Remove an unnecessary 'use strict'.

.gitignore

@@ -1 +1,2 @@
+lib
 node_modules

.travis.yml

@@ -1,10 +1,12 @@
 language: node_js
 
 node_js:
-  - "0.6"
   - "0.8"
   - "0.10"
-  - "0.11"
+  - "0.12"
+  - "iojs"
 
 before_install:
-  - '[ "${TRAVIS_NODE_VERSION}" = "0.6" ] && npm conf set strict-ssl false || true'
+  - '[ "${TRAVIS_NODE_VERSION}" != "0.8" ] || npm install -g npm@~1.4.0'
+
+script: make test

CHANGELOG.md

@@ -0,0 +1,14 @@
+### 0.1.2 / 2014-12-18
+
+* Don't allow configure() to be called with unrecognized options
+
+### 0.1.1 / 2014-12-15
+
+* Fix race condition when using context takeover, where adjacent messages have
+  data listeners bound at the same time and end up duplicating output
+* Use `DeflateRaw.flush()` correctly on v0.10 so that optimal compression is
+  achieved
+
+### 0.1.0 / 2014-12-13
+
+* Initial release

Makefile

@@ -0,0 +1,19 @@
+SHELL := /bin/bash
+PATH  := node_modules/.bin:$(PATH)
+
+source_files := $(shell find src -name '*.js')
+target_files := $(source_files:src/%.js=lib/%.js)
+
+.PHONY: all clean test
+
+all: $(target_files)
+
+lib/%.js: src/%.js
+	mkdir -p $(dir $@)
+	babel $< --out-file $@ --source-maps true
+
+clean:
+	rm -rf lib
+
+test: all
+	jstest spec/runner.js

README.md

@@ -41,12 +41,12 @@ exts.add(deflate);
 
 The set of available options can be split into two sets: those that control the
 session's compressor for outgoing messages and do not need to be communicated to
-the peer, and those that are negoatiated as part of the protocol. The settings
+the peer, and those that are negotiated as part of the protocol. The settings
 only affecting the compressor are described fully in the [zlib
 documentation](http://nodejs.org/api/zlib.html#zlib_options):
 
 * `level`: sets the compression level, can be an integer from `0` to `9`, or one
-  of the contants `zlib.Z_NO_COMPRESSION`, `zlib.Z_BEST_SPEED`,
+  of the constants `zlib.Z_NO_COMPRESSION`, `zlib.Z_BEST_SPEED`,
   `zlib.Z_BEST_COMPRESSION`, or `zlib.Z_DEFAULT_COMPRESSION`
 * `memLevel`: sets how much memory the compressor allocates, can be an integer
   from `1` to `9`, or one of the constants `zlib.Z_MIN_MEMLEVEL`,
@@ -72,22 +72,21 @@ can be used to set the local session's behaviour and control that of the peer:
 
 (The MIT License)
 
-Copyright (c) 2014 James Coglan
+Copyright (c) 2014-2015 James Coglan
 
 Permission is hereby granted, free of charge, to any person obtaining a copy of
 this software and associated documentation files (the 'Software'), to deal in
 the Software without restriction, including without limitation the rights to
-use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
-of the Software, and to permit persons to whom the Software is furnished to do
-so, subject to the following conditions:
+use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
+the Software, and to permit persons to whom the Software is furnished to do so,
+subject to the following conditions:
 
 The above copyright notice and this permission notice shall be included in all
 copies or substantial portions of the Software.
 
 THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
-AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
-OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
-SOFTWARE.
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
+IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

