mountlib: refactor before adding serve docker (#5415)

Co-authored-by: Ivan Andreev <ivandeex@gmail.com>

cmd/mountlib/utils.go

@@ -0,0 +1,55 @@
+package mountlib
+
+import (
+	"io"
+	"os"
+	"runtime"
+
+	"github.com/pkg/errors"
+	"github.com/rclone/rclone/fs"
+)
+
+// CheckMountEmpty checks if folder is empty
+func CheckMountEmpty(mountpoint string) error {
+	fp, fpErr := os.Open(mountpoint)
+
+	if fpErr != nil {
+		return errors.Wrap(fpErr, "Can not open: "+mountpoint)
+	}
+	defer fs.CheckClose(fp, &fpErr)
+
+	_, fpErr = fp.Readdirnames(1)
+
+	if fpErr == io.EOF {
+		return nil
+	}
+
+	msg := "Directory is not empty: " + mountpoint + " If you want to mount it anyway use: --allow-non-empty option"
+	if fpErr == nil {
+		return errors.New(msg)
+	}
+	return errors.Wrap(fpErr, msg)
+}
+
+// ClipBlocks clips the blocks pointed to the OS max
+func ClipBlocks(b *uint64) {
+	var max uint64
+	switch runtime.GOOS {
+	case "windows":
+		if runtime.GOARCH == "386" {
+			max = (1 << 32) - 1
+		} else {
+			max = (1 << 43) - 1
+		}
+	case "darwin":
+		// OSX FUSE only supports 32 bit number of blocks
+		// https://github.com/osxfuse/osxfuse/issues/396
+		max = (1 << 32) - 1
+	default:
+		// no clipping
+		return
+	}
+	if *b > max {
+		*b = max
+	}
+}