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Filename : sender.js
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/* eslint no-unused-vars: ["error", { "varsIgnorePattern": "^Duplex" }] */

'use strict';

const { Duplex } = require('stream');
const { randomFillSync } = require('crypto');

const PerMessageDeflate = require('./permessage-deflate');
const { EMPTY_BUFFER } = require('./constants');
const { isValidStatusCode } = require('./validation');
const { mask: applyMask, toBuffer } = require('./buffer-util');

const kByteLength = Symbol('kByteLength');
const maskBuffer = Buffer.alloc(4);
const RANDOM_POOL_SIZE = 8 * 1024;
let randomPool;
let randomPoolPointer = RANDOM_POOL_SIZE;

/**
 * HyBi Sender implementation.
 */
class Sender {
  /**
   * Creates a Sender instance.
   *
   * @param {Duplex} socket The connection socket
   * @param {Object} [extensions] An object containing the negotiated extensions
   * @param {Function} [generateMask] The function used to generate the masking
   *     key
   */
  constructor(socket, extensions, generateMask) {
    this._extensions = extensions || {};

    if (generateMask) {
      this._generateMask = generateMask;
      this._maskBuffer = Buffer.alloc(4);
    }

    this._socket = socket;

    this._firstFragment = true;
    this._compress = false;

    this._bufferedBytes = 0;
    this._deflating = false;
    this._queue = [];
  }

  /**
   * Frames a piece of data according to the HyBi WebSocket protocol.
   *
   * @param {(Buffer|String)} data The data to frame
   * @param {Object} options Options object
   * @param {Boolean} [options.fin=false] Specifies whether or not to set the
   *     FIN bit
   * @param {Function} [options.generateMask] The function used to generate the
   *     masking key
   * @param {Boolean} [options.mask=false] Specifies whether or not to mask
   *     `data`
   * @param {Buffer} [options.maskBuffer] The buffer used to store the masking
   *     key
   * @param {Number} options.opcode The opcode
   * @param {Boolean} [options.readOnly=false] Specifies whether `data` can be
   *     modified
   * @param {Boolean} [options.rsv1=false] Specifies whether or not to set the
   *     RSV1 bit
   * @return {(Buffer|String)[]} The framed data
   * @public
   */
  static frame(data, options) {
    let mask;
    let merge = false;
    let offset = 2;
    let skipMasking = false;

    if (options.mask) {
      mask = options.maskBuffer || maskBuffer;

      if (options.generateMask) {
        options.generateMask(mask);
      } else {
        if (randomPoolPointer === RANDOM_POOL_SIZE) {
          /* istanbul ignore else  */
          if (randomPool === undefined) {
            //
            // This is lazily initialized because server-sent frames must not
            // be masked so it may never be used.
            //
            randomPool = Buffer.alloc(RANDOM_POOL_SIZE);
          }

          randomFillSync(randomPool, 0, RANDOM_POOL_SIZE);
          randomPoolPointer = 0;
        }

        mask[0] = randomPool[randomPoolPointer++];
        mask[1] = randomPool[randomPoolPointer++];
        mask[2] = randomPool[randomPoolPointer++];
        mask[3] = randomPool[randomPoolPointer++];
      }

      skipMasking = (mask[0] | mask[1] | mask[2] | mask[3]) === 0;
      offset = 6;
    }

    let dataLength;

    if (typeof data === 'string') {
      if (
        (!options.mask || skipMasking) &&
        options[kByteLength] !== undefined
      ) {
        dataLength = options[kByteLength];
      } else {
        data = Buffer.from(data);
        dataLength = data.length;
      }
    } else {
      dataLength = data.length;
      merge = options.mask && options.readOnly && !skipMasking;
    }

    let payloadLength = dataLength;

    if (dataLength >= 65536) {
      offset += 8;
      payloadLength = 127;
    } else if (dataLength > 125) {
      offset += 2;
      payloadLength = 126;
    }

    const target = Buffer.allocUnsafe(merge ? dataLength + offset : offset);

    target[0] = options.fin ? options.opcode | 0x80 : options.opcode;
    if (options.rsv1) target[0] |= 0x40;

    target[1] = payloadLength;

    if (payloadLength === 126) {
      target.writeUInt16BE(dataLength, 2);
    } else if (payloadLength === 127) {
      target[2] = target[3] = 0;
      target.writeUIntBE(dataLength, 4, 6);
    }

    if (!options.mask) return [target, data];

    target[1] |= 0x80;
    target[offset - 4] = mask[0];
    target[offset - 3] = mask[1];
    target[offset - 2] = mask[2];
    target[offset - 1] = mask[3];

