Initial Go project structure, docs, build and CI

internal/textutil/units.go

@@ -0,0 +1,125 @@
+package textutil
+
+import (
+	"fmt"
+	"strconv"
+	"time"
+)
+
+// SI selects decimal units (kB, MB, …). The default is IEC (KiB, MiB, …).
+// It is set once at start-up, before any goroutines format sizes.
+var SI bool
+
+var (
+	iecUnits = []string{"B", "KiB", "MiB", "GiB", "TiB", "PiB", "EiB"}
+	siUnits  = []string{"B", "kB", "MB", "GB", "TB", "PB", "EB"}
+)
+
+func scaled(n int64) (float64, string) {
+	base, units := 1024.0, iecUnits
+	if SI {
+		base, units = 1000.0, siUnits
+	}
+	neg := n < 0
+	v := float64(n)
+	if neg {
+		v = -v
+	}
+	i := 0
+	for v >= base && i < len(units)-1 {
+		v /= base
+		i++
+	}
+	if neg {
+		v = -v
+	}
+	return v, units[i]
+}
+
+func num(v float64, unit string) string {
+	a := v
+	if a < 0 {
+		a = -a
+	}
+	switch {
+	case unit == "B":
+		return strconv.FormatFloat(v, 'f', 0, 64)
+	case a < 10:
+		return strconv.FormatFloat(v, 'f', 2, 64)
+	case a < 100:
+		return strconv.FormatFloat(v, 'f', 1, 64)
+	default:
+		return strconv.FormatFloat(v, 'f', 0, 64)
+	}
+}
+
+// Size formats a byte count, e.g. "86.4 GiB".
+func Size(n int64) string {
+	v, u := scaled(n)
+	return num(v, u) + " " + u
+}
+
+// SizeCompact formats a byte count in at most ~7 cells, e.g. "86GiB".
+func SizeCompact(n int64) string {
+	v, u := scaled(n)
+	a := v
+	if a < 0 {
+		a = -a
+	}
+	if u != "B" && a < 10 {
+		return strconv.FormatFloat(v, 'f', 1, 64) + u
+	}
+	return strconv.FormatFloat(v, 'f', 0, 64) + u
+}
+
+// SignedSize formats a delta with an explicit sign.
+func SignedSize(n int64) string {
+	if n > 0 {
+		return "+" + Size(n)
+	}
+	if n < 0 {
+		return "-" + Size(-n)
+	}
+	return "±0 B"
+}
+
+// Count formats an integer with thousands separators.
+func Count(n int64) string {
+	s := strconv.FormatInt(n, 10)
+	neg := false
+	if n < 0 {
+		neg, s = true, s[1:]
+	}
+	out := make([]byte, 0, len(s)+len(s)/3)
+	for i := range len(s) {
+		if i > 0 && (len(s)-i)%3 == 0 {
+			out = append(out, ',')
+		}
+		out = append(out, s[i])
+	}
+	if neg {
+		return "-" + string(out)
+	}
+	return string(out)
+}
+
+// Duration formats an elapsed time as mm:ss or h:mm:ss.
+func Duration(d time.Duration) string {
+	s := int64(d.Seconds())
+	if s >= 3600 {
+		return fmt.Sprintf("%d:%02d:%02d", s/3600, s/60%60, s%60)
+	}
+	return fmt.Sprintf("%02d:%02d", s/60, s%60)
+}
+
+// Percent formats part/whole as a percentage.
+func Percent(part, whole int64) string {
+	if whole <= 0 {
+		return "–"
+	}
+	p := float64(part) * 100 / float64(whole)
+	if p < 10 {
+		return strconv.FormatFloat(p, 'f', 1, 64) + "%"
+	}
+	return strconv.FormatFloat(p, 'f', 0, 64) + "%"
+}