Range request handling

README.md

@@ -265,12 +265,14 @@ These are the methods used by the package (they can all return a `Promise` or be
 ```js
 await handler(request, response, undefined, {
   stat(path) {},
-  createReadStream(path) {},
+  createReadStream(path, config) {}
   readdir(path) {},
   sendError(absolutePath, response, acceptsJSON, root, handlers, config, error) {}
 });
 ```
 
+**NOTE:** It's important that – for native methods like `createReadStream` – all arguments are passed on to the native call.
+
 ## Use Cases
 
 There are two environments in which [ZEIT](https://zeit.co) uses this package:

package.json

@@ -69,6 +69,7 @@
     "mime-types": "2.1.18",
     "minimatch": "3.0.4",
     "path-is-inside": "1.0.2",
-    "path-to-regexp": "2.2.1"
+    "path-to-regexp": "2.2.1",
+    "range-parser": "1.2.0"
   }
 }

src/index.js

@@ -12,6 +12,7 @@ const mime = require('mime-types');
 const bytes = require('bytes');
 const contentDisposition = require('content-disposition');
 const isPathInside = require('path-is-inside');
+const parseRange = require('range-parser');
 
 // Other
 const directoryTemplate = require('./directory');
@@ -197,7 +198,8 @@ const getHeaders = async (customHeaders = [], current, absolutePath, stats) => {
 			// only happens if it cannot find a appropiate value.
 			'Content-Disposition': contentDisposition(base, {
 				type: 'inline'
-			})
+			}),
+			'Accept-Ranges': 'bytes'
 		};
 
 		const contentType = mime.contentType(base);
@@ -637,9 +639,35 @@ module.exports = async (request, response, config = {}, methods = {}) => {
 		});
 	}
 
-	const stream = await handlers.createReadStream(absolutePath);
+	const streamOpts = {};
+
+	// TODO ? if-range
+	if (request.headers.range) {
+		const range = parseRange(stats.size, request.headers.range);
+
+		if (typeof range === 'object' && range.type === 'bytes') {
+			const {start, end} = range[0];
+			streamOpts.start = start;
+			streamOpts.end = end;
+
+			response.statusCode = 206;
+		} else {
+			response.statusCode = 416;
+			response.setHeader('Content-Range', `bytes */${stats.size}`);
+		}
+	}
+
+	// TODO ? multiple ranges
+
+	const stream = await handlers.createReadStream(absolutePath, streamOpts);
 	const headers = await getHeaders(config.headers, current, absolutePath, stats);
 
+	// eslint-disable-next-line no-undefined
+	if (streamOpts.start !== undefined && streamOpts.end !== undefined) {
+		headers['Content-Range'] = `bytes ${streamOpts.start}-${streamOpts.end}/${stats.size}`;
+		headers['Content-Length'] = streamOpts.end - streamOpts.start + 1;
+	}
+
 	// We need to check for `headers.ETag` being truthy first, otherwise it will
 	// match `undefined` being equal to `undefined`, which is true.
 	//

test/integration.js

@@ -869,9 +869,9 @@ test('set `createReadStream` handler to async function', async t => {
 
 	// eslint-disable-next-line no-undefined
 	const url = await getUrl(undefined, {
-		createReadStream: async file => {
+		createReadStream: async (file, opts) => {
 			await sleep(2000);
-			return fs.createReadStream(file);
+			return fs.createReadStream(file, opts);
 		}
 	});
 
@@ -1013,13 +1013,13 @@ test('modify config in `createReadStream` handler', async t => {
 	};
 
 	const url = await getUrl(config, {
-		createReadStream: async file => {
+		createReadStream: async (file, opts) => {
 			config.headers.unshift({
 				source: name,
 				headers: [header]
 			});
 
-			return fs.createReadStream(file);
+			return fs.createReadStream(file, opts);
 		}
 	});
 
@@ -1069,3 +1069,49 @@ test('automatically handle ETag headers for normal files', async t => {
 
 	t.is(cacheResponse.status, 304);
 });
+
+test('range request', async t => {
+	const name = 'docs.md';
+	const related = path.join(fixturesFull, name);
+
+	const content = await fs.readFile(related);
+	const url = await getUrl();
+	const response = await fetch(`${url}/${name}`, {
+		headers: {
+			Range: 'bytes=0-10'
+		}
+	});
+
+	const range = response.headers.get('content-range');
+	const length = Number(response.headers.get('content-length'));
+	t.is(range, `bytes 0-10/${content.length}`);
+	t.is(length, 11);
+	t.is(response.status, 206);
+
+	const text = await response.text();
+	const spec = content.toString().substr(0, 11);
+	t.is(text, spec);
+});
+
+test('range request not satisfiable', async t => {
+	const name = 'docs.md';
+	const related = path.join(fixturesFull, name);
+
+	const content = await fs.readFile(related);
+	const url = await getUrl();
+	const response = await fetch(`${url}/${name}`, {
+		headers: {
+			Range: 'bytes=10-1'
+		}
+	});
+
+	const range = response.headers.get('content-range');
+	const length = Number(response.headers.get('content-length'));
+	t.is(range, `bytes */${content.length}`);
+	t.is(length, content.length);
+	t.is(response.status, 416);
+
+	const text = await response.text();
+	const spec = content.toString();
+	t.is(text, spec);
+});

yarn.lock

@@ -3228,6 +3228,10 @@ randomatic@^3.0.0:
     kind-of "^6.0.0"
     math-random "^1.0.1"
 
+range-parser@1.2.0:
+  version "1.2.0"
+  resolved "https://registry.yarnpkg.com/range-parser/-/range-parser-1.2.0.tgz#f49be6b487894ddc40dcc94a322f611092e00d5e"
+
 raw-body@2.3.2:
   version "2.3.2"
   resolved "https://registry.yarnpkg.com/raw-body/-/raw-body-2.3.2.tgz#bcd60c77d3eb93cde0050295c3f379389bc88f89"