src/header.js
/*! resol-vbus | Copyright (c) 2013-present, Daniel Wippermann | MIT license */
const { sprintf } = require('sprintf-js');
const { applyDefaultOptions } = require('./utils');
const crc7Table = [
0x00, 0x09, 0x12, 0x1b, 0x24, 0x2d, 0x36, 0x3f,
0x48, 0x41, 0x5a, 0x53, 0x6c, 0x65, 0x7e, 0x77,
0x19, 0x10, 0x0b, 0x02, 0x3d, 0x34, 0x2f, 0x26,
0x51, 0x58, 0x43, 0x4a, 0x75, 0x7c, 0x67, 0x6e,
0x32, 0x3b, 0x20, 0x29, 0x16, 0x1f, 0x04, 0x0d,
0x7a, 0x73, 0x68, 0x61, 0x5e, 0x57, 0x4c, 0x45,
0x2b, 0x22, 0x39, 0x30, 0x0f, 0x06, 0x1d, 0x14,
0x63, 0x6a, 0x71, 0x78, 0x47, 0x4e, 0x55, 0x5c,
0x64, 0x6d, 0x76, 0x7f, 0x40, 0x49, 0x52, 0x5b,
0x2c, 0x25, 0x3e, 0x37, 0x08, 0x01, 0x1a, 0x13,
0x7d, 0x74, 0x6f, 0x66, 0x59, 0x50, 0x4b, 0x42,
0x35, 0x3c, 0x27, 0x2e, 0x11, 0x18, 0x03, 0x0a,
0x56, 0x5f, 0x44, 0x4d, 0x72, 0x7b, 0x60, 0x69,
0x1e, 0x17, 0x0c, 0x05, 0x3a, 0x33, 0x28, 0x21,
0x4f, 0x46, 0x5d, 0x54, 0x6b, 0x62, 0x79, 0x70,
0x07, 0x0e, 0x15, 0x1c, 0x23, 0x2a, 0x31, 0x38,
0x41, 0x48, 0x53, 0x5a, 0x65, 0x6c, 0x77, 0x7e,
0x09, 0x00, 0x1b, 0x12, 0x2d, 0x24, 0x3f, 0x36,
0x58, 0x51, 0x4a, 0x43, 0x7c, 0x75, 0x6e, 0x67,
0x10, 0x19, 0x02, 0x0b, 0x34, 0x3d, 0x26, 0x2f,
0x73, 0x7a, 0x61, 0x68, 0x57, 0x5e, 0x45, 0x4c,
0x3b, 0x32, 0x29, 0x20, 0x1f, 0x16, 0x0d, 0x04,
0x6a, 0x63, 0x78, 0x71, 0x4e, 0x47, 0x5c, 0x55,
0x22, 0x2b, 0x30, 0x39, 0x06, 0x0f, 0x14, 0x1d,
0x25, 0x2c, 0x37, 0x3e, 0x01, 0x08, 0x13, 0x1a,
0x6d, 0x64, 0x7f, 0x76, 0x49, 0x40, 0x5b, 0x52,
0x3c, 0x35, 0x2e, 0x27, 0x18, 0x11, 0x0a, 0x03,
0x74, 0x7d, 0x66, 0x6f, 0x50, 0x59, 0x42, 0x4b,
0x17, 0x1e, 0x05, 0x0c, 0x33, 0x3a, 0x21, 0x28,
0x5f, 0x56, 0x4d, 0x44, 0x7b, 0x72, 0x69, 0x60,
0x0e, 0x07, 0x1c, 0x15, 0x2a, 0x23, 0x38, 0x31,
0x46, 0x4f, 0x54, 0x5d, 0x62, 0x6b, 0x70, 0x79
];
class Header {
/**
* Creates a new Header instance and optionally initializes its members
* with the given values
*
* @constructs
* @param {object} [options] Initialization values for this instance's members
* @param {Date} [options.timestamp] {@link Header#timestamp}
* @param {number} [options.channel] {@link Header#channel}
* @param {number} [options.destinationAddress] {@link Header#destinationAddress}
* @param {number} [options.sourceAddress] {@link Header#sourceAddress}
*
* @classdesc
* All VBus models are sub-classes of this Header class. The Header class provides
* a generic interface and the common properties that all (currently three)
* different types of VBus models can use.
