298 lines
8.6 KiB
Go
298 lines
8.6 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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"strconv"
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inf "gopkg.in/inf.v0"
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)
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// Scale is used for getting and setting the base-10 scaled value.
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// Base-2 scales are omitted for mathematical simplicity.
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// See Quantity.ScaledValue for more details.
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type Scale int32
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// infScale adapts a Scale value to an inf.Scale value.
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func (s Scale) infScale() inf.Scale {
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return inf.Scale(-s) // inf.Scale is upside-down
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}
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const (
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Nano Scale = -9
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Micro Scale = -6
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Milli Scale = -3
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Kilo Scale = 3
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Mega Scale = 6
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Giga Scale = 9
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Tera Scale = 12
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Peta Scale = 15
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Exa Scale = 18
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)
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var (
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Zero = int64Amount{}
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// Used by quantity strings - treat as read only
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zeroBytes = []byte("0")
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)
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// int64Amount represents a fixed precision numerator and arbitrary scale exponent. It is faster
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// than operations on inf.Dec for values that can be represented as int64.
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type int64Amount struct {
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value int64
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scale Scale
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}
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// Sign returns 0 if the value is zero, -1 if it is less than 0, or 1 if it is greater than 0.
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func (a int64Amount) Sign() int {
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switch {
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case a.value == 0:
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return 0
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case a.value > 0:
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return 1
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default:
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return -1
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}
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}
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// AsInt64 returns the current amount as an int64 at scale 0, or false if the value cannot be
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// represented in an int64 OR would result in a loss of precision. This method is intended as
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// an optimization to avoid calling AsDec.
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func (a int64Amount) AsInt64() (int64, bool) {
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if a.scale == 0 {
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return a.value, true
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}
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if a.scale < 0 {
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// TODO: attempt to reduce factors, although it is assumed that factors are reduced prior
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// to the int64Amount being created.
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return 0, false
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}
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return positiveScaleInt64(a.value, a.scale)
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}
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// AsScaledInt64 returns an int64 representing the value of this amount at the specified scale,
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// rounding up, or false if that would result in overflow. (1e20).AsScaledInt64(1) would result
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// in overflow because 1e19 is not representable as an int64. Note that setting a scale larger
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// than the current value may result in loss of precision - i.e. (1e-6).AsScaledInt64(0) would
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// return 1, because 0.000001 is rounded up to 1.
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func (a int64Amount) AsScaledInt64(scale Scale) (result int64, ok bool) {
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if a.scale < scale {
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result, _ = negativeScaleInt64(a.value, scale-a.scale)
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return result, true
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}
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return positiveScaleInt64(a.value, a.scale-scale)
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}
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// AsDec returns an inf.Dec representation of this value.
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func (a int64Amount) AsDec() *inf.Dec {
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var base inf.Dec
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base.SetUnscaled(a.value)
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base.SetScale(inf.Scale(-a.scale))
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return &base
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}
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// Cmp returns 0 if a and b are equal, 1 if a is greater than b, or -1 if a is less than b.
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func (a int64Amount) Cmp(b int64Amount) int {
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switch {
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case a.scale == b.scale:
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// compare only the unscaled portion
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case a.scale > b.scale:
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result, remainder, exact := divideByScaleInt64(b.value, a.scale-b.scale)
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if !exact {
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return a.AsDec().Cmp(b.AsDec())
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}
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if result == a.value {
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switch {
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case remainder == 0:
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return 0
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case remainder > 0:
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return -1
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default:
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return 1
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}
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}
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b.value = result
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default:
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result, remainder, exact := divideByScaleInt64(a.value, b.scale-a.scale)
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if !exact {
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return a.AsDec().Cmp(b.AsDec())
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}
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if result == b.value {
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switch {
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case remainder == 0:
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return 0
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case remainder > 0:
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return 1
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default:
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return -1
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}
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}
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a.value = result
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}
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switch {
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case a.value == b.value:
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return 0
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case a.value < b.value:
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return -1
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default:
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return 1
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}
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}
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// Add adds two int64Amounts together, matching scales. It will return false and not mutate
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// a if overflow or underflow would result.
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func (a *int64Amount) Add(b int64Amount) bool {
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switch {
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case b.value == 0:
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return true
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case a.value == 0:
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a.value = b.value
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a.scale = b.scale
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return true
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case a.scale == b.scale:
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c, ok := int64Add(a.value, b.value)
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if !ok {
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return false
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}
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a.value = c
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case a.scale > b.scale:
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c, ok := positiveScaleInt64(a.value, a.scale-b.scale)
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if !ok {
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return false
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}
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c, ok = int64Add(c, b.value)
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if !ok {
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return false
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}
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a.scale = b.scale
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a.value = c
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default:
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c, ok := positiveScaleInt64(b.value, b.scale-a.scale)
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if !ok {
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return false
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}
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c, ok = int64Add(a.value, c)
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if !ok {
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return false
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}
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a.value = c
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}
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return true
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}
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// Sub removes the value of b from the current amount, or returns false if underflow would result.
