Show download count info in release list (#10124)

* Show download count info in release list

* Use go-humanize

vendor/github.com/dustin/go-humanize/si.go

@@ -0,0 +1,123 @@
+package humanize
+
+import (
+	"errors"
+	"math"
+	"regexp"
+	"strconv"
+)
+
+var siPrefixTable = map[float64]string{
+	-24: "y", // yocto
+	-21: "z", // zepto
+	-18: "a", // atto
+	-15: "f", // femto
+	-12: "p", // pico
+	-9:  "n", // nano
+	-6:  "µ", // micro
+	-3:  "m", // milli
+	0:   "",
+	3:   "k", // kilo
+	6:   "M", // mega
+	9:   "G", // giga
+	12:  "T", // tera
+	15:  "P", // peta
+	18:  "E", // exa
+	21:  "Z", // zetta
+	24:  "Y", // yotta
+}
+
+var revSIPrefixTable = revfmap(siPrefixTable)
+
+// revfmap reverses the map and precomputes the power multiplier
+func revfmap(in map[float64]string) map[string]float64 {
+	rv := map[string]float64{}
+	for k, v := range in {
+		rv[v] = math.Pow(10, k)
+	}
+	return rv
+}
+
+var riParseRegex *regexp.Regexp
+
+func init() {
+	ri := `^([\-0-9.]+)\s?([`
+	for _, v := range siPrefixTable {
+		ri += v
+	}
+	ri += `]?)(.*)`
+
+	riParseRegex = regexp.MustCompile(ri)
+}
+
+// ComputeSI finds the most appropriate SI prefix for the given number
+// and returns the prefix along with the value adjusted to be within
+// that prefix.
+//
+// See also: SI, ParseSI.
+//
+// e.g. ComputeSI(2.2345e-12) -> (2.2345, "p")
+func ComputeSI(input float64) (float64, string) {
+	if input == 0 {
+		return 0, ""
+	}
+	mag := math.Abs(input)
+	exponent := math.Floor(logn(mag, 10))
+	exponent = math.Floor(exponent/3) * 3
+
+	value := mag / math.Pow(10, exponent)
+
+	// Handle special case where value is exactly 1000.0
+	// Should return 1 M instead of 1000 k
+	if value == 1000.0 {
+		exponent += 3
+		value = mag / math.Pow(10, exponent)
+	}
+
+	value = math.Copysign(value, input)
+
+	prefix := siPrefixTable[exponent]
+	return value, prefix
+}
+
+// SI returns a string with default formatting.
+//
+// SI uses Ftoa to format float value, removing trailing zeros.
+//
+// See also: ComputeSI, ParseSI.
+//
+// e.g. SI(1000000, "B") -> 1 MB
+// e.g. SI(2.2345e-12, "F") -> 2.2345 pF
+func SI(input float64, unit string) string {
+	value, prefix := ComputeSI(input)
+	return Ftoa(value) + " " + prefix + unit
+}
+
+// SIWithDigits works like SI but limits the resulting string to the
+// given number of decimal places.
+//
+// e.g. SIWithDigits(1000000, 0, "B") -> 1 MB
+// e.g. SIWithDigits(2.2345e-12, 2, "F") -> 2.23 pF
+func SIWithDigits(input float64, decimals int, unit string) string {
+	value, prefix := ComputeSI(input)
+	return FtoaWithDigits(value, decimals) + " " + prefix + unit
+}
+
+var errInvalid = errors.New("invalid input")
+
+// ParseSI parses an SI string back into the number and unit.
+//
+// See also: SI, ComputeSI.
+//
+// e.g. ParseSI("2.2345 pF") -> (2.2345e-12, "F", nil)
+func ParseSI(input string) (float64, string, error) {
+	found := riParseRegex.FindStringSubmatch(input)
+	if len(found) != 4 {
+		return 0, "", errInvalid
+	}
+	mag := revSIPrefixTable[found[2]]
+	unit := found[3]
+
+	base, err := strconv.ParseFloat(found[1], 64)
+	return base * mag, unit, err
+}