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Add nullable support throughout the whole library.

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This requires reference types that can be null to be annotated by a ? operator, similar to value types.

This gives the advantage that the compiler can warn against any null dereference exceptions, of which this commits elimits a few.

To make the underlying protocol implementation not any more complicated and to eliminate existing problems, and not that precise error reporting, I replaced some return null statements with explicit Exceptions. This lead to the assumption that those core protocoll functions always return non-null objects if they do not throw, making the PLC code simpler.

Adjust some NotConnected tests to look for explicit PlcException instead of NullReferenceException.
This commit is contained in:
Serge Camille
2020-08-19 21:10:24 +02:00
parent e68ca64596
commit bd8177d39e
13 changed files with 159 additions and 73 deletions
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24
S7.Net/PlcSynchronous.cs
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@@ -19,6 +19,7 @@ namespace S7.Net
try
{
var stream = GetStreamIfAvailable();
stream.Write(ConnectionRequest.GetCOTPConnectionRequest(CPU, Rack, Slot), 0, 22);
var response = COTP.TPDU.Read(stream);
if (response.PDUType != 0xd0) //Connect Confirm
@@ -52,7 +53,7 @@ namespace S7.Net
tcpClient = new TcpClient();
ConfigureConnection();
tcpClient.Connect(IP, Port);
stream = tcpClient.GetStream();
_stream = tcpClient.GetStream();
}
catch (SocketException sex)
{
@@ -106,7 +107,7 @@ namespace S7.Net
/// <param name="varType">Type of the variable/s that you are reading</param>
/// <param name="bitAdr">Address of bit. If you want to read DB1.DBX200.6, set 6 to this parameter.</param>
/// <param name="varCount"></param>
public object Read(DataType dataType, int db, int startByteAdr, VarType varType, int varCount, byte bitAdr = 0)
public object? Read(DataType dataType, int db, int startByteAdr, VarType varType, int varCount, byte bitAdr = 0)
{
int cntBytes = VarTypeToByteLength(varType, varCount);
byte[] bytes = ReadBytes(dataType, db, startByteAdr, cntBytes);
@@ -119,8 +120,8 @@ namespace S7.Net
/// If the read was not successful, check LastErrorCode or LastErrorString.
/// </summary>
/// <param name="variable">Input strings like "DB1.DBX0.0", "DB20.DBD200", "MB20", "T45", etc.</param>
/// <returns>Returns an object that contains the value. This object must be cast accordingly.</returns>
public object Read(string variable)
/// <returns>Returns an object that contains the value. This object must be cast accordingly. If no data has been read, null will be returned</returns>
public object? Read(string variable)
{
var adr = new PLCAddress(variable);
return Read(adr.DataType, adr.DbNumber, adr.StartByte, adr.VarType, 1, (byte)adr.BitNumber);
@@ -132,8 +133,8 @@ namespace S7.Net
/// <param name="structType">Type of the struct to be readed (es.: TypeOf(MyStruct)).</param>
/// <param name="db">Address of the DB.</param>
/// <param name="startByteAdr">Start byte address. If you want to read DB1.DBW200, this is 200.</param>
/// <returns>Returns a struct that must be cast.</returns>
public object ReadStruct(Type structType, int db, int startByteAdr = 0)
/// <returns>Returns a struct that must be cast. If no data has been read, null will be returned</returns>
public object? ReadStruct(Type structType, int db, int startByteAdr = 0)
{
int numBytes = Struct.GetStructSize(structType);
// now read the package
@@ -188,7 +189,7 @@ namespace S7.Net
/// <param name="db">Index of the DB; es.: 1 is for DB1</param>
/// <param name="startByteAdr">Start byte address. If you want to read DB1.DBW200, this is 200.</param>
/// <returns>An instance of the class with the values read from the PLC. If no data has been read, null will be returned</returns>
public T ReadClass<T>(int db, int startByteAdr = 0) where T : class
public T? ReadClass<T>(int db, int startByteAdr = 0) where T : class
{
return ReadClass(() => Activator.CreateInstance<T>(), db, startByteAdr);
}
@@ -202,7 +203,7 @@ namespace S7.Net
/// <param name="db">Index of the DB; es.: 1 is for DB1</param>
/// <param name="startByteAdr">Start byte address. If you want to read DB1.DBW200, this is 200.</param>
/// <returns>An instance of the class with the values read from the PLC. If no data has been read, null will be returned</returns>
public T ReadClass<T>(Func<T> classFactory, int db, int startByteAdr = 0) where T : class
public T? ReadClass<T>(Func<T> classFactory, int db, int startByteAdr = 0) where T : class
{
var instance = classFactory();
int readBytes = ReadClass(instance, db, startByteAdr);
@@ -340,6 +341,7 @@ namespace S7.Net
private byte[] ReadBytesWithSingleRequest(DataType dataType, int db, int startByteAdr, int count)
{
var stream = GetStreamIfAvailable();
byte[] bytes = new byte[count];
try
{
@@ -375,6 +377,8 @@ namespace S7.Net
{
AssertPduSizeForWrite(dataItems);
var stream = GetStreamIfAvailable();
var message = new ByteArray();
var length = S7WriteMultiple.CreateRequest(message, dataItems);
stream.Write(message.Array, 0, length);
@@ -385,6 +389,7 @@ namespace S7.Net
private void WriteBytesWithASingleRequest(DataType dataType, int db, int startByteAdr, byte[] value)
{
var stream = GetStreamIfAvailable();
int varCount = 0;
try
{
@@ -429,6 +434,7 @@ namespace S7.Net
private void WriteBitWithASingleRequest(DataType dataType, int db, int startByteAdr, int bitAdr, bool bitValue)
{
var stream = GetStreamIfAvailable();
int varCount = 0;
try
@@ -484,6 +490,8 @@ namespace S7.Net
//replies with bigger PDU size in connection setup.
AssertPduSizeForRead(dataItems);
var stream = GetStreamIfAvailable();
try
{
// first create the header