@signageos/front-applet-extension-nexmosphere/es6/SerialPortReadlineParser.js

Nexmosphere extension for signageOS Front Applet

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
const events_1 = require("events");
const DELIMITER = '\r\n';
/**
 * Wraps raw serial port instance and buffers received data until CRLF is received and then emits entire data chunks delimited by CRLF
 *
 * Serial port doesn't emit data in some logical order. It's a pure stream of data, where some logical piece of data might come in
 * one chunk, 2 chunks or even 2 consecutive logical pieces of data could come in a single chunk.
 *
 * This class buffers that data and looks for CRLF characters and treats those as delimiters between logical pieces of data.
 *
 * For example, sender sends these messages over the serial port:
 *
 * AAA\r\n
 * BBB\r\n
 * CCC\r\n
 *
 * But the way they're emitted by the serial port might look like this:
 *
 * AA
 * A\r
 * \nBBB\r\nCC
 * C\r\n
 *
 * This class buffers the first 2 chunks and doesn't emit any events.
 * When the third chunk is received, it finally emits "AAA" (CRLF delimiter is discarded),
 * then it also emits "BBB" and buffers "CC".
 * When the final chunk is received, it emits "CCC".
 */
class SerialPortReadlineParser {
    constructor(serialPort) {
        this.serialPort = serialPort;
        this.dataBuffer = '';
        this.eventEmitter = new events_1.EventEmitter();
        this.bindEvents();
    }
    onData(listener) {
        this.eventEmitter.on('data', listener);
    }
    bindEvents() {
        this.serialPort.onData((data) => this.handleData(data));
    }
    handleData(data) {
        this.dataBuffer += this.convertDataToString(data);
        let position;
        while ((position = this.dataBuffer.indexOf(DELIMITER)) !== -1) {
            const message = this.dataBuffer.slice(0, position);
            this.eventEmitter.emit('data', message);
            this.dataBuffer = this.dataBuffer.slice(position + DELIMITER.length);
        }
    }
    convertDataToString(data) {
        return [...data].map((char) => String.fromCharCode(char)).join('');
    }
}
exports.default = SerialPortReadlineParser;
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