dynatrace-cordova-outsystems-plugin/node_modules/ws/lib/permessage-deflate.js

This plugin gives you the ability to use the Dynatrace instrumentation in your hybrid application (Cordova, Ionic, ..). It uses the Mobile Agent, the JavaScript Agent and the Javascript Bridge. The Mobile Agent will give you all device specific values con

'use strict';

const Limiter = require('async-limiter');
const zlib = require('zlib');

const bufferUtil = require('./buffer-util');
const { kStatusCode, NOOP } = require('./constants');

const TRAILER = Buffer.from([0x00, 0x00, 0xff, 0xff]);
const EMPTY_BLOCK = Buffer.from([0x00]);

const kPerMessageDeflate = Symbol('permessage-deflate');
const kTotalLength = Symbol('total-length');
const kCallback = Symbol('callback');
const kBuffers = Symbol('buffers');
const kError = Symbol('error');

//
// We limit zlib concurrency, which prevents severe memory fragmentation
// as documented in https://github.com/nodejs/node/issues/8871#issuecomment-250915913
// and https://github.com/websockets/ws/issues/1202
//
// Intentionally global; it's the global thread pool that's an issue.
//
let zlibLimiter;

/**
 * permessage-deflate implementation.
 */
class PerMessageDeflate {
  /**
   * Creates a PerMessageDeflate instance.
   *
   * @param {Object} options Configuration options
   * @param {Boolean} options.serverNoContextTakeover Request/accept disabling
   *     of server context takeover
   * @param {Boolean} options.clientNoContextTakeover Advertise/acknowledge
   *     disabling of client context takeover
   * @param {(Boolean|Number)} options.serverMaxWindowBits Request/confirm the
   *     use of a custom server window size
   * @param {(Boolean|Number)} options.clientMaxWindowBits Advertise support
   *     for, or request, a custom client window size
   * @param {Object} options.zlibDeflateOptions Options to pass to zlib on deflate
   * @param {Object} options.zlibInflateOptions Options to pass to zlib on inflate
   * @param {Number} options.threshold Size (in bytes) below which messages
   *     should not be compressed
   * @param {Number} options.concurrencyLimit The number of concurrent calls to
   *     zlib
   * @param {Boolean} isServer Create the instance in either server or client
   *     mode
   * @param {Number} maxPayload The maximum allowed message length
   */
  constructor(options, isServer, maxPayload) {
    this._maxPayload = maxPayload | 0;
    this._options = options || {};
    this._threshold =
      this._options.threshold !== undefined ? this._options.threshold : 1024;
    this._isServer = !!isServer;
    this._deflate = null;
    this._inflate = null;

    this.params = null;

    if (!zlibLimiter) {
      const concurrency =
        this._options.concurrencyLimit !== undefined
          ? this._options.concurrencyLimit
          : 10;
      zlibLimiter = new Limiter({ concurrency });
    }
  }

  /**
   * @type {String}
   */
  static get extensionName() {
    return 'permessage-deflate';
  }

  /**
   * Create an extension negotiation offer.
   *
   * @return {Object} Extension parameters
   * @public
   */
  offer() {
    const params = {};

    if (this._options.serverNoContextTakeover) {
      params.server_no_context_takeover = true;
    }
    if (this._options.clientNoContextTakeover) {
      params.client_no_context_takeover = true;
    }
    if (this._options.serverMaxWindowBits) {
      params.server_max_window_bits = this._options.serverMaxWindowBits;
    }
    if (this._options.clientMaxWindowBits) {
      params.client_max_window_bits = this._options.clientMaxWindowBits;
    } else if (this._options.clientMaxWindowBits == null) {
      params.client_max_window_bits = true;
    }

    return params;
  }

  /**
   * Accept an extension negotiation offer/response.
   *
   * @param {Array} configurations The extension negotiation offers/reponse
   * @return {Object} Accepted configuration
   * @public
   */
  accept(configurations) {
    configurations = this.normalizeParams(configurations);

    this.params = this._isServer
      ? this.acceptAsServer(configurations)
      : this.acceptAsClient(configurations);

    return this.params;
  }

  /**
   * Releases all resources used by the extension.
   *
   * @public
   */
  cleanup() {
    if (this._inflate) {
      this._inflate.close();
      this._inflate = null;
    }

    if (this._deflate) {
      this._deflate.close();
      this._deflate = null;
    }
  }

