(feat) Add auto-discovery in k8s | Adarsh

vendor/k8s.io/apimachinery/pkg/api/resource/scale_int.go

@@ -0,0 +1,95 @@
+/*
+Copyright 2015 The Kubernetes Authors.
+
+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 (
+	"math"
+	"math/big"
+	"sync"
+)
+
+var (
+	// A sync pool to reduce allocation.
+	intPool  sync.Pool
+	maxInt64 = big.NewInt(math.MaxInt64)
+)
+
+func init() {
+	intPool.New = func() interface{} {
+		return &big.Int{}
+	}
+}
+
+// scaledValue scales given unscaled value from scale to new Scale and returns
+// an int64. It ALWAYS rounds up the result when scale down. The final result might
+// overflow.
+//
+// scale, newScale represents the scale of the unscaled decimal.
+// The mathematical value of the decimal is unscaled * 10**(-scale).
+func scaledValue(unscaled *big.Int, scale, newScale int) int64 {
+	dif := scale - newScale
+	if dif == 0 {
+		return unscaled.Int64()
+	}
+
+	// Handle scale up
+	// This is an easy case, we do not need to care about rounding and overflow.
+	// If any intermediate operation causes overflow, the result will overflow.
+	if dif < 0 {
+		return unscaled.Int64() * int64(math.Pow10(-dif))
+	}
+
+	// Handle scale down
+	// We have to be careful about the intermediate operations.
+
+	// fast path when unscaled < max.Int64 and exp(10,dif) < max.Int64
+	const log10MaxInt64 = 19
+	if unscaled.Cmp(maxInt64) < 0 && dif < log10MaxInt64 {
+		divide := int64(math.Pow10(dif))
+		result := unscaled.Int64() / divide
+		mod := unscaled.Int64() % divide
+		if mod != 0 {
+			return result + 1
+		}
+		return result
+	}
+
+	// We should only convert back to int64 when getting the result.
+	divisor := intPool.Get().(*big.Int)
+	exp := intPool.Get().(*big.Int)
+	result := intPool.Get().(*big.Int)
+	defer func() {
+		intPool.Put(divisor)
+		intPool.Put(exp)
+		intPool.Put(result)
+	}()
+
+	// divisor = 10^(dif)
+	// TODO: create loop up table if exp costs too much.
+	divisor.Exp(bigTen, exp.SetInt64(int64(dif)), nil)
+	// reuse exp
+	remainder := exp
+
+	// result = unscaled / divisor
+	// remainder = unscaled % divisor
+	result.DivMod(unscaled, divisor, remainder)
+	if remainder.Sign() != 0 {
+		return result.Int64() + 1
+	}
+
+	return result.Int64()
+}