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quantity.go
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quantity.go
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package quantity
import (
"encoding"
"errors"
"math/big"
)
var (
// ErrInvalidQuantity is the error returned on malformed arguments.
ErrInvalidQuantity = errors.New("invalid quantity")
// ErrInsufficientBalance is the error returned when an operation
// fails due to insufficient balance.
ErrInsufficientBalance = errors.New("insufficient balance")
// ErrInvalidAccount is the error returned when an operation fails
// due to a missing account.
ErrInvalidAccount = errors.New("invalid account")
_ encoding.BinaryMarshaler = (*Quantity)(nil)
_ encoding.BinaryUnmarshaler = (*Quantity)(nil)
zero big.Int
)
// Quantity is a arbitrary precision unsigned integer that never underflows.
type Quantity struct {
inner big.Int
}
// Clone copies a Quantity.
func (q *Quantity) Clone() *Quantity {
tmp := NewQuantity()
tmp.inner.Set(&q.inner)
return tmp
}
// MarshalBinary encodes a Quantity into binary form.
func (q *Quantity) MarshalBinary() ([]byte, error) {
return append([]byte{}, q.inner.Bytes()...), nil
}
// UnmarshalBinary decodes a byte slice into a Quantity.
func (q *Quantity) UnmarshalBinary(data []byte) error {
var tmp big.Int
tmp.SetBytes(data)
q.inner.Set(&tmp)
if !q.IsValid() {
return ErrInvalidQuantity
}
return nil
}
// MarshalText encodes a Quantity into text form.
func (q Quantity) MarshalText() ([]byte, error) {
return q.inner.MarshalText()
}
// UnmarshalText decodes a text slice into a Quantity.
func (q *Quantity) UnmarshalText(text []byte) error {
var tmp big.Int
if err := tmp.UnmarshalText(text); err != nil {
return err
}
q.inner.Set(&tmp)
if !q.IsValid() {
return ErrInvalidQuantity
}
return nil
}
// FromInt64 converts from an int64 to a Quantity.
func (q *Quantity) FromInt64(n int64) error {
return q.FromBigInt(big.NewInt(n))
}
// FromUint64 converts from an uint64 to a Quantity.
func (q *Quantity) FromUint64(n uint64) error {
var tmp big.Int
tmp.SetUint64(n)
return q.FromBigInt(&tmp)
}
// FromBigInt converts from a big.Int to a Quantity.
func (q *Quantity) FromBigInt(n *big.Int) error {
if n == nil || !isValid(n) {
return ErrInvalidQuantity
}
q.inner.Set(n)
return nil
}
// ToBigInt converts from a Quantity to a big.Int.
func (q *Quantity) ToBigInt() *big.Int {
var tmp big.Int
tmp.Set(&q.inner)
return &tmp
}
// Add adds n to q, returning an error if n < 0 or n == nil.
func (q *Quantity) Add(n *Quantity) error {
if n == nil || !n.IsValid() {
return ErrInvalidQuantity
}
q.inner.Add(&q.inner, &n.inner)
return nil
}
// Sub subtracts exactly n from q, returning an error if q < n, n < 0 or
// n == nil.
func (q *Quantity) Sub(n *Quantity) error {
if n == nil || !n.IsValid() {
return ErrInvalidQuantity
}
if q.inner.Cmp(&n.inner) == -1 {
return ErrInsufficientBalance
}
q.inner.Sub(&q.inner, &n.inner)
return nil
}
// SubUpTo subtracts up to n from q, and returns the amount subtracted,
// returning an error if n < 0 or n == nil.
func (q *Quantity) SubUpTo(n *Quantity) (*Quantity, error) {
if n == nil || !n.IsValid() {
return nil, ErrInvalidQuantity
}
var amount big.Int
switch q.Cmp(n) {
case -1:
amount.Set(&q.inner)
default:
amount.Set(&n.inner)
}
q.inner.Sub(&q.inner, &amount)
return &Quantity{inner: amount}, nil
}
// Mul multiplies n with q, returning an error if n < 0 or n == nil.
func (q *Quantity) Mul(n *Quantity) error {
if n == nil || !n.IsValid() {
return ErrInvalidQuantity
}
q.inner.Mul(&q.inner, &n.inner)
return nil
}
// Quo divides q with n, returning an error if n <= 0 or n == nil.
func (q *Quantity) Quo(n *Quantity) error {
if n == nil || !n.IsValid() || n.IsZero() {
return ErrInvalidQuantity
}
q.inner.Quo(&q.inner, &n.inner)
return nil
}
// Cmp returns -1 if q < n, 0 if q == n, and 1 if q > n.
func (q *Quantity) Cmp(n *Quantity) int {
return q.inner.Cmp(&n.inner)
}
// IsZero returns true iff the quantity is zero.
func (q *Quantity) IsZero() bool {
return q.inner.CmpAbs(&zero) == 0
}
// String returns the string representation of q.
func (q Quantity) String() string {
// Return the string representation of inner directly if the value
// is invalid, for the purpose of error messages.
if !q.IsValid() {
return q.inner.String()
}
var tmp big.Int
tmp.Abs(&q.inner)
return tmp.String()
}
// IsValid returns true iff the quantity is in the valid range.
func (q *Quantity) IsValid() bool {
return isValid(&q.inner)
}
// New creates a new Quantity, initialized to zero.
func NewQuantity() (q *Quantity) {
return &Quantity{}
}
// NewFromUint64 creates a new Quantity from an uint64 or panics.
func NewFromUint64(n uint64) *Quantity {
var q Quantity
if err := q.FromUint64(n); err != nil {
panic(err)
}
return &q
}
func isValid(n *big.Int) bool {
return n.Cmp(&zero) >= 0
}
// Move moves exactly n from src to dst. On failures neither src nor dst
// are altered.
func Move(dst, src, n *Quantity) error {
if dst == nil || src == nil {
return ErrInvalidAccount
}
if src == n {
n = n.Clone()
}
if err := src.Sub(n); err != nil {
return err
}
_ = dst.Add(n)
return nil
}
// MoveUpTo moves up to n from src to dst, and returns the amount moved.
// On failures neither src nor dst are altered.
func MoveUpTo(dst, src, n *Quantity) (*Quantity, error) {
if dst == nil || src == nil {
return nil, ErrInvalidAccount
}
amount, err := src.SubUpTo(n)
if err != nil {
return nil, err
}
_ = dst.Add(amount)
return amount, nil
}