mirror of
https://github.com/go-gitea/gitea.git
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253 lines
5.5 KiB
Go
253 lines
5.5 KiB
Go
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package decimal
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import (
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"encoding/binary"
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"errors"
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"fmt"
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"math"
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"math/big"
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"strings"
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)
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// Decimal represents decimal type in the Microsoft Open Specifications: http://msdn.microsoft.com/en-us/library/ee780893.aspx
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type Decimal struct {
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integer [4]uint32 // Little-endian
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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 (
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scaletblflt64 [39]float64
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int10 big.Int
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int1e5 big.Int
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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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int10.SetInt64(10)
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int1e5.SetInt64(1e5)
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}
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const autoScale = 100
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// SetInteger sets the ind'th element in the integer array
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func (d *Decimal) SetInteger(integer uint32, ind uint8) {
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d.integer[ind] = integer
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}
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// SetPositive sets the positive member
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func (d *Decimal) SetPositive(positive bool) {
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d.positive = positive
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}
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// SetPrec sets the prec member
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func (d *Decimal) SetPrec(prec uint8) {
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d.prec = prec
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}
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// SetScale sets the scale member
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func (d *Decimal) SetScale(scale uint8) {
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d.scale = scale
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}
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// IsPositive returns true if the Decimal is positive
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func (d *Decimal) IsPositive() bool {
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return d.positive
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}
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// ToFloat64 converts decimal to a 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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// BigInt converts decimal to a bigint
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func (d Decimal) BigInt() big.Int {
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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 x
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}
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// Bytes converts decimal to a scaled byte slice
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func (d Decimal) Bytes() []byte {
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x := d.BigInt()
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return ScaleBytes(x.String(), d.scale)
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}
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// UnscaledBytes converts decimal to a unscaled byte slice
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func (d Decimal) UnscaledBytes() []byte {
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x := d.BigInt()
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return x.Bytes()
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}
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// String converts decimal to a string
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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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// Float64ToDecimal converts float64 to decimal
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func Float64ToDecimal(f float64) (Decimal, error) {
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return Float64ToDecimalScale(f, autoScale)
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}
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// Float64ToDecimalScale converts float64 to decimal; user can specify the scale
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func Float64ToDecimalScale(f float64, scale uint8) (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 <= scale; 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 && scale == autoScale {
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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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if mod-math.Trunc(mod) >= 0.5 {
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dec.integer[i] = uint32(mod) + 1
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}
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}
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return dec, nil
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}
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// Int64ToDecimalScale converts float64 to decimal; user can specify the scale
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func Int64ToDecimalScale(v int64, scale uint8) Decimal {
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positive := v >= 0
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if !positive {
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if v == math.MinInt64 {
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// Special case - can't negate
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return Decimal{
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integer: [4]uint32{0, 0x80000000, 0, 0},
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positive: false,
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prec: 20,
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scale: 0,
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}
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}
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v = -v
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}
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return Decimal{
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integer: [4]uint32{uint32(v), uint32(v >> 32), 0, 0},
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positive: positive,
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prec: 20,
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scale: scale,
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}
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}
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// StringToDecimalScale converts string to decimal
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func StringToDecimalScale(v string, outScale uint8) (Decimal, error) {
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var r big.Int
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var unscaled string
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var inScale int
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point := strings.LastIndexByte(v, '.')
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if point == -1 {
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inScale = 0
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unscaled = v
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} else {
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inScale = len(v) - point - 1
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unscaled = v[:point] + v[point+1:]
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}
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if inScale > math.MaxUint8 {
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return Decimal{}, fmt.Errorf("can't parse %q as a decimal number: scale too large", v)
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}
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_, ok := r.SetString(unscaled, 10)
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if !ok {
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return Decimal{}, fmt.Errorf("can't parse %q as a decimal number", v)
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}
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if inScale > int(outScale) {
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return Decimal{}, fmt.Errorf("can't parse %q as a decimal number: scale %d is larger than the scale %d of the target column", v, inScale, outScale)
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}
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for inScale < int(outScale) {
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if int(outScale)-inScale >= 5 {
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r.Mul(&r, &int1e5)
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inScale += 5
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} else {
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r.Mul(&r, &int10)
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inScale++
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}
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}
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bytes := r.Bytes()
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if len(bytes) > 16 {
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return Decimal{}, fmt.Errorf("can't parse %q as a decimal number: precision too large", v)
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}
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var out [4]uint32
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for i, b := range bytes {
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pos := len(bytes) - i - 1
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out[pos/4] += uint32(b) << uint(pos%4*8)
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}
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return Decimal{
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integer: out,
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positive: r.Sign() >= 0,
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prec: 20,
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scale: uint8(inScale),
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}, nil
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}
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// ScaleBytes converts a stringified decimal to a scaled byte slice
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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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