159 lines
4.5 KiB
JavaScript
159 lines
4.5 KiB
JavaScript
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import { Transport } from "../transport.js";
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import { randomString } from "../util.js";
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import { encodePayload, decodePayload } from "engine.io-parser";
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import debugModule from "debug"; // debug()
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const debug = debugModule("engine.io-client:polling"); // debug()
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export class Polling extends Transport {
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constructor() {
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super(...arguments);
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this._polling = false;
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}
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get name() {
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return "polling";
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}
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/**
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* Opens the socket (triggers polling). We write a PING message to determine
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* when the transport is open.
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*
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* @protected
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*/
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doOpen() {
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this._poll();
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}
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/**
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* Pauses polling.
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*
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* @param {Function} onPause - callback upon buffers are flushed and transport is paused
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* @package
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*/
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pause(onPause) {
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this.readyState = "pausing";
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const pause = () => {
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debug("paused");
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this.readyState = "paused";
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onPause();
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};
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if (this._polling || !this.writable) {
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let total = 0;
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if (this._polling) {
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debug("we are currently polling - waiting to pause");
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total++;
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this.once("pollComplete", function () {
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debug("pre-pause polling complete");
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--total || pause();
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});
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}
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if (!this.writable) {
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debug("we are currently writing - waiting to pause");
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total++;
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this.once("drain", function () {
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debug("pre-pause writing complete");
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--total || pause();
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});
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}
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}
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else {
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pause();
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}
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}
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/**
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* Starts polling cycle.
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*
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* @private
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*/
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_poll() {
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debug("polling");
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this._polling = true;
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this.doPoll();
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this.emitReserved("poll");
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}
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/**
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* Overloads onData to detect payloads.
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*
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* @protected
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*/
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onData(data) {
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debug("polling got data %s", data);
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const callback = (packet) => {
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// if its the first message we consider the transport open
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if ("opening" === this.readyState && packet.type === "open") {
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this.onOpen();
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}
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// if its a close packet, we close the ongoing requests
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if ("close" === packet.type) {
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this.onClose({ description: "transport closed by the server" });
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return false;
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}
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// otherwise bypass onData and handle the message
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this.onPacket(packet);
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};
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// decode payload
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decodePayload(data, this.socket.binaryType).forEach(callback);
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// if an event did not trigger closing
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if ("closed" !== this.readyState) {
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// if we got data we're not polling
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this._polling = false;
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this.emitReserved("pollComplete");
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if ("open" === this.readyState) {
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this._poll();
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}
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else {
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debug('ignoring poll - transport state "%s"', this.readyState);
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}
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}
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}
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/**
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* For polling, send a close packet.
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*
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* @protected
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*/
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doClose() {
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const close = () => {
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debug("writing close packet");
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this.write([{ type: "close" }]);
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};
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if ("open" === this.readyState) {
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debug("transport open - closing");
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close();
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}
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else {
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// in case we're trying to close while
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// handshaking is in progress (GH-164)
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debug("transport not open - deferring close");
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this.once("open", close);
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}
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}
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/**
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* Writes a packets payload.
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*
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* @param {Array} packets - data packets
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* @protected
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*/
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write(packets) {
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this.writable = false;
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encodePayload(packets, (data) => {
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this.doWrite(data, () => {
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this.writable = true;
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this.emitReserved("drain");
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});
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});
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}
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/**
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* Generates uri for connection.
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*
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* @private
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*/
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uri() {
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const schema = this.opts.secure ? "https" : "http";
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const query = this.query || {};
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// cache busting is forced
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if (false !== this.opts.timestampRequests) {
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query[this.opts.timestampParam] = randomString();
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}
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if (!this.supportsBinary && !query.sid) {
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query.b64 = 1;
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}
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return this.createUri(schema, query);
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}
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}
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