prepack/lib/debugger/common/channel/MessagePackager.js

Execute a JS bundle, serialize global state and side effects to a snapshot that can be quickly restored.

"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.MessagePackager = void 0;

var _invariant = _interopRequireDefault(require("../invariant.js"));

function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }

/**
 * Copyright (c) 2017-present, Facebook, Inc.
 * All rights reserved.
 *
 * This source code is licensed under the BSD-style license found in the
 * LICENSE file in the root directory of this source tree. An additional grant
 * of patent rights can be found in the PATENTS file in the same directory.
 */

/*  strict */
const LENGTH_SEPARATOR = "--"; // Package a message sent or unpackage a message received

class MessagePackager {
  constructor(isAdapter) {
    this._isAdapter = isAdapter;
  }

  // package a message to be sent
  package(contents) {
    // format: <length>--<contents>
    return contents.length + LENGTH_SEPARATOR + contents;
  } // unpackage a message received, verify it, and return it
  // returns null if no message or the message is only partially read
  // errors if the message violates the format


  unpackage(contents) {
    // format: <length>--<contents>
    let separatorIndex = contents.indexOf(LENGTH_SEPARATOR); // if the separator is not written in yet --> partial read

    if (separatorIndex === -1) {
      return null;
    }

    let messageLength = parseInt(contents.slice(0, separatorIndex), 10); // if the part before the separator is not a valid length, it is a
    // violation of protocol

    (0, _invariant.default)(!isNaN(messageLength));
    let startIndex = separatorIndex + LENGTH_SEPARATOR.length;
    let endIndex = startIndex + messageLength; // there should only be one message in the contents at a time

    (0, _invariant.default)(contents.length <= startIndex + messageLength); // if we didn't read the whole message yet --> partial read

    if (contents.length < endIndex) {
      return null;
    }

    let message = contents.slice(startIndex, endIndex);
    return message;
  }

}

exports.MessagePackager = MessagePackager;
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