feat(math): add mutative api for BigDec.BigInt() (#6993)

* add API BigIntMut for BigDec

* Update osmomath/decimal.go

Co-authored-by: Matt, Park <45252226+mattverse@users.noreply.github.com>

* rename

* changelog

---------

Co-authored-by: Matt, Park <45252226+mattverse@users.noreply.github.com>

CHANGELOG.md

@@ -49,6 +49,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Features
 
+* [#6804](https://github.com/osmosis-labs/osmosis/pull/6993) feat(math): add mutative api for BigDec.BigInt()
 * [#6804](https://github.com/osmosis-labs/osmosis/pull/6804) feat: track and query protocol rev across all modules
 
 ### Fix Localosmosis docker-compose with state.

osmomath/decimal.go

@@ -248,6 +248,15 @@ func (d BigDec) BigInt() *big.Int {
 	return cp.Set(d.i)
 }
 
+// BigIntMut converts BigDec to big.Int, mutative the input
+func (d BigDec) ToBigInt() *big.Int {
+	if d.IsNil() {
+		return nil
+	}
+
+	return d.i
+}
+
 // addition
 func (d BigDec) Add(d2 BigDec) BigDec {
 	copy := d.Clone()

osmomath/decimal_test.go

@@ -1701,3 +1701,23 @@ func (s *decimalTestSuite) TestQuoTruncate_MutativeAndNonMutative() {
 		})
 	}
 }
+
+func (s *decimalTestSuite) TestBigIntMut() {
+	r := big.NewInt(30)
+	d := osmomath.NewBigDecFromBigInt(r)
+
+	// Compare value of BigInt & BigIntMut
+	s.Require().Equal(d.BigInt(), d.ToBigInt())
+
+	// Modify BigIntMut() pointer and ensure i.BigIntMut() & i.BigInt() change
+	p1 := d.ToBigInt()
+	p1.SetInt64(40)
+	s.Require().Equal(big.NewInt(40), d.ToBigInt())
+	s.Require().Equal(big.NewInt(40), d.BigInt())
+
+	// Modify big.Int() pointer and ensure i.BigIntMut() & i.BigInt() don't change
+	p2 := d.BigInt()
+	p2.SetInt64(50)
+	s.Require().NotEqual(big.NewInt(50), d.ToBigInt())
+	s.Require().NotEqual(big.NewInt(50), d.BigInt())
+}