/usr/share/gocode/src/golang.org/x/text/internal/number/decimal.go is in golang-golang-x-text-dev 0.0~git20170627.0.6353ef0-1ubuntu2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 | // Copyright 2017 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
//go:generate stringer -type RoundingMode
package number
import (
"math"
"strconv"
)
// RoundingMode determines how a number is rounded to the desired precision.
type RoundingMode byte
const (
ToNearestEven RoundingMode = iota // towards the nearest integer, or towards an even number if equidistant.
ToNearestZero // towards the nearest integer, or towards zero if equidistant.
ToNearestAway // towards the nearest integer, or away from zero if equidistant.
ToPositiveInf // towards infinity
ToNegativeInf // towards negative infinity
ToZero // towards zero
AwayFromZero // away from zero
numModes
)
// A RoundingContext indicates how a number should be converted to digits.
type RoundingContext struct {
Mode RoundingMode
Increment int32 // if > 0, round to Increment * 10^-Scale
Precision int32 // maximum number of significant digits.
Scale int32 // maximum number of decimals after the dot.
}
const maxIntDigits = 20
// A Decimal represents floating point number represented in digits of the base
// in which a number is to be displayed. Digits represents a number [0, 1.0),
// and the absolute value represented by Decimal is Digits * 10^Exp.
// Leading and trailing zeros may be omitted and Exp may point outside a valid
// position in Digits.
//
// Examples:
// Number Decimal
// 12345 Digits: [1, 2, 3, 4, 5], Exp: 5
// 12.345 Digits: [1, 2, 3, 4, 5], Exp: 2
// 12000 Digits: [1, 2], Exp: 5
// 0.00123 Digits: [1, 2, 3], Exp: -2
type Decimal struct {
Digits []byte // mantissa digits, big-endian
Exp int32 // exponent
Neg bool
Inf bool // Takes precedence over Digits and Exp.
NaN bool // Takes precedence over Inf.
buf [maxIntDigits]byte
}
// normalize retuns a new Decimal with leading and trailing zeros removed.
func (d *Decimal) normalize() (n Decimal) {
n = *d
b := n.Digits
// Strip leading zeros. Resulting number of digits is significant digits.
for len(b) > 0 && b[0] == 0 {
b = b[1:]
n.Exp--
}
// Strip trailing zeros
for len(b) > 0 && b[len(b)-1] == 0 {
b = b[:len(b)-1]
}
if len(b) == 0 {
n.Exp = 0
}
n.Digits = b
return n
}
func (d *Decimal) clear() {
b := d.Digits
if b == nil {
b = d.buf[:0]
}
*d = Decimal{}
d.Digits = b[:0]
}
func (x *Decimal) String() string {
if x.NaN {
return "NaN"
}
var buf []byte
if x.Neg {
buf = append(buf, '-')
}
if x.Inf {
buf = append(buf, "Inf"...)
return string(buf)
}
switch {
case len(x.Digits) == 0:
buf = append(buf, '0')
case x.Exp <= 0:
// 0.00ddd
buf = append(buf, "0."...)
buf = appendZeros(buf, -int(x.Exp))
buf = appendDigits(buf, x.Digits)
case /* 0 < */ int(x.Exp) < len(x.Digits):
// dd.ddd
buf = appendDigits(buf, x.Digits[:x.Exp])
buf = append(buf, '.')
buf = appendDigits(buf, x.Digits[x.Exp:])
default: // len(x.Digits) <= x.Exp
// ddd00
buf = appendDigits(buf, x.Digits)
buf = appendZeros(buf, int(x.Exp)-len(x.Digits))
}
return string(buf)
}
func appendDigits(buf []byte, digits []byte) []byte {
for _, c := range digits {
buf = append(buf, c+'0')
}
return buf
}
// appendZeros appends n 0 digits to buf and returns buf.
func appendZeros(buf []byte, n int) []byte {
for ; n > 0; n-- {
buf = append(buf, '0')
}
return buf
}
func (d *Decimal) round(mode RoundingMode, n int) {
if n >= len(d.Digits) {
return
}
// Make rounding decision: The result mantissa is truncated ("rounded down")
// by default. Decide if we need to increment, or "round up", the (unsigned)
// mantissa.
inc := false
switch mode {
case ToNegativeInf:
inc = d.Neg
case ToPositiveInf:
inc = !d.Neg
case ToZero:
// nothing to do
case AwayFromZero:
inc = true
case ToNearestEven:
inc = d.Digits[n] > 5 || d.Digits[n] == 5 &&
(len(d.Digits) > n+1 || n == 0 || d.Digits[n-1]&1 != 0)
case ToNearestAway:
inc = d.Digits[n] >= 5
case ToNearestZero:
inc = d.Digits[n] > 5 || d.Digits[n] == 5 && len(d.Digits) > n+1
default:
panic("unreachable")
}
if inc {
d.roundUp(n)
} else {
d.roundDown(n)
}
}
// roundFloat rounds a floating point number.
func (r RoundingMode) roundFloat(x float64) float64 {
// Make rounding decision: The result mantissa is truncated ("rounded down")
// by default. Decide if we need to increment, or "round up", the (unsigned)
// mantissa.
