Add base option for BN.fromString

lib/crypto/bn.js

@@ -21,9 +21,9 @@ BN.fromNumber = function(n) {
   return new BN(n);
 };
 
-BN.fromString = function(str) {
+BN.fromString = function(str, base) {
   $.checkArgument(_.isString(str));
-  return new BN(str);
+  return new BN(str, base);
 };
 
 BN.fromBuffer = function(buf, opts) {

test/crypto/bn.js

@@ -79,9 +79,9 @@ describe('BN', function() {
     it('should make BN from a string', function() {
       BN.fromString('5').toString().should.equal('5');
     });
-    it('should work with 7fffff0000000000000000000000000000000000000000000000000000000000', function() {
-      BN.fromString('7fffff0000000000000000000000000000000000000000000000000000000000')
-      .toString().should.equal('7fffff0000000000000000000000000000000000000000000000000000000000');
+    it('should work with hex string', function() {
+      BN.fromString('7fffff0000000000000000000000000000000000000000000000000000000000', 16)
+      .toString(16).should.equal('7fffff0000000000000000000000000000000000000000000000000000000000');
     });
   });