  /**
   *  Accept an extension negotiation offer.
   *
   * @param {Array} offers The extension negotiation offers
   * @return {Object} Accepted configuration
   * @private
   */
  acceptAsServer(offers) {
    const opts = this._options;
    const accepted = offers.find((params) => {
      if (
        (opts.serverNoContextTakeover === false &&
          params.server_no_context_takeover) ||
        (params.server_max_window_bits &&
          (opts.serverMaxWindowBits === false ||
            (typeof opts.serverMaxWindowBits === 'number' &&
              opts.serverMaxWindowBits > params.server_max_window_bits))) ||
        (typeof opts.clientMaxWindowBits === 'number' &&
          !params.client_max_window_bits)
      ) {
        return false;
      }

      return true;
    });

    if (!accepted) {
      throw new Error('None of the extension offers can be accepted');
    }

    if (opts.serverNoContextTakeover) {
      accepted.server_no_context_takeover = true;
    }
    if (opts.clientNoContextTakeover) {
      accepted.client_no_context_takeover = true;
    }
    if (typeof opts.serverMaxWindowBits === 'number') {
      accepted.server_max_window_bits = opts.serverMaxWindowBits;
    }
    if (typeof opts.clientMaxWindowBits === 'number') {
      accepted.client_max_window_bits = opts.clientMaxWindowBits;
    } else if (
      accepted.client_max_window_bits === true ||
      opts.clientMaxWindowBits === false
    ) {
      delete accepted.client_max_window_bits;
    }

    return accepted;
  }

  /**
   * Accept the extension negotiation response.
   *
   * @param {Array} response The extension negotiation response
   * @return {Object} Accepted configuration
   * @private
   */
  acceptAsClient(response) {
    const params = response[0];

    if (
      this._options.clientNoContextTakeover === false &&
      params.client_no_context_takeover
    ) {
      throw new Error('Unexpected parameter "client_no_context_takeover"');
    }

    if (!params.client_max_window_bits) {
      if (typeof this._options.clientMaxWindowBits === 'number') {
        params.client_max_window_bits = this._options.clientMaxWindowBits;
      }
    } else if (
      this._options.clientMaxWindowBits === false ||
      (typeof this._options.clientMaxWindowBits === 'number' &&
        params.client_max_window_bits > this._options.clientMaxWindowBits)
    ) {
      throw new Error(
        'Unexpected or invalid parameter "client_max_window_bits"'
      );
    }

    return params;
  }

  /**
   * Normalize parameters.
   *
   * @param {Array} configurations The extension negotiation offers/reponse
   * @return {Array} The offers/response with normalized parameters
   * @private
   */
  normalizeParams(configurations) {
    configurations.forEach((params) => {
      Object.keys(params).forEach((key) => {
        var value = params[key];

        if (value.length > 1) {
          throw new Error(`Parameter "${key}" must have only a single value`);
        }

        value = value[0];

        if (key === 'client_max_window_bits') {
          if (value !== true) {
            const num = +value;
            if (!Number.isInteger(num) || num < 8 || num > 15) {
              throw new TypeError(
                `Invalid value for parameter "${key}": ${value}`
              );
            }
            value = num;
          } else if (!this._isServer) {
            throw new TypeError(
              `Invalid value for parameter "${key}": ${value}`
            );
          }
        } else if (key === 'server_max_window_bits') {
          const num = +value;
          if (!Number.isInteger(num) || num < 8 || num > 15) {
            throw new TypeError(
              `Invalid value for parameter "${key}": ${value}`
            );
          }
          value = num;
        } else if (
          key === 'client_no_context_takeover' ||
          key === 'server_no_context_takeover'
        ) {
          if (value !== true) {
            throw new TypeError(
              `Invalid value for parameter "${key}": ${value}`
            );
          }
        } else {
          throw new Error(`Unknown parameter "${key}"`);
        }

        params[key] = value;
      });
    });

    return configurations;
  }

  /**
   * Decompress data. Concurrency limited by async-limiter.
   *
   * @param {Buffer} data Compressed data
   * @param {Boolean} fin Specifies whether or not this is the last fragment
   * @param {Function} callback Callback
   * @public
   */
  decompress(data, fin, callback) {
    zlibLimiter.push((done) => {
      this._decompress(data, fin, (err, result) => {
        done();
        callback(err, result);
      });
    });
  }

  /**
   * Compress data. Concurrency limited by async-limiter.
   *
   * @param {Buffer} data Data to compress
   * @param {Boolean} fin Specifies whether or not this is the last fragment
   * @param {Function} callback Callback
   * @public
   */
  compress(data, fin, callback) {
    zlibLimiter.push((done) => {
      this._compress(data, fin, (err, result) => {
        done();
        callback(err, result);
      });
    });
  }

