https://github.com/mafintosh/merkle-tree-stream

A stream that generates a merkle tree based on the incoming data.
https://github.com/mafintosh/merkle-tree-stream

Last synced: 6 days ago
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A stream that generates a merkle tree based on the incoming data.

• Host: GitHub
• URL: https://github.com/mafintosh/merkle-tree-stream
• Owner: mafintosh
• License: mit
• Created: 2015-11-14T17:42:25.000Z (about 9 years ago)
• Default Branch: master
• Last Pushed: 2022-02-25T08:01:45.000Z (almost 3 years ago)
• Last Synced: 2025-01-02T00:07:49.322Z (13 days ago)
• Language: JavaScript
• Homepage:
• Size: 15.6 KB
• Stars: 105
• Watchers: 5
• Forks: 12
• Open Issues: 8
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

Awesome Lists containing this project

• awesome-peer-to-peer - merkle-stream
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README

        
# merkle-tree-stream

A stream that generates a merkle tree based on the incoming data.

```

npm install merkle-tree-stream

```

[![build status](http://img.shields.io/travis/mafintosh/merkle-tree-stream.svg?style=flat)](http://travis-ci.org/mafintosh/merkle-tree-stream)

## Usage

``` js

var MerkleTreeStream = require('merkle-tree-stream')

var crypto = require('crypto')

var stream = new MerkleTreeStream({

  leaf: function (leaf, roots) {

    // this function should hash incoming data

    // roots in the current partial roots of the merkle tree

    return crypto.createHash('sha256').update(leaf.data).digest()

  },

  parent: function (a, b) {

    // hash two merkle tree node hashes into a new parent hash

    return crypto.createHash('sha256').update(a.hash).update(b.hash).digest()

  }

})

stream.write('hello')

stream.write('hashed')

stream.write('world')

stream.on('data', function (data) {

  console.log(data)

})

```

Running the above will print

```

{ index: 0,

  parent: 1,

  hash: ,

  data:  } // 'hello' as buffer

{ index: 2,

  parent: 1,

  hash: ,

  data:  } // 'hashed' as buffer

{ index: 1,

  parent: 3,

  hash: ,

  data: null }

{ index: 4,

  parent: 5,

  hash: ,

  data:  } // 'world' as buffer

```

`index` is the tree node index. all even numbers are data nodes (will have a non-null `data` property).

`parent` is the index of a tree node's parent node.

`hash` is the hash of a tree node.

You can always access the current partial roots of the merkle tree by accessing `stream.roots`.

If the number of nodes written to the stream is not a power of `2` then `stream.roots` will

contain more than 1 node (at most `log2(number-of-nodes-written)`). Otherwise it will contain just a single root.

Optionally you can also pass in an array of `roots` in the options map as `{roots: roots}` to continue adding data

to a previously generated merkle tree.

## Low-level interface

A non stream low-level interface can required by doing `require('merkle-tree-stream/generator')`.

``` js

var MerkleGenerator = require('merkle-tree-stream/generator')

var gen = new MerkleGenerator({leaf: ..., parent: ...}) // same options as above

var nodes = gen.next('some data')

console.log(nodes) // returns the tree nodes generated, similar to the stream output

console.log(gen.roots) // contains the current roots nodes

```

## Related

See [mafintosh/flat-tree](https://github.com/mafintosh/flat-tree) for more information about

how node/parent indexes are calculated.

## License

MIT