></param>
/// <param name="epoch"></param>
/// <param name="logPageSizeBits"></param>
public unsafe ScanIteratorBase(long beginAddress, long endAddress, ScanBufferingMode scanBufferingMode, LightEpoch epoch, int logPageSizeBits)
{
// If we are protected when creating the iterator, we do not need per-GetNext protection
if (!epoch.ThisInstanceProtected())
{
this.epoch = epoch;
}
this.beginAddress = beginAddress;
this.endAddress = endAddress;
this.logPageSizeBits = logPageSizeBits;
currentAddress = -1;
nextAddress = beginAddress;
if (scanBufferingMode == ScanBufferingMode.SinglePageBuffering)
{
frameSize = 1;
}
else if (scanBufferingMode == ScanBufferingMode.DoublePageBuffering)
{
frameSize = 2;
}
else if (scanBufferingMode == ScanBufferingMode.NoBuffering)
{
frameSize = 0;
return;
}
loaded = new CountdownEvent[frameSize];
loadedCancel = new CancellationTokenSource[frameSize];
loadedPage = new long[frameSize];
nextLoadedPage = new long[frameSize];
for (int i = 0; i < frameSize; i++)
{
loadedPage[i] = -1;
nextLoadedPage[i] = -1;
loadedCancel[i] = new CancellationTokenSource();
}
}
