private void SaveValues(IEnumerable <T> values, int currentTransaction)
{
if (stream == null)
{
throw new InvalidOperationException("No active stream.");
}
lock (stream)
{
var indexStreamPosition = stream.Position;
// Acquire lock on end of file (for appending)
// This will prevent another thread from writing at the same time, or reading before it is flushed.
if (LockEnabled && stream is FileStream)
{
NativeLockFile.LockFile((FileStream)stream, indexStreamPosition, long.MaxValue - indexStreamPosition, true);
}
try
{
// Make sure we read up entries up to end of file (or skip it if AutoLoadNewValues is not set)
if (AutoLoadNewValues)
{
RefreshData(stream.Length);
}
else
{
stream.Position = stream.Length;
}
foreach (var value in values)
{
WriteEntry(stream, value);
}
stream.Flush();
// Transfer from temporary mapping to real mapping (so that loadedIdMap is updated in right order)
lock (lockObject)
{
RemoveUnsaved(values, currentTransaction);
foreach (var value in values)
{
AddLoaded(value);
}
}
}
finally
{
if (LockEnabled && stream is FileStream)
{
NativeLockFile.UnlockFile((FileStream)stream, indexStreamPosition, long.MaxValue - indexStreamPosition);
}
}
}
}
/// <summary>
/// Refreshes URL to ObjectId mapping from the latest results in the index file.
/// </summary>
/// <returns>True on success.</returns>
public bool LoadNewValues()
{
if (stream == null)
{
throw new InvalidOperationException("No active stream.");
}
lock (stream)
{
var position = stream.Position;
var fileSize = stream.Length;
if (position == fileSize)
{
return(true);
}
// Lock content that will be read.
// This lock doesn't prevent concurrent writing since we lock only until current known filesize.
// In the case where fileSize was taken at the time of an incomplete append, this lock will also wait for completion of the last write.
// Note: Maybe we should release the lock quickly so that two threads can read at the same time?
// Or if the previously described case doesn't happen, maybe no lock at all is required?
// Otherwise, last possibility would be deterministic filesize (with size encoded at the beginning of each block).
if (LockEnabled && stream is FileStream)
{
NativeLockFile.LockFile((FileStream)stream, position, long.MaxValue - position, false);
}
try
{
// update the size after the lock
fileSize = stream.Length;
RefreshData(fileSize);
}
finally
{
// Release the lock
if (LockEnabled && stream is FileStream)
{
NativeLockFile.UnlockFile((FileStream)stream, position, long.MaxValue - position);
}
}
return(true);
}
}