Fw::FilePacket Classes

1 Introduction

This module provides a type Fw::FilePacket. It represents an ISF file packet.

2 Design

The file packet format is similar to the Protocol Data Unit (PDU) format defined in the CCSDS File Delivery Protocol (CFDP). See § 5 of the CCSDS File Delivery Protocol (CFDP) Recommended Standard.

Each file packet contains the following data:

• The packet type (1 byte): one of START (0), DATA (1), END (2), or CANCEL (3).

• The sequence index (4 bytes): an unsigned integer that identifies each packet. The sequence index starts at zero for each file and increases by one for each successive packet within the file.

• The packet data (variable). The packet data format depends upon the packet type. The following subsections describe the formats for the different types.

2.1 START Packets

A start packet has packet type START and sequence index zero. Its data consists of the following:

• The file size in bytes (4 bytes).

• The length of the source path in bytes (1 byte).

• The source path (variable).

• The length of the destination path in bytes (1 byte).

• The destination path (variable).

2.2 DATA Packets

A data packet has packet type DATA. Its data consists of the following:

• The byte offset into the entire file of the file data in this packet (4 bytes).

• The length of the file data in bytes (2 bytes).

• The file data (variable).

2.3 END Packets

An end packet has packet type END. Its data consists of the following:

• The 32-bit hash value, computed from the file data as described in the CFDP protocol (4 bytes).

2.4 CANCEL Packets

A cancel packet has packet type CANCEL. It has no data.