server: Z21 better checksum calculation

- Tweak XpressNet checksum code to accept custom message size
- Renamed LanX::calcChecksum() to LanX::updateChecksum()
- Added LanX::isChecksumValid()
- Internally reuse XpressNet checksum code
- Removed old commented function in LanXGetLocoInfo

server/src/hardware/protocol/xpressnet/messages.cpp

@@ -25,10 +25,9 @@
 
 namespace XpressNet {
 
-uint8_t calcChecksum(const Message& msg)
+uint8_t calcChecksum(const Message& msg, const int dataSize)
 {
   const uint8_t* p = reinterpret_cast<const uint8_t*>(&msg);
-  const int dataSize = msg.dataSize();
   uint8_t checksum = p[0];
   for(int i = 1; i <= dataSize; i++)
     checksum ^= p[i];
@@ -40,9 +39,9 @@ void updateChecksum(Message& msg)
   *(reinterpret_cast<uint8_t*>(&msg) + msg.dataSize() + 1) = calcChecksum(msg);
 }
 
-bool isChecksumValid(const Message& msg)
+bool isChecksumValid(const Message& msg, const int dataSize)
 {
-  return calcChecksum(msg) == *(reinterpret_cast<const uint8_t*>(&msg) + msg.dataSize() + 1);
+  return calcChecksum(msg, dataSize) == *(reinterpret_cast<const uint8_t*>(&msg) + dataSize + 1);
 }
 
 std::string toString(const Message& message, bool raw)

server/src/hardware/protocol/xpressnet/messages.hpp

@@ -40,9 +40,14 @@ constexpr uint8_t idFeedbackBroadcast = 0x40;
 
 struct Message;
 
-uint8_t calcChecksum(const Message& msg);
+inline uint8_t calcChecksum(const Message& msg);
+uint8_t calcChecksum(const Message& msg, const int dataSize);
+
 void updateChecksum(Message& msg);
-bool isChecksumValid(const Message& msg);
+
+inline bool isChecksumValid(const Message& msg);
+bool isChecksumValid(const Message& msg, const int dataSize);
+
 std::string toString(const Message& message, bool raw = false);
 
 struct Message
@@ -591,6 +596,16 @@ namespace RoSoftS88XpressNetLI
   };
 }
 
+inline uint8_t calcChecksum(const Message& msg)
+{
+  return calcChecksum(msg, msg.dataSize());
+}
+
+inline bool isChecksumValid(const Message& msg)
+{
+  return isChecksumValid(msg, msg.dataSize());
+}
+
 }
 
 inline bool operator ==(const XpressNet::Message& lhs, const XpressNet::Message& rhs)

server/src/hardware/protocol/z21/clientkernel.cpp

@@ -22,7 +22,6 @@
 
 #include "clientkernel.hpp"
 #include "messages.hpp"
-#include "../xpressnet/messages.hpp"
 #include "../../decoder/decoder.hpp"
 #include "../../decoder/decoderchangeflags.hpp"
 #include "../../input/inputcontroller.hpp"
@@ -64,7 +63,7 @@ void ClientKernel::receive(const Message& message)
     {
       const auto& lanX = static_cast<const LanX&>(message);
 
-      if(!XpressNet::isChecksumValid(*reinterpret_cast<const XpressNet::Message*>(&lanX.xheader)))
+      if(!LanX::isChecksumValid(lanX))
         break;
 
       switch(lanX.xheader)
@@ -349,7 +348,7 @@ void ClientKernel::decoderChanged(const Decoder& decoder, DecoderChangeFlags cha
       cmd.setSpeedStep(speedStep);
     }
 
-    cmd.checksum = XpressNet::calcChecksum(*reinterpret_cast<const XpressNet::Message*>(&cmd.xheader));
+    cmd.updateChecksum();
     postSend(cmd);
   }
   else if(has(changes, DecoderChangeFlags::FunctionValue))

server/src/hardware/protocol/z21/iohandler/simulationiohandler.cpp

@@ -60,7 +60,7 @@ bool SimulationIOHandler::send(const Message& message)
               response.db1 |= Z21_CENTRALSTATE_EMERGENCYSTOP;
             if(!m_trackPowerOn)
               response.db1 |= Z21_CENTRALSTATE_TRACKVOLTAGEOFF;
-            response.calcChecksum();
+            response.updateChecksum();
             reply(response);
           }
           else if(message == LanXSetTrackPowerOn())

