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|
package strconv
import (
"math"
"unicode/utf8"
)
// ParseNumber parses a byte-slice and returns the number it represents and the amount of decimals.
// If an invalid character is encountered, it will stop there.
func ParseNumber(b []byte, groupSym rune, decSym rune) (int64, int, int) {
n, dec := 0, 0
sign := int64(1)
price := int64(0)
hasDecimals := false
if 0 < len(b) && b[0] == '-' {
sign = -1
n++
}
for n < len(b) {
if '0' <= b[n] && b[n] <= '9' {
digit := sign * int64(b[n]-'0')
if sign == 1 && (math.MaxInt64/10 < price || math.MaxInt64-digit < price*10) {
break
} else if sign == -1 && (price < math.MinInt64/10 || price*10 < math.MinInt64-digit) {
break
}
price *= 10
price += digit
if hasDecimals {
dec++
}
n++
} else if r, size := utf8.DecodeRune(b[n:]); !hasDecimals && (r == groupSym || r == decSym) {
if r == decSym {
hasDecimals = true
}
n += size
} else {
break
}
}
return price, dec, n
}
// AppendNumber will append an int64 formatted as a number with the given number of decimal digits.
func AppendNumber(b []byte, price int64, dec int, groupSize int, groupSym rune, decSym rune) []byte {
if dec < 0 {
dec = 0
}
if utf8.RuneLen(groupSym) == -1 {
groupSym = '.'
}
if utf8.RuneLen(decSym) == -1 {
decSym = ','
}
sign := int64(1)
if price < 0 {
sign = -1
}
// calculate size
n := LenInt(price)
if dec < n && 0 < groupSize && groupSym != 0 {
n += utf8.RuneLen(groupSym) * (n - dec - 1) / groupSize
}
if 0 < dec {
if n <= dec {
n = 1 + dec // zero and decimals
}
n += utf8.RuneLen(decSym)
}
if sign == -1 {
n++
}
// resize byte slice
i := len(b)
if cap(b) < i+n {
b = append(b, make([]byte, n)...)
} else {
b = b[:i+n]
}
// print fractional-part
i += n - 1
if 0 < dec {
for 0 < dec {
c := byte(sign*(price%10)) + '0'
price /= 10
b[i] = c
dec--
i--
}
i -= utf8.RuneLen(decSym)
utf8.EncodeRune(b[i+1:], decSym)
}
// print integer-part
if price == 0 {
b[i] = '0'
if sign == -1 {
b[i-1] = '-'
}
return b
}
j := 0
for price != 0 {
if 0 < groupSize && groupSym != 0 && 0 < j && j%groupSize == 0 {
i -= utf8.RuneLen(groupSym)
utf8.EncodeRune(b[i+1:], groupSym)
}
c := byte(sign*(price%10)) + '0'
price /= 10
b[i] = c
i--
j++
}
if sign == -1 {
b[i] = '-'
}
return b
}
|
