Add transfer logging output (#77)

Co-authored-by: Dane Everitt <dane@daneeveritt.com>

system/utils.go

@@ -2,6 +2,7 @@ package system
 
 import (
 	"context"
+	"fmt"
 	"sync"
 	"sync/atomic"
 	"time"
@@ -23,6 +24,18 @@ func Every(ctx context.Context, d time.Duration, work func(t time.Time)) {
 	}()
 }
 
+func FormatBytes(b int64) string {
+	if b < 1024 {
+		return fmt.Sprintf("%d B", b)
+	}
+	div, exp := int64(1024), 0
+	for n := b / 1024; n >= 1024; n /= 1024 {
+		div *= 1024
+		exp++
+	}
+	return fmt.Sprintf("%.1f %ciB", float64(b)/float64(div), "KMGTPE"[exp])
+}
+
 type AtomicBool struct {
 	flag uint32
 }