Implement OpenSSL::BN#abs

Provides an efficant way to garentee positive values

.gitignore

@@ -8,3 +8,5 @@
 ext/openssl/mkmf.log
 ext/openssl/Makefile
 ext/openssl/extconf.h
+.DS_Store
+.idea/

ext/openssl/ossl_bn.c

@@ -960,6 +960,29 @@ ossl_bn_uminus(VALUE self)
  return obj;
 }
 
+/*
+ * call-seq:
+ * bn.abs -> aBN
+ */
+static VALUE
+ossl_bn_abs(VALUE self)
+{
+ VALUE obj;
+ BIGNUM *bn1, *bn2;
+
+ GetBN(self, bn1);
+ if (BN_is_negative(bn1)) {
+ obj = NewBN(cBN);
+ bn2 = BN_dup(bn1);
+ if (!bn2) { ossl_raise(eBNError, "BN_dup"); }
+ SetBN(obj, bn2);
+ BN_set_negative(bn2, 0);
+ return obj;
+ } else {
+ return self;
+ }
+}
+
 #define BIGNUM_CMP(func) \
  static VALUE \
  ossl_bn_##func(VALUE self, VALUE other) \
@@ -1176,6 +1199,7 @@ Init_ossl_bn(void)
 
  rb_define_method(cBN, "+@", ossl_bn_uplus, 0);
  rb_define_method(cBN, "-@", ossl_bn_uminus, 0);
+ rb_define_method(cBN, "abs", ossl_bn_abs, 0);
 
  rb_define_method(cBN, "+", ossl_bn_add, 1);
  rb_define_method(cBN, "-", ossl_bn_sub, 1);

test/openssl/test_bn.rb

@@ -114,6 +114,19 @@ def test_sqr
  assert_equal(100, 10.to_bn.sqr)
  end
 
+ def test_abs
+ assert_equal(@e1, @e2.abs)
+ assert_equal(@e3, @e4.abs)
+ assert_not_equal(@e2, @e2.abs)
+ assert_not_equal(@e4, @e4.abs)
+ assert_false(@e2.abs.negative?)
+ assert_false(@e4.abs.negative?)
+ assert_true((-@e1.abs).negative?)
+ assert_true((-@e2.abs).negative?)
+ assert_true((-@e3.abs).negative?)
+ assert_true((-@e4.abs).negative?)
+ end
+
  def test_four_ops
  assert_equal(3, 1.to_bn + 2)
  assert_equal(-1, 1.to_bn + -2)