lib/client_session.js

@@ -1,77 +0,0 @@
-'use strict';
-
-var util    = require('util'),
-    common  = require('./common'),
-    Session = require('./session');
-
-var ClientSession = function(options) {
-  Session.call(this, options);
-};
-util.inherits(ClientSession, Session);
-
-ClientSession.validParams = function(params) {
-  if (!common.validParams(params)) return false;
-
-  if (params.hasOwnProperty('client_max_window_bits')) {
-    if (common.VALID_WINDOW_BITS.indexOf(params.client_max_window_bits) < 0)
-      return false;
-  }
-  return true;
-};
-
-ClientSession.prototype.generateOffer = function() {
-  var offer = {};
-
-  if (this._acceptNoContextTakeover)
-    offer.client_no_context_takeover = true;
-
-  if (this._acceptMaxWindowBits !== undefined) {
-    if (common.VALID_WINDOW_BITS.indexOf(this._acceptMaxWindowBits) < 0) {
-      throw new Error('Invalid value for maxWindowBits');
-    }
-    offer.client_max_window_bits = this._acceptMaxWindowBits;
-  } else {
-    offer.client_max_window_bits = true;
-  }
-
-  if (this._requestNoContextTakeover)
-    offer.server_no_context_takeover = true;
-
-  if (this._requestMaxWindowBits !== undefined) {
-    if (common.VALID_WINDOW_BITS.indexOf(this._requestMaxWindowBits) < 0) {
-      throw new Error('Invalid valud for requestMaxWindowBits');
-    }
-    offer.server_max_window_bits = this._requestMaxWindowBits;
-  }
-
-  return offer;
-};
-
-ClientSession.prototype.activate = function(params) {
-  if (!ClientSession.validParams(params)) return false;
-
-  if (this._acceptMaxWindowBits && params.client_max_window_bits) {
-    if (params.client_max_window_bits > this._acceptMaxWindowBits) return false;
-  }
-
-  if (this._requestNoContextTakeover && !params.server_no_context_takeover)
-    return false;
-
-  if (this._requestMaxWindowBits) {
-    if (!params.server_max_window_bits) return false;
-    if (params.server_max_window_bits > this._requestMaxWindowBits) return false;
-  }
-
-  this._ownContextTakeover = !(this._acceptNoContextTakeover || params.client_no_context_takeover);
-  this._ownWindowBits = Math.min(
-    this._acceptMaxWindowBits || common.DEFAULT_MAX_WINDOW_BITS,
-    params.client_max_window_bits || common.DEFAULT_MAX_WINDOW_BITS
-  );
-
-  this._peerContextTakeover = !params.server_no_context_takeover;
-  this._peerWindowBits = params.server_max_window_bits || common.DEFAULT_MAX_WINDOW_BITS;
-
-  return true;
-};
-
-module.exports = ClientSession;

lib/common.js

@@ -1,51 +0,0 @@
-'use strict';
-
-var common = {
-  VALID_PARAMS: [
-    'server_no_context_takeover',
-    'client_no_context_takeover',
-    'server_max_window_bits',
-    'client_max_window_bits'
-  ],
-
-  DEFAULT_MAX_WINDOW_BITS: 15,
-  VALID_WINDOW_BITS: [8, 9, 10, 11, 12, 13, 14, 15],
-
-  concat: function(buffers, length) {
-    var buffer = new Buffer(length),
-        offset = 0;
-
-    for (var i = 0, n = buffers.length; i < n; i++) {
-      buffers[i].copy(buffer, offset);
-      offset += buffers[i].length;
-    }
-    return buffer;
-  },
-
-  fetch: function(options, key, _default) {
-    if (options.hasOwnProperty(key))
-      return options[key];
-    else
-      return _default;
-  },
-
-  validParams: function(params) {
-    var keys = Object.keys(params), i = keys.length;
-    while (i--) {
-      if (this.VALID_PARAMS.indexOf(keys[i]) < 0) return false;
-      if (params[keys[i]] instanceof Array) return false;
-    }
-    if (params.hasOwnProperty('server_no_context_takeover')) {
-      if (params.server_no_context_takeover !== true) return false;
-    }
-    if (params.hasOwnProperty('client_no_context_takeover')) {
-      if (params.client_no_context_takeover !== true) return false;
-    }
-    if (params.hasOwnProperty('server_max_window_bits')) {
-      if (this.VALID_WINDOW_BITS.indexOf(params.server_max_window_bits) < 0) return false;
-    }
-    return true;
-  }
-};
-
-module.exports = common;

