rosbag/src/web/index.ts

`rosbag` is a node.js & browser compatible module for reading [rosbag](http://wiki.ros.org/rosbag) binary data files.

// Copyright (c) 2018-present, Cruise LLC

// This source code is licensed under the Apache License, Version 2.0,
// found in the LICENSE file in the root directory of this source tree.
// You may not use this file except in compliance with the License.

import { Buffer } from "buffer";
import {
  MessageReader,
  MessageWriter,
  parseMessageDefinition,
  rosPrimitiveTypes,
  TimeUtil,
  extractFields,
  extractTime,
} from "../index";
import type { Callback } from "../types";
import Bag, { OpenBag } from "../bag";
import BagReader from "../BagReader";

// browser reader for Blob|File objects
export class Reader {
  _blob: Blob;
  _size: number;

  constructor(blob: Blob) {
    this._blob = blob;
    this._size = blob.size;
  }

  // read length (bytes) starting from offset (bytes)
  // callback(err, buffer)
  read(offset: number, length: number, cb: Callback<Buffer>) {
    const reader = new FileReader();

    reader.onload = function onload() {
      reader.onload = null;
      reader.onerror = null;
      setImmediate(cb, null, reader.result ? Buffer.from(reader.result as ArrayBuffer) : undefined);
    };

    reader.onerror = function onerror() {
      reader.onload = null;
      reader.onerror = null;
      setImmediate(cb, new Error(reader.error ? reader.error.message : "Unknown reader error."));
    };

    reader.readAsArrayBuffer(this._blob.slice(offset, offset + length));
  }

  // return the size of the file
  size() {
    return this._size;
  }
}

const open = async (file: File | string): Promise<OpenBag> => {
  if (!(file instanceof Blob)) {
    throw new Error(
      "Expected file to be a File or Blob. Make sure you are correctly importing the node or web version of Bag."
    );
  }

  const bag = new Bag(new BagReader(new Reader(file)));
  await bag.open();
  return bag as OpenBag;
};

Bag.open = open;

// These exports must match ../index.ts
export * from "../types";
export {
  TimeUtil,
  Bag,
  BagReader,
  MessageReader,
  MessageWriter,
  open,
  parseMessageDefinition,
  rosPrimitiveTypes,
  extractFields,
  extractTime,
};
export default Bag;