Module @helia/car

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()
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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()
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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()
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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)
})
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