Fix handling of byte count fields

The various byte count fields are all unsigned byte however the incoming
data are loaded in a QByteArray which returns signed char. This patch
fixes this by converting the field value to quint8.

[ChangeLog][Modbus] Fixed handling of packets with payloads longer than
127 bytes.

Task-number: QTBUG-54834
Change-Id: I699c4cf0cea9933bef6c040c573d2d6e6a113920
Reviewed-by: André Hartmann <aha_1980@gmx.de>

1 files changed, 19 insertions, 0 deletions

diff --git a/tests/auto/qmodbuspdu/tst_qmodbuspdu.cpp b/tests/auto/qmodbuspdu/tst_qmodbuspdu.cpp
index 76bfea3..9c74a6c 100644
--- a/tests/auto/qmodbuspdu/tst_qmodbuspdu.cpp
+++ b/tests/auto/qmodbuspdu/tst_qmodbuspdu.cpp
@@ -803,6 +803,25 @@ private slots:
             quint8(0xff)); // dummy additional data
         QCOMPARE(QModbusResponse::calculateDataSize(rdi), 22);
     }
+
+    void testCalculateLongDataSize()
+    {
+        QByteArray longData = QByteArray(128, ' ');
+        longData[0] = longData.size();
+        const QModbusResponse response(QModbusResponse::ReadCoils, longData);
+        QCOMPARE(QModbusResponse::calculateDataSize(response), 1 + longData.size());
+
+        const QModbusRequest wfrRequest(QModbusPdu::WriteFileRecord, longData);
+        QCOMPARE(QModbusRequest::calculateDataSize(wfrRequest), 1 + longData.size());
+
+        longData = QByteArray(4 + 128, ' ');
+        longData[4] = 128;
+        const QModbusRequest wmcRequest(QModbusPdu::WriteMultipleCoils, longData);
+        QCOMPARE(QModbusRequest::calculateDataSize(wmcRequest), 1 + longData.size());
+
+        const QModbusRequest wmrRequest(QModbusPdu::WriteMultipleRegisters, longData);
+        QCOMPARE(QModbusRequest::calculateDataSize(wmrRequest), 1 + longData.size());
+    }
 };
 
 QTEST_MAIN(tst_QModbusPdu)