allow custom compression for custom Accept-Encoding Fixes #59

README.md

@@ -136,6 +136,28 @@ The default value is `zlib.Z_DEFAULT_WINDOWBITS`, or `15`.
 See [Node.js documentation](http://nodejs.org/api/zlib.html#zlib_memory_usage_tuning)
 regarding the usage.
 
+##### compressor
+
+Allows you to specify your own compression stream for a given Content-Encoding.
+
+```js
+var opts = {
+  compressor: {
+    br: brotliStreamEncoder,
+    lzma: lzmaStreamEncoder,
+  },
+};
+```
+
+Where the custom compressor is a function that returns effectively a transform
+stream. ex:
+
+```js
+function brotliStreamEncoder (opts) {
+  return brotli.compressStream(opts);
+};
+```
+
 #### .filter
 
 The default `filter` function. This is used to construct a custom filter

index.js

@@ -173,7 +173,17 @@ function compression(options) {
 
       // compression method
       var accept = accepts(req)
-      var method = accept.encoding(['gzip', 'deflate', 'identity'])
+      var method = null
+      var acceptableEncodings = ['gzip', 'deflate', 'identity']
+
+      // If we support a custom encoding and a custom encoding was requested
+      if (opts.compressor) {
+        method = accept.encoding(Object.keys(opts.compressor).concat(acceptableEncodings))
+      }
+
+      if (!method) {
+        method = accept.encoding(acceptableEncodings)
+      }
 
       // we really don't prefer deflate
       if (method === 'deflate' && accept.encoding(['gzip'])) {
@@ -188,9 +198,13 @@ function compression(options) {
 
       // compression stream
       debug('%s compression', method)
-      stream = method === 'gzip'
-        ? zlib.createGzip(opts)
-        : zlib.createDeflate(opts)
+      if (method === 'gzip') {
+        stream = zlib.createGzip(opts)
+      } else if (method === 'deflate') {
+        stream = zlib.createDeflate(opts)
+      } else if (opts.compressor && method in opts.compressor) {
+        stream = opts.compressor[method](opts)
+      }
 
       // add bufferred listeners to stream
       addListeners(stream, stream.on, listeners)

package.json

@@ -19,7 +19,8 @@
   "devDependencies": {
     "istanbul": "0.3.21",
     "mocha": "2.3.3",
-    "supertest": "1.1.0"
+    "supertest": "1.1.0",
+    "through": "2.3.8"
   },
   "files": [
     "LICENSE",

test/compression.js

@@ -3,6 +3,7 @@ var bytes = require('bytes');
 var crypto = require('crypto');
 var http = require('http');
 var request = require('supertest');
+var through = require('through');
 
 var compression = require('..');
 
@@ -478,6 +479,14 @@ describe('compression()', function(){
     })
   })
 
+  function createCompressor () {
+    return through(function (d) {
+      this.queue(d.toString().split('').reverse().join(''))
+    }, function () {
+      this.queue(null)
+    })
+  }
+
   describe('when "Accept-Encoding: deflate, gzip"', function () {
     it('should respond with gzip', function (done) {
       var server = createServer({ threshold: 0 }, function (req, res) {
@@ -490,6 +499,76 @@ describe('compression()', function(){
       .set('Accept-Encoding', 'deflate, gzip')
       .expect('Content-Encoding', 'gzip', done)
     })
+
+    it('should respond with gzip even when a custom compressor is specified but not requested', function (done) {
+      var opts = {
+        threshold: 0,
+        compressor: {
+          'bingo': createCompressor
+        }
+      }
+      var server = createServer(opts, function (req, res) {
+        res.setHeader('Content-Type', 'text/plain')
+        res.end('hello, world')
+      })
+
+      request(server)
+      .get('/')
+      .set('Accept-Encoding', 'gzip, deflate')
+      .expect('Content-Encoding', 'gzip', done)
+    })
+  })
+
+  describe('when "Accept-Encoding: custom"', function () {
+    it('should not use content encoding without a custom compressor function', function (done) {
+      var server = createServer({ threshold: 0 }, function (req, res) {
+        res.setHeader('Content-Type', 'text/plain')
+        res.end('hello, world')
+      })
+
+      request(server)
+      .get('/')
+      .set('Accept-Encoding', 'custom')
+      .expect(shouldNotHaveHeader('Content-Encoding'))
+      .expect(200, 'hello, world', done)
+    })
+
+    it('should use content encoding with a custom compressor function', function (done) {
+      var opts = {
+        threshold: 0,
+        compressor: {
+          'bingo': createCompressor
+        }
+      }
+      var server = createServer(opts, function (req, res) {
+        res.setHeader('Content-Type', 'text/plain')
+        res.end('hello, world')
+      })
+
+      request(server)
+      .get('/')
+      .set('Accept-Encoding', 'bingo, gzip')
+      .expect('Content-Encoding', 'bingo')
+      .expect(200, 'dlrow ,olleh', done)
+    })
+
+    it('should obey q= priorities', function (done) {
+      var opts = {
+        threshold: 0,
+        compressor: {
+          'bingo': createCompressor
+        }
+      }
+      var server = createServer(opts, function (req, res) {
+        res.setHeader('Content-Type', 'text/plain')
+        res.end('hello, world')
+      })
+
+      request(server)
+      .get('/')
+      .set('Accept-Encoding', 'bingo;q=0.001, gzip')
+      .expect('Content-Encoding', 'gzip', done)
+    })
   })
 
   describe('when "Cache-Control: no-transform" response header', function () {