Block: add checkMerkleRoot

src/block.js

@@ -1,3 +1,4 @@
+var createHash = require('create-hash')
 var bufferutils = require('./bufferutils')
 var bcrypto = require('./crypto')
 var bufferCompare = require('buffer-compare')
@@ -133,6 +134,35 @@ Block.calculateTarget = function (bits) {
   return target
 }
 
+Block.calculateMerkleRoot = function (transactions) {
+  var length = transactions.length
+  if (length === 0) throw TypeError('Cannot compute merkle root for zero transactions')
+
+  var hashes = transactions.map(function (transaction) { return transaction.getHash() })
+
+  while (length > 1) {
+    var j = 0
+
+    for (var i = 0; i < length; i += 2, ++j) {
+      var hasher = createHash('sha256')
+      hasher.update(hashes[i])
+      hasher.update(i + 1 !== length ? hashes[i + 1] : hashes[i])
+      hashes[j] = bcrypto.sha256(hasher.digest())
+    }
+
+    length = j
+  }
+
+  return hashes[0]
+}
+
+Block.prototype.checkMerkleRoot = function () {
+  if (!this.transactions) return false
+
+  var actualMerkleRoot = Block.calculateMerkleRoot(this.transactions)
+  return bufferCompare(this.merkleRoot, actualMerkleRoot) === 0
+}
+
 Block.prototype.checkProofOfWork = function () {
   var hash = bufferReverse(this.getHash())
   var target = Block.calculateTarget(this.bits)