server/src/hardware/protocol/z21/messages.cpp

@@ -21,6 +21,7 @@
  */
 
 #include "messages.hpp"
+#include "../xpressnet/messages.hpp"
 #include "../../decoder/decoder.hpp"
 #include "../../../core/objectproperty.tpp"
 #include "../../../utils/tohex.hpp"
@@ -291,7 +292,21 @@ LanXLocoInfo::LanXLocoInfo(const Decoder& decoder) :
     setSpeedStep(Decoder::throttleToSpeedStep(decoder.throttle, speedSteps()));
   for(const auto &function : *decoder.functions)
     setFunction(function->number, function->value);
-  calcChecksum();
+  updateChecksum();
+}
+
+void LanX::updateChecksum(uint8_t len)
+{
+  uint8_t val = XpressNet::calcChecksum(*reinterpret_cast<const XpressNet::Message*>(&xheader), len);
+  uint8_t* checksum = &xheader + len + 1;
+  *checksum = val;
+}
+
+bool LanX::isChecksumValid(const LanX &lanX)
+{
+  const XpressNet::Message& msg = *reinterpret_cast<const XpressNet::Message*>(&lanX.xheader);
+  int dataSize = msg.dataSize();
+  return XpressNet::isChecksumValid(msg, dataSize);
 }
 
 }

server/src/hardware/protocol/z21/messages.hpp

@@ -265,18 +265,15 @@ struct LanX : Message
   {
   }
 
-  void calcChecksum(uint8_t len)
+  void updateChecksum(uint8_t len);
+
+  inline void updateChecksum()
   {
-    uint8_t* checksum = &xheader + len + 1;
-    *checksum = xheader;
-    for(uint8_t* db = &xheader + 1; db < checksum; db++)
-      *checksum ^= *db;
+    updateChecksum(xheader & 0x0F);
   }
 
-  inline void calcChecksum()
-  {
-    calcChecksum(xheader & 0x0F);
-  }
+  static bool isChecksumValid(const LanX& lanX);
+
 } ATTRIBUTE_PACKED;
 static_assert(sizeof(LanX) == 5);
 
@@ -402,7 +399,7 @@ struct LanXGetTurnoutInfo : LanX
     , db0(address >> 8)
     , db1(address & 0xFF)
   {
-    calcChecksum();
+    updateChecksum();
   }
 
   uint16_t address() const
@@ -436,7 +433,7 @@ struct LanXSetTurnout : LanX
     if(linearAddress & 0x0001)
       db2 |= db2Port;
 
-    calcChecksum();
+    updateChecksum();
   }
 
   uint16_t address() const
@@ -490,7 +487,7 @@ struct LanXGetLocoInfo : LanX
     LanX(sizeof(LanXGetLocoInfo),  0xE3)
   {
     setAddress(address, longAddress);
-    calcChecksum();
+    updateChecksum();
   }
 
   inline uint16_t address() const
@@ -508,11 +505,6 @@ struct LanXGetLocoInfo : LanX
     addressHigh = longAddress ? (0xC0 | (address >> 8)) : 0x00;
     addressLow = longAddress ? address & 0xFF : address & 0x7F;
   }
-
-  /*inline void calcChecksum()
-  {
-    checksum = xheader ^ db0 ^ addressHigh ^ addressLow;
-  }*/
 } ATTRIBUTE_PACKED;
 static_assert(sizeof(LanXGetLocoInfo) == 9);
 
@@ -641,7 +633,7 @@ struct LanXSetLocoFunction : LanX
     setAddress(address, longAddress);
     setFunctionIndex(functionIndex);
     setSwitchType(value);
-    calcChecksum();
+    updateChecksum();
   }
 
   inline uint16_t address() const
@@ -926,7 +918,7 @@ struct LanXGetVersionReply : LanX
   {
     setXBusVersion(_xBusVersion);
     commandStationId = _commandStationId;
-    calcChecksum();
+    updateChecksum();
   }
 
   inline uint8_t xBusVersion() const
@@ -962,7 +954,7 @@ struct LanXGetFirmwareVersionReply : LanX
   {
     setVersionMajor(_major);
     setVersionMinor(_minor);
-    calcChecksum();
+    updateChecksum();
   }
 
   inline uint8_t versionMajor() const
@@ -1271,7 +1263,7 @@ struct LanXLocoInfo : LanX
     }
   }
 
-  void calcChecksum()
+  void updateChecksum()
   {
     checksum = xheader;
     for(uint8_t* db = &addressHigh; db < &checksum; db++)

server/src/hardware/protocol/z21/serverkernel.cpp

@@ -109,7 +109,7 @@ void ServerKernel::receiveFrom(const Message& message, IOHandler::ClientId clien
               response.db1 |= Z21_CENTRALSTATE_EMERGENCYSTOP;
             if(m_trackPowerOn != TriState::True)
               response.db1 |= Z21_CENTRALSTATE_TRACKVOLTAGEOFF;
-            response.calcChecksum();
+            response.updateChecksum();
             sendTo(response, clientId);
           }
           else if(message == LanXSetTrackPowerOn())