permessage-deflate/lib/client_session.js

Per-message DEFLATE compression extension for WebSocket connections

'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 value 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.MAX_WINDOW_BITS,
    params.client_max_window_bits || common.MAX_WINDOW_BITS
  );

  this._peerContextTakeover = !params.server_no_context_takeover;
  this._peerWindowBits = params.server_max_window_bits || common.MAX_WINDOW_BITS;

  return true;
};

module.exports = ClientSession;