lib/permessage_deflate.js

@@ -1,32 +0,0 @@
-'use strict';
-
-var ClientSession = require('./client_session'),
-    ServerSession = require('./server_session');
-
-var PermessageDeflate = {
-  configure: function(options) {
-    var opts = this._options || {};
-    for (var key in opts) options[key] = opts[key];
-    return Object.create(this, {_options: {value: options}});
-  },
-
-  createClientSession: function() {
-    return new ClientSession(this._options || {});
-  },
-
-  createServerSession: function(offers) {
-    for (var i = 0, n = offers.length; i < n; i++) {
-      if (ServerSession.validParams(offers[i]))
-        return new ServerSession(this._options || {}, offers[i]);
-    }
-    return null;
-  },
-
-  name: 'permessage-deflate',
-  type: 'permessage',
-  rsv1: true,
-  rsv2: false,
-  rsv3: false
-};
-
-module.exports = PermessageDeflate;

lib/server_session.js

@@ -1,62 +0,0 @@
-'use strict';
-
-var util    = require('util'),
-    common  = require('./common'),
-    Session = require('./session');
-
-var ServerSession = function(options, params) {
-  Session.call(this, options);
-  this._params = params;
-};
-util.inherits(ServerSession, Session);
-
-ServerSession.validParams = function(params) {
-  if (!common.validParams(params)) return false;
-
-  if (params.hasOwnProperty('client_max_window_bits')) {
-    if ([true].concat(common.VALID_WINDOW_BITS).indexOf(params.client_max_window_bits) < 0)
-      return false;
-  }
-  return true;
-};
-
-ServerSession.prototype.generateResponse = function() {
-  var params = {};
-
-  // https://tools.ietf.org/html/draft-ietf-hybi-permessage-compression#section-8.1.1.1
-  if (this._acceptNoContextTakeover || this._params.server_no_context_takeover)
-    params.server_no_context_takeover = true;
-
-  // https://tools.ietf.org/html/draft-ietf-hybi-permessage-compression#section-8.1.1.2
-  if (this._requestNoContextTakeover || this._params.client_no_context_takeover)
-    params.client_no_context_takeover = true;
-
-  // https://tools.ietf.org/html/draft-ietf-hybi-permessage-compression#section-8.1.2.1
-  var acceptMax, serverMax;
-  if (this._acceptMaxWindowBits || this._params.server_max_window_bits) {
-    acceptMax = this._acceptMaxWindowBits || common.DEFAULT_MAX_WINDOW_BITS;
-    serverMax = this._params.server_max_window_bits || common.DEFAULT_MAX_WINDOW_BITS;
-    params.server_max_window_bits = Math.min(acceptMax, serverMax);
-  }
-
-  // https://tools.ietf.org/html/draft-ietf-hybi-permessage-compression#section-8.1.2.2
-  var clientMax = this._params.client_max_window_bits, requestMax;
-  if (clientMax) {
-    if (clientMax === true) {
-      if (this._requestMaxWindowBits) params.client_max_window_bits = this._requestMaxWindowBits;
-    } else {
-      requestMax = this._requestMaxWindowBits || common.DEFAULT_MAX_WINDOW_BITS;
-      params.client_max_window_bits = Math.min(requestMax, clientMax);
-    }
-  }
-
-  this._ownContextTakeover = !params.server_no_context_takeover;
-  this._ownWindowBits = params.server_max_window_bits || common.DEFAULT_MAX_WINDOW_BITS;
-
-  this._peerContextTakeover = !params.client_no_context_takeover;
-  this._peerWindowBits = params.client_max_window_bits || common.DEFAULT_MAX_WINDOW_BITS;
-
-  return params;
-};
-
-module.exports = ServerSession;

