github.com/spi-ca/misc@v1.0.1/nums/digits.go (about)

     1  package nums
     2  
     3  import (
     4  	"github.com/spi-ca/misc/strutil"
     5  	"strings"
     6  )
     7  
     8  // SplitSignFromInt64 decomposes a signed integer with a sign and positive integer.
     9  func SplitSignFromInt64(src int64) (sign bool, dst uint64) {
    10  	signedInteger := uint64(src)
    11  	sign = 1 == (signedInteger >> 63)
    12  
    13  	//Two's complement!!
    14  	if sign {
    15  		dst = 1 + (signedInteger ^ (1<<64 - 1))
    16  	} else {
    17  		dst = signedInteger & (1<<63 - 1)
    18  	}
    19  	return
    20  }
    21  
    22  // MergeSignFromUInt64 composes a signed integer with a sign and positive integer.
    23  func MergeSignFromUInt64(sign bool, src uint64) (dst int64) {
    24  	//Two's complement!!
    25  	if sign {
    26  		dst = -int64(src & (1<<63 - 1))
    27  	} else {
    28  		dst = int64(src & (1<<63 - 1))
    29  	}
    30  	return
    31  }
    32  
    33  // FractionalStringify is a formatting function for a fractional part number.
    34  func FractionalStringify(fractional, fractionalLength int, showPoint bool) (formatted string) {
    35  	if fractionalLength == 0 {
    36  		return
    37  	}
    38  	var builder strings.Builder
    39  
    40  	partialFormatted := strutil.FormatIntToStringReversed(fractional)
    41  	if leftDigits := fractionalLength - len(partialFormatted); leftDigits < 0 {
    42  		builder.WriteString(partialFormatted[-leftDigits:])
    43  	} else {
    44  		builder.WriteString(partialFormatted)
    45  		for ; leftDigits > 0; leftDigits-- {
    46  			builder.WriteByte('0')
    47  		}
    48  	}
    49  
    50  	if showPoint {
    51  		builder.WriteByte('.')
    52  	}
    53  
    54  	return strutil.Reverse(builder.String())
    55  }