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package mssql
import (
"encoding/binary"
"errors"
"math"
"math/big"
)
// http://msdn.microsoft.com/en-us/library/ee780893.aspx
type Decimal struct {
integer [4]uint32
positive bool
prec uint8
scale uint8
}
var scaletblflt64 [39]float64
func (d Decimal) ToFloat64() float64 {
val := float64(0)
for i := 3; i >= 0; i-- {
val *= 0x100000000
val += float64(d.integer[i])
}
if !d.positive {
val = -val
}
if d.scale != 0 {
val /= scaletblflt64[d.scale]
}
return val
}
const autoScale = 100
func Float64ToDecimal(f float64) (Decimal, error) {
return Float64ToDecimalScale(f, autoScale)
}
func Float64ToDecimalScale(f float64, scale uint8) (Decimal, error) {
var dec Decimal
if math.IsNaN(f) {
return dec, errors.New("NaN")
}
if math.IsInf(f, 0) {
return dec, errors.New("Infinity can't be converted to decimal")
}
dec.positive = f >= 0
if !dec.positive {
f = math.Abs(f)
}
if f > 3.402823669209385e+38 {
return dec, errors.New("Float value is out of range")
}
dec.prec = 20
var integer float64
for dec.scale = 0; dec.scale <= scale; dec.scale++ {
integer = f * scaletblflt64[dec.scale]
_, frac := math.Modf(integer)
if frac == 0 && scale == autoScale {
break
}
}
for i := 0; i < 4; i++ {
mod := math.Mod(integer, 0x100000000)
integer -= mod
integer /= 0x100000000
dec.integer[i] = uint32(mod)
}
return dec, nil
}
func init() {
var acc float64 = 1
for i := 0; i <= 38; i++ {
scaletblflt64[i] = acc
acc *= 10
}
}
func (d Decimal) BigInt() big.Int {
bytes := make([]byte, 16)
binary.BigEndian.PutUint32(bytes[0:4], d.integer[3])
binary.BigEndian.PutUint32(bytes[4:8], d.integer[2])
binary.BigEndian.PutUint32(bytes[8:12], d.integer[1])
binary.BigEndian.PutUint32(bytes[12:16], d.integer[0])
var x big.Int
x.SetBytes(bytes)
if !d.positive {
x.Neg(&x)
}
return x
}
func (d Decimal) Bytes() []byte {
x := d.BigInt()
return scaleBytes(x.String(), d.scale)
}
func (d Decimal) UnscaledBytes() []byte {
x := d.BigInt()
return x.Bytes()
}
func scaleBytes(s string, scale uint8) []byte {
z := make([]byte, 0, len(s)+1)
if s[0] == '-' || s[0] == '+' {
z = append(z, byte(s[0]))
s = s[1:]
}
pos := len(s) - int(scale)
if pos <= 0 {
z = append(z, byte('0'))
} else if pos > 0 {
z = append(z, []byte(s[:pos])...)
}
if scale > 0 {
z = append(z, byte('.'))
for pos < 0 {
z = append(z, byte('0'))
pos++
}
z = append(z, []byte(s[pos:])...)
}
return z
}
func (d Decimal) String() string {
return string(d.Bytes())
}
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