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307 lines
6.4 KiB
307 lines
6.4 KiB
// Copyright (C) MongoDB, Inc. 2017-present.
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//
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// Licensed under the Apache License, Version 2.0 (the "License"); you may
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// not use this file except in compliance with the License. You may obtain
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// a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
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//
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// Based on gopkg.in/mgo.v2/bson by Gustavo Niemeyer
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// See THIRD-PARTY-NOTICES for original license terms.
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package primitive
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import (
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"fmt"
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"strconv"
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"strings"
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)
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// Decimal128 holds decimal128 BSON values.
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type Decimal128 struct {
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h, l uint64
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}
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// NewDecimal128 creates a Decimal128 using the provide high and low uint64s.
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func NewDecimal128(h, l uint64) Decimal128 {
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return Decimal128{h: h, l: l}
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}
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// GetBytes returns the underlying bytes of the BSON decimal value as two uint16 values. The first
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// contains the most first 8 bytes of the value and the second contains the latter.
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func (d Decimal128) GetBytes() (uint64, uint64) {
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return d.h, d.l
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}
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// String returns a string representation of the decimal value.
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func (d Decimal128) String() string {
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var pos int // positive sign
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var e int // exponent
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var h, l uint64 // significand high/low
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if d.h>>63&1 == 0 {
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pos = 1
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}
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switch d.h >> 58 & (1<<5 - 1) {
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case 0x1F:
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return "NaN"
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case 0x1E:
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return "-Infinity"[pos:]
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}
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l = d.l
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if d.h>>61&3 == 3 {
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// Bits: 1*sign 2*ignored 14*exponent 111*significand.
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// Implicit 0b100 prefix in significand.
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e = int(d.h>>47&(1<<14-1)) - 6176
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//h = 4<<47 | d.h&(1<<47-1)
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// Spec says all of these values are out of range.
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h, l = 0, 0
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} else {
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// Bits: 1*sign 14*exponent 113*significand
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e = int(d.h>>49&(1<<14-1)) - 6176
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h = d.h & (1<<49 - 1)
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}
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// Would be handled by the logic below, but that's trivial and common.
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if h == 0 && l == 0 && e == 0 {
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return "-0"[pos:]
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}
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var repr [48]byte // Loop 5 times over 9 digits plus dot, negative sign, and leading zero.
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var last = len(repr)
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var i = len(repr)
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var dot = len(repr) + e
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var rem uint32
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Loop:
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for d9 := 0; d9 < 5; d9++ {
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h, l, rem = divmod(h, l, 1e9)
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for d1 := 0; d1 < 9; d1++ {
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// Handle "-0.0", "0.00123400", "-1.00E-6", "1.050E+3", etc.
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if i < len(repr) && (dot == i || l == 0 && h == 0 && rem > 0 && rem < 10 && (dot < i-6 || e > 0)) {
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e += len(repr) - i
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i--
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repr[i] = '.'
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last = i - 1
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dot = len(repr) // Unmark.
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}
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c := '0' + byte(rem%10)
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rem /= 10
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i--
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repr[i] = c
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// Handle "0E+3", "1E+3", etc.
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if l == 0 && h == 0 && rem == 0 && i == len(repr)-1 && (dot < i-5 || e > 0) {
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last = i
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break Loop
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}
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if c != '0' {
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last = i
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}
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// Break early. Works without it, but why.
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if dot > i && l == 0 && h == 0 && rem == 0 {
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break Loop
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}
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}
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}
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repr[last-1] = '-'
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last--
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if e > 0 {
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return string(repr[last+pos:]) + "E+" + strconv.Itoa(e)
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}
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if e < 0 {
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return string(repr[last+pos:]) + "E" + strconv.Itoa(e)
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}
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return string(repr[last+pos:])
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}
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func divmod(h, l uint64, div uint32) (qh, ql uint64, rem uint32) {
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div64 := uint64(div)
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a := h >> 32
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aq := a / div64
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ar := a % div64
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b := ar<<32 + h&(1<<32-1)
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bq := b / div64
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br := b % div64
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c := br<<32 + l>>32
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cq := c / div64
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cr := c % div64
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d := cr<<32 + l&(1<<32-1)
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dq := d / div64
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dr := d % div64
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return (aq<<32 | bq), (cq<<32 | dq), uint32(dr)
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}
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var dNaN = Decimal128{0x1F << 58, 0}
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var dPosInf = Decimal128{0x1E << 58, 0}
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var dNegInf = Decimal128{0x3E << 58, 0}
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func dErr(s string) (Decimal128, error) {
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return dNaN, fmt.Errorf("cannot parse %q as a decimal128", s)
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}
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//ParseDecimal128 takes the given string and attempts to parse it into a valid
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// Decimal128 value.