  /**
   * Decompress data.
   *
   * @param {Buffer} data Compressed data
   * @param {Boolean} fin Specifies whether or not this is the last fragment
   * @param {Function} callback Callback
   * @private
   */
  _decompress(data, fin, callback) {
    const endpoint = this._isServer ? 'client' : 'server';

    if (!this._inflate) {
      const key = `${endpoint}_max_window_bits`;
      const windowBits =
        typeof this.params[key] !== 'number'
          ? zlib.Z_DEFAULT_WINDOWBITS
          : this.params[key];

      this._inflate = zlib.createInflateRaw(
        Object.assign({}, this._options.zlibInflateOptions, { windowBits })
      );
      this._inflate[kPerMessageDeflate] = this;
      this._inflate[kTotalLength] = 0;
      this._inflate[kBuffers] = [];
      this._inflate.on('error', inflateOnError);
      this._inflate.on('data', inflateOnData);
    }

    this._inflate[kCallback] = callback;

    this._inflate.write(data);
    if (fin) this._inflate.write(TRAILER);

    this._inflate.flush(() => {
      const err = this._inflate[kError];

      if (err) {
        this._inflate.close();
        this._inflate = null;
        callback(err);
        return;
      }

      const data = bufferUtil.concat(
        this._inflate[kBuffers],
        this._inflate[kTotalLength]
      );

      if (fin && this.params[`${endpoint}_no_context_takeover`]) {
        this._inflate.close();
        this._inflate = null;
      } else {
        this._inflate[kTotalLength] = 0;
        this._inflate[kBuffers] = [];
      }

      callback(null, data);
    });
  }

  /**
   * Compress data.
   *
   * @param {Buffer} data Data to compress
   * @param {Boolean} fin Specifies whether or not this is the last fragment
   * @param {Function} callback Callback
   * @private
   */
  _compress(data, fin, callback) {
    if (!data || data.length === 0) {
      process.nextTick(callback, null, EMPTY_BLOCK);
      return;
    }

    const endpoint = this._isServer ? 'server' : 'client';

    if (!this._deflate) {
      const key = `${endpoint}_max_window_bits`;
      const windowBits =
        typeof this.params[key] !== 'number'
          ? zlib.Z_DEFAULT_WINDOWBITS
          : this.params[key];

      this._deflate = zlib.createDeflateRaw(
        Object.assign({}, this._options.zlibDeflateOptions, { windowBits })
      );

      this._deflate[kTotalLength] = 0;
      this._deflate[kBuffers] = [];

      //
      // An `'error'` event is emitted, only on Node.js < 10.0.0, if the
      // `zlib.DeflateRaw` instance is closed while data is being processed.
      // This can happen if `PerMessageDeflate#cleanup()` is called at the wrong
      // time due to an abnormal WebSocket closure.
      //
      this._deflate.on('error', NOOP);
      this._deflate.on('data', deflateOnData);
    }

    this._deflate.write(data);
    this._deflate.flush(zlib.Z_SYNC_FLUSH, () => {
      if (!this._deflate) {
        //
        // This `if` statement is only needed for Node.js < 10.0.0 because as of
        // commit https://github.com/nodejs/node/commit/5e3f5164, the flush
        // callback is no longer called if the deflate stream is closed while
        // data is being processed.
        //
        return;
      }

      var data = bufferUtil.concat(
        this._deflate[kBuffers],
        this._deflate[kTotalLength]
      );

      if (fin) data = data.slice(0, data.length - 4);

      if (fin && this.params[`${endpoint}_no_context_takeover`]) {
        this._deflate.close();
        this._deflate = null;
      } else {
        this._deflate[kTotalLength] = 0;
        this._deflate[kBuffers] = [];
      }

      callback(null, data);
    });
  }
}

module.exports = PerMessageDeflate;

/**
 * The listener of the `zlib.DeflateRaw` stream `'data'` event.
 *
 * @param {Buffer} chunk A chunk of data
 * @private
 */
function deflateOnData(chunk) {
  this[kBuffers].push(chunk);
  this[kTotalLength] += chunk.length;
}

/**
 * The listener of the `zlib.InflateRaw` stream `'data'` event.
 *
 * @param {Buffer} chunk A chunk of data
 * @private
 */
function inflateOnData(chunk) {
  this[kTotalLength] += chunk.length;

  if (
    this[kPerMessageDeflate]._maxPayload < 1 ||
    this[kTotalLength] <= this[kPerMessageDeflate]._maxPayload
  ) {
    this[kBuffers].push(chunk);
    return;
  }

  this[kError] = new RangeError('Max payload size exceeded');
  this[kError][kStatusCode] = 1009;
  this.removeListener('data', inflateOnData);
  this.reset();
}

/**
 * The listener of the `zlib.InflateRaw` stream `'error'` event.
 *
 * @param {Error} err The emitted error
 * @private
 */
function inflateOnError(err) {
  //
  // There is no need to call `Zlib#close()` as the handle is automatically
  // closed when an error is emitted.
  //
  this[kPerMessageDeflate]._inflate = null;
  err[kStatusCode] = 1007;
  this[kCallback](err);
}