From 7da4c7925a0cd8006eb7f47143d47d42a03ef8ac Mon Sep 17 00:00:00 2001
From: Manuel Araoz <manuelaraoz@gmail.com>
Date: Mon, 16 Mar 2015 12:55:49 -0300
Subject: [PATCH 1/3] lazy calc for xpubkey in HDPrivateKey

---
 lib/hdprivatekey.js | 29 ++++++++++++++++++++++-------
 test/hdkeys.js      |  5 +++++
 2 files changed, 27 insertions(+), 7 deletions(-)

diff --git a/lib/hdprivatekey.js b/lib/hdprivatekey.js
index dbf842d90..a5e7b1e63 100644
--- a/lib/hdprivatekey.js
+++ b/lib/hdprivatekey.js
@@ -423,14 +423,29 @@ HDPrivateKey.prototype._buildFromBuffers = function(arg) {
     fingerPrint: fingerPrint
   });
 
-  var HDPublicKey = require('./hdpublickey');
-  var hdPublicKey = new HDPublicKey(this);
-
-  JSUtil.defineImmutable(this, {
-    hdPublicKey: hdPublicKey,
-    xpubkey: hdPublicKey.xpubkey
+  this._hdPublicKey = null;
+  Object.defineProperty(this, 'hdPublicKey', {
+    configurable: false,
+    enumerable: true,
+    get: function() {
+      if (!this._hdPublicKey) {
+        var HDPublicKey = require('./hdpublickey');
+        this._hdPublicKey = new HDPublicKey(this);
+      }
+      return this._hdPublicKey;
+    }
+  });
+  Object.defineProperty(this, 'xpubkey', {
+    configurable: false,
+    enumerable: true,
+    get: function() {
+      if (!this._hdPublicKey) {
+        var HDPublicKey = require('./hdpublickey');
+        this._hdPublicKey = new HDPublicKey(this);
+      }
+      return this._hdPublicKey.xpubkey;
+    }
   });
-
   return this;
 };
 
diff --git a/test/hdkeys.js b/test/hdkeys.js
index 36900a0d5..2ea1d5185 100644
--- a/test/hdkeys.js
+++ b/test/hdkeys.js
@@ -76,6 +76,11 @@ describe('BIP32 compliance', function() {
     publicKey.toString().should.equal(publicKey.xpubkey);
   });
 
+  it('cache for xpubkey works for test vector 1', function() {
+    var pk = HDPrivateKey(vector1_m_private);
+    pk.xpubkey.should.equal(pk.xpubkey);
+  });
+
   it('should get the extended public key from the extended private key for test vector 1', function() {
     HDPrivateKey(vector1_m_private).xpubkey.should.equal(vector1_m_public);
   });

From 21266570d49851b9c40577fb4c7f5322967c2d8f Mon Sep 17 00:00:00 2001
From: Manuel Araoz <manuelaraoz@gmail.com>
Date: Mon, 16 Mar 2015 13:01:00 -0300
Subject: [PATCH 2/3] refactor code

---
 lib/hdprivatekey.js | 20 ++++++++++++--------
 1 file changed, 12 insertions(+), 8 deletions(-)

diff --git a/lib/hdprivatekey.js b/lib/hdprivatekey.js
index a5e7b1e63..08052efd3 100644
--- a/lib/hdprivatekey.js
+++ b/lib/hdprivatekey.js
@@ -365,6 +365,15 @@ HDPrivateKey.fromSeed = function(hexa, network) {
   });
 };
 
+
+
+HDPrivateKey.prototype._calcHDPublicKey = function() {
+  if (!this._hdPublicKey) {
+    var HDPublicKey = require('./hdpublickey');
+    this._hdPublicKey = new HDPublicKey(this);
+  }
+};
+
 /**
  * Receives a object with buffers in all the properties and populates the
  * internal structure
@@ -424,14 +433,12 @@ HDPrivateKey.prototype._buildFromBuffers = function(arg) {
   });
 
   this._hdPublicKey = null;
+
   Object.defineProperty(this, 'hdPublicKey', {
     configurable: false,
     enumerable: true,
     get: function() {
-      if (!this._hdPublicKey) {
-        var HDPublicKey = require('./hdpublickey');
-        this._hdPublicKey = new HDPublicKey(this);
-      }
+      this._calcHDPublicKey();
       return this._hdPublicKey;
     }
   });
@@ -439,10 +446,7 @@ HDPrivateKey.prototype._buildFromBuffers = function(arg) {
     configurable: false,
     enumerable: true,
     get: function() {
-      if (!this._hdPublicKey) {
-        var HDPublicKey = require('./hdpublickey');
-        this._hdPublicKey = new HDPublicKey(this);
-      }
+      this._calcHDPublicKey();
       return this._hdPublicKey.xpubkey;
     }
   });

From 56c1e8c00087ce371c49a68d040ba2c331d3fcbe Mon Sep 17 00:00:00 2001
From: Manuel Araoz <manuelaraoz@gmail.com>
Date: Fri, 20 Mar 2015 16:01:05 -0300
Subject: [PATCH 3/3] fix test for hdkey cache

---
 test/hdkeys.js       | 5 -----
 test/hdprivatekey.js | 8 ++++++++
 2 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/test/hdkeys.js b/test/hdkeys.js
index 2ea1d5185..36900a0d5 100644
--- a/test/hdkeys.js
+++ b/test/hdkeys.js
@@ -76,11 +76,6 @@ describe('BIP32 compliance', function() {
     publicKey.toString().should.equal(publicKey.xpubkey);
   });
 
-  it('cache for xpubkey works for test vector 1', function() {
-    var pk = HDPrivateKey(vector1_m_private);
-    pk.xpubkey.should.equal(pk.xpubkey);
-  });
-
   it('should get the extended public key from the extended private key for test vector 1', function() {
     HDPrivateKey(vector1_m_private).xpubkey.should.equal(vector1_m_public);
   });
diff --git a/test/hdprivatekey.js b/test/hdprivatekey.js
index bd54bbc81..55782f455 100644
--- a/test/hdprivatekey.js
+++ b/test/hdprivatekey.js
@@ -100,6 +100,14 @@ describe('HDPrivate key interface', function() {
       testnetKey.publicKey.network.should.equal(Networks.testnet);
       livenetKey.publicKey.network.should.equal(Networks.livenet);
     });
+
+    it('cache for xpubkey works', function() {
+      var privateKey = new HDPrivateKey(xprivkey);
+      should.not.exist(privateKey._hdPublicKey);
+      privateKey.xpubkey.should.equal(privateKey.xpubkey);
+      should.exist(privateKey._hdPublicKey);
+    });
+
   });
 
   it('inspect() displays correctly', function() {