feat: Adding support for brolti

Author: nicksrandall

README.md

@@ -11,6 +11,9 @@ The following compression codings are supported:
 
   - deflate
   - gzip
+  - br (brotli)
+
+**Note** Brotli is supported only since Node.js versions v11.7.0 and v10.16.0.
 
 ## Install
 
@@ -44,7 +47,8 @@ as compressing will transform the body.
 
 `compression()` accepts these properties in the options object. In addition to
 those listed below, [zlib](http://nodejs.org/api/zlib.html) options may be
-passed in to the options object.
+passed in to the options object or
+[brotli](https://nodejs.org/api/zlib.html#zlib_class_brotlioptions) options.
 
 ##### chunkSize
 
@@ -101,6 +105,20 @@ The default value is `zlib.Z_DEFAULT_MEMLEVEL`, or `8`.
 See [Node.js documentation](http://nodejs.org/api/zlib.html#zlib_memory_usage_tuning)
 regarding the usage.
 
+##### params *(brotli only)* - [key-value object containing indexed Brotli parameters](https://nodejs.org/api/zlib.html#zlib_brotli_constants)
+
+  - `zlib.constants.BROTLI_PARAM_MODE`
+    - `zlib.constants.BROTLI_MODE_GENERIC` (default)
+    - `zlib.constants.BROTLI_MODE_TEXT`, adjusted for UTF-8 text
+    - `zlib.constants.BROTLI_MODE_FONT`, adjusted for WOFF 2.0 fonts
+  - `zlib.constants.BROTLI_PARAM_QUALITY`
+    - Ranges from `zlib.constants.BROTLI_MIN_QUALITY` to
+      `zlib.constants.BROTLI_MAX_QUALITY`, with a default of
+      `4` (which is not node's default but the most optimal).
+
+Note that here the default is set to compression level 4. This is a balanced setting with a very good speed and a very good
+compression ratio.
+
 ##### strategy
 
 This is used to tune the compression algorithm. This value only affects the

index.js

@@ -22,6 +22,7 @@ var debug = require('debug')('compression')
 var onHeaders = require('on-headers')
 var vary = require('vary')
 var zlib = require('zlib')
+var objectAssign = require('object-assign')
 
 /**
  * Module exports.
@@ -30,6 +31,12 @@ var zlib = require('zlib')
 module.exports = compression
 module.exports.filter = shouldCompress
 
+/**
+ * @const
+ * whether current node version has brotli support
+ */
+var hasBrotliSupport = 'createBrotliCompress' in zlib
+
 /**
  * Module variables.
  * @private
@@ -48,6 +55,17 @@ var cacheControlNoTransformRegExp = /(?:^|,)\s*?no-transform\s*?(?:,|$)/
 function compression (options) {
   var opts = options || {}
 
+  if (hasBrotliSupport) {
+    // set the default level to a reasonable value with balanced speed/ratio
+    if (opts.params === undefined) {
+      opts.params = {}
+    }
+
+    if (opts.params[zlib.constants.BROTLI_PARAM_QUALITY] === undefined) {
+      opts.params[zlib.constants.BROTLI_PARAM_QUALITY] = 4
+    }
+  }
+
   // options
   var filter = opts.filter || shouldCompress
   var threshold = bytes.parse(opts.threshold)
@@ -173,14 +191,12 @@ function compression (options) {
         return
       }
 
-      // compression method
-      var accept = accepts(req)
-      var method = accept.encoding(['gzip', 'deflate', 'identity'])
+      // force proper priorization
+      var headers = objectAssign({}, req.headers, { 'accept-encoding': prioritize(req.headers['accept-encoding']) })
 
-      // we really don't prefer deflate
-      if (method === 'deflate' && accept.encoding(['gzip'])) {
-        method = accept.encoding(['gzip', 'identity'])
-      }
+      // compression method
+      var accept = accepts(objectAssign({}, res, { headers: headers }))
+      var method = accept.encoding(['br', 'gzip', 'deflate', 'identity'])
 
       // negotiation failed
       if (!method || method === 'identity') {
@@ -192,7 +208,9 @@ function compression (options) {
       debug('%s compression', method)
       stream = method === 'gzip'
         ? zlib.createGzip(opts)
-        : zlib.createDeflate(opts)
+        : method === 'br'
+          ? zlib.createBrotliCompress(opts)
+          : zlib.createDeflate(opts)
 
       // add buffered listeners to stream
       addListeners(stream, stream.on, listeners)
@@ -286,3 +304,47 @@ function toBuffer (chunk, encoding) {
     ? Buffer.from(chunk, encoding)
     : chunk
 }
+
+/**
+ * Most browsers send "br" (brolti) as the last value in
+ * in the 'Accept-Encoding' header which causes it to be
+ * depriorited according to the spec.
+ *
+ * This is typically not what end users actually want so here
+ * we force the "br" (brotli) value to first in the list so that
+ * it will get properly prioritized and used.
+ *
+ * It's worth noting that although this is not "spec compliant",
+ * we belive it follows a well-established convention.
+ *
+ * @private
+ */
+function prioritize (str) {
+  return str && str.split(',')
+    .sort(sortEncodings)
+    .join(',')
+}
+
+/**
+ * Sort compression encodings in order of our preference:
+ * br > gzip > deflate
+ *
+ * @private
+ */
+function sortEncodings (a, b) {
+  if (a.indexOf('br') >= 0) {
+    return -1
+  }
+  if (a.indexOf('gzip') >= 0) {
+    return b.indexOf('br') >= 0 ? 1 : -1
+  }
+  // we need these inverse rules to fix a stable sort bug
+  // found in node 10.x
+  if (b.indexOf('br') >= 0) {
+    return 1
+  }
+  if (b.indexOf('gzip') >= 0) {
+    return 1
+  }
+  return 0
+}

package.json

@@ -13,6 +13,7 @@
     "bytes": "3.0.0",
     "compressible": "~2.0.17",
     "debug": "2.6.9",
+    "object-assign": "4.1.1",
     "on-headers": "~1.0.2",
     "safe-buffer": "5.2.0",
     "vary": "~1.1.2"