@jimpick/hyperdrive-hyperdb-backend

Hyperdrive

Hyperdrive is a secure, real time distributed file system

npm install hyperdrive

Usage

Hyperdrive aims to implement the same API as Node.js' core fs module.

var hyperdrive = require('hyperdrive')
var archive = hyperdrive('./my-first-hyperdrive') // content will be stored in this folder

archive.writeFile('/hello.txt', 'world', function (err) {
  if (err) throw err
  archive.readdir('/', function (err, list) {
    if (err) throw err
    console.log(list) // prints ['hello.txt']
    archive.readFile('/hello.txt', 'utf-8', function (err, data) {
      if (err) throw err
      console.log(data) // prints 'world'
    })
  })
})

A big difference is that you can replicate the file system to other computers! All you need is a stream.

var net = require('net')

// ... on one machine

var server = net.createServer(function (socket) {
  socket.pipe(archive.replicate()).pipe(socket)
})

server.listen(10000)

// ... on another

var clonedArchive = hyperdrive('./my-cloned-hyperdrive', origKey)
var socket = net.connect(10000)

socket.pipe(clonedArchive.replicate()).pipe(socket)

It also comes with build in versioning and real time replication. See more below.

API

var archive = hyperdrive(storage, [key], [options])

Create a new hyperdrive. Storage should be a function or a string.

If storage is a string content will be stored inside that folder.

If storage is a function it is called with a string name for each abstract-random-access instance that is needed to store the archive.

Options include:

{
  sparse: true, // only download data on content feed when it is specifically requested
  sparseMetadata: true // only download data on metadata feed when requested
  metadataStorageCacheSize: 65536 // how many entries to use in the metadata hypercore's LRU cache
  contentStorageCacheSize: 65536 // how many entries to use in the content hypercore's LRU cache
  treeCacheSize: 65536 // how many entries to use in the append-tree's LRU cache
}

Note that a cloned hyperdrive archive can be "sparse". Usually (by setting sparse: true) this means that the content is not downloaded until you ask for it, but the entire metadata feed is still downloaded. If you want a very sparse archive, where even the metadata feed is not downloaded until you request it, then you should also set sparseMetadata: true.

var stream = archive.replicate([options])

Replicate this archive. Options include

{
  live: false, // keep replicating
  download: true, // download data from peers?
  upload: true // upload data to peers?
}

archive.version

Get the current version of the archive (incrementing number).

archive.key

The public key identifying the archive.

archive.discoveryKey

A key derived from the public key that can be used to discovery other peers sharing this archive.

archive.writable

A boolean indicating whether the archive is writable.

archive.on('ready')

Emitted when the archive is fully ready and all properties has been populated.

archive.on('error', err)

Emitted when a critical error during load happened.

var oldDrive = archive.checkout(version)

Checkout a readonly copy of the archive at an old version.

archive.download([path], [callback])

Download all files in path of current version. If no path is specified this will download all files.

You can use this with .checkout(version) to download a specific version of the archive.

archive.checkout(version).download()

var stream = archive.history([options])

Get a stream of all changes and their versions from this archive.

var stream = archive.createReadStream(name, [options])

Read a file out as a stream. Similar to fs.createReadStream.

Options include:

{
  start: optionalByteOffset, // similar to fs
  end: optionalInclusiveByteEndOffset, // similar to fs
  length: optionalByteLength
}

archive.readFile(name, [options], callback)

Read an entire file into memory. Similar to fs.readFile.

Options can either be an object or a string

Options include:

{
  encoding: string
  cached: true|false // default: false,
}

or a string can be passed as options to simply set the encoding - similar to fs.

If cached is set to true, this function returns results only if they have already been downloaded.

var stream = archive.createDiffStream(version, [options])

Diff this archive this another version. version can both be a version number of a checkout instance of the archive. The data objects looks like this

{
  type: 'put' | 'del',
  name: '/some/path/name.txt',
  value: {
    // the stat object
  }
}

var stream = archive.createWriteStream(name, [options])

Write a file as a stream. Similar to fs.createWriteStream. If options.cached is set to true, this function returns results only if they have already been downloaded.

archive.writeFile(name, buffer, [options], [callback])

Write a file from a single buffer. Similar to fs.writeFile.

archive.unlink(name, [callback])

Unlinks (deletes) a file. Similar to fs.unlink.

archive.mkdir(name, [options], [callback])

Explictly create an directory. Similar to fs.mkdir

archive.rmdir(name, [callback])

Delete an empty directory. Similar to fs.rmdir.

archive.readdir(name, [options], [callback])

Lists a directory. Similar to fs.readdir.

Options include:

{
    cached: true|false, // default: false
}

If cached is set to true, this function returns results from the local version of the archive’s append-tree. Default behavior is to fetch the latest remote version of the archive before returning list of directories.

archive.stat(name, callback)

Stat an entry. Similar to fs.stat. Sample output:

Stat {
  dev: 0,
  nlink: 1,
  rdev: 0,
  blksize: 0,
  ino: 0,
  mode: 16877,
  uid: 0,
  gid: 0,
  size: 0,
  offset: 0,
  blocks: 0,
  atime: 2017-04-10T18:59:00.147Z,
  mtime: 2017-04-10T18:59:00.147Z,
  ctime: 2017-04-10T18:59:00.147Z,
  linkname: undefined }

The output object includes methods similar to fs.stat:

var stat = archive.stat('/hello.txt')
stat.isDirectory()
stat.isFile()

archive.lstat(name, callback)

Stat an entry but do not follow symlinks. Similar to fs.lstat.

archive.access(name, callback)

Similar to fs.access.

archive.open(name, flags, [mode], callback)

Open a file and get a file descriptor back. Similar to fs.open.

Note that currently only read mode is supported in this API.

archive.read(fd, buf, offset, len, position, callback)

Read from a file descriptor into a buffer. Similar to fs.read.

archive.close(fd, [callback])

Close a file. Similar to fs.close.

archive.close([callback])

Closes all open resources used by the archive. The archive should no longer be used after calling this.