*
* Header instances can either be created by calling the constructor function or
* by passing a Buffer object containing the binary VBus data to the class method
* `HeaderSubClass.fromLiveBuffer`.
*
* @see Packet
* @see Datagram
* @see Telegram
*/
constructor(options) {
applyDefaultOptions(this, options, /** @lends Header.prototype */ {
/**
* Timestamp of this header
* @type {Date}
* @default now
*/
timestamp: null,
/**
* VBus channel of this header
* @type {number}
* @default 0
*/
channel: 0,
/**
* VBus address of this header's destination
* @type {number}
* @default 0
*/
destinationAddress: 0,
/**
* VBus address of this header's source
* @type {number}
* @default
*/
sourceAddress: 0,
minorVersion: 0,
});
if (!this.timestamp) {
this.timestamp = new Date();
}
}
/**
* Creates a representation of this Header instance that can be
* transmitted over a Connection. If no buffer is given as an
* arguments, it creates a new one that is big enough to hold
* the representation.
*
* Must be implemented by sub-class.
*
* @abstract
* @param {Buffer} [buffer] Buffer object to store data in
* @param {number} [start] Start index in the buffer
* @param {number} [end] End index in the buffer
* @returns {Buffer} Buffer object containing the data
*/
toLiveBuffer(/* buffer, start, end */) {
throw new Error('Must be implemented by sub-class');
}
/**
* Returns the protocol version of this Header instance as a 8-bit
* number. The high nibble is used for the major version, the low
* nibble for the minor version. For example: a header with protocol
* version 2.0 would return `0x20`.
*
* Must be implemented by sub-class.
*
* @abstract
* @returns {number} Protocol version
*/
getProtocolVersion() {
throw new Error('Must be implemented by sub-class');
}
/**
* Returns an info number about this Header instance. It can be used
* for sorting purposes (to distinguish Header objects that would
* otherwise compare as equal).
*
* @returns {number} Info value
*/
getInfo() {
return 0;
}
/**
* Returns a string identifier describing this Header instance.
* It contains at least:
*
* - channel
* - destination address
* - source address
* - protocol version
*
* Sub-classes can extend that information. The structure of this
* identifier is implementation specific, do not rely on it!
*
* @returns {string} Identifier
*/
getId() {
return sprintf('%02X_%04X_%04X_%02X', this.channel, this.destinationAddress, this.sourceAddress, this.getProtocolVersion());
}
/**
* Compares this Header instance to another one.
*
* Sub-classes can extend the comparison to include specific
* information.
*
* @param {Header} that Another Header instance to compare to.
* @returns {number} Returns a number
*
* - less than 0 if `this < that`
* - greater than 0 if `this > that`
* - equal to to if `this == that`
*/
compareTo(that) {
let result = this.channel - that.channel;
if (result === 0) {
result = this.destinationAddress - that.destinationAddress;
}
if (result === 0) {
result = this.sourceAddress - that.sourceAddress;
}
if (result === 0) {
result = this.getProtocolVersion() - that.getProtocolVersion();
}
return result;
}
/**
* Creates a Header instance from a representation that was
* received over a Connection.
*
* Must be implemented by sub-class.
*
* @abstract
* @param {Buffer} buffer Buffer that contains the representation
* @param {number} start Start index in the buffer
* @param {number} end End index in the buffer
* @returns {Header} Header instance created from the representation
*/
static fromLiveBuffer(/* buffer, start, end */) {
throw new Error('Must be implemented by sub-class');
}
/**
* Calculates the VBus checksum (according to version x.0 specification)
* over a part of a Buffer instance.
*
* @param {Buffer} buffer Buffer to calc checksum for
* @param {number} start Start index in the buffer
* @param {number} end End index in the buffer
* @returns {number} Calculated checksum
*/
static calcChecksumV0(buffer, start, end) {
let checksum = 0;
for (let index = start; index < end; index++) {
checksum = (checksum + buffer [index]) & 0x7F;
}
checksum = (0x7F - checksum);
return checksum;
}
/**
* Calculates the VBus checksum (according to version x.0 specification)
* over a part of a Buffer instance and compares it the checksum byte
* stored at the `end` position.
