hash-chain

Hash Chain implementation using Blake2b

Usage

var HashChain = require('hash-chain')

Persistence:

var chain = // ...
const fs = require('fs')
const fd = fs.open('filename')
fs.write(fd, chain.offset, 0, 4)
fs.write(fd, chain.chain)
fs.close(fd)

const fs = require('fs')
const data = fs.readFile('filename')

var chain = new HashChain(data.subarray(4), data.readUInt32LE(0))

API

const seed = HashChain.seedgen([buf])

Generate a new seed, optionally into an existing Buffer buf.

const ch = HashChain.generate(seed, n, [offset = 0])

Generate and instantiate a new HashChain from seed Buffer with n elements.seed must be HashChain.SEEDBYTES long. Optionally offset the chain.

const ch = HashChain.fromAnchors(anchors, dist, [offset = 0])

Generate and instantiate a new lazy HashChain a list of anchor points, with dist elements between each anchor. Optionally offset the chain. This will only keep a buffer of dist points in memory, lazily generating missing points as they're accessed.

const ch = new HashChain(chainBuf, baseOffset = 0)

Instantiate a new HashChain from an existing chainBuf at offset.

const chainBuf = ch.chain

Read the Buffer used in the chain ch

const offset = ch.offset

Read the current integer offset

const len = ch.length

Total number of elements in the chain

const elm = ch.get(offset)

Get the element as a Buffer at offset from the offset given in the constructor. Normally HashChains only move forward, but giving a negative integer allows you to go back. This does not increment the internal counter.

for (const elm of ch) (Symbol.iterator)

Iterate over the elements in the chain using an Iterator

const anchors = ch.anchors(dist)

Generate anchor points with dist elements between each anchor. This can be used to optimise initialisation of an existing chain at the expense of more disk space.

Install

npm install hash-chain

License

ISC