feat(web-server): Allow Range headers in web server.

This does not support multiple-ranges.

Closes #2140

docs/config/02-files.md

@@ -126,7 +126,15 @@ proxies: {
 },
 ```
 
+## Webserver features
+
+* [Range requests][].
+* In-memory caching of files.
+* Watching for updates in the files.
+* Proxies to alter file paths.
+
 
 [glob]: https://github.com/isaacs/node-glob
 [preprocessors]: preprocessors.html
 [minimatch]: https://github.com/isaacs/minimatch
+[Range requests]: https://en.wikipedia.org/wiki/Byte_serving

lib/middleware/common.js

@@ -29,9 +29,47 @@ var serve404 = function (response, path) {
 var createServeFile = function (fs, directory, config) {
   var cache = Object.create(null)
 
-  return function (filepath, response, transform, content, doNotCache) {
+  return function (filepath, rangeHeader, response, transform, content, doNotCache) {
     var responseData
 
+    var convertForRangeRequest = function () {
+      // If the header is invalid, ignore
+      if (!rangeHeader.startsWith('bytes=')) {
+        return 200
+      }
+
+      responseData = new Buffer(responseData)
+
+      var ranges = rangeHeader.substr(6)
+      if (ranges.indexOf(',') >= 0) {
+        // Multiple ranges are not supported.
+        responseData = new Buffer(0)
+        return 416  // Requested range not satisfiable
+      }
+      var parts = /^([0-9]*)-([0-9]*)$/.exec(ranges)
+      if (!parts || (!parts[1] && !parts[2])) {
+        return 200
+      }
+      var start, end
+      if (parts[1]) {
+        start = Number(parts[1])
+        end = parts[2] ? Number(parts[2]) : responseData.length
+      } else {
+        end = responseData.length
+        start = responseData.length - Number(parts[2])
+      }
+      if (end <= start) {
+        responseData = new Buffer(0)
+        return 416  // Requested range not satisfiable
+      }
+
+      response.setHeader(
+          'Content-Range',
+          'bytes ' + start + '-' + end + '/' + responseData.length)
+      responseData = responseData.slice(start, end + 1)
+      return 206
+    }
+
     if (directory) {
       filepath = directory + filepath
     }
@@ -57,7 +95,12 @@ var createServeFile = function (fs, directory, config) {
       // call custom transform fn to transform the data
       responseData = transform && transform(content) || content
 
-      response.writeHead(200)
+      if (rangeHeader) {
+        var code = convertForRangeRequest()
+        response.writeHead(code)
+      } else {
+        response.writeHead(200)
+      }
 
       log.debug('serving (cached): ' + filepath)
       return response.end(responseData)
@@ -77,7 +120,12 @@ var createServeFile = function (fs, directory, config) {
       // call custom transform fn to transform the data
       responseData = transform && transform(data.toString()) || data
 
-      response.writeHead(200)
+      if (rangeHeader) {
+        var code = convertForRangeRequest()
+        response.writeHead(code)
+      } else {
+        response.writeHead(200)
+      }
 
       log.debug('serving: ' + filepath)
       return response.end(responseData)

lib/middleware/karma.js

@@ -89,6 +89,7 @@ var createKarmaMiddleware = function (
     var jsVersion = injector.get('config.jsVersion')
 
     var requestUrl = request.normalizedUrl.replace(/\?.*/, '')
+    var requestedRangeHeader = request.headers['range']
 
     // redirect /__karma__ to /__karma__ (trailing slash)
     if (requestUrl === urlRoot.substr(0, urlRoot.length - 1)) {
@@ -107,7 +108,7 @@ var createKarmaMiddleware = function (
 
     // serve client.html
     if (requestUrl === '/') {
-      return serveStaticFile('/client.html', response, function (data) {
+      return serveStaticFile('/client.html', requestedRangeHeader, response, function (data) {
         return data
           .replace('\n%X_UA_COMPATIBLE%', getXUACompatibleMetaElement(request.url))
           .replace('%X_UA_COMPATIBLE_URL%', getXUACompatibleUrl(request.url))
@@ -118,15 +119,15 @@ var createKarmaMiddleware = function (
     var jsFiles = ['/karma.js', '/context.js', '/debug.js']
     var isRequestingJsFile = jsFiles.indexOf(requestUrl) !== -1
     if (isRequestingJsFile) {
-      return serveStaticFile(requestUrl, response, function (data) {
+      return serveStaticFile(requestUrl, requestedRangeHeader, response, function (data) {
         return data.replace('%KARMA_URL_ROOT%', urlRoot)
           .replace('%KARMA_VERSION%', VERSION)
       })
     }
 
     // serve the favicon
     if (requestUrl === '/favicon.ico') {
-      return serveStaticFile(requestUrl, response)
+      return serveStaticFile(requestUrl, requestedRangeHeader, response)
     }
 
     // serve context.html - execution context within the iframe
@@ -152,7 +153,7 @@ var createKarmaMiddleware = function (
           requestedFileUrl = requestUrl
         }
 
-        fileServer(requestedFileUrl, response, function (data) {
+        fileServer(requestedFileUrl, requestedRangeHeader, response, function (data) {
           common.setNoCacheHeaders(response)
 
           var scriptTags = files.included.map(function (file) {

lib/middleware/source_files.js

@@ -30,9 +30,10 @@ var createSourceFilesMiddleware = function (filesPromise, serveFile, basePath, u
     return filesPromise.then(function (files) {
       // TODO(vojta): change served to be a map rather then an array
       var file = findByPath(files.served, requestedFilePath)
+      var rangeHeader = request.headers['range']
 
       if (file) {
-        serveFile(file.contentPath || file.path, response, function () {
+        serveFile(file.contentPath || file.path, rangeHeader, response, function () {
           if (/\?\w+/.test(request.url)) {
             // files with timestamps - cache one year, rely on timestamps
             common.setHeavyCacheHeaders(response)

test/unit/middleware/source_files.spec.js

@@ -59,6 +59,52 @@ describe('middleware.source_files', function () {
     return files.resolve({included: [], served: list})
   }
 
+  describe('Range headers', function () {
+    beforeEach(function () {
+      servedFiles([
+        new File('/src/some.js')
+      ])
+    })
+
+    it('allows single explicit ranges', function () {
+      return request(server)
+        .get('/absolute/src/some.js')
+        .set('Range', 'bytes=3-6')
+        .expect('Content-Range', 'bytes 3-6/9')
+        .expect(206, 'sour')
+    })
+
+    it('allows single range with no end', function () {
+      return request(server)
+        .get('/absolute/src/some.js')
+        .set('Range', 'bytes=3-')
+        .expect('Content-Range', 'bytes 3-9/9')
+        .expect(206, 'source')
+    })
+
+    it('allows single range with suffix', function () {
+      return request(server)
+        .get('/absolute/src/some.js')
+        .set('Range', 'bytes=-5')
+        .expect('Content-Range', 'bytes 4-9/9')
+        .expect(206, 'ource')
+    })
+
+    it('doesn\'t support multiple ranges', function () {
+      return request(server)
+        .get('/absolute/src/some.js')
+        .set('Range', 'bytes=0-2,-3')
+        .expect(416, '')
+    })
+
+    it('will return 416', function () {
+      return request(server)
+        .get('/absolute/src/some.js')
+        .set('Range', 'bytes=20-')
+        .expect(416, '')
+    })
+  })
+
   it('should serve absolute js source files ignoring timestamp', function () {
     servedFiles([
       new File('/src/some.js')