81 lines
1.6 KiB
Go
81 lines
1.6 KiB
Go
|
package fixedn
|
||
|
|
|
||
|
|
import (
|
||
|
|
"errors"
|
||
|
|
"fmt"
|
||
|
|
"math/big"
|
||
|
|
"strconv"
|
||
|
|
"strings"
|
||
|
|
)
|
||
|
|
|
||
|
|
const maxAllowedPrecision = 16
|
||
|
|
|
||
|
|
// ErrInvalidFormat is returned when decimal format is invalid.
|
||
|
|
var ErrInvalidFormat = errors.New("invalid decimal format")
|
||
|
|
|
||
|
|
var _pow10 []*big.Int
|
||
|
|
|
||
|
|
func init() {
|
||
|
|
var p = int64(1)
|
||
|
|
for i := 0; i <= maxAllowedPrecision; i++ {
|
||
|
|
_pow10 = append(_pow10, big.NewInt(p))
|
||
|
|
p *= 10
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
func pow10(n int) *big.Int {
|
||
|
|
last := len(_pow10) - 1
|
||
|
|
if n <= last {
|
||
|
|
return _pow10[n]
|
||
|
|
}
|
||
|
|
p := new(big.Int)
|
||
|
|
p.Mul(_pow10[last], _pow10[1])
|
||
|
|
for i := last + 1; i < n; i++ {
|
||
|
|
p.Mul(p, _pow10[1])
|
||
|
|
}
|
||
|
|
return p
|
||
|
|
}
|
||
|
|
|
||
|
|
// ToString converts big decimal with specified precision to string.
|
||
|
|
func ToString(bi *big.Int, precision int) string {
|
||
|
|
var dp, fp big.Int
|
||
|
|
dp.QuoRem(bi, pow10(precision), &fp)
|
||
|
|
|
||
|
|
var s = dp.String()
|
||
|
|
if fp.Sign() == 0 {
|
||
|
|
return s
|
||
|
|
}
|
||
|
|
frac := fp.Uint64()
|
||
|
|
trimmed := 0
|
||
|
|
for ; frac%10 == 0; frac /= 10 {
|
||
|
|
trimmed++
|
||
|
|
}
|
||
|
|
return s + "." + fmt.Sprintf("%0"+strconv.FormatUint(uint64(precision-trimmed), 10)+"d", frac)
|
||
|
|
}
|
||
|
|
|
||
|
|
// FromString converts string to a big decimal with specified precision.
|
||
|
|
func FromString(s string, precision int) (*big.Int, error) {
|
||
|
|
parts := strings.SplitN(s, ".", 2)
|
||
|
|
bi, ok := new(big.Int).SetString(parts[0], 10)
|
||
|
|
if !ok {
|
||
|
|
return nil, ErrInvalidFormat
|
||
|
|
}
|
||
|
|
bi.Mul(bi, pow10(precision))
|
||
|
|
if len(parts) == 1 {
|
||
|
|
return bi, nil
|
||
|
|
}
|
||
|
|
|
||
|
|
if len(parts[1]) > precision {
|
||
|
|
return nil, ErrInvalidFormat
|
||
|
|
}
|
||
|
|
fp, ok := new(big.Int).SetString(parts[1], 10)
|
||
|
|
if !ok {
|
||
|
|
return nil, ErrInvalidFormat
|
||
|
|
}
|
||
|
|
fp.Mul(fp, pow10(precision-len(parts[1])))
|
||
|
|
if bi.Sign() == -1 {
|
||
|
|
return bi.Sub(bi, fp), nil
|
||
|
|
}
|
||
|
|
return bi.Add(bi, fp), nil
|
||
|
|
}
|