lib/session.js

@@ -1,103 +0,0 @@
-'use strict';
-
-var zlib   = require('zlib'),
-    common = require('./common');
-
-var Session = function(options) {
-  this._level    = common.fetch(options, 'level',    zlib.Z_DEFAULT_LEVEL);
-  this._memLevel = common.fetch(options, 'memLevel', zlib.Z_DEFAULT_MEMLEVEL);
-  this._strategy = common.fetch(options, 'strategy', zlib.Z_DEFAULT_STRATEGY);
-
-  this._acceptNoContextTakeover  = common.fetch(options, 'noContextTakeover', false);
-  this._acceptMaxWindowBits      = common.fetch(options, 'maxWindowBits', undefined);
-  this._requestNoContextTakeover = common.fetch(options, 'requestNoContextTakeover', false);
-  this._requestMaxWindowBits     = common.fetch(options, 'requestMaxWindowBits', undefined);
-};
-
-Session.prototype.processIncomingMessage = function(message, callback) {
-  if (!message.rsv1) return callback(null, message);
-
-  var inflate = this._getInflate(),
-      chunks  = [message.data, new Buffer([0x00, 0x00, 0xff, 0xff])],
-      self    = this;
-
-  this._processMessage(inflate, chunks, function(error, data) {
-    if (!self._inflate && inflate.close) inflate.close();
-    if (error) return callback(error, null);
-    message.data = data;
-    callback(null, message);
-  });
-};
-
-Session.prototype.processOutgoingMessage = function(message, callback) {
-  var deflate = this._getDeflate(),
-      self    = this;
-
-  this._processMessage(deflate, [message.data], function(error, data) {
-    if (!self._deflate && deflate.close) deflate.close();
-    if (error) return callback(error, null);
-    message.rsv1 = true;
-    message.data = data.slice(0, data.length - 4);
-    callback(null, message);
-  });
-};
-
-Session.prototype.close = function() {
-  if (this._inflate && this._inflate.close) this._inflate.close();
-  this._inflate = null;
-
-  if (this._deflate && this._deflate.close) this._deflate.close();
-  this._deflate = null;
-};
-
-Session.prototype._getInflate = function() {
-  if (this._inflate) return this._inflate;
-  var inflate = zlib.createInflateRaw({windowBits: this._peerWindowBits});
-  if (this._peerContextTakeover) this._inflate = inflate;
-  return inflate;
-};
-
-Session.prototype._getDeflate = function() {
-  if (this._deflate) return this._deflate;
-
-  var deflate = zlib.createDeflateRaw({
-    windowBits: this._ownWindowBits,
-    level:      this._level,
-    memLevel:   this._memLevel,
-    strategy:   this._strategy
-  });
-  if (this._ownContextTakeover) this._deflate = deflate;
-  return deflate;
-};
-
-Session.prototype._processMessage = function(codec, data, callback) {
-  var chunks = [],
-      length = 0;
-
-  var return_ = function(error, result) {
-    return_ = function() {};
-    codec.removeListener('data', onData);
-    codec.removeListener('error', onError);
-    codec = null;
-    callback(error, result);
-  };
-
-  var onData = function(chunk) {
-    chunks.push(chunk);
-    length += chunk.length;
-  };
-
-  var onError = function(error) {
-    return_(error, null);
-  };
-
-  codec.on('data', onData);
-  codec.on('error', onError);
-  data.forEach(function(c) { codec.write(c) });
-
-  codec.flush(function() {
-    return_(null, common.concat(chunks, length));
-  });
-};
-
-module.exports = Session;

package.json

@@ -5,12 +5,10 @@
 , "keywords"        : ["websocket", "compression", "deflate"]
 , "license"         : "MIT"
 
-, "version"         : "0.1.0"
+, "version"         : "0.1.3"
 , "engines"         : {"node": ">=0.6.0"}
 , "main"            : "./lib/permessage_deflate"
-, "devDependencies" : {"jstest": ""}
-
-, "scripts"         : {"test": "jstest spec/runner.js"}
+, "devDependencies" : {"babel": "", "jstest": ""}
 
 , "repository"      : { "type"  : "git"
                       , "url"   : "git://github.com/faye/permessage-deflate-node.git"

spec/runner.js

@@ -1,2 +1,4 @@
+require('babel/polyfill');
+
 require('./client_session_spec')
 require('./server_session_spec')

