Feature/merkle utils (#102)

* Add util and test for the merkle tree

* Add test clarification

* Bump package version

Author: antouhou

lib/util/merkletree.js

@@ -0,0 +1,43 @@
+/* eslint-disable */
+var doubleSha256 = require('../crypto/hash').sha256sha256;
+
+/**
+ * Builds a merkle tree of all passed hashes
+ * @link https://en.bitcoin.it/wiki/Protocol_specification#Merkle_Trees
+ * @param {Buffer[]} hashes
+ * @returns {Buffer[]} - An array with each level of the tree after the other.
+ */
+function getMerkleTree(hashes) {
+  // Copy all buffers in the tree to avoid unexpected behaviour
+  var tree = hashes.map(Buffer.from);
+
+  var j = 0;
+  for (var size = hashes.length; size > 1; size = Math.floor((size + 1) / 2)) {
+    for (var i = 0; i < size; i += 2) {
+      var i2 = Math.min(i + 1, size - 1);
+      var buf = Buffer.concat([tree[j + i], tree[j + i2]]);
+      tree.push(Buffer.from(doubleSha256(buf), 'hex'));
+    }
+    j += size;
+  }
+
+  return tree;
+}
+
+/**
+ * Copies root of the passed tree to a new Buffer and returns it
+ * @param {Buffer[]} merkleTree
+ * @returns {Buffer|undefined} - A buffer of the merkle root hash
+ */
+function getMerkleRoot(merkleTree) {
+  if (merkleTree.length === 0) {
+    return undefined;
+  }
+  // Copy root buffer
+  return Buffer.from(merkleTree[merkleTree.length - 1]);
+}
+
+module.exports = {
+  getMerkleTree: getMerkleTree,
+  getMerkleRoot: getMerkleRoot
+};

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@dashevo/dashcore-lib",
-  "version": "0.16.2",
+  "version": "0.16.3",
   "description": "A pure and powerful JavaScript Dash library.",
   "author": "Dash Core Group, Inc. <dev@dash.org>",
   "main": "index.js",

test/util/merkletree.js

@@ -0,0 +1,56 @@
+/* eslint-disable */
+var expect = require('chai').expect;
+var merkleTreeUtil = require('../../lib/util/merkletree');
+var getMerkleTree = merkleTreeUtil.getMerkleTree;
+var getMerkleRoot = merkleTreeUtil.getMerkleRoot;
+
+var hashes = [
+  Buffer.from('6b86b273ff34fce19d6b804eff5a3f5747ada4eaa22f1d49c01e52ddb7875b4b', 'hex'),
+  Buffer.from('bf7e815688420059a4a77c66ad8d154487a25f3fcee73e36514f66fbc26ae91a', 'hex'),
+  Buffer.from('18083d9866ba7fde28e819520ff4a4e9a7c871fe7929d997c84aebe7ae8b9385', 'hex')
+];
+
+var expectedTree = [
+  Buffer.from('6b86b273ff34fce19d6b804eff5a3f5747ada4eaa22f1d49c01e52ddb7875b4b', 'hex'),
+  Buffer.from('bf7e815688420059a4a77c66ad8d154487a25f3fcee73e36514f66fbc26ae91a', 'hex'),
+  Buffer.from('18083d9866ba7fde28e819520ff4a4e9a7c871fe7929d997c84aebe7ae8b9385', 'hex'),
+  Buffer.from('509051b275340cb2c5bf784764c4ca4505a2d96178e8166523145ce496dd1c24', 'hex'),
+  Buffer.from('30b07f4b48fac0ff36f1ba88198267392d4b684db4eb8dff313722c86fab17e4', 'hex'),
+  Buffer.from('f7be256fbaef5f3f5eb1d0807852a396314c11a964848b57e6a38b8e82c8777b', 'hex')
+];
+
+describe('merkleTree', function () {
+  describe('getMerkleTree', function () {
+    it('should build a proper merkle tree', function () {
+      var tree = getMerkleTree(hashes);
+
+      expect(tree).to.be.an('array');
+      // Three leaves, two nodes and a root, 6 in total
+      expect(tree.length).to.be.equal(6);
+      tree.forEach(function (node, index) {
+        expect(node).to.be.instanceOf(Buffer);
+        // sha256 is 32 bytes
+        expect(node.length).to.be.equal(32);
+        expect(node).to.be.deep.equal(expectedTree[index]);
+      });
+    });
+  });
+  describe('getMerkleRoot', function () {
+    it('should return a copy of merkle root from merkle tree', function () {
+      var tree = getMerkleTree(hashes);
+      var root = getMerkleRoot(tree);
+
+      // Last element of the tree is root
+      expect(root).to.be.deep.equal(expectedTree[5]);
+
+      // Test that resulted buffer is decoupled from the tree
+      root.reverse();
+      expect(root).to.be.not.deep.equal(expectedTree[5]);
+    });
+    it('should return undefined if tree is empty', function () {
+      var root = getMerkleRoot([]);
+
+      expect(root).to.be.undefined;
+    });
+  });
+});