refactor byte unit formatting, add unit-specific display precision

cwidgets/util.go

@@ -1,53 +1,84 @@
 package cwidgets
 
 import (
-	"fmt"
 	"strconv"
 )
 
 const (
-	kb = 1024
-	mb = kb * 1024
-	gb = mb * 1024
-	tb = gb * 1024
+	// byte ratio constants
+	_           = iota
+	kib float64 = 1 << (10 * iota)
+	mib
+	gib
+	tib
+	pib
 )
 
-// convenience method
-func ByteFormatInt(n int) string {
-	return ByteFormat(int64(n))
+var (
+	units = []float64{
+		1,
+		kib,
+		mib,
+		gib,
+		tib,
+		pib,
+	}
+
+	// short, full unit labels
+	labels = [][2]string{
+		[2]string{"B", "B"},
+		[2]string{"K", "KiB"},
+		[2]string{"M", "MiB"},
+		[2]string{"G", "GiB"},
+		[2]string{"T", "TiB"},
+		[2]string{"P", "PiB"},
+	}
+
+	// maximum displayed precision per unit
+	maxPrecision = []int{
+		0, // B
+		0, // kib
+		1, // mib
+		1, // gib
+		2, // tib
+		2, // pib
+	}
+)
+
+// convenience methods
+func ByteFormat(n int) string          { return byteFormat(float64(n), false) }
+func ByteFormatShort(n int) string     { return byteFormat(float64(n), true) }
+func ByteFormat64(n int64) string      { return byteFormat(float64(n), false) }
+func ByteFormat64Short(n int64) string { return byteFormat(float64(n), true) }
+
+func byteFormat(n float64, short bool) string {
+	i := len(units) - 1
+
+	for i > 0 {
+		if n >= units[i] {
+			n /= units[i]
+			break
+		}
+		i--
+	}
+
+	if short {
+		return unpadFloat(n, maxPrecision[i]) + labels[i][0]
+	}
+	return unpadFloat(n, maxPrecision[i]) + labels[i][1]
 }
 
-func ByteFormat(n int64) string {
-	if n < kb {
-		return fmt.Sprintf("%sB", strconv.FormatInt(n, 10))
-	}
-	if n < mb {
-		n = n / kb
-		return fmt.Sprintf("%sK", strconv.FormatInt(n, 10))
-	}
-	if n < gb {
-		n = n / mb
-		return fmt.Sprintf("%sM", strconv.FormatInt(n, 10))
-	}
-	if n < tb {
-		nf := float64(n) / gb
-		return fmt.Sprintf("%sG", unpadFloat(nf))
-	}
-	nf := float64(n) / tb
-	return fmt.Sprintf("%sT", unpadFloat(nf))
+func unpadFloat(f float64, maxp int) string {
+	return strconv.FormatFloat(f, 'f', getPrecision(f, maxp), 64)
 }
 
-func unpadFloat(f float64) string {
-	return strconv.FormatFloat(f, 'f', getPrecision(f), 64)
-}
-
-func getPrecision(f float64) int {
+func getPrecision(f float64, maxp int) int {
 	frac := int((f - float64(int(f))) * 100)
-	if frac == 0 {
+	if frac == 0 || maxp == 0 {
 		return 0
 	}
-	if frac%10 == 0 {
+	if frac%10 == 0 || maxp < 2 {
 		return 1
 	}
-	return 2 // default precision
+	return maxp
 }