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