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func (a *int64Amount) Sub(b int64Amount) bool {
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return a.Add(int64Amount{value: -b.value, scale: b.scale})
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}
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// AsScale adjusts this amount to set a minimum scale, rounding up, and returns true iff no precision
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// was lost. (1.1e5).AsScale(5) would return 1.1e5, but (1.1e5).AsScale(6) would return 1e6.
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func (a int64Amount) AsScale(scale Scale) (int64Amount, bool) {
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if a.scale >= scale {
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return a, true
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}
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result, exact := negativeScaleInt64(a.value, scale-a.scale)
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return int64Amount{value: result, scale: scale}, exact
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}
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// AsCanonicalBytes accepts a buffer to write the base-10 string value of this field to, and returns
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// either that buffer or a larger buffer and the current exponent of the value. The value is adjusted
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// until the exponent is a multiple of 3 - i.e. 1.1e5 would return "110", 3.
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func (a int64Amount) AsCanonicalBytes(out []byte) (result []byte, exponent int32) {
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mantissa := a.value
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exponent = int32(a.scale)
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amount, times := removeInt64Factors(mantissa, 10)
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exponent += int32(times)
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// make sure exponent is a multiple of 3
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var ok bool
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switch exponent % 3 {
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case 1, -2:
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amount, ok = int64MultiplyScale10(amount)
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if !ok {
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return infDecAmount{a.AsDec()}.AsCanonicalBytes(out)
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}
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exponent = exponent - 1
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case 2, -1:
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amount, ok = int64MultiplyScale100(amount)
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if !ok {
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return infDecAmount{a.AsDec()}.AsCanonicalBytes(out)
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}
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exponent = exponent - 2
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}
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return strconv.AppendInt(out, amount, 10), exponent
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}
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// AsCanonicalBase1024Bytes accepts a buffer to write the base-1024 string value of this field to, and returns
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// either that buffer or a larger buffer and the current exponent of the value. 2048 is 2 * 1024 ^ 1 and would
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// return []byte("2048"), 1.
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func (a int64Amount) AsCanonicalBase1024Bytes(out []byte) (result []byte, exponent int32) {
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value, ok := a.AsScaledInt64(0)
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if !ok {
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return infDecAmount{a.AsDec()}.AsCanonicalBase1024Bytes(out)
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}
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amount, exponent := removeInt64Factors(value, 1024)
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return strconv.AppendInt(out, amount, 10), exponent
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}
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// infDecAmount implements common operations over an inf.Dec that are specific to the quantity
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// representation.
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type infDecAmount struct {
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*inf.Dec
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}
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// AsScale adjusts this amount to set a minimum scale, rounding up, and returns true iff no precision
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// was lost. (1.1e5).AsScale(5) would return 1.1e5, but (1.1e5).AsScale(6) would return 1e6.
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func (a infDecAmount) AsScale(scale Scale) (infDecAmount, bool) {
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tmp := &inf.Dec{}
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tmp.Round(a.Dec, scale.infScale(), inf.RoundUp)
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return infDecAmount{tmp}, tmp.Cmp(a.Dec) == 0
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}
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// AsCanonicalBytes accepts a buffer to write the base-10 string value of this field to, and returns
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// either that buffer or a larger buffer and the current exponent of the value. The value is adjusted
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// until the exponent is a multiple of 3 - i.e. 1.1e5 would return "110", 3.
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func (a infDecAmount) AsCanonicalBytes(out []byte) (result []byte, exponent int32) {
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mantissa := a.Dec.UnscaledBig()
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exponent = int32(-a.Dec.Scale())
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amount := big.NewInt(0).Set(mantissa)
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// move all factors of 10 into the exponent for easy reasoning
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amount, times := removeBigIntFactors(amount, bigTen)
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exponent += times
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// make sure exponent is a multiple of 3
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for exponent%3 != 0 {
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amount.Mul(amount, bigTen)
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exponent--
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}
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return append(out, amount.String()...), exponent
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}
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// AsCanonicalBase1024Bytes accepts a buffer to write the base-1024 string value of this field to, and returns
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// either that buffer or a larger buffer and the current exponent of the value. 2048 is 2 * 1024 ^ 1 and would
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// return []byte("2048"), 1.
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func (a infDecAmount) AsCanonicalBase1024Bytes(out []byte) (result []byte, exponent int32) {
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tmp := &inf.Dec{}
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tmp.Round(a.Dec, 0, inf.RoundUp)
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amount, exponent := removeBigIntFactors(tmp.UnscaledBig(), big1024)
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return append(out, amount.String()...), exponent
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}
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