mirror of
https://github.com/ceph/ceph-csi.git
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311 lines
7.3 KiB
Go
311 lines
7.3 KiB
Go
/*
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Copyright 2014 The Kubernetes Authors.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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package resource
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import (
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"math/big"
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inf "gopkg.in/inf.v0"
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)
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const (
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// maxInt64Factors is the highest value that will be checked when removing factors of 10 from an int64.
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// It is also the maximum decimal digits that can be represented with an int64.
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maxInt64Factors = 18
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)
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var (
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// Commonly needed big.Int values-- treat as read only!
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bigTen = big.NewInt(10)
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bigZero = big.NewInt(0)
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bigOne = big.NewInt(1)
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bigThousand = big.NewInt(1000)
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big1024 = big.NewInt(1024)
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// Commonly needed inf.Dec values-- treat as read only!
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decZero = inf.NewDec(0, 0)
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decOne = inf.NewDec(1, 0)
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// Largest (in magnitude) number allowed.
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maxAllowed = infDecAmount{inf.NewDec((1<<63)-1, 0)} // == max int64
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// The maximum value we can represent milli-units for.
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// Compare with the return value of Quantity.Value() to
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// see if it's safe to use Quantity.MilliValue().
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MaxMilliValue = int64(((1 << 63) - 1) / 1000)
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)
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const mostNegative = -(mostPositive + 1)
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const mostPositive = 1<<63 - 1
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// int64Add returns a+b, or false if that would overflow int64.
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func int64Add(a, b int64) (int64, bool) {
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c := a + b
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switch {
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case a > 0 && b > 0:
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if c < 0 {
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return 0, false
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}
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case a < 0 && b < 0:
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if c > 0 {
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return 0, false
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}
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if a == mostNegative && b == mostNegative {
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return 0, false
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}
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}
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return c, true
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}
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// int64Multiply returns a*b, or false if that would overflow or underflow int64.
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func int64Multiply(a, b int64) (int64, bool) {
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if a == 0 || b == 0 || a == 1 || b == 1 {
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return a * b, true
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}
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if a == mostNegative || b == mostNegative {
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return 0, false
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}
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c := a * b
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return c, c/b == a
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}
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// int64MultiplyScale returns a*b, assuming b is greater than one, or false if that would overflow or underflow int64.
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// Use when b is known to be greater than one.
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func int64MultiplyScale(a int64, b int64) (int64, bool) {
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if a == 0 || a == 1 {
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return a * b, true
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}
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if a == mostNegative && b != 1 {
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return 0, false
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}
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c := a * b
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return c, c/b == a
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}
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// int64MultiplyScale10 multiplies a by 10, or returns false if that would overflow. This method is faster than
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// int64Multiply(a, 10) because the compiler can optimize constant factor multiplication.
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func int64MultiplyScale10(a int64) (int64, bool) {
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if a == 0 || a == 1 {
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return a * 10, true
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}
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if a == mostNegative {
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return 0, false
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}
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c := a * 10
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return c, c/10 == a
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}
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// int64MultiplyScale100 multiplies a by 100, or returns false if that would overflow. This method is faster than
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// int64Multiply(a, 100) because the compiler can optimize constant factor multiplication.
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func int64MultiplyScale100(a int64) (int64, bool) {
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if a == 0 || a == 1 {
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return a * 100, true
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}
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if a == mostNegative {
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return 0, false
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}
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c := a * 100
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return c, c/100 == a
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}
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// int64MultiplyScale1000 multiplies a by 1000, or returns false if that would overflow. This method is faster than
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// int64Multiply(a, 1000) because the compiler can optimize constant factor multiplication.
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func int64MultiplyScale1000(a int64) (int64, bool) {
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if a == 0 || a == 1 {
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return a * 1000, true
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}
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if a == mostNegative {
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return 0, false
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}
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c := a * 1000
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return c, c/1000 == a
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}
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// positiveScaleInt64 multiplies base by 10^scale, returning false if the
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// value overflows. Passing a negative scale is undefined.
