ExcerptTailer and TailerDirection

[Marcus]

Hi all

I am reading with a ExcerptTailer (SingleChronicleQueue, version 4.5.15) from the queue and change the direction of reading. 

I get some unexpected behavior I don't understand. Can someone tell me if I am doing or understanding something wrong, 

or if this simply a bug?

First, I insert 4 values (for example the integer values 0-4) into the queue. `idx` indicates their index position in the queue:

Value |  Idx

------+------

  0   |   52

  1   |   53

  2   |   54

  3   |   55

I then read with the ExerptTailer the values. The following table shows the operation ('read' for reading a value from the queue 

and 'toggle' for changing the read direction of the Tailer), the return value and the tailer state after the performed operation:

Op      | Return value |  Tailer state

--------+--------------+----------------------------

read          0           direction=FORWARD,  idx 53

read          1           direction=FORWARD,  idx 54

toggle        -           direction=BACKWARD, idx 54

read          2           direction=BACKWARD, idx 53

read          1           direction=BACKWARD, idx 52

toggle        -           direction=FORWARD,  idx 52

So far, so good. For the next 'read' operation I would now expect to get the value '0' back, the value at index position 52. 

However, if I now read the next value I get:

read          2           direction=FORWARD,  idx 53

read          3           direction=FORWARD,  idx 54

toggle        -           direction=BACKWARD, idx 54

read          2           direction=BACKWARD, idx 53

Does this make sense and where is my misunderstanding?

Thanks & regards,

marcus

[Rob Austin]

It looks like you may have found a bug, can you create a test case with this, and then issue a pull request, we will merge in your pull request and fix the issue.

Regards

Rob