Merge 616d1c4 into b7880ea

bitpay · Aug 6, 2015 · 8687e4d · 8687e4d
2 parents b7880ea + 616d1c4
commit 8687e4d
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Showing 2 changed files with 25 additions and 1 deletion.
diff --git a/lib/transaction/transaction.js b/lib/transaction/transaction.js
@@ -126,7 +126,22 @@ Object.defineProperty(Transaction.prototype, 'outputAmount', ioProperty);
  * @return {Buffer}
  */
 Transaction.prototype._getHash = function() {
-  return Hash.sha256sha256(this.toBuffer());
+  var buf = this.toBuffer();
+
+  // Check if we computed this hash before
+  if (this._hashMemo && buf.equals(this._hashMemo.buf)) {
+    return this._hashMemo.hash;
+  }
+
+  var hash = Hash.sha256sha256(buf);
+
+  // Memoize buf/hash pair
+  this._hashMemo = {
+    buf: buf,
+    hash: hash
+  };
+
+  return hash;
 };
 
 /**

diff --git a/test/transaction/transaction.js b/test/transaction/transaction.js
@@ -85,6 +85,15 @@ describe('Transaction', function() {
     transaction.id.should.equal(tx_1_id);
   });
 
+  it('transaction hash is only computed once for the same data', function() {
+    var transaction = new Transaction(tx_1_hex);
+    var hash = transaction.hash;
+    hash.should.equal(transaction.hash);
+    transaction._getHash().should.equal(transaction._hashMemo.hash);
+    transaction.inputs.pop();
+    hash.should.not.equal(transaction.hash);
+  });
+
   it('serializes an empty transaction', function() {
     var transaction = new Transaction();
     transaction.uncheckedSerialize().should.equal(tx_empty_hex);