    if (skipMasking) return [target, data];

    if (merge) {
      applyMask(data, mask, target, offset, dataLength);
      return [target];
    }

    applyMask(data, mask, data, 0, dataLength);
    return [target, data];
  }

  /**
   * Sends a close message to the other peer.
   *
   * @param {Number} [code] The status code component of the body
   * @param {(String|Buffer)} [data] The message component of the body
   * @param {Boolean} [mask=false] Specifies whether or not to mask the message
   * @param {Function} [cb] Callback
   * @public
   */
  close(code, data, mask, cb) {
    let buf;

    if (code === undefined) {
      buf = EMPTY_BUFFER;
    } else if (typeof code !== 'number' || !isValidStatusCode(code)) {
      throw new TypeError('First argument must be a valid error code number');
    } else if (data === undefined || !data.length) {
      buf = Buffer.allocUnsafe(2);
      buf.writeUInt16BE(code, 0);
    } else {
      const length = Buffer.byteLength(data);

      if (length > 123) {
        throw new RangeError('The message must not be greater than 123 bytes');
      }

      buf = Buffer.allocUnsafe(2 + length);
      buf.writeUInt16BE(code, 0);

      if (typeof data === 'string') {
        buf.write(data, 2);
      } else {
        buf.set(data, 2);
      }
    }

    const options = {
      [kByteLength]: buf.length,
      fin: true,
      generateMask: this._generateMask,
      mask,
      maskBuffer: this._maskBuffer,
      opcode: 0x08,
      readOnly: false,
      rsv1: false
    };

    if (this._deflating) {
      this.enqueue([this.dispatch, buf, false, options, cb]);
    } else {
      this.sendFrame(Sender.frame(buf, options), cb);
    }
  }

  /**
   * Sends a ping message to the other peer.
   *
   * @param {*} data The message to send
   * @param {Boolean} [mask=false] Specifies whether or not to mask `data`
   * @param {Function} [cb] Callback
   * @public
   */
  ping(data, mask, cb) {
    let byteLength;
    let readOnly;

    if (typeof data === 'string') {
      byteLength = Buffer.byteLength(data);
      readOnly = false;
    } else {
      data = toBuffer(data);
      byteLength = data.length;
      readOnly = toBuffer.readOnly;
    }

    if (byteLength > 125) {
      throw new RangeError('The data size must not be greater than 125 bytes');
    }

    const options = {
      [kByteLength]: byteLength,
      fin: true,
      generateMask: this._generateMask,
      mask,
      maskBuffer: this._maskBuffer,
      opcode: 0x09,
      readOnly,
      rsv1: false
    };

    if (this._deflating) {
      this.enqueue([this.dispatch, data, false, options, cb]);
    } else {
      this.sendFrame(Sender.frame(data, options), cb);
    }
  }

  /**
   * Sends a pong message to the other peer.
   *
   * @param {*} data The message to send
   * @param {Boolean} [mask=false] Specifies whether or not to mask `data`
   * @param {Function} [cb] Callback
   * @public
   */
  pong(data, mask, cb) {
    let byteLength;
    let readOnly;

    if (typeof data === 'string') {
      byteLength = Buffer.byteLength(data);
      readOnly = false;
    } else {
      data = toBuffer(data);
      byteLength = data.length;
      readOnly = toBuffer.readOnly;
    }

    if (byteLength > 125) {
      throw new RangeError('The data size must not be greater than 125 bytes');
    }

    const options = {
      [kByteLength]: byteLength,
      fin: true,
      generateMask: this._generateMask,
      mask,
      maskBuffer: this._maskBuffer,
      opcode: 0x0a,
      readOnly,
      rsv1: false
    };

    if (this._deflating) {
      this.enqueue([this.dispatch, data, false, options, cb]);
    } else {
      this.sendFrame(Sender.frame(data, options), cb);
    }
  }

