advlib-ble-services
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Wireless advertising packet decoding library for Bluetooth Low Energy service data. We believe in an open Internet of Things.
250 lines (213 loc) • 6.43 kB
JavaScript
/**
* Copyright reelyActive 2015-2026
* We believe in an open Internet of Things
*/
const utils = require('./utils');
const MIN_DATA_LENGTH_BYTES = 4;
const MIN_EDDYSTONE_URL_FRAME_LENGTH = 4;
const EDDYSTONE_UID_TRUNCATED_FRAME_LENGTH = 18;
const EDDYSTONE_UID_FRAME_LENGTH = 20;
const EDDYSTONE_TLM_FRAME_LENGTH = 14;
const EDDYSTONE_ETLM_FRAME_LENGTH = 18;
const EDDYSTONE_EID_FRAME_LENGTH = 10;
const TX_POWER_OFFSET = 1;
const NAMESPACE_OFFSET = 2;
const INSTANCE_OFFSET = 12;
const SCHEME_PREFIX_OFFSET = 2;
const URL_OFFSET = 3;
const VERSION_OFFSET = 1;
const BATTERY_OFFSET = 2;
const TEMPERATURE_OFFSET = 4;
const ADV_CNT_OFFSET = 6;
const SEC_CNT_OFFSET = 10;
const ETLM_OFFSET = 2;
const SALT_OFFSET = 14;
const MIC_OFFSET = 16;
const EID_OFFSET = 2;
const NAMESPACE_LENGTH = 10;
const INSTANCE_LENGTH = 6;
const FIND_HUB_URI = "https://sniffypedia.org/Service/Find_Hub/";
/**
* Process Eddystone service data.
* @param {Object} data The raw service data as a hexadecimal-string or Buffer.
* @return {Object} The processed Eddystone data as JSON.
*/
function process(data) {
let buf = utils.convertToBuffer(data);
if((buf === null) || (buf.length < MIN_DATA_LENGTH_BYTES)) {
return null;
}
let frameType = buf.readUInt8();
switch(frameType) {
case 0x00:
return processEddystoneUID(buf);
case 0x10:
return processEddystoneURL(buf);
case 0x20:
return processEddystoneTLM(buf);
case 0x30:
return processEddystoneEID(buf);
case 0x40: // Nearby mode?
case 0x41: // Separated mode?
return processFindHub(buf);
}
return null;
}
/**
* Process Eddystone-UID service data.
* @param {Object} data The raw service data as a Buffer.
* @return {Object} The processed Eddystone-UID data as JSON.
*/
function processEddystoneUID(data) {
let isInvalidLength = ((data.length !== EDDYSTONE_UID_FRAME_LENGTH) &&
(data.length !== EDDYSTONE_UID_TRUNCATED_FRAME_LENGTH));
if(isInvalidLength) {
return null;
}
let txPower = data.readInt8(TX_POWER_OFFSET);
let namespace = data.toString('hex', NAMESPACE_OFFSET,
NAMESPACE_OFFSET + NAMESPACE_LENGTH);
let instance = data.toString('hex', INSTANCE_OFFSET,
INSTANCE_OFFSET + INSTANCE_LENGTH);
let deviceId = namespace + utils.SIGNATURE_SEPARATOR + instance;
return { txPower: txPower, deviceIds: [ deviceId ] };
}
/**
* Process Eddystone-URL service data.
* @param {Object} data The raw service data as a Buffer.
* @return {Object} The processed Eddystone-URL data as JSON.
*/
function processEddystoneURL(data) {
let isInvalidLength = (data.length < MIN_EDDYSTONE_URL_FRAME_LENGTH);
if(isInvalidLength) {
return null;
}
let txPower = data.readInt8(TX_POWER_OFFSET);
let schemePrefix = data.readUInt8(SCHEME_PREFIX_OFFSET);
let url;
switch(schemePrefix) {
case 0x00:
url = 'http://www.';
break;
case 0x01:
url = 'https://www.';
break;
case 0x02:
url = 'http://';
break;
case 0x03:
url = 'https://';
break;
default:
return null;
}
for(let index = URL_OFFSET; index < data.length; index++) {
let char = convertToUrlChar(data.readUInt8(index));
if(char === null) {
return null;
}
url += char;
}
return { txPower: txPower, uri: url };
}
/**
* Process Eddystone-TLM service data.
* @param {Object} data The raw service data as a Buffer.
* @return {Object} The processed Eddystone-TLM data as JSON.
*/
function processEddystoneTLM(data) {
let isInvalidLength = ((data.length !== EDDYSTONE_TLM_FRAME_LENGTH) &&
(data.length !== EDDYSTONE_ETLM_FRAME_LENGTH));
if(isInvalidLength) {
return null;
}
let version = data.readUInt8(VERSION_OFFSET);
switch(version) {
case 0x00: // Unencrypted
let batteryVoltage = data.readUInt16BE(BATTERY_OFFSET) / 1000;
let temperature = utils.parseSigned88(data.subarray(TEMPERATURE_OFFSET,
TEMPERATURE_OFFSET + 2));
let txCount = data.readUInt32BE(ADV_CNT_OFFSET);
let uptime = data.readUInt32BE(SEC_CNT_OFFSET) * 100;
return { batteryVoltage: batteryVoltage,
temperature: temperature,
txCount: txCount,
uptime: uptime };
case 0x01: // Encrypted
let encrypted = {
data: data.toString('hex', ETLM_OFFSET, SALT_OFFSET),
salt: data.readUInt16BE(SALT_OFFSET),
checksum: data.readUInt16BE(MIC_OFFSET),
method: 'eddystone-etlm'
};
return { encrypted: encrypted };
}
return null;
}
/**
* Process Eddystone-EID service data.
* @param {Object} data The raw service data as a Buffer.
* @return {Object} The processed Eddystone-EID data as JSON.
*/
function processEddystoneEID(data) {
let isInvalidLength = (data.length !== EDDYSTONE_EID_FRAME_LENGTH);
if(isInvalidLength) {
return null;
}
let txPower = data.readInt8(TX_POWER_OFFSET);
let eid = data.toString('hex', EID_OFFSET);
let deviceId = eid + utils.SIGNATURE_SEPARATOR + '0';// TODO: 64-bit EID type?
return { txPower: txPower, deviceIds: [ deviceId ] };
}
/**
* Process Find Hub service data.
* @param {Object} data The raw service data as a Buffer.
* @return {Object} The processed Find Hub data as JSON.
*/
function processFindHub(data) {
return { uri: FIND_HUB_URI };
}
/**
* Convert the given byte code to a character.
* @param {Number} code The code as an (unsigned) integer.
* @return {String} The character.
*/
function convertToUrlChar(code) {
let isInvalideCode = (((code >= 14) && (code <= 32)) || (code >= 127));
if(isInvalideCode) {
return null;
}
switch(code) {
case 0x00:
return '.com/';
case 0x01:
return '.org/';
case 0x02:
return '.edu/';
case 0x03:
return '.net/';
case 0x04:
return '.info/';
case 0x05:
return '.biz/';
case 0x06:
return '.gov/';
case 0x07:
return '.com';
case 0x08:
return '.org';
case 0x09:
return '.edu';
case 0x0a:
return '.net';
case 0x0b:
return '.info';
case 0x0c:
return '.biz';
case 0x0d:
return '.gov';
default:
return String.fromCharCode(code);
}
}
module.exports.process = process;