64 lines
1.1 KiB
Go
64 lines
1.1 KiB
Go
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package strconv
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import (
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"math"
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)
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func ParseDecimal(b []byte) (float64, int) {
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i := 0
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start := i
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dot := -1
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trunk := -1
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n := uint64(0)
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for ; i < len(b); i++ {
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c := b[i]
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if '0' <= c && c <= '9' {
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if trunk == -1 {
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if math.MaxUint64/10 < n {
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trunk = i
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} else {
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n *= 10
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n += uint64(c - '0')
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}
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}
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} else if dot == -1 && c == '.' {
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dot = i
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} else {
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break
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}
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}
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if i == start || i == start+1 && dot == start {
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return 0.0, 0
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}
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f := float64(n)
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mantExp := int64(0)
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if dot != -1 {
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if trunk == -1 {
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trunk = i
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}
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mantExp = int64(trunk - dot - 1)
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} else if trunk != -1 {
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mantExp = int64(trunk - i)
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}
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exp := -mantExp
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// copied from strconv/atof.go
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if exp == 0 {
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return f, i
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} else if 0 < exp && exp <= 15+22 { // int * 10^k
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// If exponent is big but number of digits is not,
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// can move a few zeros into the integer part.
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if 22 < exp {
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f *= float64pow10[exp-22]
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exp = 22
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}
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if -1e15 <= f && f <= 1e15 {
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return f * float64pow10[exp], i
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}
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} else if exp < 0 && -22 <= exp { // int / 10^k
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return f / float64pow10[-exp], i
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}
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return f * math.Pow10(int(-mantExp)), i
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}
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