generator.js

// a more low level interface to the merkle tree stream.
// useful for certain applications the require non-streamy access to the algos.
// versioned by the same semver as the stream interface.

const flat = require('flat-tree')

module.exports = class MerkleGenerator {
  constructor (opts, roots) {
    if (!opts || !opts.leaf || !opts.parent) throw new Error('opts.leaf and opts.parent required')

    this.roots = roots || opts.roots || []
    this.blocks = this.roots.length ? 1 + flat.rightSpan(this.roots[this.roots.length - 1].index) / 2 : 0

    for (let i = 0; i < this.roots.length; i++) {
      const r = this.roots[i]
      if (r && !r.parent) r.parent = flat.parent(r.index)
    }

    this._leaf = opts.leaf
    this._parent = opts.parent
  }

  next (data, nodes) {
    if (!Buffer.isBuffer(data)) data = Buffer.from(data)
    if (!nodes) nodes = []

    const index = 2 * this.blocks++

    let leaf = {
      index: index,
      parent: flat.parent(index),
      hash: null,
      size: data.length,
      data: data
    }

    leaf.hash = this._leaf(leaf, this.roots)
    this.roots.push(leaf)
    nodes.push(leaf)

    while (this.roots.length > 1) {
      const left = this.roots[this.roots.length - 2]
      const right = this.roots[this.roots.length - 1]

      if (left.parent !== right.parent) break

      this.roots.pop()
      this.roots[this.roots.length - 1] = leaf = {
        index: left.parent,
        parent: flat.parent(left.parent),
        hash: this._parent(left, right),
        size: left.size + right.size,
        data: null
      }
      nodes.push(leaf)
    }

    return nodes
  }
}