Add an int64 quantity implementation

Provides fast transformations of int64 scaled values with overflow to
inf.Dec as needed. Attempts to reduce allocations and expensive
operations in the critical path.

Alters the public signature of Quantity to encourage more efficient use

pkg/api/resource/amount_test.go

@@ -0,0 +1,111 @@
+/*
+Copyright 2014 The Kubernetes Authors All rights reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package resource
+
+import (
+	"testing"
+)
+
+func TestInt64AmountAsInt64(t *testing.T) {
+	for _, test := range []struct {
+		value  int64
+		scale  Scale
+		result int64
+		ok     bool
+	}{
+		{100, 0, 100, true},
+		{100, 1, 1000, true},
+		{100, -5, 0, false},
+		{100, 100, 0, false},
+	} {
+		r, ok := int64Amount{value: test.value, scale: test.scale}.AsInt64()
+		if r != test.result {
+			t.Errorf("%v: unexpected result: %d", test, r)
+		}
+		if ok != test.ok {
+			t.Errorf("%v: unexpected ok: %t", test, ok)
+		}
+	}
+}
+
+func TestInt64AmountAdd(t *testing.T) {
+	for _, test := range []struct {
+		a, b, c int64Amount
+		ok      bool
+	}{
+		{int64Amount{value: 100, scale: 1}, int64Amount{value: 10, scale: 2}, int64Amount{value: 200, scale: 1}, true},
+		{int64Amount{value: 100, scale: 1}, int64Amount{value: 1, scale: 2}, int64Amount{value: 110, scale: 1}, true},
+		{int64Amount{value: 100, scale: 1}, int64Amount{value: 1, scale: 100}, int64Amount{value: 1, scale: 100}, false},
+		{int64Amount{value: -5, scale: 2}, int64Amount{value: 50, scale: 1}, int64Amount{value: 0, scale: 1}, true},
+		{int64Amount{value: -5, scale: 2}, int64Amount{value: 5, scale: 2}, int64Amount{value: 0, scale: 2}, true},
+
+		{int64Amount{value: mostPositive, scale: -1}, int64Amount{value: 1, scale: -1}, int64Amount{value: 0, scale: -1}, false},
+		{int64Amount{value: mostPositive, scale: -1}, int64Amount{value: 0, scale: -1}, int64Amount{value: mostPositive, scale: -1}, true},
+		{int64Amount{value: mostPositive / 10, scale: 1}, int64Amount{value: 10, scale: 0}, int64Amount{value: mostPositive, scale: -1}, false},
+	} {
+		c := test.a
+		ok := c.Add(test.b)
+		if ok != test.ok {
+			t.Errorf("%v: unexpected ok: %t", test, ok)
+		}
+		if ok {
+			if c != test.c {
+				t.Errorf("%v: unexpected result: %d", test, c)
+			}
+		} else {
+			if c != test.a {
+				t.Errorf("%v: overflow addition mutated source: %d", test, c)
+			}
+		}
+
+		// addition is commutative
+		c = test.b
+		if ok := c.Add(test.a); ok != test.ok {
+			t.Errorf("%v: unexpected ok: %t", test, ok)
+		}
+		if ok {
+			if c != test.c {
+				t.Errorf("%v: unexpected result: %d", test, c)
+			}
+		} else {
+			if c != test.b {
+				t.Errorf("%v: overflow addition mutated source: %d", test, c)
+			}
+		}
+	}
+}
+func TestInt64AsCanonicalString(t *testing.T) {
+	for _, test := range []struct {
+		value    int64
+		scale    Scale
+		result   string
+		exponent int32
+	}{
+		{100, 0, "100", 0},
+		{100, 1, "1", 3},
+		{100, -1, "10", 0},
+		{10800, -10, "1080", -9},
+	} {
+		r, exp := int64Amount{value: test.value, scale: test.scale}.AsCanonicalBytes(nil)
+		if string(r) != test.result {
+			t.Errorf("%v: unexpected result: %s", test, r)
+		}
+		if exp != test.exponent {
+			t.Errorf("%v: unexpected exponent: %d", test, exp)
+		}
+	}
+}