IPFS unixFS Engine

JavaScript implementation of the layout and chunking mechanisms used by IPFS to handle Files

Lead Maintainer

Alex Potsides

Table of Contents

• Install
• Usage
  • Example Importer
  • Importer API
    • const add = new Importer(dag)
  • Example Exporter
  • Exporter: API
  • new Exporter(hash, dagService)
• Contribute
• License

Install

> npm install ipfs-unixfs-engine

Usage

Importer

Importer example

Let's create a little directory to import:

> cd /tmp
> mkdir foo
> echo 'hello' > foo/bar
> echo 'world' > foo/quux

And write the importing logic:

const Importer = require('ipfs-unixfs-engine').Importer

// You need to create and pass an ipld-resolve instance
// https://github.com/ipld/js-ipld-resolver
const filesAddStream = new Importer(<ipld-resolver instance>)

// An array to hold the return of nested file/dir info from the importer
// A root DAG Node is received upon completion

const res = []

// Import path /tmp/foo/bar
const rs = fs.createReadStream(file)
const rs2 = fs.createReadStream(file2)
const input = { path: '/tmp/foo/bar', content: rs }
const input2 = { path: '/tmp/foo/quxx', content: rs2 }

// Listen for the data event from the importer stream
filesAddStream.on('data', (info) => res.push(info))

// The end event of the stream signals that the importer is done
filesAddStream.on('end', () => console.log('Finished filesAddStreaming files!'))

// Calling write on the importer to filesAddStream the file/object tuples
filesAddStream.write(input)
filesAddStream.write(input2)
filesAddStream.end()

When run, the stat of DAG Node is outputted for each file on data event until the root:

{ multihash: <Buffer 12 20 bd e2 2b 57 3f 6f bd 7c cc 5a 11 7f 28 6c a2 9a 9f c0 90 e1 d4 16 d0 5f 42 81 ec 0c 2a 7f 7f 93>,
  size: 39243,
  path: '/tmp/foo/bar' }

{ multihash: <Buffer 12 20 bd e2 2b 57 3f 6f bd 7c cc 5a 11 7f 28 6c a2 9a 9f c0 90 e1 d4 16 d0 5f 42 81 ec 0c 2a 7f 7f 93>,
  size: 59843,
  path: '/tmp/foo/quxx' }

{ multihash: <Buffer 12 20 bd e2 2b 57 3f 6f bd 7c cc 5a 11 7f 28 6c a2 9a 9f c0 90 e1 d4 16 d0 5f 42 81 ec 0c 2a 7f 7f 93>,
  size: 93242,
  path: '/tmp/foo' }

{ multihash: <Buffer 12 20 bd e2 2b 57 3f 6f bd 7c cc 5a 11 7f 28 6c a2 9a 9f c0 90 e1 d4 16 d0 5f 42 81 ec 0c 2a 7f 7f 93>,
  size: 94234,
  path: '/tmp' }

Importer API

const Importer = require('ipfs-unixfs-engine').Importer

const import = new Importer(dag [, options])

The import object is a duplex pull stream that takes objects of the form:

{
  path: 'a name',
  content: (Buffer or Readable stream)
}

import will output file info objects as files get stored in IPFS. When stats on a node are emitted they are guaranteed to have been written.

dag is an instance of the IPLD Resolver or the js-ipfs dag api

The input's file paths and directory structure will be preserved in the dag-pb created nodes.

options is an JavaScript option that might include the following keys:

• wrap (boolean, defaults to false): if true, a wrapping node will be created
• shardSplitThreshold (positive integer, defaults to 1000): the number of directory entries above which we decide to use a sharding directory builder (instead of the default flat one)
• chunker (string, defaults to "fixed"): the chunking strategy. Now only supports "fixed"
• chunkerOptions (object, optional): the options for the chunker. Defaults to an object with the following properties:
  • maxChunkSize (positive integer, defaults to 262144): the maximum chunk size for the fixed chunker.
• strategy (string, defaults to "balanced"): the DAG builder strategy name. Supports:
  • flat: flat list of chunks
  • balanced: builds a balanced tree
  • trickle: builds a trickle tree
• maxChildrenPerNode (positive integer, defaults to 174): the maximum children per node for the balanced and trickle DAG builder strategies
• layerRepeat (positive integer, defaults to 4): (only applicable to the trickle DAG builder strategy). The maximum repetition of parent nodes for each layer of the tree.
• reduceSingleLeafToSelf (boolean, defaults to true): optimization for, when reducing a set of nodes with one node, reduce it to that node.
• dirBuilder (object): the options for the directory builder
  • hamt (object): the options for the HAMT sharded directory builder
    • bits (positive integer, defaults to 8): the number of bits at each bucket of the HAMT
• progress (function): a function that will be called with the byte length of chunks as a file is added to ipfs.
• onlyHash (boolean, defaults to false): Only chunk and hash - do not write to disk
• hashAlg (string): multihash hashing algorithm to use
• cidVersion (integer, default 0): the CID version to use when storing the data (storage keys are based on the CID, including it's version)
• rawLeaves (boolean, defaults to false): When a file would span multiple DAGNodes, if this is true the leaf nodes will not be wrapped in UnixFS protobufs and will instead contain the raw file bytes
• leafType (string, defaults to 'file') what type of UnixFS node leaves should be - can be 'file' or 'raw' (ignored when rawLeaves is true)

Exporter

Exporter example

// Create an export source pull-stream cid or ipfs path you want to export and a
// <dag or ipld-resolver instance> to fetch the file from
const filesStream = Exporter(<cid or ipfsPath>, <dag or ipld-resolver instance>)

// Pipe the return stream to console
filesStream.on('data', (file) => file.content.pipe(process.stdout))

Exporter API

const Exporter = require('ipfs-unixfs-engine').Exporter

new Exporter(, , )

Uses the given dag API or an ipld-resolver instance to fetch an IPFS UnixFS object(s) by their multiaddress.

Creates a new readable stream in object mode that outputs objects of the form

{
  path: 'a name',
  content: (Buffer or Readable stream)
}

offset and length

offset and length arguments can optionally be passed to the reader function. These will cause the returned stream to only emit bytes starting at offset and with length of length.

See the tests for examples of using these arguments.

const exporter = require('ipfs-unixfs-engine').exporter
const pull = require('pull-stream')
const drain = require('pull-stream/sinks/drain')

pull(
  exporter(cid, ipldResolver, {
    offset: 0,
    length: 10
  })
  drain((file) => {
    // file.content is a pull stream containing only the first 10 bytes of the file
  })
)

Errors

Errors are received by pull-stream sinks.

const exporter = require('ipfs-unixfs-engine').exporter
const pull = require('pull-stream')
const collect = require('pull-stream/sinks/collect')

pull(
  exporter(cid, ipldResolver)
  collect((error, chunks) => {
    // handle the error
  })
)

Contribute

Feel free to join in. All welcome. Open an issue!

This repository falls under the IPFS Code of Conduct.

License

MIT