implemented required encoding negotiator without 3rd party dependency

encoding_negotiator.js

@@ -0,0 +1,78 @@
+var zlib = require('zlib')
+
+/**
+ * @const
+ * whether current node version has brotli support
+ */
+var hasBrotliSupport = 'createBrotliCompress' in zlib
+
+var supportedEncodings = hasBrotliSupport
+  ? ['br', 'gzip', 'deflate', 'identity']
+  : ['gzip', 'deflate', 'identity']
+
+var preferredEncodings = hasBrotliSupport
+  ? ['br', 'gzip']
+  : ['gzip']
+
+function negotiateEncoding (header) {
+  header = header || ''
+
+  var insts = header.split(',')
+  var decoded = []
+
+  for (var i = 0; i < insts.length; i++) {
+    var inst = insts[i].match(/^\s*?([^\s;]+?)\s*?(?:;(.*))?$/)
+    if (!inst) continue
+
+    var encoding = inst[1]
+    if (supportedEncodings.indexOf(encoding) === -1) {
+      continue
+    }
+
+    var q = 1
+    if (inst[2]) {
+      var params = inst[2].split(';')
+      for (var j = 0; j < params.length; j++) {
+        var p = params[j].trim().split('=')
+        if (p[0] === 'q') {
+          q = parseFloat(p[1])
+          break
+        }
+      }
+    }
+
+    if (q < 0 || q > 1) { // invalid
+      continue
+    }
+
+    decoded.push({ encoding: encoding, q: q, i: i })
+  }
+
+  decoded.sort((a, b) => {
+    if (a.q !== b.q) {
+      return b.q - a.q // higher quality first
+    }
+
+    var aPreferred = preferredEncodings.indexOf(a.encoding)
+    var bPreferred = preferredEncodings.indexOf(b.encoding)
+
+    if (aPreferred === -1 && bPreferred === -1) {
+      return a.i - b.i // consider the original order
+    }
+
+    if (aPreferred !== -1 && bPreferred !== -1) {
+      return aPreferred - bPreferred // consider the preferred order
+    }
+
+    return aPreferred === -1 ? 1 : -1 // preferred first
+  })
+
+  if (decoded.length > 0) {
+    return decoded[0].encoding
+  }
+
+  return null
+}
+
+module.exports.hasBrotliSupport = hasBrotliSupport
+module.exports.negotiateEncoding = negotiateEncoding

index.js

@@ -22,8 +22,8 @@ var objectAssign = require('object-assign')
 var onHeaders = require('on-headers')
 var vary = require('vary')
 var zlib = require('zlib')
-
-var Encodings = require('./lib/encodings')
+var hasBrotliSupport = require('./encoding_negotiator').hasBrotliSupport
+var negotiateEncoding = require('./encoding_negotiator').negotiateEncoding
 
 /**
  * Module exports.
@@ -50,7 +50,7 @@ var cacheControlNoTransformRegExp = /(?:^|,)\s*?no-transform\s*?(?:,|$)/
 function compression (options) {
   var opts = options || {}
 
-  if (Encodings.hasBrotliSupport) {
+  if (hasBrotliSupport) {
     // set the default level to a reasonable value with balanced speed/ratio
     if (opts.params === undefined) {
       opts = objectAssign({}, opts)
@@ -189,12 +189,10 @@ function compression (options) {
       }
 
       // compression method
-      var encodings = new Encodings()
-      encodings.parseAcceptEncoding(req.headers['accept-encoding'] || 'identity')
-      var method = encodings.getPreferredContentEncoding()
+      var method = negotiateEncoding(req.headers['accept-encoding']) || 'identity'
 
       // negotiation failed
-      if (!method || method === 'identity') {
+      if (method === 'identity') {
         nocompress('not acceptable')
         return
       }

package.json

@@ -9,7 +9,6 @@
   "license": "MIT",
   "repository": "expressjs/compression",
   "dependencies": {
-    "accepts": "~1.3.7",
     "bytes": "3.0.0",
     "compressible": "~2.0.17",
     "debug": "2.6.9",