@helia/car

Import/export car files from Helia

About

@helia/car provides import and export methods to read/write Car files to Helia's blockstore.

See the Car interface for all available operations.

By default it supports dag-pb, dag-cbor, dag-json and raw CIDs, more esoteric DAG walkers can be passed as an init option.

Example - Exporting a DAG as a CAR file

import { createHelia } from 'helia'
import { car } from '@helia/car'
import { CID } from 'multiformats/cid'
import nodeFs from 'node:fs'

const helia = await createHelia()
const cid = CID.parse('QmFoo...')

const c = car(helia)
const out = nodeFs.createWriteStream('example.car')

for await (const buf of c.export(cid, {
  signal: AbortSignal.timeout(5_000)
})) {
  out.write(buf)
}

out.end()

Example - Exporting a part of a UnixFS DAG as a CAR file

Here the graph traversal will start at root and include the blocks for root, /foo, /bar, and all the blocks that make up baz.txt.

If there are other files/directories in the UnixFS DAG under root, they will not be included.

root will be the only entry in the CAR file roots.

import { createHelia } from 'helia'
import { car, UnixFSPath } from '@helia/car'
import { CID } from 'multiformats/cid'
import nodeFs from 'node:fs'

const helia = await createHelia()
const root = CID.parse('QmFoo...')

const c = car(helia)
const out = nodeFs.createWriteStream('example.car')

for await (const buf of c.export(root, {
  signal: AbortSignal.timeout(5_000),
  traversal: new UnixFSPath('/foo/bar/baz.txt')
})) {
  out.write(buf)
}

out.end()

Example - Including traversal path above the root in a CAR

The includeTraversalBlocks option will include the traversal blocks in the CAR when they would otherwise be excluded (for example when the traversal starts in a parent of the export root).

Here baz is the CID for baz.txt.

The CAR file will include the blocks for parent, /foo, /bar, and /baz.txt.

baz will be the only entry in the CAR file roots.

import { createHelia } from 'helia'
import { car, UnixFSPath } from '@helia/car'
import { CID } from 'multiformats/cid'
import nodeFs from 'node:fs'

const helia = await createHelia()
const parent = CID.parse('QmFoo...')
const baz = CID.parse('QmBar...')

const c = car(helia)
const out = nodeFs.createWriteStream('example.car')

for await (const buf of c.export(baz, {
  signal: AbortSignal.timeout(5_000),
  traversal: new UnixFSPath(parent, '/foo/bar/baz.txt'),
  includeTraversalBlocks: true
})) {
  out.write(buf)
}

out.end()

Example - Importing all blocks from a CAR file

import { createHelia } from 'helia'
import { unixfs } from '@helia/unixfs'
import { car } from '@helia/car'
import { CarReader } from '@ipld/car'
import { Readable } from 'node:stream'
import nodeFs from 'node:fs'

const helia = await createHelia({
  // ... helia config
})

// import the car
const inStream = nodeFs.createReadStream('example.car')
const reader = await CarReader.fromIterable(inStream)

const c = car(helia)
await c.import(reader, {
  signal: AbortSignal.timeout(5_000)
})

Install

$ npm i @helia/car

Browser <script> tag

Loading this module through a script tag will make its exports available as HeliaCar in the global namespace.

<script src="https://unpkg.com/@helia/car/dist/index.min.js"></script>

API Docs

• https://ipfs.github.io/helia/modules/_helia_car.html

License

Licensed under either of

• Apache 2.0, (LICENSE-APACHE / http://www.apache.org/licenses/LICENSE-2.0)
• MIT (LICENSE-MIT / http://opensource.org/licenses/MIT)

Contribute

Contributions welcome! Please check out the issues.

Also see our contributing document for more information on how we work, and about contributing in general.

Please be aware that all interactions related to this repo are subject to the IPFS Code of Conduct.

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.