abs := x
if x < 0 {
abs = -x
}
i, f := math.Modf(abs)
if f == 0.0 {
return x
}
inc := false
switch r {
case ToNegativeInf:
inc = x < 0
case ToPositiveInf:
inc = x >= 0
case ToZero:
// nothing to do
case AwayFromZero:
inc = true
case ToNearestEven:
// TODO: check overflow
inc = f > 0.5 || f == 0.5 && int64(i)&1 != 0
case ToNearestAway:
inc = f >= 0.5
case ToNearestZero:
inc = f > 0.5
default:
panic("unreachable")
}
if inc {
i += 1
}
if abs != x {
i = -i
}
return i
}
func (x *Decimal) roundUp(n int) {
if n < 0 || n >= len(x.Digits) {
return // nothing to do
}
// find first digit < 9
for n > 0 && x.Digits[n-1] >= 9 {
n--
}
if n == 0 {
// all digits are 9s => round up to 1 and update exponent
x.Digits[0] = 1 // ok since len(x.Digits) > n
x.Digits = x.Digits[:1]
x.Exp++
return
}
x.Digits[n-1]++
x.Digits = x.Digits[:n]
// x already trimmed
}
func (x *Decimal) roundDown(n int) {
if n < 0 || n >= len(x.Digits) {
return // nothing to do
}
x.Digits = x.Digits[:n]
trim(x)
}
// trim cuts off any trailing zeros from x's mantissa;
// they are meaningless for the value of x.
func trim(x *Decimal) {
i := len(x.Digits)
for i > 0 && x.Digits[i-1] == 0 {
i--
}
x.Digits = x.Digits[:i]
if i == 0 {
x.Exp = 0
}
}
// A Converter converts a number into decimals according to the given rounding
// criteria.
type Converter interface {
Convert(d *Decimal, r *RoundingContext)
}
const (
signed = true
unsigned = false
)
// Convert converts the given number to the decimal representation using the
// supplied RoundingContext.
func (d *Decimal) Convert(r *RoundingContext, number interface{}) {
switch f := number.(type) {
case Converter:
d.clear()
f.Convert(d, r)
case float32:
d.ConvertFloat(r, float64(f), 32)
case float64:
d.ConvertFloat(r, f, 64)
case int:
d.ConvertInt(r, signed, uint64(f))
case int8:
d.ConvertInt(r, signed, uint64(f))
case int16:
d.ConvertInt(r, signed, uint64(f))
case int32:
d.ConvertInt(r, signed, uint64(f))
case int64:
d.ConvertInt(r, signed, uint64(f))
case uint:
d.ConvertInt(r, unsigned, uint64(f))
case uint8:
d.ConvertInt(r, unsigned, uint64(f))
case uint16:
d.ConvertInt(r, unsigned, uint64(f))
case uint32:
d.ConvertInt(r, unsigned, uint64(f))
case uint64:
d.ConvertInt(r, unsigned, f)
// TODO:
// case string: if produced by strconv, allows for easy arbitrary pos.
// case reflect.Value:
// case big.Float
// case big.Int
// case big.Rat?
// catch underlyings using reflect or will this already be done by the
// message package?
}
}
// ConvertInt converts an integer to decimals.
func (d *Decimal) ConvertInt(r *RoundingContext, signed bool, x uint64) {
if r.Increment > 0 {
// TODO: if uint64 is too large, fall back to float64
if signed {
d.ConvertFloat(r, float64(int64(x)), 64)
} else {
d.ConvertFloat(r, float64(x), 64)
}
return
}
d.clear()
if signed && int64(x) < 0 {
x = uint64(-int64(x))
d.Neg = true
}
d.fillIntDigits(x)
d.Exp = int32(len(d.Digits))
}
// ConvertFloat converts a floating point number to decimals.
func (d *Decimal) ConvertFloat(r *RoundingContext, x float64, size int) {
d.clear()
if math.IsNaN(x) {
d.NaN = true
return
}
abs := x
if x < 0 {
d.Neg = true
abs = -x
}
if math.IsInf(abs, 1) {
d.Inf = true
return
}
// Simple case: decimal notation
if r.Scale > 0 || r.Increment > 0 || r.Precision == 0 {
if int(r.Scale) > len(scales) {
x *= math.Pow(10, float64(r.Scale))
} else {
x *= scales[r.Scale]
}
if r.Increment > 0 {
inc := float64(r.Increment)
x /= float64(inc)
x = r.Mode.roundFloat(x)
x *= inc
} else {
x = r.Mode.roundFloat(x)
}
d.fillIntDigits(uint64(math.Abs(x)))
d.Exp = int32(len(d.Digits)) - r.Scale
return
}
// Nasty case (for non-decimal notation).
// Asides from being inefficient, this result is also wrong as it will
// apply ToNearestEven rounding regardless of the user setting.
// TODO: expose functionality in strconv so we can avoid this hack.
// Something like this would work:
// AppendDigits(dst []byte, x float64, base, size, prec int) (digits []byte, exp, accuracy int)
// TODO: This only supports the nearest even rounding mode.
prec := int(r.Precision)
if prec > 0 {
prec--
}
b := strconv.AppendFloat(d.Digits, abs, 'e', prec, size)
i := 0
k := 0
// No need to check i < len(b) as we always have an 'e'.
for {
if c := b[i]; '0' <= c && c <= '9' {
b[k] = c - '0'
k++
} else if c != '.' {
break
}
i++
}
d.Digits = b[:k]
i += len("e")
pSign := i
exp := 0
for i++; i < len(b); i++ {
exp *= 10
exp += int(b[i] - '0')
}
if b[pSign] == '-' {
exp = -exp
}
d.Exp = int32(exp) + 1
}
func (d *Decimal) fillIntDigits(x uint64) {
if cap(d.Digits) < maxIntDigits {
d.Digits = d.buf[:]
} else {
d.Digits = d.buf[:maxIntDigits]
}
i := 0
for ; x > 0; x /= 10 {
d.Digits[i] = byte(x % 10)
i++
}
d.Digits = d.Digits[:i]
for p := 0; p < i; p++ {
i--
d.Digits[p], d.Digits[i] = d.Digits[i], d.Digits[p]
}
}
var scales [70]float64
func init() {
x := 1.0
for i := range scales {
scales[i] = x
x *= 10
}
}
|