block: build merkleTree to verify merkleRoot on regular blocks.

lib/bcoin/block.js

@@ -1,4 +1,5 @@
 var bcoin = require('../bcoin');
+var hash = require('hash.js');
 var utils = bcoin.utils;
 
 function Block(data, subtype) {
@@ -36,6 +37,7 @@ function Block(data, subtype) {
       return tx.hash('hex');
     });
     this.tx = this.hashes.slice();
+    this.invalid = !this._checkBlock();
   }
 
   this._hash = null;
@@ -80,7 +82,6 @@ Block.prototype._verifyMerkle = function verifyMerkle() {
   var height = 0;
 
   if (this.subtype === 'block') {
-    this.invalid = !utils.testTarget(this.bits, this.hash());
     return;
   }
 
@@ -158,3 +159,38 @@ Block.fromJSON = function fromJSON(json) {
 
   return block;
 };
+
+Block.prototype._phash = function phash(p1begin, p1end, p2begin, p2end) {
+  var pblank = '';
+  var hash1 = hash.sha256();
+  hash1.update(p1begin === p1end ? pblank : p1begin, 'hex');
+  hash1.update(p2begin === p2end ? pblank : p2begin, 'hex');
+  hash1 = hash1.digest('hex');
+  var hash2 = hash.sha256();
+  hash2.update(hash1, 'hex');
+  hash2 = hash2.digest('hex');
+  return hash2;
+};
+
+Block.prototype._buildMerkle = function buildMerkle() {
+  var merkleTree = [];
+  for (var i = 0; i < this.txs.length; i++) {
+    merkleTree.push(this.txs[i].hash('hex'));
+  }
+  var j = 0;
+  for (var size = this.txs.length; size > 1; size = ((size + 1) / 2) | 0) {
+    for (var i = 0; i < size; i += 2) {
+      var i2 = Math.min(i + 1, size - 1);
+      merkleTree.push(
+        this._phash(merkleTree[j+i],  merkleTree[j+i+1],
+                    merkleTree[j+i2], merkleTree[j+i2+1]));
+    }
+    j += size;
+  }
+  return merkleTree;
+};
+
+Block.prototype._checkBlock = function checkBlock() {
+  this.merkleTree = this._buildMerkle();
+  return this.merkleTree[this.merkleTree.length-1] === this.merkleRoot;
+};