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

307 lines
6.4 KiB

// 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 (
"fmt"
"strconv"
"strings"
)
// 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 uint16 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 pos int // positive sign
var e int // exponent
var h, l uint64 // significand high/low
if d.h>>63&1 == 0 {
pos = 1
}
switch d.h >> 58 & (1<<5 - 1) {
case 0x1F:
return "NaN"
case 0x1E:
return "-Infinity"[pos:]
}
l = d.l
if d.h>>61&3 == 3 {
// Bits: 1*sign 2*ignored 14*exponent 111*significand.
// Implicit 0b100 prefix in significand.
e = int(d.h>>47&(1<<14-1)) - 6176
//h = 4<<47 | d.h&(1<<47-1)
// Spec says all of these values are out of range.
h, l = 0, 0
} else {
// Bits: 1*sign 14*exponent 113*significand
e = int(d.h>>49&(1<<14-1)) - 6176
h = d.h & (1<<49 - 1)
}
// Would be handled by the logic below, but that's trivial and common.
if h == 0 && l == 0 && e == 0 {
return "-0"[pos:]
}
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) + e
var rem uint32
Loop:
for d9 := 0; d9 < 5; d9++ {
h, l, rem = divmod(h, l, 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 || l == 0 && h == 0 && rem > 0 && rem < 10 && (dot < i-6 || e > 0)) {
e += 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 l == 0 && h == 0 && rem == 0 && i == len(repr)-1 && (dot < i-5 || e > 0) {
last = i
break Loop
}
if c != '0' {
last = i
}
// Break early. Works without it, but why.
if dot > i && l == 0 && h == 0 && rem == 0 {
break Loop
}
}
}
repr[last-1] = '-'
last--
if e > 0 {
return string(repr[last+pos:]) + "E+" + strconv.Itoa(e)
}
if e < 0 {
return string(repr[last+pos:]) + "E" + strconv.Itoa(e)
}
return string(repr[last+pos:])
}
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)
}
//ParseDecimal128 takes the given string and attempts to parse it into a valid
// Decimal128 value.
func ParseDecimal128(s string) (Decimal128, error) {
orig := s
if s == "" {
return dErr(orig)
}
neg := s[0] == '-'
if neg || s[0] == '+' {
s = s[1:]
}
if (len(s) == 3 || len(s) == 8) && (s[0] == 'N' || s[0] == 'n' || s[0] == 'I' || s[0] == 'i') {
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)
}
var h, l uint64
var e int
var add, ovr uint32
var mul uint32 = 1
var dot = -1
var digits = 0
var i = 0
for i < len(s) {
c := s[i]
if mul == 1e9 {
h, l, ovr = muladd(h, l, mul, add)
mul, add = 1, 0
if ovr > 0 || h&((1<<15-1)<<49) > 0 {
return dErr(orig)
}
}
if c >= '0' && c <= '9' {
i++
if c > '0' || digits > 0 {
digits++
}
if digits > 34 {
if c == '0' {
// Exact rounding.
e++
continue
}
return dErr(orig)
}
mul *= 10
add *= 10
add += uint32(c - '0')
continue
}
if c == '.' {
i++
if dot >= 0 || i == 1 && len(s) == 1 {
return dErr(orig)
}
if i == len(s) {
break
}
if s[i] < '0' || s[i] > '9' || e > 0 {
return dErr(orig)
}
dot = i
continue
}
break
}
if i == 0 {
return dErr(orig)
}
if mul > 1 {
h, l, ovr = muladd(h, l, mul, add)
if ovr > 0 || h&((1<<15-1)<<49) > 0 {
return dErr(orig)
}
}
if dot >= 0 {
e += dot - i
}
if i+1 < len(s) && (s[i] == 'E' || s[i] == 'e') {
i++
eneg := s[i] == '-'
if eneg || s[i] == '+' {
i++
if i == len(s) {
return dErr(orig)
}
}
n := 0
for i < len(s) && n < 1e4 {
c := s[i]
i++
if c < '0' || c > '9' {
return dErr(orig)
}
n *= 10
n += int(c - '0')
}
if eneg {
n = -n
}
e += n
for e < -6176 {
// Subnormal.
var div uint32 = 1
for div < 1e9 && e < -6176 {
div *= 10
e++
}
var rem uint32
h, l, rem = divmod(h, l, div)
if rem > 0 {
return dErr(orig)
}
}
for e > 6111 {
// Clamped.
var mul uint32 = 1
for mul < 1e9 && e > 6111 {
mul *= 10
e--
}
h, l, ovr = muladd(h, l, mul, 0)
if ovr > 0 || h&((1<<15-1)<<49) > 0 {
return dErr(orig)
}
}
if e < -6176 || e > 6111 {
return dErr(orig)
}
}
if i < len(s) {
return dErr(orig)
}
h |= uint64(e+6176) & uint64(1<<14-1) << 49
if neg {
h |= 1 << 63
}
return Decimal128{h, l}, nil
}
func muladd(h, l uint64, mul uint32, add uint32) (resh, resl uint64, overflow uint32) {
mul64 := uint64(mul)
a := mul64 * (l & (1<<32 - 1))
b := a>>32 + mul64*(l>>32)
c := b>>32 + mul64*(h&(1<<32-1))
d := c>>32 + mul64*(h>>32)
a = a&(1<<32-1) + uint64(add)
b = b&(1<<32-1) + a>>32
c = c&(1<<32-1) + b>>32
d = d&(1<<32-1) + c>>32
return (d<<32 | c&(1<<32-1)), (b<<32 | a&(1<<32-1)), uint32(d >> 32)
}