add specification for Fullhan .FLS files

[armijnhemel]

A fairly simple file format for a Chinese brand of IP cameras. Basically it is a header, with a number of entries, each containing a name, offset and length and then data. I don't know what each field means, so there is also a big chunk of "unknown". The header also contains two names, which I think refer to a model and submodel, or a chip and a board, or something like that. I could not find reliable information about that.

[armijnhemel]

It seems like other (cheap) brands are also using this file format, so I guess that it is not specific to Fullhan. What should we rename it to?

[KOLANICH]

kaitai-io/kaitai_struct#1031 should be related.

[KOLANICH]

meta:
  id: fullhan_fls
  title: Fullhan FLS
  license: CC0-1.0
  endian: le
  encoding: UTF-8
doc: |
  Test files:
  - https://www.nvripc.com/new-chinese-ip-camera-firmwares-update/
  - https://www.herospeed.net/hs/ipc_test/fuhan/
seq:
  - id: header
    type: header
  - id: blob
    size: header.len_file - sizeof<header>
    type: body
types:
  header:
    seq:
      - id: model
        size: 8
        type: strz
      - id: submodel
        size: 8
        type: strz
      - id: len_file
        type: u4
      - id: num_entries
        type: u4
  body:
    seq:
      - id: entries
        type: entry
        repeat: expr
        repeat-expr: _root.header.num_entries
      - id: blob_area
        size-eos: true
        type: dummy
    instances:
      lea_blob_area:
        -affected-by: 84
        #value: entries._sizeof
        value: _root.header.num_entries * sizeof<entry>
      lea_lea_blob_area_global:
        value: sizeof<header> + lea_blob_area
    types:
      dummy: {}
      entry:
        seq:
          - id: name
            size: 128
            type: strz
          - id: len_data
            type: u4
          - id: ofs_data
            type: u4
          - id: unknown
            size: 120
        instances:
          offs_base_blob_area:
            -affected-by: 1031
            value: ofs_data - _parent.lea_lea_blob_area_global
          data:
            -affected-by: 1031
            io: _parent.blob_area._io
            pos: offs_base_blob_area
            size: len_data

[generalmimon]

Thanks for declaring where to find test files (I'll check them out), but I think /doc should also include some general description of the format. You put the .ksy spec in the firmware directory, which suggests that the format is somehow firmware-related, but anything beyond that is left to the reader to guess. I guess it's a firmware update format of IP cameras of a certain brand Fullhan? At least one or two sentences would go a long way for someone not knowing the purpose of the format or perhaps trying to find a .ksy spec for it via certain keywords.