Share your code. npm Orgs help your team discover, share, and reuse code. Create a free org »


    IPFS unixFS Engine

    standard-readme compliant Build Status Coverage Status Dependency Status js-standard-style

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

    Table of Contents


    > npm install ipfs-unixfs-engine



    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
    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

    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 false): 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)


    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')
      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 are received by pull-stream sinks.

    const exporter = require('ipfs-unixfs-engine').exporter
    const pull = require('pull-stream')
    const drain = require('pull-stream/sinks/collect')
      exporter(cid, ipldResolver)
      collect((error, chunks) => {
        // handle the error


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

    This repository falls under the IPFS Code of Conduct.





    npm i ipfs-unixfs-engine

    Downloadsweekly downloads








    last publish


    • avatar