Use HTTP range requests (responses) to serve mp4 from assets

Summary:
This PR solves a problem when video assets are used from third-party React Native components (e.g. [react-native-video](https://github.com/brentvatne/react-native-video). The video will not work while the assets are served from the react native packager because the used video component (iOS) relies on HTTP range requests.

I added a small fix that allows ranged requests (e.g. mp4) to be served in ranges.

To test this:

1. make new react native project
1. add [react-native-video](https://github.com/brentvatne/react-native-video) to xcode project
1. add video component to your project
```
import Video from 'react-native-video';
var resolveAssetSource = require('react-native/Libraries/Image/resolveAssetSource');
/* ... /*
render() {
    let source = resolveAssetSource(require('./someVideoFile.mp4')) || {};
    return <Video /*....*/ source={source} />;
}
```

That should not work (if video is smaller than a few megabytes, open app a few times). Then add my fix, that should do the trick.
Closes #8219

Reviewed By: davidaurelio

Differential Revision: D3542485

Pulled By: frantic

fbshipit-source-id: e4f2e4d3aaafa8445e965259bf04ad107dba8a4f

package.json

@@ -188,7 +188,8 @@
  "xmldoc": "^0.4.0",
  "yargs": "^3.24.0",
  "yeoman-environment": "~1.2.7",
- "yeoman-generator": "^0.20.3"
+ "yeoman-generator": "^0.20.3",
+ "mime-types": "2.1.11"
  },
  "devDependencies": {
  "babel-eslint": "^6.0.0",

packager/react-packager/src/Server/__tests__/Server-test.js

@@ -349,6 +349,19 @@ describe('processRequest', () => {
  expect(AssetServer.prototype.get).toBeCalledWith('imgs/a.png', 'ios');
  expect(res.end).toBeCalledWith('i am image');
  });
+
+ it('should serve range request', () => {
+ const req = {url: '/assets/imgs/a.png?platform=ios', headers: {range: 'bytes=0-3'}};
+ const res = {end: jest.fn(), writeHead: jest.fn()};
+ const mockData = 'i am image';
+
+ AssetServer.prototype.get.mockImpl(() => Promise.resolve(mockData));
+
+ server.processRequest(req, res);
+ jest.runAllTimers();
+ expect(AssetServer.prototype.get).toBeCalledWith('imgs/a.png', 'ios');
+ expect(res.end).toBeCalledWith(mockData.slice(0, 3));
+ });
  });
 
  describe('buildbundle(options)', () => {

packager/react-packager/src/Server/index.js

@@ -19,6 +19,7 @@ const SourceMapConsumer = require('source-map').SourceMapConsumer;
 const declareOpts = require('../lib/declareOpts');
 const path = require('path');
 const url = require('url');
+const mime = require('mime-types');
 
 function debounce(fn, delay) {
  var timeout;
@@ -396,13 +397,33 @@ class Server {
  });
  }
 
+ _rangeRequestMiddleware(req, res, data, assetPath) {
+ if (req.headers && req.headers.range) {
+ const [rangeStart, rangeEnd] = req.headers.range.replace(/bytes=/, '').split('-');
+ const dataStart = parseInt(rangeStart, 10);
+ const dataEnd = rangeEnd ? parseInt(rangeEnd, 10) : data.length - 1;
+ const chunksize = (dataEnd - dataStart) + 1;
+
+ res.writeHead(206, {
+ 'Accept-Ranges': 'bytes',
+ 'Content-Length': chunksize,
+ 'Content-Range': `bytes ${dataStart}-${dataEnd}/${data.length}`,
+ 'Content-Type': mime.lookup(path.basename(assetPath[1]))
+ });
+
+ return data.slice(dataStart, dataEnd);
+ }
+
+ return data;
+ }
+
  _processAssetsRequest(req, res) {
  const urlObj = url.parse(req.url, true);
  const assetPath = urlObj.pathname.match(/^\/assets\/(.+)$/);
  const assetEvent = Activity.startEvent(`processing asset request ${assetPath[1]}`);
  this._assetServer.get(assetPath[1], urlObj.query.platform)
  .then(
- data => res.end(data),
+ data => res.end(this._rangeRequestMiddleware(req, res, data, assetPath)),
  error => {
  console.error(error.stack);
  res.writeHead('404');