refactor(usb): move usbconfig to a seperated package

internal/usbgadget/utils.go

@@ -0,0 +1,63 @@
+package usbgadget
+
+import (
+	"bytes"
+	"fmt"
+	"os"
+	"path/filepath"
+)
+
+// Helper function to get absolute value of float64
+func abs(x float64) float64 {
+	if x < 0 {
+		return -x
+	}
+	return x
+}
+
+func joinPath(basePath string, paths []string) string {
+	pathArr := append([]string{basePath}, paths...)
+	return filepath.Join(pathArr...)
+}
+
+func ensureSymlink(linkPath string, target string) error {
+	if _, err := os.Lstat(linkPath); err == nil {
+		currentTarget, err := os.Readlink(linkPath)
+		if err != nil || currentTarget != target {
+			err = os.Remove(linkPath)
+			if err != nil {
+				return fmt.Errorf("failed to remove existing symlink %s: %w", linkPath, err)
+			}
+		}
+	} else if !os.IsNotExist(err) {
+		return fmt.Errorf("failed to check if symlink exists: %w", err)
+	}
+
+	if err := os.Symlink(target, linkPath); err != nil {
+		return fmt.Errorf("failed to create symlink from %s to %s: %w", linkPath, target, err)
+	}
+
+	return nil
+}
+
+func (u *UsbGadget) writeIfDifferent(filePath string, content []byte, permMode os.FileMode) error {
+	if _, err := os.Stat(filePath); err == nil {
+		oldContent, err := os.ReadFile(filePath)
+		if err == nil {
+			if bytes.Equal(oldContent, content) {
+				u.log.Tracef("skipping writing to %s as it already has the correct content", filePath)
+				return nil
+			}
+
+			if len(oldContent) == len(content)+1 &&
+				bytes.Equal(oldContent[:len(content)], content) &&
+				oldContent[len(content)] == 10 {
+				u.log.Tracef("skipping writing to %s as it already has the correct content", filePath)
+				return nil
+			}
+
+			u.log.Tracef("writing to %s as it has different content old%v new%v", filePath, oldContent, content)
+		}
+	}
+	return os.WriteFile(filePath, content, permMode)
+}