Did you know ... Search Documentation:
Pack logtalk -- logtalk-3.100.1/docs/handbook/_sources/libraries/ccsds_time_fields.rst.txt

.. _library_ccsds_time_fields:

ccsds_time_fields

The ccsds_time_fields library adds the self-describing time-field layer that is missing between raw embedded time bytes and the format-specific objects in ccsds_time_codes.

This library covers CCSDS binary P-fields for:

  • CUC time fields using 1 to 7 coarse octets and 0 to 10 fine octets, including the two-octet extended P-field encoding
  • CDS time fields using 16-bit or 24-bit day segments and either no submillisecond segment, a 16-bit microsecond segment, or a 32-bit picosecond segment
  • CCS time fields using either calendar or day-of-year encoding and up to 6 BCD fraction octets

Representation

Descriptors are represented using the compound terms:

::

cuc_descriptor(CoarseOctets, FineOctets, Epoch) cds_descriptor(DaySegmentOctets, SubmillisecondOctets, Epoch) ccs_descriptor(CalendarVariant, FractionOctets)

Where:

  • Epoch is either ccsds_epoch or unix_epoch
  • CalendarVariant is either calendar or day_of_year This library uses the existing ccsds_time_codes objects to parse and generate the T-field bytes once the descriptor has been decoded.

    For the current scope, the agency-defined epoch bit in CUC and CDS descriptors is mapped to the existing unix_epoch atom so callers can keep using the same time-code objects and terms already provided by ccsds_time_codes.

Parsing and generating

To parse a self-describing CUC time field:

::

| ?- ccsds_time_fields::parse(bytes([0x1E, 0x00, 0x00, 0x01, 0x00, 0x00, 0x80]), Descriptor, TimeCode).

To parse a self-describing extended CUC time field:

::

| ?- ccsds_time_fields::parse(bytes([0x9F, 0x28, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x80]), Descriptor, TimeCode).

To generate the same time field from a descriptor and a time-code term:

::

| ?- ccsds_time_fields::generate(bytes(Bytes), cuc_descriptor(4, 2, ccsds_epoch), cuc_time(256, 128)).

To parse a self-describing CDS time field:

::

| ?- ccsds_time_fields::parse(bytes([0x40, 0x00, 0x01, 0x00, 0x00, 0x07, 0xD0]), Descriptor, TimeCode).

To parse a self-describing CDS time field with a 32-bit submillisecond segment:

::

| ?- ccsds_time_fields::parse(bytes([0x4E, 0x00, 0x00, 0x01, 0x00, 0x00, 0x07, 0xD0, 0x1D, 0xCD, 0x65, 0x00]), Descriptor, TimeCode).

To generate a self-describing CCS day-of-year time field:

::

| ?- ccsds_time_fields::generate(bytes(Bytes), ccs_descriptor(day_of_year, 1), ccs_ordinal_time(2026, 128, 14, 30, 45, 67)).

Descriptor helpers

The library also provides helper predicates for descriptor introspection:

  • valid_descriptor/1
  • format/2
  • epoch/2 For example:

    ::

    | ?- ccsds_time_fields::format(cds_descriptor(3, 4, unix_epoch), Format).

    | ?- ccsds_time_fields::epoch(ccs_descriptor(calendar, 1), Epoch).

API documentation

Open the `../../apis/library_index.html#ccsds_time_fields <../../apis/library_index.html#ccsds_time_fields>`__ link in a web browser.

Loading

To load all entities in this library, load the loader.lgt file:

::

| ?- logtalk_load(ccsds_time_fields(loader)).

Testing

To test this library predicates, load the tester.lgt file:

::

| ?- logtalk_load(ccsds_time_fields(tester)).