♻ Extract response handler

src/cdn/funcs/handleResponse.ts

@@ -0,0 +1,48 @@
+import * as http from 'http';
+
+/** Too avoid  */
+const MAX_MEMORY_SIZE = 100 * 1024 * 1024;
+
+export default function handleResponse(
+  resolve: (value: ArrayBuffer) => void,
+  reject: (reason: string) => void,
+  response: http.IncomingMessage,
+) {
+  //Check that file exists (200 HTTP status code)
+  if (response.statusCode !== 200) {
+    return reject(`Expected status code 200 but received ${response.statusCode}`);
+  }
+
+  //Check file size
+  const headerLength = Number(response.headers['content-length']);
+  if (headerLength > MAX_MEMORY_SIZE) {
+    return reject('File size too large to be handled in memory.');
+  }
+
+  //If we receive a part of the response, store it
+  const chunkList: Buffer[] = [];
+  let totalLength = 0;
+  response.on('data', (chunk: Buffer) => {
+    totalLength += chunk.length;
+
+    //Exit early if we received too much data
+    if (totalLength > headerLength) {
+      return reject(`Expected length ${headerLength} but received at least ${totalLength}`);
+    }
+
+    //Add chunk to array
+    chunkList.push(chunk);
+  });
+
+  //If we finished reading response, check for correctness and return it
+  response.on('end', () => {
+    //Check that length is correct
+    if (totalLength !== headerLength) {
+      return reject(`Expected length ${headerLength} but received ${totalLength}`);
+    }
+
+    //Return file contents as ArrayBuffer
+    const fileContents = Buffer.concat(chunkList, totalLength);
+    return resolve(fileContents.buffer as ArrayBuffer);
+  });
+}

src/cdn/funcs/resolveDns.ts

@@ -1,4 +1,4 @@
-/* --- DNS resolver for the CDN storing SWTOR's patch files ---
+/* --- DNS resolver for the CDN storing SWTOR’s patch files ---
 |
 | The SWTOR launcher first connects to cdn-patch.swtor.com,
 | there the traffic is split onto Akamai and Level3, and
@@ -28,7 +28,7 @@
 
 import { exec} from 'child_process';
 import * as dns from 'dns';
-import { IDnsResult } from '../interfaces/IDnsResult';
+import { IDnsResult } from '../../interfaces/IDnsResult';
 
 //TODO: send e-mail with the error
 const assert = (cond: boolean) => { if (!cond) { console.warn('Assert failed'); } };
@@ -39,7 +39,7 @@ async function resolveDns(domain: string): Promise<IDnsResult[]> {
       //check given string for correctness to prevent injection attacks
       if (!domain.match(/^[a-z0-9]+([-.]{1}[a-z0-9]+)*\.[a-z]{2,3}$/)) { return resolve([]); }
 
-      //Check Level3/North_America separetely
+      //Check Level3/North_America separately
       if (domain !== 'cdn-patch.swtor.com') {
           dns.resolve4(domain, { ttl: true }, (err, result) => {
             return resolve(result.map(({ address, ttl }) => ({ address, ttl, type: 'level3-us' as IDnsResult['type'] })));

src/cdn/getUrlContents.ts

@@ -1,41 +1,19 @@
 import * as http from 'http';
+import handleResponse from './funcs/handleResponse';
 
-const MAX_MEMORY_SIZE = 100 * 1024 * 1024;
-
+/** Downloads the given URL into memory and returns it as an ArrayBuffer. Throws error if download fails or file is too large to be handled in memory. */
 export default function getUrlContents({ host, path }: {host: string, path: string}): Promise<ArrayBuffer> {
   return new Promise((resolve, reject) => {
     const request = http.request({
       family: 4,
       host,
       path,
-    }, (response) => {
-      if (response.statusCode !== 200) {
-        return reject(`Expected status code 200 but received ${response.statusCode}`);
-      }
-      const headerLength = Number(response.headers['content-length']);
-      if (headerLength > MAX_MEMORY_SIZE) {
-        reject('File size too large to be handled in memory.');
+    }, handleResponse.bind(null, resolve, (reason: string) => { request.abort(); reject(reason); }));
+
+    //In case of connection errors, exit early
+    request.on('error', (error) => {
       request.abort();
-        return;
-      }
-
-      const chunkList: Buffer[] = [];
-      let totalLength = 0;
-      response.on('data', (chunk: Buffer) => {
-        chunkList.push(chunk);
-        totalLength += chunk.length;
-      });
-      response.on('end', () => {
-        if (totalLength !== headerLength) {
-          return reject(`Expected length ${headerLength} but received ${totalLength}`);
-        }
-        const fileContents = Buffer.concat(chunkList, totalLength);
-        resolve(fileContents.buffer as ArrayBuffer);
-      });
-    });
-
-    request.on('error', (e) => {
-      reject(e);
+      return reject(error);
     });
     request.end();
   });

src/cdn/heartbeatDns.ts

@@ -1,5 +1,5 @@
 import { IServerEntry } from '../interfaces/IDnsResult';
-import resolveDns from './resolveDns';
+import resolveDns from './funcs/resolveDns';
 
 /** Time when this script started, for delta time calculations */
 const startTime = Date.now();