Move hashFile function to common place

common/helpers.ts

@@ -1,3 +1,6 @@
+import fs from 'fs';
+import { keccak256 } from 'js-sha3';
+
 /**
  * Returns true if and only if the value is null or undefined.
  *
@@ -18,3 +21,12 @@ export function isObject (value: any): boolean {
   // to confirm it's just an object.
   return typeof value === 'object' && !Array.isArray(value);
 }
+
+/**
+ * Returns the keccak256 hash of a file.
+ *
+ * @param path The path to the file to be hashed.
+ */
+export function hashFile (path: string): string {
+  return '0x' + keccak256(fs.readFileSync(path, { encoding: 'binary' }));
+}

downloader.ts

@@ -1,7 +1,7 @@
 import * as fs from 'fs';
 import { https } from 'follow-redirects';
 import MemoryStream from 'memorystream';
-import { keccak256 } from 'js-sha3';
+import { hashFile } from './common/helpers';
 
 function getVersionList (host: string): Promise<string> {
   console.log('Retrieving available version list...');
@@ -44,7 +44,7 @@ function downloadBinary (host: string, outputName: string, releaseFile: string,
       response.pipe(file);
       file.on('finish', function () {
         file.close();
-        const hash = '0x' + keccak256(fs.readFileSync(outputName, { encoding: 'binary' }));
+        const hash = hashFile(outputName);
         if (expectedHash !== hash) {
           reject(new Error('Hash mismatch: expected ' + expectedHash + ' but got ' + hash));
         } else {

test/downloader.ts

@@ -3,9 +3,10 @@ import tape from 'tape';
 import nock from 'nock';
 import fs from 'fs';
 import path from 'path';
-import { keccak256 } from 'js-sha3';
 import { https } from 'follow-redirects';
 import downloader from '../downloader';
+import { keccak256 } from 'js-sha3';
+import { hashFile } from '../common/helpers';
 
 const assets = path.resolve(__dirname, 'resources/assets');
 
@@ -15,10 +16,6 @@ tape.onFinish(() => {
   }
 });
 
-function hash (filePath: string): string {
-  return '0x' + keccak256(fs.readFileSync(filePath, { encoding: 'binary' }));
-}
-
 function generateTestFile (t: tape.Test, content: string): tmp.FileResult {
   // As the `keep` option is set to true the removeCallback must be called by the caller
   // to cleanup the files after the test.
@@ -126,7 +123,7 @@ tape('Download binary', async function (t) {
         server.origin,
         targetFilename,
         file.name,
-        hash(file.name)
+        hashFile(file.name)
       );
 
       if (!fs.existsSync(targetFilename)) {