// ParseQuantity turns str into a Quantity, or returns an error.
func ParseQuantity(str string) (*Quantity, error) {
parts := splitRE.FindStringSubmatch(strings.TrimSpace(str))
// regexp returns are entire match, followed by an entry for each () section.
if len(parts) != 3 {
return nil, ErrFormatWrong
}
amount := new(inf.Dec)
if _, ok := amount.SetString(parts[1]); !ok {
return nil, ErrNumeric
}
base, exponent, format, ok := quantitySuffixer.interpret(suffix(parts[2]))
if !ok {
return nil, ErrSuffix
}
// So that no one but us has to think about suffixes, remove it.
if base == 10 {
amount.SetScale(amount.Scale() + inf.Scale(-exponent))
} else if base == 2 {
// numericSuffix = 2 ** exponent
numericSuffix := big.NewInt(1).Lsh(bigOne, uint(exponent))
ub := amount.UnscaledBig()
amount.SetUnscaledBig(ub.Mul(ub, numericSuffix))
}
// Cap at min/max bounds.
sign := amount.Sign()
if sign == -1 {
amount.Neg(amount)
}
// This rounds non-zero values up to the minimum representable
// value, under the theory that if you want some resources, you
// should get some resources, even if you asked for way too small
// of an amount.
// Arguably, this should be inf.RoundHalfUp (normal rounding), but
// that would have the side effect of rounding values < .5m to zero.
if v, ok := amount.Unscaled(); v != int64(0) || !ok {
amount.Round(amount, 3, inf.RoundUp)
}
// The max is just a simple cap.
if amount.Cmp(maxAllowed) > 0 {
amount.Set(maxAllowed)
}
if format == BinarySI && amount.Cmp(decOne) < 0 && amount.Cmp(decZero) > 0 {
// This avoids rounding and hopefully confusion, too.
format = DecimalSI
}
if sign == -1 {
amount.Neg(amount)
}
return &Quantity{amount, format}, nil
}