src/client_session.js

@@ -0,0 +1,69 @@
+import Session from './session';
+import * as common from './common';
+
+export default class ClientSession extends Session {
+  static validParams(params) {
+    if (!common.validParams(params)) return false;
+
+    if (params.hasOwnProperty('client_max_window_bits')) {
+      if (common.VALID_WINDOW_BITS.indexOf(params.client_max_window_bits) < 0)
+        return false;
+    }
+    return true;
+  }
+
+  generateOffer() {
+    let offer = {};
+
+    if (this._acceptNoContextTakeover)
+      offer.client_no_context_takeover = true;
+
+    if (this._acceptMaxWindowBits !== undefined) {
+      if (common.VALID_WINDOW_BITS.indexOf(this._acceptMaxWindowBits) < 0) {
+        throw new Error('Invalid value for maxWindowBits');
+      }
+      offer.client_max_window_bits = this._acceptMaxWindowBits;
+    } else {
+      offer.client_max_window_bits = true;
+    }
+
+    if (this._requestNoContextTakeover)
+      offer.server_no_context_takeover = true;
+
+    if (this._requestMaxWindowBits !== undefined) {
+      if (common.VALID_WINDOW_BITS.indexOf(this._requestMaxWindowBits) < 0) {
+        throw new Error('Invalid valud for requestMaxWindowBits');
+      }
+      offer.server_max_window_bits = this._requestMaxWindowBits;
+    }
+
+    return offer;
+  }
+
+  activate(params) {
+    if (!ClientSession.validParams(params)) return false;
+
+    if (this._acceptMaxWindowBits && params.client_max_window_bits) {
+      if (params.client_max_window_bits > this._acceptMaxWindowBits) return false;
+    }
+
+    if (this._requestNoContextTakeover && !params.server_no_context_takeover)
+      return false;
+
+    if (this._requestMaxWindowBits) {
+      if (!params.server_max_window_bits) return false;
+      if (params.server_max_window_bits > this._requestMaxWindowBits) return false;
+    }
+
+    this._ownContextTakeover = !(this._acceptNoContextTakeover || params.client_no_context_takeover);
+    this._ownWindowBits = Math.min(
+      this._acceptMaxWindowBits || common.DEFAULT_MAX_WINDOW_BITS,
+      params.client_max_window_bits || common.DEFAULT_MAX_WINDOW_BITS
+    );
+
+    this._peerContextTakeover = !params.server_no_context_takeover;
+    this._peerWindowBits = params.server_max_window_bits || common.DEFAULT_MAX_WINDOW_BITS;
+
+    return true;
+  }
+}

src/common.js

@@ -0,0 +1,44 @@
+const  VALID_PARAMS = [
+  'server_no_context_takeover',
+  'client_no_context_takeover',
+  'server_max_window_bits',
+  'client_max_window_bits'
+];
+
+export const DEFAULT_MAX_WINDOW_BITS = 15;
+export const VALID_WINDOW_BITS = [8, 9, 10, 11, 12, 13, 14, 15];
+
+export function concat(buffers, length) {
+  let buffer = new Buffer(length),
+      offset = 0;
+
+  for (let buf of buffers) {
+    buf.copy(buffer, offset);
+    offset += buf.length;
+  }
+  return buffer;
+}
+
+export function validateOptions(options, validKeys) {
+  for (let key in options) {
+    if (validKeys.indexOf(key) < 0)
+      throw new Error(`Unrecognized option: ${key}`);
+  }
+}
+
+export function validParams(params) {
+  for (let key of Object.keys(params)) {
+    if (VALID_PARAMS.indexOf(key) < 0) return false;
+    if (params[key] instanceof Array) return false;
+  }
+  if (params.hasOwnProperty('server_no_context_takeover')) {
+    if (params.server_no_context_takeover !== true) return false;
+  }
+  if (params.hasOwnProperty('client_no_context_takeover')) {
+    if (params.client_no_context_takeover !== true) return false;
+  }
+  if (params.hasOwnProperty('server_max_window_bits')) {
+    if (this.VALID_WINDOW_BITS.indexOf(params.server_max_window_bits) < 0) return false;
+  }
+  return true;
+}

