@lichtblick/rosbag   

@lichtblick/rosbag is a node.js & browser compatible module for reading rosbag binary data files.

Installation

``
npm install @lichtblick/rosbag
`

or

`
yarn add @lichtblick/rosbag
`

Quick start

The most common way to interact with a rosbag is to read data records for a specific set of topics. The rosbag format encodes type information for topics, and rosbag reads this type information and parses the data records into JavaScript objects and arrays.

Here is an example of reading messages from a rosbag in node.js:

`typescript
import { Bag } from "@lichtblick/rosbag";
import { FileReader } from "@lichtblick/rosbag/node";

async function logMessagesFromFooBar() {
// open a new bag with a speific file reader
const bag = new Bag(new FileReader("../path/to/ros.bag"));

await bag.open();

for await (const result of bag.messageIterator({ topics: ["/foo", "/bar"] })) {
// topic is the topic the data record was in
// in this case it will be either '/foo' or '/bar'
console.log(result.topic);

// message is the parsed payload
// this payload will likely differ based on the topic
console.log(result.message);
}
}

logMessagesFromFooBar();
`

API

$3

`typescript
class Bag {
// the time of the earliest message in the bag
startTime: Time,

// the time of the last message in the bag
endTime: Time,

// a hash of connection records by their id
connections: { [number]: Connection },

// an array of ChunkInfos describing the chunks within the bag
chunkInfos: Array,
}
`

$3

`typescript
const options = {
// decompression callbacks:
// if your bag is compressed you can supply a callback to decompress it
// based on the compression type. The callback should accept a buffer of compressed bytes
// and return a buffer of uncompressed bytes. For examples on how to decompress lz4 and bz2 compressed bags
// please see the tests here: https://github.com/cruise-automation/rosbag.js/blob/545529344c8c2a0b3a3126646d065043c2d67d84/src/bag.test.js#L167-L192
// The decompression callback is also passed the uncompressedByteLength which is stored in the bag.
// This byte length can be used with some decompression libraries to increase decompression efficiency.
decompress?: {
bz2?: (buffer: Uint8Array, uncompressedByteLength: number) => Uint8Array,
lz4?: (buffer: Uint8Array, uncompressedByteLength: number) => Uint8Array,
},

// Toggle the message deserialization behavior. By default, messages are deserialized into javascript objects. You can override this behavior by setting this to false.
parse?: boolean;
}
`

$3

bag.messageIterator method returns an Async Iterator for messages in the file. Each item is a MessageEvent.

$3

`typescript
const options {
// an optional array of topics used to filter down
// which data records will be read
// the default is all records on all topics
topics?: Array,

// an optional Time instance used to filter data records
// to only those which start on or after the given start time
// the default is undefined which will apply no filter
start?: Time,
}
`

$3

`typescript
const messageEvent {
// the topic from which the current record was read
topic: string,

// the receive time of the message
timestamp: Time

// the raw buffer data from the data record
// a node.js buffer in node & an array buffer in the browser
data: Uint8Array,

// the parsed message contents as a JavaScript object
// this can contain nested complex types
// and arrays of complex & simple types
// If parsing is disabled this field is set to undefined
message?: { [string]: unknown },
}
`

$3

`typescript
class Connection {
// the id of the connection
conn: number,

// the topic for the connection
topic: string,

// the md5 hash for the connection message definition
md5sum: string,

// the rosbag formatted message definition for records on this connection's topic
messageDefinition: string,
}
``