JSPM

#modified merkle patricia tree

This is an implementation of the modified merkle patricia tree as specified in the Ethereum's yellow paper.

The modified Merkle Patricia tree (trie) provides a persistent data structure to map between arbitrary-length binary data (byte arrays). It is defined in terms of a mutable data structure to map between 256-bit binary fragments and arbitrary-length binary data. The core of the trie, and its sole requirement in terms of the protocol specification is to provide a single 32-byte value that identifies a given set of key-value pairs.
- Ethereum's yellow paper

Installation

• npm install merkle-patricia-tree

Usage

var Trie = require('merkle-patricia-tree'),
levelup = require('levelup'),
db = levelup('./testdb'),
trie = new Trie(db); 

trie.put('test', 'one', function () {
  trie.get('test', function (err, value) {
    if(value) console.log(value.toString())
  });
});

API

new new Trie([db], [root])

new Trie([root])

Creates a new Trie object

• db - A instance of levelup or compatiable API. If no db is null or left undefined then the the trie will be stored in memory vai memdown
• root - A hex String or Buffer for the root of a prevously stored trie.

Trie Properties

• root - The root of the trie as a Buffer
• isCheckpoint - A Boolean determining if you are saving to a checkpoint or directly to the db
• EMPTY_TRIE_ROOT - A buffer that is a the Root for an empty trie.

Trie Methods

trie.put(key, value, cb)

Stores a give value at the give key

• key - the key as a Buffer or String
• value - the value to be stored
• cb - a callback Function which is given the argumnet err - for an errors that may have occured

trie.get(key, cb)

Retrieves a value stored at a key

• key - the key as a Buffer or String
• cb - a callback Function which is given the argumnets err - for an errors that may have occured and vlue - The found value in a Buffer or if no value was found null.

trie.delete(key, cb)

Removes a value

• key - the key as a Buffer or String
• cb - a callback Function which is given the argumnet err - for an errors that may have occured

trie.checkpoint()

Creates a checkpoint that can later be reverted to or commited. After this is called, no changes to the trie will be permanently saved until commit is called.

trie.commit(cb)

Commits a checkpoint to the trie

• cb - a callback Function

trie.revert()

revets the trie to the state it was at when checkpoint was first called

trie.batch(operations)

Give an hash of operation adds them to the DB - operations a hash of key/values to add to the trie. example
javascript var ops = { 'dog': 'dogecoin', 'cat': 'meow', 'bird': '' //delete bird }

trie.deleteState([stateRoot], cb)

Deletes all the nodes of a given stateroot. If no stateroot is given then it will delete the current state.

• cb - a callback Function

trie.createReadStream()

returns a read stream. The data event is given an Object hat has two propeties; the key and the value. Both should be Buffers.

examples

see this blog post

Testing

npm test
Test use mocha