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func ParseDecimal128(s string) (Decimal128, error) {
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orig := s
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if s == "" {
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return dErr(orig)
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}
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neg := s[0] == '-'
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if neg || s[0] == '+' {
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s = s[1:]
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}
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if (len(s) == 3 || len(s) == 8) && (s[0] == 'N' || s[0] == 'n' || s[0] == 'I' || s[0] == 'i') {
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if s == "NaN" || s == "nan" || strings.EqualFold(s, "nan") {
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return dNaN, nil
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}
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if s == "Inf" || s == "inf" || strings.EqualFold(s, "inf") || strings.EqualFold(s, "infinity") {
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if neg {
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return dNegInf, nil
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}
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return dPosInf, nil
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}
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return dErr(orig)
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}
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var h, l uint64
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var e int
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var add, ovr uint32
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var mul uint32 = 1
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var dot = -1
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var digits = 0
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var i = 0
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for i < len(s) {
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c := s[i]
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if mul == 1e9 {
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h, l, ovr = muladd(h, l, mul, add)
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mul, add = 1, 0
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if ovr > 0 || h&((1<<15-1)<<49) > 0 {
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return dErr(orig)
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}
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}
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if c >= '0' && c <= '9' {
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i++
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if c > '0' || digits > 0 {
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digits++
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}
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if digits > 34 {
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if c == '0' {
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// Exact rounding.
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e++
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continue
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}
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return dErr(orig)
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}
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mul *= 10
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add *= 10
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add += uint32(c - '0')
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continue
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}
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if c == '.' {
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i++
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if dot >= 0 || i == 1 && len(s) == 1 {
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return dErr(orig)
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}
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if i == len(s) {
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break
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}
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if s[i] < '0' || s[i] > '9' || e > 0 {
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return dErr(orig)
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}
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dot = i
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continue
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}
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break
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}
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if i == 0 {
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return dErr(orig)
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}
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if mul > 1 {
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h, l, ovr = muladd(h, l, mul, add)
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if ovr > 0 || h&((1<<15-1)<<49) > 0 {
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return dErr(orig)
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}
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}
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if dot >= 0 {
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e += dot - i
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}
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if i+1 < len(s) && (s[i] == 'E' || s[i] == 'e') {
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i++
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eneg := s[i] == '-'
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if eneg || s[i] == '+' {
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i++
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if i == len(s) {
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return dErr(orig)
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}
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}
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n := 0
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for i < len(s) && n < 1e4 {
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c := s[i]
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i++
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if c < '0' || c > '9' {
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return dErr(orig)
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}
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n *= 10
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n += int(c - '0')
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}
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if eneg {
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n = -n
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}
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e += n
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for e < -6176 {
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// Subnormal.
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var div uint32 = 1
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for div < 1e9 && e < -6176 {
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div *= 10
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e++
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}
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var rem uint32
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h, l, rem = divmod(h, l, div)
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if rem > 0 {
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return dErr(orig)
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}
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}
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for e > 6111 {
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// Clamped.
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var mul uint32 = 1
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for mul < 1e9 && e > 6111 {
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mul *= 10
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e--
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}
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h, l, ovr = muladd(h, l, mul, 0)
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if ovr > 0 || h&((1<<15-1)<<49) > 0 {
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return dErr(orig)
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}
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}
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if e < -6176 || e > 6111 {
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return dErr(orig)
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}
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}
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if i < len(s) {
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return dErr(orig)
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}
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h |= uint64(e+6176) & uint64(1<<14-1) << 49
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if neg {
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h |= 1 << 63
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}
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return Decimal128{h, l}, nil
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}
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func muladd(h, l uint64, mul uint32, add uint32) (resh, resl uint64, overflow uint32) {
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mul64 := uint64(mul)
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a := mul64 * (l & (1<<32 - 1))
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b := a>>32 + mul64*(l>>32)
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c := b>>32 + mul64*(h&(1<<32-1))
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d := c>>32 + mul64*(h>>32)
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a = a&(1<<32-1) + uint64(add)
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b = b&(1<<32-1) + a>>32
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c = c&(1<<32-1) + b>>32
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d = d&(1<<32-1) + c>>32
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return (d<<32 | c&(1<<32-1)), (b<<32 | a&(1<<32-1)), uint32(d >> 32)
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}
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