src/permessage_deflate.js

@@ -0,0 +1,42 @@
+import ClientSession from './client_session';
+import ServerSession from './server_session';
+import { validateOptions } from './common';
+
+const VALID_OPTIONS = [
+  'level',
+  'memLevel',
+  'strategy',
+  'noContextTakeover',
+  'maxWindowBits',
+  'requestNoContextTakeover',
+  'requestMaxWindowBits'
+];
+
+const PermessageDeflate = {
+  configure(options) {
+    validateOptions(options, VALID_OPTIONS);
+    let opts = this._options || {};
+    for (let key in opts) options[key] = opts[key];
+    return Object.create(this, {_options: {value: options}});
+  },
+
+  createClientSession() {
+    return new ClientSession(this._options || {});
+  },
+
+  createServerSession(offers) {
+    for (let offer of offers) {
+      if (ServerSession.validParams(offer))
+        return new ServerSession(this._options || {}, offer);
+    }
+    return null;
+  },
+
+  name: 'permessage-deflate',
+  type: 'permessage',
+  rsv1: true,
+  rsv2: false,
+  rsv3: false
+};
+
+export default PermessageDeflate;

src/server_session.js

@@ -0,0 +1,58 @@
+import Session from './session';
+import * as common from './common';
+
+export default class ServerSession extends Session {
+  constructor(options, params) {
+    super(options);
+    this._params = params;
+  }
+
+  static validParams(params) {
+    if (!common.validParams(params)) return false;
+
+    if (params.hasOwnProperty('client_max_window_bits')) {
+      if ([true].concat(common.VALID_WINDOW_BITS).indexOf(params.client_max_window_bits) < 0)
+        return false;
+    }
+    return true;
+  }
+
+  generateResponse() {
+    let params = {};
+
+    // https://tools.ietf.org/html/draft-ietf-hybi-permessage-compression#section-8.1.1.1
+    if (this._acceptNoContextTakeover || this._params.server_no_context_takeover)
+      params.server_no_context_takeover = true;
+
+    // https://tools.ietf.org/html/draft-ietf-hybi-permessage-compression#section-8.1.1.2
+    if (this._requestNoContextTakeover || this._params.client_no_context_takeover)
+      params.client_no_context_takeover = true;
+
+    // https://tools.ietf.org/html/draft-ietf-hybi-permessage-compression#section-8.1.2.1
+    let acceptMax, serverMax;
+    if (this._acceptMaxWindowBits || this._params.server_max_window_bits) {
+      acceptMax = this._acceptMaxWindowBits || common.DEFAULT_MAX_WINDOW_BITS;
+      serverMax = this._params.server_max_window_bits || common.DEFAULT_MAX_WINDOW_BITS;
+      params.server_max_window_bits = Math.min(acceptMax, serverMax);
+    }
+
+    // https://tools.ietf.org/html/draft-ietf-hybi-permessage-compression#section-8.1.2.2
+    let clientMax = this._params.client_max_window_bits, requestMax;
+    if (clientMax) {
+      if (clientMax === true) {
+        if (this._requestMaxWindowBits) params.client_max_window_bits = this._requestMaxWindowBits;
+      } else {
+        requestMax = this._requestMaxWindowBits || common.DEFAULT_MAX_WINDOW_BITS;
+        params.client_max_window_bits = Math.min(requestMax, clientMax);
+      }
+    }
+
+    this._ownContextTakeover = !params.server_no_context_takeover;
+    this._ownWindowBits = params.server_max_window_bits || common.DEFAULT_MAX_WINDOW_BITS;
+
+    this._peerContextTakeover = !params.client_no_context_takeover;
+    this._peerWindowBits = params.client_max_window_bits || common.DEFAULT_MAX_WINDOW_BITS;
+
+    return params;
+  }
+}