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func positiveScaleInt64(base int64, scale Scale) (int64, bool) {
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switch scale {
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case 0:
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return base, true
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case 1:
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return int64MultiplyScale10(base)
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case 2:
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return int64MultiplyScale100(base)
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case 3:
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return int64MultiplyScale1000(base)
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case 6:
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return int64MultiplyScale(base, 1000000)
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case 9:
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return int64MultiplyScale(base, 1000000000)
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default:
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value := base
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var ok bool
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for i := Scale(0); i < scale; i++ {
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if value, ok = int64MultiplyScale(value, 10); !ok {
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return 0, false
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}
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}
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return value, true
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}
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}
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// negativeScaleInt64 reduces base by the provided scale, rounding up, until the
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// value is zero or the scale is reached. Passing a negative scale is undefined.
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// The value returned, if not exact, is rounded away from zero.
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func negativeScaleInt64(base int64, scale Scale) (result int64, exact bool) {
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if scale == 0 {
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return base, true
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}
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value := base
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var fraction bool
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for i := Scale(0); i < scale; i++ {
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if !fraction && value%10 != 0 {
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fraction = true
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}
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value = value / 10
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if value == 0 {
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if fraction {
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if base > 0 {
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return 1, false
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}
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return -1, false
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}
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return 0, true
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}
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}
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if fraction {
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if base > 0 {
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value++
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} else {
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value--
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}
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}
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return value, !fraction
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}
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func pow10Int64(b int64) int64 {
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switch b {
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case 0:
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return 1
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case 1:
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return 10
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case 2:
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return 100
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case 3:
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return 1000
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case 4:
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return 10000
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case 5:
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return 100000
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case 6:
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return 1000000
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case 7:
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return 10000000
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case 8:
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return 100000000
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case 9:
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return 1000000000
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case 10:
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return 10000000000
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case 11:
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return 100000000000
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case 12:
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return 1000000000000
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case 13:
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return 10000000000000
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case 14:
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return 100000000000000
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case 15:
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return 1000000000000000
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case 16:
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return 10000000000000000
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case 17:
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return 100000000000000000
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case 18:
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return 1000000000000000000
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default:
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return 0
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}
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}
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// negativeScaleInt64 returns the result of dividing base by scale * 10 and the remainder, or
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// false if no such division is possible. Dividing by negative scales is undefined.
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func divideByScaleInt64(base int64, scale Scale) (result, remainder int64, exact bool) {
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if scale == 0 {
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return base, 0, true
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}
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// the max scale representable in base 10 in an int64 is 18 decimal places
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if scale >= 18 {
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return 0, base, false
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}
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divisor := pow10Int64(int64(scale))
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return base / divisor, base % divisor, true
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}
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// removeInt64Factors divides in a loop; the return values have the property that
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// value == result * base ^ scale
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func removeInt64Factors(value int64, base int64) (result int64, times int32) {
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times = 0
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result = value
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negative := result < 0
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if negative {
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result = -result
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}
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switch base {
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// allow the compiler to optimize the common cases
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case 10:
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for result >= 10 && result%10 == 0 {
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times++
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result = result / 10
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}
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// allow the compiler to optimize the common cases
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case 1024:
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for result >= 1024 && result%1024 == 0 {
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times++
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result = result / 1024
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}
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default:
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for result >= base && result%base == 0 {
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times++
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result = result / base
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}
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}
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if negative {
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result = -result
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}
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return result, times
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}
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// removeBigIntFactors divides in a loop; the return values have the property that
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// d == result * factor ^ times
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// d may be modified in place.
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// If d == 0, then the return values will be (0, 0)
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func removeBigIntFactors(d, factor *big.Int) (result *big.Int, times int32) {
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q := big.NewInt(0)
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m := big.NewInt(0)
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for d.Cmp(bigZero) != 0 {
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q.DivMod(d, factor, m)
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if m.Cmp(bigZero) != 0 {
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break
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}
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times++
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d, q = q, d
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}
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return d, times
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}
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