serve sftp: extract function refactoring for handling hashsum commands

cmd/serve/sftp/connection.go

@@ -100,56 +100,7 @@ func (c *conn) execCommand(ctx context.Context, out io.Writer, command string) (
 		if binary == "sha1sum" {
 			ht = hash.SHA1
 		}
-		if !c.vfs.Fs().Hashes().Contains(ht) {
+		return c.handleHashsumCommand(ctx, out, ht, args)
-			return fmt.Errorf("%v hash not supported", ht)
-		}
-		var hashSum string
-		if args == "" {
-			// empty hash for no input
-			if ht == hash.MD5 {
-				hashSum = "d41d8cd98f00b204e9800998ecf8427e"
-			} else {
-				hashSum = "da39a3ee5e6b4b0d3255bfef95601890afd80709"
-			}
-			args = "-"
-		} else {
-			node, err := c.vfs.Stat(args)
-			if err != nil {
-				return fmt.Errorf("hash failed finding file %q: %w", args, err)
-			}
-			if node.IsDir() {
-				return errors.New("can't hash directory")
-			}
-			o, ok := node.DirEntry().(fs.ObjectInfo)
-			if !ok {
-				fs.Debugf(args, "File uploading - reading hash from VFS cache")
-				in, err := node.Open(os.O_RDONLY)
-				if err != nil {
-					return fmt.Errorf("hash vfs open failed: %w", err)
-				}
-				defer func() {
-					_ = in.Close()
-				}()
-				h, err := hash.NewMultiHasherTypes(hash.NewHashSet(ht))
-				if err != nil {
-					return fmt.Errorf("hash vfs create multi-hasher failed: %w", err)
-				}
-				_, err = io.Copy(h, in)
-				if err != nil {
-					return fmt.Errorf("hash vfs copy failed: %w", err)
-				}
-				hashSum = h.Sums()[ht]
-			} else {
-				hashSum, err = o.Hash(ctx, ht)
-				if err != nil {
-					return fmt.Errorf("hash failed: %w", err)
-				}
-			}
-		}
-		_, err = fmt.Fprintf(out, "%s  %s\n", hashSum, args)
-		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
@@ -189,6 +140,61 @@ func (c *conn) execCommand(ctx context.Context, out io.Writer, command string) (
 	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)
+	}
+	var hashSum string
+	if args == "" {
+		// empty hash for no input
+		if ht == hash.MD5 {
+			hashSum = "d41d8cd98f00b204e9800998ecf8427e"
+		} else {
+			hashSum = "da39a3ee5e6b4b0d3255bfef95601890afd80709"
+		}
+		args = "-"
+	} else {
+		node, err := c.vfs.Stat(args)
+		if err != nil {
+			return fmt.Errorf("hash failed finding file %q: %w", args, err)
+		}
+		if node.IsDir() {
+			return errors.New("can't hash directory")
+		}
+		o, ok := node.DirEntry().(fs.ObjectInfo)
+		if !ok {
+			fs.Debugf(args, "File uploading - reading hash from VFS cache")
+			in, err := node.Open(os.O_RDONLY)
+			if err != nil {
+				return fmt.Errorf("hash vfs open failed: %w", err)
+			}
+			defer func() {
+				_ = in.Close()
+			}()
+			h, err := hash.NewMultiHasherTypes(hash.NewHashSet(ht))
+			if err != nil {
+				return fmt.Errorf("hash vfs create multi-hasher failed: %w", err)
+			}
+			_, err = io.Copy(h, in)
+			if err != nil {
+				return fmt.Errorf("hash vfs copy failed: %w", err)
+			}
+			hashSum = h.Sums()[ht]
+		} else {
+			hashSum, err = o.Hash(ctx, ht)
+			if err != nil {
+				return fmt.Errorf("hash failed: %w", err)
+			}
+		}
+	}
+	_, err = fmt.Fprintf(out, "%s  %s\n", hashSum, args)
+	if err != nil {
+		return fmt.Errorf("send output failed: %w", err)
+	}
+	return nil
+}
+
 // handle a new incoming channel request
 func (c *conn) handleChannel(newChannel ssh.NewChannel) {
 	fs.Debugf(c.what, "Incoming channel: %s\n", newChannel.ChannelType())