From 2d77efdafb3c3ee17ea8448028b535ea77457cd3 Mon Sep 17 00:00:00 2001
From: Clayton Coleman <ccoleman@redhat.com>
Date: Wed, 28 Apr 2021 13:07:50 -0400
Subject: [PATCH] quantity: Allow a new quantity to be created directly from
 inf.Dec

The normal way to do complex math for quantities would be with
inf.Dec which we allow you to get from a quantity. Once you perform
that math it should be easier to go back to a quantity.
---
 .../k8s.io/apimachinery/pkg/api/resource/quantity.go   |  9 +++++++++
 .../apimachinery/pkg/api/resource/quantity_test.go     | 10 ++++++++++
 2 files changed, 19 insertions(+)

diff --git a/staging/src/k8s.io/apimachinery/pkg/api/resource/quantity.go b/staging/src/k8s.io/apimachinery/pkg/api/resource/quantity.go
index 8d718945d06..2395656cc90 100644
--- a/staging/src/k8s.io/apimachinery/pkg/api/resource/quantity.go
+++ b/staging/src/k8s.io/apimachinery/pkg/api/resource/quantity.go
@@ -696,6 +696,15 @@ func (q *Quantity) UnmarshalJSON(value []byte) error {
 	return nil
 }
 
+// NewDecimalQuantity returns a new Quantity representing the given
+// value in the given format.
+func NewDecimalQuantity(b inf.Dec, format Format) *Quantity {
+	return &Quantity{
+		d:      infDecAmount{&b},
+		Format: format,
+	}
+}
+
 // NewQuantity returns a new Quantity representing the given
 // value in the given format.
 func NewQuantity(value int64, format Format) *Quantity {
diff --git a/staging/src/k8s.io/apimachinery/pkg/api/resource/quantity_test.go b/staging/src/k8s.io/apimachinery/pkg/api/resource/quantity_test.go
index 3c341d056f8..cb459b69d45 100644
--- a/staging/src/k8s.io/apimachinery/pkg/api/resource/quantity_test.go
+++ b/staging/src/k8s.io/apimachinery/pkg/api/resource/quantity_test.go
@@ -392,6 +392,16 @@ func TestQuantityParse(t *testing.T) {
 				got.AsDec()
 			}
 
+			for _, format := range []Format{DecimalSI, BinarySI, DecimalExponent} {
+				// ensure we are not simply checking pointer equality by creating a new inf.Dec
+				var copied inf.Dec
+				copied.Add(inf.NewDec(0, inf.Scale(0)), got.AsDec())
+				q := NewDecimalQuantity(copied, format)
+				if c := q.Cmp(got); c != 0 {
+					t.Errorf("%v: round trip from decimal back to quantity is not comparable: %d: %#v vs %#v", item.input, c, got, q)
+				}
+			}
+
 			// verify that we can decompose the input and get the same result by building up from the base.
 			positive, _, num, denom, suffix, err := parseQuantityString(item.input)
 			if err != nil {