src/session.js

@@ -0,0 +1,156 @@
+import zlib from 'zlib';
+import { concat } from './common';
+
+export default class Session {
+  constructor({ level    = zlib.Z_DEFAULT_LEVEL,
+                memLevel = zlib.Z_DEFAULT_MEMLEVEL,
+                strategy = zlib.Z_DEFAULT_STRATEGY,
+
+                noContextTakeover = false,
+                maxWindowBits,
+                requestNoContextTakeover = false,
+                requestMaxWindowBits }) {
+
+    this._level    = level;
+    this._memLevel = memLevel;
+    this._strategy = strategy;
+
+    this._acceptNoContextTakeover  = noContextTakeover;
+    this._acceptMaxWindowBits      = maxWindowBits;
+    this._requestNoContextTakeover = requestNoContextTakeover;
+    this._requestMaxWindowBits     = requestMaxWindowBits;
+
+    this._queueIn  = [];
+    this._queueOut = [];
+  }
+
+  processIncomingMessage(message, callback) {
+    if (!message.rsv1) return callback(null, message);
+    if (this._lockIn) return this._queueIn.push([message, callback]);
+
+    let [inflate, chunks, length] = [this._getInflate(), [], 0];
+    if (this._inflate) this._lockIn = true;
+
+    let return_ = (error, message) => {
+      return_ = () => {};
+
+      inflate.removeListener('data', onData);
+      inflate.removeListener('error', onError);
+      if (!this._inflate && inflate.close) inflate.close();
+
+      this._lockIn = false;
+      let next = this._queueIn.shift();
+      if (next) this.processIncomingMessage.apply(this, next);
+
+      callback(error, message);
+    };
+
+    let onData = (data) => {
+      chunks.push(data);
+      length += data.length;
+    };
+
+    let onError = (error) => return_(error, null);
+
+    inflate.on('data', onData);
+    inflate.on('error', onError);
+
+    inflate.write(message.data);
+    inflate.write(new Buffer([0x00, 0x00, 0xff, 0xff]));
+
+    inflate.flush(() => {
+      message.data = concat(chunks, length);
+      return_(null, message);
+    });
+  }
+
+  processOutgoingMessage(message, callback) {
+    if (this._lockOut) return this._queueOut.push([message, callback]);
+
+    let [deflate, chunks, length] = [this._getDeflate(), [], 0];
+    if (this._deflate) this._lockOut = true;
+
+    let return_ = (error, message) => {
+      return_ = () => {};
+
+      deflate.removeListener('data', onData);
+      deflate.removeListener('error', onError);
+      if (!this._deflate && deflate.close) deflate.close();
+
+      this._lockOut = false;
+      let next = this._queueOut.shift();
+      if (next) this.processOutgoingMessage.apply(this, next);
+
+      callback(error, message);
+    };
+
+    let onData = (data) => {
+      chunks.push(data);
+      length += data.length;
+    };
+
+    let onError = (error) => return_(error, null);
+
+    deflate.on('data', onData);
+    deflate.on('error', onError);
+    deflate.write(message.data);
+
+    let onFlush = () => {
+      let data = concat(chunks, length);
+      message.data = data.slice(0, data.length - 4);
+      message.rsv1 = true;
+      return_(null, message);
+    };
+
+    if (deflate.params !== undefined)
+      deflate.flush(zlib.Z_SYNC_FLUSH, onFlush);
+    else
+      deflate.flush(onFlush);
+  }
+
+  close() {
+    if (this._inflate && this._inflate.close) this._inflate.close();
+    this._inflate = null;
+
+    if (this._deflate && this._deflate.close) this._deflate.close();
+    this._deflate = null;
+  }
+
+  _getInflate() {
+    if (this._inflate) return this._inflate;
+    let inflate = zlib.createInflateRaw({windowBits: this._peerWindowBits});
+    if (this._peerContextTakeover) this._inflate = inflate;
+    return inflate;
+  }
+
+  _getDeflate() {
+    if (this._deflate) return this._deflate;
+
+    let deflate = zlib.createDeflateRaw({
+      windowBits: this._ownWindowBits,
+      level:      this._level,
+      memLevel:   this._memLevel,
+      strategy:   this._strategy
+    });
+
+    let flush = deflate.flush;
+
+    // This monkey-patch is needed to make Node 0.10 produce optimal output.
+    // Without this it uses Z_FULL_FLUSH and effectively drops all its context
+    // state on every flush.
+
+    if (deflate._flushFlag !== undefined && deflate.params === undefined)
+      deflate.flush = function(callback) {
+        let ws = this._writableState;
+        if (ws.ended || ws.ending || ws.needDrain) {
+          flush.call(this, callback);
+        } else {
+          this._flushFlag = zlib.Z_SYNC_FLUSH;
+          this.write(new Buffer(0), '', callback);
+        }
+      };
+
+    if (this._ownContextTakeover) this._deflate = deflate;
+    return deflate;
+  }
+}