/// <summary>
/// Observes first <see cref="count"/> records from reversed list
/// where version is less or equal to <see cref="max"/>.
/// </summary>
/// <param name="max">Max version observed.</param>
/// <param name="count">Max count of observed records.</param>
/// <param name="observer">Observer action.</param>
public void ObserveTill(long max, int count, Action <TapeRecord> observer)
{
// It's assumed that FileTapeStream uses Versions as index
// and Version will increase by one without gaps.
// Read backward
var start = Math.Min(max, _cache.GetCurrentVersion());
var end = Math.Max(start - count, 0);
var totalCount = (int)(start - end);
var index = 0;
while (true)
{
var readCount = Math.Min(BatchSize, totalCount - index);
if (readCount == 0)
{
break;
}
var records = _cache.ReadRecords(start - readCount - index, readCount).ToArray();
if (records.Length == 0)
{
break;
}
foreach (var record in records.Reverse())
{
observer(record);
}
index += records.Length;
}
}
