Use IEC prefixes for file sizes

This to clear any confusion around file size.

As reported at #205, some OS, or desktop environments, or applications,
or whatever, show file sizes using SI units (ie.  multiples of 1000),
while others use IEC units (multiples of 1024). And both might use the
suffixes KB, MB, GB and TB for it. So users get confused.

For example, a file that is said to be "3.5 GB" in the Mirrorbits page,
will then appear as "3.8 GB" after download in the GNOME file manager,
because GNOME prefers SI units.

So let's use the IEC prefixes (Ki, Mi, Gi and Ti) in the Mirrorbits web
pages, that should clear any ambiguity.

Closes: #205

Author: elboulangero

utils/utils.go

@@ -104,12 +104,12 @@ func IsStopped(stop <-chan struct{}) bool {
 
 // ReadableSize returns a file size in a human readable form
 func ReadableSize(value int64) string {
-	units := []string{"bytes", "KB", "MB", "GB", "TB"}
+	units := []string{"bytes", "KiB", "MiB", "GiB", "TiB"}
 
 	v := float64(value)
 
 	for _, u := range units {
-		if v < 1024 || u == "TB" {
+		if v < 1024 || u == "TiB" {
 			return fmt.Sprintf("%3.1f %s", v, u)
 		}
 		v /= 1024

utils/utils_test.go

@@ -118,7 +118,7 @@ func TestIsStopped(t *testing.T) {
 
 func TestReadableSize(t *testing.T) {
 	ivalues := []int64{0, 1, 1024, 1000000}
-	svalues := []string{"0.0 bytes", "1.0 bytes", "1.0 KB", "976.6 KB"}
+	svalues := []string{"0.0 bytes", "1.0 bytes", "1.0 KiB", "976.6 KiB"}
 
 	for i := range ivalues {
 		if r := ReadableSize(ivalues[i]); r != svalues[i] {