gitea/vendor/go.mongodb.org/mongo-driver/bson/primitive/decimal.go

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// Copyright (C) MongoDB, Inc. 2017-present.
//
// Licensed under the Apache License, Version 2.0 (the "License"); you may
// not use this file except in compliance with the License. You may obtain
// a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
//
// Based on gopkg.in/mgo.v2/bson by Gustavo Niemeyer
// See THIRD-PARTY-NOTICES for original license terms.
package primitive
import (
"errors"
"fmt"
"math/big"
"regexp"
"strconv"
"strings"
)
// These constants are the maximum and minimum values for the exponent field in a decimal128 value.
const (
MaxDecimal128Exp = 6111
MinDecimal128Exp = -6176
)
// These errors are returned when an invalid value is parsed as a big.Int.
var (
ErrParseNaN = errors.New("cannot parse NaN as a *big.Int")
ErrParseInf = errors.New("cannot parse Infinity as a *big.Int")
ErrParseNegInf = errors.New("cannot parse -Infinity as a *big.Int")
)
// Decimal128 holds decimal128 BSON values.
type Decimal128 struct {
h, l uint64
}
// NewDecimal128 creates a Decimal128 using the provide high and low uint64s.
func NewDecimal128(h, l uint64) Decimal128 {
return Decimal128{h: h, l: l}
}
// GetBytes returns the underlying bytes of the BSON decimal value as two uint64 values. The first
// contains the most first 8 bytes of the value and the second contains the latter.
func (d Decimal128) GetBytes() (uint64, uint64) {
return d.h, d.l
}
// String returns a string representation of the decimal value.
func (d Decimal128) String() string {
var posSign int // positive sign
var exp int // exponent
var high, low uint64 // significand high/low
if d.h>>63&1 == 0 {
posSign = 1
}
switch d.h >> 58 & (1<<5 - 1) {
case 0x1F:
return "NaN"
case 0x1E:
return "-Infinity"[posSign:]
}
low = d.l
if d.h>>61&3 == 3 {
// Bits: 1*sign 2*ignored 14*exponent 111*significand.
// Implicit 0b100 prefix in significand.
exp = int(d.h >> 47 & (1<<14 - 1))
//high = 4<<47 | d.h&(1<<47-1)
// Spec says all of these values are out of range.
high, low = 0, 0
} else {
// Bits: 1*sign 14*exponent 113*significand
exp = int(d.h >> 49 & (1<<14 - 1))
high = d.h & (1<<49 - 1)
}
exp += MinDecimal128Exp
// Would be handled by the logic below, but that's trivial and common.
if high == 0 && low == 0 && exp == 0 {
return "-0"[posSign:]
}
var repr [48]byte // Loop 5 times over 9 digits plus dot, negative sign, and leading zero.
var last = len(repr)
var i = len(repr)
var dot = len(repr) + exp
var rem uint32
Loop:
for d9 := 0; d9 < 5; d9++ {
high, low, rem = divmod(high, low, 1e9)
for d1 := 0; d1 < 9; d1++ {
// Handle "-0.0", "0.00123400", "-1.00E-6", "1.050E+3", etc.
if i < len(repr) && (dot == i || low == 0 && high == 0 && rem > 0 && rem < 10 && (dot < i-6 || exp > 0)) {
exp += len(repr) - i
i--
repr[i] = '.'
last = i - 1
dot = len(repr) // Unmark.
}
c := '0' + byte(rem%10)
rem /= 10
i--
repr[i] = c
// Handle "0E+3", "1E+3", etc.
if low == 0 && high == 0 && rem == 0 && i == len(repr)-1 && (dot < i-5 || exp > 0) {
last = i
break Loop
}
if c != '0' {
last = i
}
// Break early. Works without it, but why.
if dot > i && low == 0 && high == 0 && rem == 0 {
break Loop
}
}
}
repr[last-1] = '-'
last--
if exp > 0 {
return string(repr[last+posSign:]) + "E+" + strconv.Itoa(exp)
}
if exp < 0 {
return string(repr[last+posSign:]) + "E" + strconv.Itoa(exp)
}
return string(repr[last+posSign:])
}
// BigInt returns significand as big.Int and exponent, bi * 10 ^ exp.
func (d Decimal128) BigInt() (bi *big.Int, exp int, err error) {
high, low := d.GetBytes()
var posSign bool // positive sign
posSign = high>>63&1 == 0
switch high >> 58 & (1<<5 - 1) {
case 0x1F:
return nil, 0, ErrParseNaN
case 0x1E:
if posSign {
return nil, 0, ErrParseInf
}
return nil, 0, ErrParseNegInf
}
if high>>61&3 == 3 {
// Bits: 1*sign 2*ignored 14*exponent 111*significand.
