/// <summary>
/// Update this position after reading another data item
/// </summary>
/// <param name="lastReadDataItem">
/// Last data item that has been read from this folder
/// </param>
public void Update(IDataItem lastReadDataItem)
{
if (Time == lastReadDataItem.DateTime)
{
++NumberOfItemsWithTheTimestampRead;
}
else
{
Time = lastReadDataItem.DateTime;
NumberOfItemsWithTheTimestampRead = 1;
}
VerificationLastReadItemHash = lastReadDataItem.GetBusinessHashCode();
}
private void SkipItemsByExactPosition()
{
Check.Require(_position.IsExact, "Position must be exact");
Check.Require(!_listReader.HasItem || _timeComparison.Compare(_listReader.Current.DateTime, _position.Time) >= 0
, "Reader must be alredy rolled forward to the position time");
IDataItem itemFromPosition = null;
string warningMessage = string.Empty;
// skipping items with the timestamp equal to the position time which had already been read
// note that in exact positions (where IsExact equals true) NumberOfItemsWithTheTimestampRead is always greater than zero,
// otherwise it's not an exact position and versification is not required;
// this loop will be executed for exact positions only, at least once (thus we either detect position restore issue or move forward
// until past the last read item as recorded in the position);
// if the file does not contain item with timestamp equal to the last read item timestamp in the exact position
// the item from position will not be found
FolderSeekStatus.PositionStatus status = FolderSeekStatus.PositionStatus.Success;
for (
int n = 0;
status == FolderSeekStatus.PositionStatus.Success && n < _position.NumberOfItemsWithTheTimestampRead;
++n)
{
if (!_listReader.HasItem || _listReader.Current.DateTime != _position.Time)
{
// using Round-trip date/time pattern: 2009-06-15T13:45:30.0900000
_log.WarnFormat("Restoring position for {0} found item by time ({1:O}) and number ({2})"
, TargetFolder.FolderKey
, _position.Time
, _position.NumberOfItemsWithTheTimestampRead);
// loop will break
status = FolderSeekStatus.PositionStatus.DataItemNotFound;
}
else
{
if (_position.NumberOfItemsWithTheTimestampRead - 1 == n)
{
// last iteration of the loop: found item by time and number
itemFromPosition = _listReader.Current;
}
// moving to the next only if time matches with position time
_listReader.MoveNext();
}
}
if (itemFromPosition != null)
{
// have item from position; check hashes
if (itemFromPosition.GetBusinessHashCode() != _position.VerificationLastReadItemHash)
{
warningMessage = string.Format(
"Restoring position for {0} found item by time and number, but its verification failed: hash in position: {1:X8}, actual: {2:X8}"
, TargetFolder.FolderKey
, _position.VerificationLastReadItemHash
, itemFromPosition.GetBusinessHashCode());
_log.Warn(warningMessage);
status = FolderSeekStatus.PositionStatus.DataItemHashMismatch;
}
else
{
_log.InfoFormat("Exact position for {0} restored successfully", TargetFolder.FolderKey);
}
}
else
{
Check.Ensure(status == FolderSeekStatus.PositionStatus.DataItemNotFound);
}
// reporting issues only
if (status != FolderSeekStatus.PositionStatus.Success)
{
MasterReader.SeekStatusCallback(new FolderSeekStatus(TargetFolder.FolderKey, status, warningMessage));
}
}
