# Svc::Ccsds::SpacePacketDeframer

The `Svc::Ccsds::SpacePacketDeframer` is an implementation of the [DeframerInterface](../../../Interfaces/docs/sdd.md) for the CCSDS [Space Packet Protocol](https://ccsds.org/Pubs/133x0b2e2.pdf).

It receives data containing a Space Packet on its input port and extracts the Space Packet. Please refer to the CCSDS [Space Packet Protocol specification (CCSDS 133.0-B-2)](https://ccsds.org/Pubs/133x0b2e2.pdf) for details on the packet format.

The `Svc::Ccsds::SpacePacketDeframer` is typically used downstream of a component that removes transfer frame headers, such as the `Svc::Ccsds::TcDeframer`. It validates the Space Packet header and extracts the payload.

## CCSDS Header Field Extraction

The `Svc::Ccsds::SpacePacketDeframer` extracts the following fields from the CCSDS Space Packet Primary Header and populates them in the output `FrameContext`:

| Field | Context Field | Description |
|---|---|---|
| Application Process Identifier (APID) | `apid` | Extracted from bits [10:0] of the Packet Identification field. Invalid APID values (per `ComCfg::Apid::isValid()`) are mapped to `INVALID_UNINITIALIZED`. |
| Secondary Header Flag | `hasSecHdr` | Extracted from bit [11] of the Packet Identification field |
| Sequence Flags | `sequenceFlags` | Extracted from bits [15:14] of the Packet Sequence Control field (0b00=Continuation, 0b01=First, 0b10=Last, 0b11=Unsegmented) |
| Packet Sequence Count | `sequenceCount` | Extracted from bits [13:0] of the Packet Sequence Control field |

## Port Descriptions

| Kind | Name | Port Type | Description |
|---|---|---|---|
| Input (guarded) | dataIn | Svc.ComDataWithContext | Port to receive data containing a Space Packet |
| Output | dataOut | Svc.ComDataWithContext | Port to output the extracted Space Packet payload |
| Output | dataReturnOut | Svc.ComDataWithContext | Port for returning ownership of received buffers |
| Input (sync) | dataReturnIn | Svc.ComDataWithContext | Port receiving back ownership of sent buffers |
| Output | validateApidSeqCount | Ccsds.ApidSequenceCount | Port to request validation of a sequence count for a given APID |
| Output | errorNotify | Ccsds.ErrorNotify | Port to send notification of deframing errors |

## Events

| Name | Severity | Description |
|---|---|---|
| InvalidLength | `warning high` | Deframing received an invalid packet length |
| InvalidPacket | `warning high` | Deframing received a malformed packet |

## Requirements

| Name | Description | Validation |
|---|---|---|
| SVC-CCSDS-SPD-001 | The SpacePacketDeframer shall deframe CCSDS Space Packets according to the CCSDS 133.0-B-2 standard. | Unit Test, Inspection |
| SVC-CCSDS-SPD-002 | The SpacePacketDeframer shall extract the user data field from valid Space Packets. | Unit Test |
| SVC-CCSDS-SPD-003 | The SpacePacketDeframer shall validate the packet length of a Space Packet Primary Header. | Unit Test |
| SVC-CCSDS-SPD-010 | The SpacePacketDeframer shall validate the Packet Version Number field and reject packets whose Packet Version Number does not match the CCSDS Space Packet Protocol, emitting `InvalidPacket` and returning the buffer. | Unit Test |
| SVC-CCSDS-SPD-009 | The SpacePacketDeframer shall emit an `InvalidLength` event if the packet length token in the header is cannot fit in the received data, and drop the received packet. | Unit Test |
| SVC-CCSDS-SPD-004 | The SpacePacketDeframer shall receive incoming data containing Space Packets via the `dataIn` port. | Unit Test |
| SVC-CCSDS-SPD-005 | The SpacePacketDeframer shall output the extracted Space Packet user data via the `dataOut` port. | Unit Test |
| SVC-CCSDS-SPD-006 | The SpacePacketDeframer shall manage buffer ownership using the `dataReturnIn` and `dataReturnOut` ports. | Unit Test, Inspection |
| SVC-CCSDS-SPD-007 | The SpacePacketDeframer shall delegate sequence count validation to another component through the `validateApidSeqCount` port. | Unit Test |
| SVC-CCSDS-SPD-008 | The SpacePacketDeframer shall perform sequence count validation for APIDs registered via `validateApidSeqCount`. | Unit Test |
| SVC-CCSDS-SPD-009 | The SpacePacketDeframer shall emit notifications on its `errorNotify` port when deframing errors occur. | Unit Test |