@ssv-embedded/ssb-assembler

This module assembles SSV/SSB fragments to packets.

API

assemblerFactory

const {assemblerFactory} = require('@ssv-embedded/ssb-assembler');
const {createAssembler} = assemblerFactors(deps);

deps is an object for providing optional dependencies:

• checkManId: Is a function implementing (manId) => valid. It must return true if the given manId is valid. Default: (manId) => manId === 0x0059 || manId === 0x0ad3.
• checkType: Is a function implementing (type) => valid. It must return true if the given type is valid. Default: (type) => type === 0x40 || type === 0x41.
• getTs: Function returning the current Unix timestamp in msec. Default: Date.now
• packetTimeout: Timeout in msec for dropping incompletely received packets. Default: 5000.

createAssembler

const assembler = createAssembler(opts);

Creates a new Assembler instance. opts is an object:

• handlePacket: Mandatory callback function: (packet) => valid. Is called if a full packet has been received. packet is an instance of Packet. The callback must return true is the received packet is valid an sequence counters should be increased.
• getSeq: Helper function (senderHash) => seq to retrieve the last seen sequence number seq for a given sender represented by the String senderHash. If the sender hasn't been seen before, this function must return undefined. Default: Internal in-memory sequence tracker. Won't be persisted once assembler is freed.
• setSeq: Helper function (senderHash, seq) => {} to set the last seen sequence number seq for a given sender represented by the String senderHash. Default: Internal in-memory sequence tracker. Won't be persisted once assembler is freed.

Class: Assembler

Method: parseFragment(fragment)

try {
	assembler.parseFragment(fragment);
} catch (err) {
	...
}

This call parses fragment. It may throw err if fragment cannot be processed. fragment is an object representing the received fragment:

• address: Mandatory. MAC address of the sending device. Format: 00:11:22:aa:dd:ff.
• gw: Mandatory. MAC address of the receiving device. Format: 00:11:22:aa:dd:ff.
• data: Mandatory. Hex-encoded string of the BLE advertisement frame's `Manufacturer Specific data.
• rssi: Optional RSSI of the advertisment frame.
• ts: Optional timestamp of the receiption time.

Class: Packet

Properties

• address: Sender of the packet
• gw: Receiver of the fragment with the highest RSSI.
• rssi: Highest seen RSSI.
• manId: Company ID.
• type: Packet type.
• seq: Sequence number.
• ts: Lowest seen timestamp.
• gwStats: Object holding stats of all seen gws.

Method: toBuffer()

const buf = packet.toBuffer();
const manId = buf.readUInt16LE(0);
const type = buf.readUInt8(2);
const seq = buf.readUInt32LE(3);
const payload = buf.slice(7);

Returns the packet including its header:

• 2B Company ID manId
• 1B Packet Type type
• 4B Sequence number seq
• nB Payload payload