# @helia/car
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> 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
```typescript
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.
```typescript
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.
```typescript
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
```typescript
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
```console
$ npm i @helia/car
```
## Browser `
```
# API Docs
-
# License
Licensed under either of
- Apache 2.0, ([LICENSE-APACHE](https://github.com/ipfs/helia/blob/main/packages/car/LICENSE-APACHE) / )
- MIT ([LICENSE-MIT](https://github.com/ipfs/helia/blob/main/packages/car/LICENSE-MIT) / )
# Contribute
Contributions welcome! Please check out [the issues](https://github.com/ipfs/helia/issues).
Also see our [contributing document](https://github.com/ipfs/community/blob/master/CONTRIBUTING_JS.md) 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](https://github.com/ipfs/community/blob/master/code-of-conduct.md).
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.
[](https://github.com/ipfs/community/blob/master/CONTRIBUTING.md)