serve sftp: extract function refactoring for handling hashsum commands

cmd/serve/sftp/connection.go

@@ -100,6 +100,48 @@ func (c *conn) execCommand(ctx context.Context, out io.Writer, command string) (
 		if binary == "sha1sum" {
 			ht = hash.SHA1
 		}
+		return c.handleHashsumCommand(ctx, out, ht, args)
+	case "echo":
+		// Special cases for legacy rclone command detection.
+		// Before rclone v1.49.0 the sftp backend used "echo 'abc' | md5sum" when
+		// detecting hash support, but was then changed to instead just execute
+		// md5sum/sha1sum (without arguments), which is handled above. The following
+		// code is therefore only necessary to support rclone versions older than
+		// v1.49.0 using a sftp remote connected to a rclone serve sftp instance
+		// running a newer version of rclone (e.g. latest).
+		switch args {
+		case "'abc' | md5sum":
+			if c.vfs.Fs().Hashes().Contains(hash.MD5) {
+				_, err = fmt.Fprintf(out, "0bee89b07a248e27c83fc3d5951213c1  -\n")
+				if err != nil {
+					return fmt.Errorf("send output failed: %w", err)
+				}
+			} else {
+				return errors.New("md5 hash not supported")
+			}
+		case "'abc' | sha1sum":
+			if c.vfs.Fs().Hashes().Contains(hash.SHA1) {
+				_, err = fmt.Fprintf(out, "03cfd743661f07975fa2f1220c5194cbaff48451  -\n")
+				if err != nil {
+					return fmt.Errorf("send output failed: %w", err)
+				}
+			} else {
+				return errors.New("sha1 hash not supported")
+			}
+		default:
+			_, err = fmt.Fprintf(out, "%s\n", args)
+			if err != nil {
+				return fmt.Errorf("send output failed: %w", err)
+			}
+		}
+	default:
+		return fmt.Errorf("%q not implemented", command)
+	}
+	return nil
+}
+
+// handleHashsumCommand is a helper to execCommand for common functionality of hashsum related commands
+func (c *conn) handleHashsumCommand(ctx context.Context, out io.Writer, ht hash.Type, args string) (err error) {
 	if !c.vfs.Fs().Hashes().Contains(ht) {
 		return fmt.Errorf("%v hash not supported", ht)
 	}
@@ -150,42 +192,6 @@ func (c *conn) execCommand(ctx context.Context, out io.Writer, command string) (
 	if err != nil {
 		return fmt.Errorf("send output failed: %w", err)
 	}
-	case "echo":
-		// Special cases for legacy rclone command detection.
-		// Before rclone v1.49.0 the sftp backend used "echo 'abc' | md5sum" when
-		// detecting hash support, but was then changed to instead just execute
-		// md5sum/sha1sum (without arguments), which is handled above. The following
-		// code is therefore only necessary to support rclone versions older than
-		// v1.49.0 using a sftp remote connected to a rclone serve sftp instance
-		// running a newer version of rclone (e.g. latest).
-		switch args {
-		case "'abc' | md5sum":
-			if c.vfs.Fs().Hashes().Contains(hash.MD5) {
-				_, err = fmt.Fprintf(out, "0bee89b07a248e27c83fc3d5951213c1  -\n")
-				if err != nil {
-					return fmt.Errorf("send output failed: %w", err)
-				}
-			} else {
-				return errors.New("md5 hash not supported")
-			}
-		case "'abc' | sha1sum":
-			if c.vfs.Fs().Hashes().Contains(hash.SHA1) {
-				_, err = fmt.Fprintf(out, "03cfd743661f07975fa2f1220c5194cbaff48451  -\n")
-				if err != nil {
-					return fmt.Errorf("send output failed: %w", err)
-				}
-			} else {
-				return errors.New("sha1 hash not supported")
-			}
-		default:
-			_, err = fmt.Fprintf(out, "%s\n", args)
-			if err != nil {
-				return fmt.Errorf("send output failed: %w", err)
-			}
-		}
-	default:
-		return fmt.Errorf("%q not implemented", command)
-	}
 	return nil
 }