From 49f5ee237780efb4006302743aa3df6c7ace5a74 Mon Sep 17 00:00:00 2001
From: Rick Mark <rick.mark@coinbase.com>
Date: Tue, 30 Mar 2021 14:50:42 -0700
Subject: [PATCH] Implement OpenSSL::BN#abs

Provides an efficant way to garentee positive values
---
 .gitignore              |  2 ++
 ext/openssl/ossl_bn.c   | 24 ++++++++++++++++++++++++
 test/openssl/test_bn.rb | 13 +++++++++++++
 3 files changed, 39 insertions(+)

diff --git a/.gitignore b/.gitignore
index 1be08834f..ef5f6582d 100644
--- a/.gitignore
+++ b/.gitignore
@@ -8,3 +8,5 @@
 ext/openssl/mkmf.log
 ext/openssl/Makefile
 ext/openssl/extconf.h
+.DS_Store
+.idea/
\ No newline at end of file
diff --git a/ext/openssl/ossl_bn.c b/ext/openssl/ossl_bn.c
index 1d43e4572..3e6208f13 100644
--- a/ext/openssl/ossl_bn.c
+++ b/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);
diff --git a/test/openssl/test_bn.rb b/test/openssl/test_bn.rb
index 547d334c6..5f6a4fb47 100644
--- a/test/openssl/test_bn.rb
+++ b/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)