How to stop a sequence when certain contion is matched?

[exaos]

As the attached picture, a sequence might stop at certain condition, e.g., when encountering some magic or next block is not the same data type. How to depict this kind of conditional reading? How about this:

seq:
  - id: data_block
    type: data_type
    repeat-if: next_is_the_same_type

[GreyCat]

Just use repeat-until with a block type that will consume both real "event blocks" and "event file footer" as a special terminator block. I have no idea what Ev-1 :: [Parmeter-1] etc stand for, but if that's just several 32-bit integers, then you can always do something like that:

seq:
  # ...
  - id: more_blocks
    type: event_block
    repeat: until
    repeat-until: _.is_terminator
type:
  event_block:
    seq:
      - id: param1
        type: u4
      - id: param2
        type: u4
      - id: params_rest
        type: u4
        repeat: expr
        repeat-expr: _root.ev_size - 2
        if: not is_terminator
    instances:
      is_terminator:
        value: param1 == 0xffffffff and param2 == 0xffffffff

[GreyCat]

Yeah, right ;) Would fix now.

[exaos]

kmax_event.zip
Thanks GreyCat! I prepared a .ksy file, and then generated the python code without error. But the python code will consume all the memory of my PC and halt my PC. Maybe it is the problem of repeat-until. Though I don't know why, I will check it again.

[webbnh]

@exaos, how big is your data file (in comparison to the amount of memory on your PC)? Your program is going to try to read all of the data into memory....

I ran into this problem in my project, and had various problems with Python and memory consumption. I ended up implementing the repeat: until in my own code, by invoking KS repeatedly until my own end condition, and carefully releasing each iteration's memory before starting the next iteration. This actually works quite well (although I ended up switching from Python to C++, for several reasons).

[exaos]

@webbnh
My test data file is less than 1MB. The typical data files are around ~20MB each. And my PC's memory is 16GB. Theoretically, I could read all data from a test file without any problem.