Add support for validation of data type values in runtime

[joachimmetz]

• signature
• known values
• integer bounds
• expression based such as size == copy_of_size for evt (use validation rules?)

[joachimmetz]

Idea add validation as validation rules:

name: tzif_file_header
type: structure
description: file header.
attributes:
  byte_order: big-endian
validation:
  - tzif_file_header.signature == "TZif"
members:
- name: signature
  type: stream
  element_data_type: byte
  number_of_elements: 4
- name: format_version
  data_type: byte

Pros:

• supports more complex multi member validation e.g.

(file_header.major_version == 3 and file_header.minor_version == 0) or
(file_header.major_version == 2 and (file_header.minor_version == 0 or file_header.minor_version == 1))

Cons:

• validation rules are programming language like logic, which makes the format less data driven

[joachimmetz]

Idea add validation in specific "format" types (e.g. signature):

name: tzif_file_header
type: structure
description: file header.
attributes:
  byte_order: big-endian
members:
- name: signature
  type: signature
  element_data_type: byte
  number_of_elements: 4
  expected_value: "TZif"
- name: format_version
  data_type: byte

Pro:

• expected value part of data type / member definition

Con:

• less flexible, need (more) specific "format" types
• unable to support validation of more than 1 member at a time

[joachimmetz]

Idea add validation as parameter of data type definition:

name: tzif_file_header
type: structure
description: file header.
attributes:
  byte_order: big-endian
members:
- name: signature
  type: stream
  element_data_type: byte
  number_of_elements: 4
  value: "TZif"
- name: format_version
  data_type: byte

Pro:

• expected value part of data type / member definition
• similar to boolean true_value and false_value

Con:

• unable to support validation of more than 1 value at a time

Alternative terms:

• accepted_value
• expected_value
• supported_value

[joachimmetz]

Support more than 1 expected value?

- name: format_version
  data_type: byte
  values: [1, 2, 3]

Keep "value: 1" as short hand for "values: [1]" ?

To support minimum and maximum bounds?

- name: format_version
  data_type: byte
  minimum_value: 1
  maximum_value: 3

Alternatives:

• value_range: min, max
• value_range: [min, max]
• value_range: [min, max)
• value_range: [min, max>

Combine minimum_value and maximum_value into range?

[joachimmetz]

Validation rules:

name: event_record
type: structure
members:
- name: size
...
- name: data_size
- name: data_offset
...
validation_rules:
- event_record.data_size == 0 and event_record.data_offset == 0
- event_record.data_size != 0 and 56 <= event_record.data_offset < event_record.size

• validation_rules or constraints?
• Member specific validation rules?