Use new configurable negotiator api for encoding sorting

Author: Mikko Tiihonen

README.md

@@ -139,6 +139,14 @@ Compression tips:
      gzip encoders. Brotli compresses generally 15-20% better than gzip.
    * Use zopfli for gzip compression for and extra 5% benefit for all browsers.
 
+Performance of serving static files is lower due to extra stats – worst case
+20% with 1 byte files to loopback client. Compared to on-the-fly compression
+the precompression is still a large win.
+
+##### encodingNegotiatorOptions
+
+Allows configuring the [encoding negotation options](https://github.com/jshttp/negotiator#sort-options).
+
 ##### root
 
 Serve files relative to `path`.

index.js

@@ -170,6 +170,10 @@ function SendStream (req, path, options) {
       ? opts.precompressionFormats
       : this._precompressionFormats
 
+  this._encodingNegotiatorOptions = opts.encodingNegotiatorOptions !== undefined
+    ? opts.encodingNegotiatorOptions
+    : { sortPreference: 'clientThenServer'}
+
   this._index = opts.index !== undefined
     ? normalizeList(opts.index, 'index option')
     : ['index.html']
@@ -386,7 +390,7 @@ SendStream.prototype.isPreconditionFailure = function isPreconditionFailure () {
 
 SendStream.prototype.getAcceptEncodingExtensions = function() {
   var self = this
-  var negotiatedEncodings = new Negotiator(this.req).encodings(self._precompressionEncodings)
+  var negotiatedEncodings = new Negotiator(this.req).encodings(self._precompressionEncodings, this._encodingNegotiatorOptions)
   var accepted = []
   for (var e = 0; e < negotiatedEncodings.length; e++) {
     var encoding = negotiatedEncodings[e]

package.json

@@ -26,7 +26,7 @@
     "http-errors": "~1.6.1",
     "mime": "1.3.4",
     "ms": "0.7.2",
-    "negotiator": "jshttp/negotiator#d9907aec0585476d9a0c4271e464f7c6e4633049",
+    "negotiator": "jshttp/negotiator#6038bf698c522c1883a1113c834e53256b35584f",
     "on-finished": "~2.3.0",
     "range-parser": "~1.2.0",
     "statuses": "~1.3.1",