// Implicit 0b100 prefix in significand.
exp = int(high >> 47 & (1<<14 - 1))
//high = 4<<47 | d.h&(1<<47-1)
// Spec says all of these values are out of range.
high, low = 0, 0
} else {
// Bits: 1*sign 14*exponent 113*significand
exp = int(high >> 49 & (1<<14 - 1))
high = high & (1<<49 - 1)
}
exp += MinDecimal128Exp
// Would be handled by the logic below, but that's trivial and common.
if high == 0 && low == 0 && exp == 0 {
if posSign {
return new(big.Int), 0, nil
}
return new(big.Int), 0, nil
}
bi = big.NewInt(0)
const host32bit = ^uint(0)>>32 == 0
if host32bit {
bi.SetBits([]big.Word{big.Word(low), big.Word(low >> 32), big.Word(high), big.Word(high >> 32)})
} else {
bi.SetBits([]big.Word{big.Word(low), big.Word(high)})
}
if !posSign {
return bi.Neg(bi), exp, nil
}
return
}
// IsNaN returns whether d is NaN.
func (d Decimal128) IsNaN() bool {
return d.h>>58&(1<<5-1) == 0x1F
}
// IsInf returns:
//
// +1 d == Infinity
// 0 other case
// -1 d == -Infinity
//
func (d Decimal128) IsInf() int {
if d.h>>58&(1<<5-1) != 0x1E {
return 0
}
if d.h>>63&1 == 0 {
return 1
}
return -1
}
// IsZero returns true if d is the empty Decimal128.
func (d Decimal128) IsZero() bool {
return d.h == 0 && d.l == 0
}
func divmod(h, l uint64, div uint32) (qh, ql uint64, rem uint32) {
div64 := uint64(div)
a := h >> 32
aq := a / div64
ar := a % div64
b := ar<<32 + h&(1<<32-1)
bq := b / div64
br := b % div64
c := br<<32 + l>>32
cq := c / div64
cr := c % div64
d := cr<<32 + l&(1<<32-1)
dq := d / div64
dr := d % div64
return (aq<<32 | bq), (cq<<32 | dq), uint32(dr)
}
var dNaN = Decimal128{0x1F << 58, 0}
var dPosInf = Decimal128{0x1E << 58, 0}
var dNegInf = Decimal128{0x3E << 58, 0}
func dErr(s string) (Decimal128, error) {
return dNaN, fmt.Errorf("cannot parse %q as a decimal128", s)
}
// match scientific notation number, example -10.15e-18
var normalNumber = regexp.MustCompile(`^(?P<int>[-+]?\d*)?(?:\.(?P<dec>\d*))?(?:[Ee](?P<exp>[-+]?\d+))?$`)
// ParseDecimal128 takes the given string and attempts to parse it into a valid
// Decimal128 value.
func ParseDecimal128(s string) (Decimal128, error) {
if s == "" {
return dErr(s)
}
matches := normalNumber.FindStringSubmatch(s)
if len(matches) == 0 {
orig := s
neg := s[0] == '-'
if neg || s[0] == '+' {
s = s[1:]
}
if s == "NaN" || s == "nan" || strings.EqualFold(s, "nan") {
return dNaN, nil
}
if s == "Inf" || s == "inf" || strings.EqualFold(s, "inf") || strings.EqualFold(s, "infinity") {
if neg {
return dNegInf, nil
}
return dPosInf, nil
}
return dErr(orig)
}
intPart := matches[1]
decPart := matches[2]
expPart := matches[3]
var err error
exp := 0
if expPart != "" {
exp, err = strconv.Atoi(expPart)
if err != nil {
return dErr(s)
}
}
if decPart != "" {
exp -= len(decPart)
}
if len(strings.Trim(intPart+decPart, "-0")) > 35 {
return dErr(s)
}
bi, ok := new(big.Int).SetString(intPart+decPart, 10)
if !ok {
return dErr(s)
}
d, ok := ParseDecimal128FromBigInt(bi, exp)
if !ok {
return dErr(s)
}
if bi.Sign() == 0 && s[0] == '-' {
d.h |= 1 << 63
}
return d, nil
}
var (
ten = big.NewInt(10)
zero = new(big.Int)
maxS, _ = new(big.Int).SetString("9999999999999999999999999999999999", 10)
)
// ParseDecimal128FromBigInt attempts to parse the given significand and exponent into a valid Decimal128 value.
func ParseDecimal128FromBigInt(bi *big.Int, exp int) (Decimal128, bool) {
//copy
bi = new(big.Int).Set(bi)
q := new(big.Int)
r := new(big.Int)
for bigIntCmpAbs(bi, maxS) == 1 {
bi, _ = q.QuoRem(bi, ten, r)
if r.Cmp(zero) != 0 {
return Decimal128{}, false
}
exp++
if exp > MaxDecimal128Exp {
return Decimal128{}, false
}
}
for exp < MinDecimal128Exp {
// Subnormal.
bi, _ = q.QuoRem(bi, ten, r)
if r.Cmp(zero) != 0 {
return Decimal128{}, false
}
exp++
}
for exp > MaxDecimal128Exp {
// Clamped.
bi.Mul(bi, ten)
if bigIntCmpAbs(bi, maxS) == 1 {
return Decimal128{}, false
}
exp--
}
b := bi.Bytes()
var h, l uint64
for i := 0; i < len(b); i++ {
if i < len(b)-8 {
h = h<<8 | uint64(b[i])
continue
}
l = l<<8 | uint64(b[i])
}
h |= uint64(exp-MinDecimal128Exp) & uint64(1<<14-1) << 49
if bi.Sign() == -1 {
h |= 1 << 63
}
return Decimal128{h: h, l: l}, true
}
// bigIntCmpAbs computes big.Int.Cmp(absoluteValue(x), absoluteValue(y)).
func bigIntCmpAbs(x, y *big.Int) int {
xAbs := bigIntAbsValue(x)
yAbs := bigIntAbsValue(y)
return xAbs.Cmp(yAbs)
}
// bigIntAbsValue returns a big.Int containing the absolute value of b.
// If b is already a non-negative number, it is returned without any changes or copies.
func bigIntAbsValue(b *big.Int) *big.Int {
if b.Sign() >= 0 {
return b // already positive
}
return new(big.Int).Abs(b)
}