refactor: use strings.Cut to simplify code

Signed-off-by: vicerace <vicerace@sohu.com>

backend/crypt/cipher.go

@@ -403,14 +403,14 @@ func (c *Cipher) deobfuscateSegment(ciphertext string) (string, error) {
 	if ciphertext == "" {
 		return "", nil
 	}
-	pos := strings.Index(ciphertext, ".")
-	if pos == -1 {
+	before, after, ok := strings.Cut(ciphertext, ".")
+	if !ok {
 		return "", ErrorNotAnEncryptedFile
 	} // No .
-	num := ciphertext[:pos]
+	num := before
 	if num == "!" {
 		// No rotation; probably original was not valid unicode
-		return ciphertext[pos+1:], nil
+		return after, nil
 	}
 	dir, err := strconv.Atoi(num)
 	if err != nil {
@@ -425,7 +425,7 @@ func (c *Cipher) deobfuscateSegment(ciphertext string) (string, error) {
 	var result bytes.Buffer
 
 	inQuote := false
-	for _, runeValue := range ciphertext[pos+1:] {
+	for _, runeValue := range after {
 		switch {
 		case inQuote:
 			_, _ = result.WriteRune(runeValue)

cmd/bisync/listing.go

@@ -389,8 +389,8 @@ func parseHash(str string) (string, string, error) {
 	if str == "-" {
 		return "", "", nil
 	}
-	if pos := strings.Index(str, ":"); pos > 0 {
-		name, val := str[:pos], str[pos+1:]
+	if before, after, ok := strings.Cut(str, ":"); ok {
+		name, val := before, after
 		if name != "" && val != "" {
 			return name, val, nil
 		}

cmd/serve/sftp/connection.go

@@ -58,10 +58,10 @@ type conn struct {
 // interoperate with the rclone sftp backend
 func (c *conn) execCommand(ctx context.Context, out io.Writer, command string) (err error) {
 	binary, args := command, ""
-	space := strings.Index(command, " ")
-	if space >= 0 {
-		binary = command[:space]
-		args = strings.TrimLeft(command[space+1:], " ")
+	before, after, ok := strings.Cut(command, " ")
+	if ok {
+		binary = before
+		args = strings.TrimLeft(after, " ")
 	}
 	args = shellUnEscape(args)
 	fs.Debugf(c.what, "exec command: binary = %q, args = %q", binary, args)

fs/bwtimetable.go

@@ -29,16 +29,16 @@ func (bp *BwPair) String() string {
 // Set the bandwidth from a string which is either
 // SizeSuffix or SizeSuffix:SizeSuffix (for tx:rx bandwidth)
 func (bp *BwPair) Set(s string) (err error) {
-	colon := strings.Index(s, ":")
+	before, after, ok := strings.Cut(s, ":")
 	stx, srx := s, ""
-	if colon >= 0 {
-		stx, srx = s[:colon], s[colon+1:]
+	if ok {
+		stx, srx = before, after
 	}
 	err = bp.Tx.Set(stx)
 	if err != nil {
 		return err
 	}
-	if colon < 0 {
+	if !ok {
 		bp.Rx = bp.Tx
 	} else {
 		err = bp.Rx.Set(srx)