extract the parsing of the SDSTransfer header part into a public

function for reuse

Author: ftl

sds/sds.go

@@ -301,8 +301,33 @@ func (r SDSShortReport) Encode(bytes []byte, bits int) ([]byte, int) {
 
 // ParseSDSTransfer parses a SDS-TRANSFER PDU from the given bytes
 func ParseSDSTransfer(bytes []byte) (SDSTransfer, error) {
+	result, userdataStart, err := ParseSDSTransferHeader(bytes)
+	if err != nil {
+		return SDSTransfer{}, err
+	}
+
+	var sdu any
+
+	switch result.Protocol {
+	case TextMessaging, ImmediateTextMessaging:
+		sdu, err = ParseTextSDU(bytes[userdataStart:])
+	case UserDataHeaderMessaging:
+		sdu, err = ParseConcatenatedTextSDU(bytes[userdataStart:])
+	default:
+		return SDSTransfer{}, fmt.Errorf("protocol 0x%x is not supported as SDS-TRANSFER content", bytes[0])
+	}
+
+	if err != nil {
+		return SDSTransfer{}, err
+	}
+	result.UserData = sdu
+
+	return result, nil
+}
+
+func ParseSDSTransferHeader(bytes []byte) (SDSTransfer, int, error) {
 	if len(bytes) < 4 {
-		return SDSTransfer{}, fmt.Errorf("SDS-TRANSFER PDU too short: %d", len(bytes))
+		return SDSTransfer{}, 0, fmt.Errorf("SDS-TRANSFER PDU too short: %d", len(bytes))
 	}
 
 	var result SDSTransfer
@@ -317,31 +342,14 @@ func ParseSDSTransfer(bytes []byte) (SDSTransfer, error) {
 	if storeForwardControl {
 		sfc, err := ParseStoreForwardControl(bytes[3:])
 		if err != nil {
-			return SDSTransfer{}, err
+			return SDSTransfer{}, 0, err
 		}
 
 		result.StoreForwardControl = sfc
 		userdataStart += sfc.Length()
 	}
 
-	var sdu any
-	var err error
-
-	switch result.Protocol {
-	case TextMessaging, ImmediateTextMessaging:
-		sdu, err = ParseTextSDU(bytes[userdataStart:])
-	case UserDataHeaderMessaging:
-		sdu, err = ParseConcatenatedTextSDU(bytes[userdataStart:])
-	default:
-		return SDSTransfer{}, fmt.Errorf("protocol 0x%x is not supported as SDS-TRANSFER content", bytes[0])
-	}
-
-	if err != nil {
-		return SDSTransfer{}, err
-	}
-	result.UserData = sdu
-
-	return result, nil
+	return result, userdataStart, nil
 }
 
 // NewTextMessageTransfer returns a new SDS-TRANSFER PDU for text messaging with the given parameters