76 lines
2.0 KiB
Go
76 lines
2.0 KiB
Go
// Copyright (C) 2019 Storj Labs, Inc.
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// See LICENSE for copying information.
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package currency
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import (
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"math"
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"strconv"
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"github.com/shopspring/decimal"
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"github.com/zeebo/errs"
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)
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var (
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maxInt64 = decimal.NewFromInt(math.MaxInt64)
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// Zero is a MicroUnit representing 0.
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Zero MicroUnit
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)
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// NewMicroUnit returns a MicroUnit with v. Much like a time.Duration, a value
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// of 1 means 1e-6 or one millionth of a unit of currency.
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func NewMicroUnit(v int64) MicroUnit {
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return MicroUnit{v: v}
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}
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// MicroUnit represents 1e-6 or one millionth of a unit of currency (e.g. one
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// millionth of a dollar). It is used instead of a floating point type to
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// prevent rounding errors.
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type MicroUnit struct{ v int64 }
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// Value returns the underlying MicroUnit value.
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func (m MicroUnit) Value() int64 { return m.v }
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// Decimal returns the a decimal form of the MicroUnit.
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func (m MicroUnit) Decimal() decimal.Decimal {
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return decimal.New(m.v, -6)
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}
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// FloatString returns a string fixed to 6 decimal places.
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func (m MicroUnit) FloatString() string {
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return m.Decimal().StringFixed(6)
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}
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// MicroUnitFromFloatString parses the string from FloatString into a MicroUnit.
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func MicroUnitFromFloatString(s string) (MicroUnit, error) {
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d, err := decimal.NewFromString(s)
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if err != nil {
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return MicroUnit{}, errs.Wrap(err)
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}
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return MicroUnitFromDecimal(d)
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}
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// MicroUnitFromDecimal returns a MicroUnit from a decimal value and returns an
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// error if there is not enough precision.
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func MicroUnitFromDecimal(d decimal.Decimal) (MicroUnit, error) {
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m := d.Shift(6).Truncate(0)
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if m.GreaterThan(maxInt64) {
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return MicroUnit{}, errs.New("%s overflows micro-unit", d)
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}
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return MicroUnit{v: m.IntPart()}, nil
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}
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// MarshalCSV does the custom marshaling of MicroUnits.
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func (m MicroUnit) MarshalCSV() (string, error) { return strconv.FormatInt(m.v, 10), nil }
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// UnmarshalCSV reads the MicroUnit in CSV form.
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func (m *MicroUnit) UnmarshalCSV(s string) (err error) {
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v, err := strconv.ParseInt(s, 10, 64)
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if err != nil {
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return err
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}
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m.v = v
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return nil
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}
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