loopback-connector/lib/binary-packer.js

// Copyright IBM Corp. 2016,2019. All Rights Reserved.
// Node module: loopback-connector
// This file is licensed under the MIT License.
// License text available at https://opensource.org/licenses/MIT

'use strict';

var createPromiseCallback = require('./utils').createPromiseCallback;
var msgpack = require('msgpack5');

module.exports = BinaryPacker;

/**
 * Create a new Packer instance that can be used to convert between JavaScript
 * objects and a binary representation in a Buffer.
 *
 * Compared to JSON, this encoding preserves the following JavaScript types:
 *  - Date
 */
function BinaryPacker() {
  this._packer = msgpack({forceFloat64: true});
  this._packer.register(1, Date, encodeDate, decodeDate);
}

/**
 * Encode the provided value to a `Buffer`.
 *
 * @param {*} value Any value (string, number, object)
 * @callback {Function} cb The callback to receive the parsed result.
 * @param {Error} err
 * @param {Buffer} data The encoded value
 * @promise
 */
BinaryPacker.prototype.encode = function(value, cb) {
  cb = cb || createPromiseCallback();
  try {
    // msgpack5 returns https://www.npmjs.com/package/bl instead of Buffer
    // use .slice() to convert to a Buffer
    var data = this._packer.encode(value).slice();
    setImmediate(function() {
      cb(null, data);
    });
  } catch (err) {
    setImmediate(function() {
      cb(err);
    });
  }
  return cb.promise;
};

/**
 * Decode the binary value back to a JavaScript value.
 * @param {Buffer} binary The binary input.
 * @callback {Function} cb The callback to receive the composed value.
 * @param {Error} err
 * @param {*} value Decoded value.
 * @promise
 */
BinaryPacker.prototype.decode = function(binary, cb) {
  cb = cb || createPromiseCallback();
  try {
    var value = this._packer.decode(binary);
    setImmediate(function() {
      cb(null, value);
    });
  } catch (err) {
    setImmediate(function() {
      cb(err);
    });
  }
  return cb.promise;
};

function encodeDate(obj) {
  return new Buffer(obj.toISOString(), 'utf8');
}

function decodeDate(buf) {
  return new Date(buf.toString('utf8'));
}