*
* @param {Buffer} buffer Buffer to calc and compare checksum for
* @param {number} start Start index in the buffer
* @param {number} end End index in the buffer
* @returns {boolean} Result whether calculated and stored checksum match
*/
static calcAndCompareChecksumV0(buffer, start, end) {
const checksum = this.calcChecksumV0(buffer, start, end);
return (buffer [end] === checksum);
}
/**
* Calculates the VBus checksum (according to version x.0 specification)
* over a part of the Buffer instance and stores it at the `end` position.
*
* @param {Buffer} buffer Buffer to calc and store checksum for
* @param {number} start Start index in the buffer
* @param {number} end End index in the buffer
* @returns {number} Calculated checksum
*/
static calcAndSetChecksumV0(buffer, start, end) {
const checksum = this.calcChecksumV0(buffer, start, end);
buffer [end] = checksum;
return checksum;
}
static calcChecksumV1(buffer, start, end) {
let crc = 0x00;
for (let index = start; index < end; index++) {
crc = crc7Table [(crc << 1) ^ buffer [index]];
}
return crc;
}
static calcChecksum(version, buffer, start, end) {
const minorVersion = (version & 0x0F);
let crc;
if (minorVersion === 0x00) {
crc = this.calcChecksumV0(buffer, start, end);
} else if (minorVersion === 0x01) {
crc = this.calcChecksumV1(buffer, start, end);
} else {
throw new Error(`Unexpected minor version ${minorVersion}`);
}
return crc;
}
static calcAndCompareChecksum(version, buffer, start, end) {
const checksum = this.calcChecksum(version, buffer, start, end);
return (buffer [end] === checksum);
}
static calcAndSetChecksum(version, buffer, start, end) {
const checksum = this.calcChecksum(version, buffer, start, end);
buffer [end] = checksum;
return checksum;
}
/**
* Copies a part of the source Buffer instance to the destination Buffer
* instance, injecting the MSBs stored in the septett byte during the process.
*
* @param {Buffer} srcBuffer Buffer to copy from
* @param {number} srcStart Start index in the source buffer
* @param {number} srcEnd End index in the source buffer
* @param {Buffer} dstBuffer Buffer to copy to
* @param {number} dstStart Start index in the destination buffer
*/
static injectSeptett(srcBuffer, srcStart, srcEnd, dstBuffer, dstStart) {
const septett = srcBuffer [srcEnd];
let srcIndex = srcStart, dstIndex = dstStart, mask = 1;
while (srcIndex < srcEnd) {
let b = srcBuffer [srcIndex];
if (septett & mask) {
b |= 0x80;
}
dstBuffer [dstIndex] = b;
srcIndex++;
dstIndex++;
mask = mask << 1;
}
}
/**
* Copies a part of the source Buffer instance to the destination Buffer
* instance, extracting the MSBs during the process and storing the septett
* byte to the destination buffer's end position.
*
* @param {Buffer} srcBuffer Buffer to copy from
* @param {number} srcStart Start index in the source buffer
* @param {number} srcEnd End index in the source buffer
* @param {Buffer} dstBuffer Buffer to copy to
* @param {number} dstStart Start index in the destination buffer
*/
static extractSeptett(srcBuffer, srcStart, srcEnd, dstBuffer, dstStart) {
let srcIndex = srcStart, dstIndex = dstStart, mask = 1, septett = 0;
while (srcIndex < srcEnd) {
let b = srcBuffer [srcIndex];
if (b & 0x80) {
b &= 0x7F;
septett |= mask;
}
dstBuffer [dstIndex] = b;
srcIndex++;
dstIndex++;
mask = mask << 1;
}
dstBuffer [dstIndex] = septett;
}
}
Object.assign(Header.prototype, /** @lends Header.prototype */ {
/**
* Timestamp of this header
* @type {Date}
* @default now
*/
timestamp: null,
/**
* VBus channel of this header
* @type {number}
* @default 0
*/
channel: 0,
/**
* VBus address of this header's destination
* @type {number}
* @default 0
*/
destinationAddress: 0,
/**
* VBus address of this header's source
* @type {number}
* @default
*/
sourceAddress: 0,
});
module.exports = Header;