const Transform = require('stream').Transform;
/**
* A transform stream that waits for a sequence of "ready" bytes before emitting a ready event and emitting data events
* @summary To use the `Ready` parser provide a byte start sequence. After the bytes have been received a ready event is fired and data events are passed through.
* @extends Transform
* @example
const SerialPort = require('serialport')
const Ready = require('@serialport/parser-ready')
const port = new SerialPort('/dev/tty-usbserial1')
const parser = port.pipe(new Ready({ delimiter: 'READY' }))
parser.on('ready', () => console.log('the ready byte sequence has been received'))
parser.on('data', console.log) // all data after READY is received
*/
class ReadyParser extends Transform {
/**
*
* @param {object} options options for the parser
* @param {string|Buffer|array} options.delimiter data to look for before emitted "ready"
*/
constructor(options) {
options = options || {};
if (options.delimiter === undefined) {
throw new TypeError('"delimiter" is not a bufferable object');
}
if (options.delimiter.length === 0) {
throw new TypeError('"delimiter" has a 0 or undefined length');
}
super(options);
this.delimiter = Buffer.from(options.delimiter);
this.readOffset = 0;
this.ready = false;
}
_transform(chunk, encoding, cb) {
if (this.ready) {
this.push(chunk);
return cb();
}
const delimiter = this.delimiter;
let chunkOffset = 0;
while (this.readOffset < delimiter.length && chunkOffset < chunk.length) {
if (delimiter[this.readOffset] === chunk[chunkOffset]) {
this.readOffset++;
} else {
this.readOffset = 0;
}
chunkOffset++;
}
if (this.readOffset === delimiter.length) {
this.ready = true;
this.emit('ready');
const chunkRest = chunk.slice(chunkOffset);
if (chunkRest.length > 0) {
this.push(chunkRest);
}
}
cb();
}
}
module.exports = ReadyParser;