binary.js

/*global Blob,File*/

/**
 * Module requirements
 */

var isArray = require('isarray');
var isBuf = require('./is-buffer');

/**
 * Replaces every Buffer | ArrayBuffer in packet with a numbered placeholder.
 *
 * @param {Object} packet - socket.io event packet
 * @return {Object} with deconstructed packet and list of buffers
 * @api public
 */

exports.deconstructPacket = function(packet) {
  var buffers = [];
  var packetData = packet.data;
  var pack = packet;
  pack.data = _deconstructPacket(packetData, buffers);
  pack.attachments = buffers.length; // number of binary 'attachments'
  return {packet: pack, buffers: buffers};
};

function _deconstructPacket(data, buffers) {
  if (!data) return data;

  if (data._fragments || isBuf(data)) {
    var placeholder = { _placeholder: true, num: buffers.length };
    buffers.push(data);
    return placeholder;
  } else if (isArray(data)) {
    var newData = new Array(data.length);
    for (var i = 0; i < data.length; i++) {
      newData[i] = _deconstructPacket(data[i], buffers);
    }
    return newData;
  } else if (typeof data === 'object' && !(data instanceof Date)) {
    var newData = {};
    for (var key in data) {
      newData[key] = _deconstructPacket(data[key], buffers);
    }
    return newData;
  }
  return data;
}

/**
 * Reconstructs a binary packet from its placeholder packet and buffers
 *
 * @param {Object} packet - event packet with placeholders
 * @param {Array} buffers - binary buffers to put in placeholder positions
 * @return {Object} reconstructed packet
 * @api public
 */

exports.reconstructPacket = function(packet, buffers) {
  packet.data = _reconstructPacket(packet.data, buffers);
  packet.attachments = undefined; // no longer useful
  return packet;
};

function _reconstructPacket(data, buffers) {
  if (!data) return data;

  if (data && data._placeholder) {
    return buffers[data.num]; // appropriate buffer (should be natural order anyway)
  } else if (isArray(data)) {
    for (var i = 0; i < data.length; i++) {
      data[i] = _reconstructPacket(data[i], buffers);
    }
  } else if (typeof data === 'object') {
    for (var key in data) {
      data[key] = _reconstructPacket(data[key], buffers);
    }
  }

  return data;
}