75 lines
2.2 KiB
JavaScript
75 lines
2.2 KiB
JavaScript
import * as msgpack from 'msgpack-lite';
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class DeviceHttpDataSource {
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constructor(dataUrl, onNewData, pollInterval=1000, startIndex = 0) {
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this.dataUrl = dataUrl;
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this.onNewData = onNewData;
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this.pollInterval = pollInterval;
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this.startIndex = startIndex;
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// msgpack setup
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this.msgpackCodec = msgpack.createCodec();
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this.msgpackCodec.addExtUnpacker(205, function (byteArr) {
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const buffer = byteArr.buffer.slice(byteArr.byteOffset, byteArr.byteLength + byteArr.byteOffset);
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const result = new Int16Array(buffer);
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return result;
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});
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this.fetchDataHttp = this.fetchDataHttp.bind(this);
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}
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getUrl(url) {
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return new Promise((accept, reject) => {
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var req = new XMLHttpRequest();
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req.open("GET", url, true);
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req.responseType = "arraybuffer";
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req.onload = function (event) {
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var resp = req.response;
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if (resp) {
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accept(resp);
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}
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};
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req.addEventListener("error", evt => reject(evt));
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req.addEventListener("abort", evt => reject(evt));
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req.send(null);
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});
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}
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async fetchDataHttp() {
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try {
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const url = this.dataUrl + "?startIdx=" + this.startIndex;
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const arrayBuffer = await this.getUrl(url);
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const decoded = msgpack.decode(new Uint8Array(arrayBuffer), { codec: this.msgpackCodec });
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this.startIndex += decoded["values"].length;
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//"values", "sessionStartTime", "startIndex"
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this.onNewData(decoded);
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} catch (err) {
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//console.log(err);
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}
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}
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start() {
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if (this.timer === null) {
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this.timer = setInterval(this.fetchDataHttp, this.pollInterval);
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return true;
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} else {
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return false;
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}
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}
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stop() {
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if (this.timer !== null) {
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clearInterval(this.timer);
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this.timer = null;
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return true;
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} else {
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return false;
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}
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}
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};
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export default DeviceHttpDataSource;
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