117 lines
3.8 KiB
Go
117 lines
3.8 KiB
Go
// Copyright (c) 2013, 2014 Conformal Systems LLC.
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// Use of this source code is governed by an ISC
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// license that can be found in the LICENSE file.
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package btcutil
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import (
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"errors"
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"math"
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"strconv"
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)
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// AmountUnit describes a method of converting an Amount to something
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// other than the base unit of a bitcoin. The value of the AmountUnit
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// is the exponent component of the decadic multiple to convert from
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// an amount in bitcoin to an amount counted in units.
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type AmountUnit int
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// These constants define various units used when describing a bitcoin
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// monetary amount.
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const (
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AmountMegaBTC AmountUnit = 6
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AmountKiloBTC AmountUnit = 3
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AmountBTC AmountUnit = 0
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AmountMilliBTC AmountUnit = -3
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AmountMicroBTC AmountUnit = -6
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AmountSatoshi AmountUnit = -8
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)
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// String returns the unit as a string. For recognized units, the SI
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// prefix is used, or "Satoshi" for the base unit. For all unrecognized
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// units, "1eN BTC" is returned, where N is the AmountUnit.
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func (u AmountUnit) String() string {
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switch u {
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case AmountMegaBTC:
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return "MBTC"
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case AmountKiloBTC:
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return "kBTC"
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case AmountBTC:
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return "BTC"
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case AmountMilliBTC:
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return "mBTC"
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case AmountMicroBTC:
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return "μBTC"
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case AmountSatoshi:
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return "Satoshi"
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default:
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return "1e" + strconv.FormatInt(int64(u), 10) + " BTC"
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}
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}
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// Amount represents the base bitcoin monetary unit (colloquially referred
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// to as a `Satoshi'). A single Amount is equal to 1e-8 of a bitcoin.
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type Amount int64
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// round converts a floating point number, which may or may not be representable
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// as an integer, to the Amount integer type by rounding to the nearest integer.
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// This is performed by adding or subtracting 0.5 depending on the sign, and
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// relying on integer truncation to round the value to the nearest Amount.
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func round(f float64) Amount {
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if f < 0 {
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return Amount(f - 0.5)
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}
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return Amount(f + 0.5)
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}
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// NewAmount creates an Amount from a floating point value representing
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// some value in bitcoin. NewAmount errors if f is NaN or +-Infinity, but
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// does not check that the amount is within the total amount of bitcoin
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// producable as f may not refer to an amount at a single moment in time.
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func NewAmount(f float64) (Amount, error) {
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// The amount is only considered invalid if it cannot be represented
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// as an integer type. This may happen if f is NaN or +-Infinity.
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switch {
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case math.IsNaN(f):
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fallthrough
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case math.IsInf(f, 1):
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fallthrough
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case math.IsInf(f, -1):
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return 0, errors.New("invalid bitcoin amount")
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}
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return round(f * SatoshiPerBitcoin), nil
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}
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// ToUnit converts a monetary amount counted in bitcoin base units to a
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// floating point value representing an amount of bitcoin.
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func (a Amount) ToUnit(u AmountUnit) float64 {
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return float64(a) / math.Pow10(int(u+8))
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}
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// ToBTC is the equivalent of calling ToUnit with AmountBTC.
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func (a Amount) ToBTC() float64 {
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return a.ToUnit(AmountBTC)
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}
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// Format formats a monetary amount counted in bitcoin base units as a
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// string for a given unit. The conversion will succeed for any unit,
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// however, known units will be formated with an appended label describing
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// the units with SI notation, or "Satoshi" for the base unit.
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func (a Amount) Format(u AmountUnit) string {
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units := " " + u.String()
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return strconv.FormatFloat(a.ToUnit(u), 'f', -int(u+8), 64) + units
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}
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// String is the equivalent of calling Format with AmountBTC.
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func (a Amount) String() string {
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return a.Format(AmountBTC)
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}
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// MulF64 multiplies an Amount by a floating point value. While this is not
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// an operation that must typically be done by a full node or wallet, it is
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// useful for services that build on top of bitcoin (for example, calculating
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// a fee by multiplying by a percentage).
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func (a Amount) MulF64(f float64) Amount {
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return round(float64(a) * f)
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}
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