  /**
   * Sends a data message to the other peer.
   *
   * @param {*} data The message to send
   * @param {Object} options Options object
   * @param {Boolean} [options.binary=false] Specifies whether `data` is binary
   *     or text
   * @param {Boolean} [options.compress=false] Specifies whether or not to
   *     compress `data`
   * @param {Boolean} [options.fin=false] Specifies whether the fragment is the
   *     last one
   * @param {Boolean} [options.mask=false] Specifies whether or not to mask
   *     `data`
   * @param {Function} [cb] Callback
   * @public
   */
  send(data, options, cb) {
    const perMessageDeflate = this._extensions[PerMessageDeflate.extensionName];
    let opcode = options.binary ? 2 : 1;
    let rsv1 = options.compress;

    let byteLength;
    let readOnly;

    if (typeof data === 'string') {
      byteLength = Buffer.byteLength(data);
      readOnly = false;
    } else {
      data = toBuffer(data);
      byteLength = data.length;
      readOnly = toBuffer.readOnly;
    }

    if (this._firstFragment) {
      this._firstFragment = false;
      if (
        rsv1 &&
        perMessageDeflate &&
        perMessageDeflate.params[
          perMessageDeflate._isServer
            ? 'server_no_context_takeover'
            : 'client_no_context_takeover'
        ]
      ) {
        rsv1 = byteLength >= perMessageDeflate._threshold;
      }
      this._compress = rsv1;
    } else {
      rsv1 = false;
      opcode = 0;
    }

    if (options.fin) this._firstFragment = true;

    if (perMessageDeflate) {
      const opts = {
        [kByteLength]: byteLength,
        fin: options.fin,
        generateMask: this._generateMask,
        mask: options.mask,
        maskBuffer: this._maskBuffer,
        opcode,
        readOnly,
        rsv1
      };

      if (this._deflating) {
        this.enqueue([this.dispatch, data, this._compress, opts, cb]);
      } else {
        this.dispatch(data, this._compress, opts, cb);
      }
    } else {
      this.sendFrame(
        Sender.frame(data, {
          [kByteLength]: byteLength,
          fin: options.fin,
          generateMask: this._generateMask,
          mask: options.mask,
          maskBuffer: this._maskBuffer,
          opcode,
          readOnly,
          rsv1: false
        }),
        cb
      );
    }
  }

  /**
   * Dispatches a message.
   *
   * @param {(Buffer|String)} data The message to send
   * @param {Boolean} [compress=false] Specifies whether or not to compress
   *     `data`
   * @param {Object} options Options object
   * @param {Boolean} [options.fin=false] Specifies whether or not to set the
   *     FIN bit
   * @param {Function} [options.generateMask] The function used to generate the
   *     masking key
   * @param {Boolean} [options.mask=false] Specifies whether or not to mask
   *     `data`
   * @param {Buffer} [options.maskBuffer] The buffer used to store the masking
   *     key
   * @param {Number} options.opcode The opcode
   * @param {Boolean} [options.readOnly=false] Specifies whether `data` can be
   *     modified
   * @param {Boolean} [options.rsv1=false] Specifies whether or not to set the
   *     RSV1 bit
   * @param {Function} [cb] Callback
   * @private
   */
  dispatch(data, compress, options, cb) {
    if (!compress) {
      this.sendFrame(Sender.frame(data, options), cb);
      return;
    }

    const perMessageDeflate = this._extensions[PerMessageDeflate.extensionName];

    this._bufferedBytes += options[kByteLength];
    this._deflating = true;
    perMessageDeflate.compress(data, options.fin, (_, buf) => {
      if (this._socket.destroyed) {
        const err = new Error(
          'The socket was closed while data was being compressed'
        );

        if (typeof cb === 'function') cb(err);

        for (let i = 0; i < this._queue.length; i++) {
          const params = this._queue[i];
          const callback = params[params.length - 1];

          if (typeof callback === 'function') callback(err);
        }

        return;
      }

      this._bufferedBytes -= options[kByteLength];
      this._deflating = false;
      options.readOnly = false;
      this.sendFrame(Sender.frame(buf, options), cb);
      this.dequeue();
    });
  }

  /**
   * Executes queued send operations.
   *
   * @private
   */
  dequeue() {
    while (!this._deflating && this._queue.length) {
      const params = this._queue.shift();

      this._bufferedBytes -= params[3][kByteLength];
      Reflect.apply(params[0], this, params.slice(1));
    }
  }

  /**
   * Enqueues a send operation.
   *
   * @param {Array} params Send operation parameters.
   * @private
   */
  enqueue(params) {
    this._bufferedBytes += params[3][kByteLength];
    this._queue.push(params);
  }

  /**
   * Sends a frame.
   *
   * @param {Buffer[]} list The frame to send
   * @param {Function} [cb] Callback
   * @private
   */
  sendFrame(list, cb) {
    if (list.length === 2) {
      this._socket.cork();
      this._socket.write(list[0]);
      this._socket.write(list[1], cb);
      this._socket.uncork();
    } else {
      this._socket.write(list[0], cb);
    }
  }
}

module.exports = Sender;