add set function to bip32

lib/bip32.js

@@ -14,9 +14,25 @@ var BIP32 = function BIP32(obj) {
   if (typeof obj === 'string') {
     var str = obj;
     this.fromString(str);
+  } else if (obj ) {
+    this.set(obj);
   }
 }
 
+BIP32.prototype.set = function(obj) {
+  this.version = typeof obj.version !== 'undefined' ? obj.version : this.version;
+  this.depth = typeof obj.depth !== 'undefined' ? obj.depth : this.depth;
+  this.parentFingerprint = obj.parentFingerprint || this.parentFingerprint;
+  this.childIndex = obj.childIndex || this.childIndex;
+  this.chainCode = obj.chainCode || this.chainCode;
+  this.key = obj.key || this.key;
+  this.hasPrivateKey = typeof obj.hasPrivateKey !== 'undefined' ? obj.hasPrivateKey : this.hasPrivateKey;
+  this.pubKeyHash = obj.pubKeyHash || this.pubKeyHash;
+  this.extendedPublicKey = obj.extendedPublicKey || this.extendedPublicKey;
+  this.extendedPrivateKey = obj.extendedPrivateKey || this.extendedPrivateKey;
+  return this;
+};
+
 BIP32.prototype.fromRandom = function(networkstr) {
   if (!networkstr)
     networkstr = 'mainnet';

test/bip32.js

@@ -40,6 +40,7 @@ describe('BIP32', function() {
     should.exist(bip32);
     new BIP32(vector1_m_private).toString().should.equal(vector1_m_private);
     BIP32(vector1_m_private).toString().should.equal(vector1_m_private);
+    BIP32(BIP32(vector1_m_private)).toString().should.equal(vector1_m_private);
   });
 
   it('should initialize test vector 1 from the extended public key', function() {
@@ -281,6 +282,24 @@ describe('BIP32', function() {
     });
   });
 
+  describe('#set', function() {
+    var bip32 = BIP32(vector1_m_private);
+    var bip322 = BIP32().set({
+      version: bip32.version,
+      depth: bip32.depth,
+      parentFingerprint: bip32.parentFingerprint,
+      childIndex: bip32.childIndex,
+      chainCode: bip32.chainCode,
+      key: bip32.key,
+      hasPrivateKey: bip32.hasPrivateKey,
+      pubKeyHash: bip32.pubKeyhash,
+      extendedPublicKey: bip32.extendedPublicKey,
+      extendedPrivateKey: bip32.extendedPrivateKey
+    });
+    bip322.toString().should.equal(bip32.toString());
+    bip322.set({}).toString().should.equal(bip32.toString());
+  });
+
   describe('#seed', function() {
 
     it('should initialize a new BIP32 correctly from test vector 1 seed', function() {