SetFilePosition Method (EasyUAFileTransferClientCore)

Sets the current position of the file handle.

Syntax

Visual Basic
C#
C++/CLI

'Declaration
 
Public Sub SetFilePosition( _
   ByVal endpointDescriptor As UAEndpointDescriptor, _
   ByVal fileNodeDescriptor As UANodeDescriptor, _
   ByVal fileHandle As UAFileHandle, _
   ByVal position As Long _
)

'Usage
 
Dim instance As EasyUAFileTransferClientCore
Dim endpointDescriptor As UAEndpointDescriptor
Dim fileNodeDescriptor As UANodeDescriptor
Dim fileHandle As UAFileHandle
Dim position As Long
 
instance.SetFilePosition(endpointDescriptor, fileNodeDescriptor, fileHandle, position)

public void SetFilePosition( 
   UAEndpointDescriptor endpointDescriptor,
   UANodeDescriptor fileNodeDescriptor,
   UAFileHandle fileHandle,
   long position
)

public:
void SetFilePosition( 
   UAEndpointDescriptor^ endpointDescriptor,
   UANodeDescriptor^ fileNodeDescriptor,
   UAFileHandle^ fileHandle,
   int64 position
)

Parameters

endpointDescriptor: Endpoint descriptor. Identifies the OPC-UA server.
fileNodeDescriptor: Node descriptor of the OPC UA file.
fileHandle: A handle indicating the access request and thus indirectly the position inside the file.
position: The position to be set for the fileHandle in the file. If a ReadFile or WriteFile method is called, it starts at that position. If the position is higher than the file size, the position is set to the end of the file.

Exceptions

Exception Description

Exception	Description
System.ArgumentNullException	A `null` reference (`Nothing` in Visual Basic) is passed to a method that does not accept it as a valid argument. This is a usage error, i.e. it will never occur (the exception will not be thrown) in a correctly written program. Your code should not catch this exception.
System.ArgumentOutOfRangeException	The value of an argument is outside the allowable range of values as defined by the invoked method. This is a usage error, i.e. it will never occur (the exception will not be thrown) in a correctly written program. Your code should not catch this exception.
OpcLabs.EasyOpc.UA.OperationModel.UAException	The OPC UA operation has failed. This operation exception in uniformly used to allow common handling of various kinds of errors. The System.Exception.InnerException always contains information about the actual error cause. This is an operation error that depends on factors external to your program, and thus cannot be always avoided. Your code must handle it appropriately.

System.ArgumentNullException

A null reference (Nothing in Visual Basic) is passed to a method that does not accept it as a valid argument.

This is a usage error, i.e. it will never occur (the exception will not be thrown) in a correctly written program. Your code should not catch this exception.

System.ArgumentOutOfRangeException

The value of an argument is outside the allowable range of values as defined by the invoked method.

This is a usage error, i.e. it will never occur (the exception will not be thrown) in a correctly written program. Your code should not catch this exception.

OpcLabs.EasyOpc.UA.OperationModel.UAException

The OPC UA operation has failed. This operation exception in uniformly used to allow common handling of various kinds of errors. The System.Exception.InnerException always contains information about the actual error cause.

This is an operation error that depends on factors external to your program, and thus cannot be always avoided. Your code must handle it appropriately.

Remarks

This method corresponds to (but is not fully identical with) the OPC UA File Transfer Method .

The fileNodeDescriptor must be an existing node in the server, of object type OpcLabs.EasyOpc.UA.AddressSpace.Standard.UAObjectTypeIds.FileType.

In OPC UA, the position is UInt64. In this method, the position is System.UInt32, and only non-negative values are valid.

Recommendation: Whenever possible, do not use this method directly, and use a higher-level abstraction instead. You can create System.IO.Stream objects for accessing the file data by using methods like OpcLabs.EasyOpc.UA.IO.Extensions.IEasyUAFileTransferExtension2.OpenOrCreateStream, or obtain them through a file provider (using IEasyUAFileTransferExtension.GetFileProvider2 or IEasyUAFileTransferExtension.GetWritableFileProvider).

Example

// Shows how to read different sections from an OPC UA file, using the file transfer client.
// Note: Consider using a higher-level abstraction, OPC UA file provider, instead.
//
// Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .

using System;
using OpcLabs.EasyOpc.UA;
using OpcLabs.EasyOpc.UA.FileTransfer;
using OpcLabs.EasyOpc.UA.OperationModel;

namespace UADocExamples.FileTransfer._EasyUAFileTransferClient
{
    class ReadAndSetFilePosition
    {
        public static void Main1()
        {
            // Unified Automation .NET based demo server (UaNETServer/UaServerNET.exe)
            UAEndpointDescriptor endpointDescriptor = "opc.tcp://localhost:48030";

            // A node that represents an instance of OPC UA FileType object.
            UANodeDescriptor fileNodeDescriptor = "nsu=http://www.unifiedautomation.com/DemoServer/ ;s=Demo.Files.TextFile";
            
            // Instantiate the file transfer client object
            var fileTransferClient = new EasyUAFileTransferClient();

            // Open the file, read two separate sections of it, and close it.
            try
            {
                Console.WriteLine("Opening file...");
                using (UAFileHandle fileHandle = fileTransferClient.OpenFile(endpointDescriptor, fileNodeDescriptor, UAOpenFileModes.Read))
                {
                    Console.WriteLine("Reading first file section...");
                    byte[] bytes1 = fileTransferClient.ReadFile(endpointDescriptor, fileNodeDescriptor, fileHandle, length:16);
                    Console.WriteLine($"First section: {BitConverter.ToString(bytes1)}");

                    Console.WriteLine("Reading second file section...");
                    byte[] bytes2 = fileTransferClient.ReadFile(endpointDescriptor, fileNodeDescriptor, fileHandle, length: 10);
                    Console.WriteLine($"Second section: {BitConverter.ToString(bytes2)}");

                    Console.WriteLine("Setting file position...");
                    fileTransferClient.SetFilePosition(endpointDescriptor, fileNodeDescriptor, fileHandle, position:100);

                    Console.WriteLine("Reading third file section...");
                    byte[] bytes3 = fileTransferClient.ReadFile(endpointDescriptor, fileNodeDescriptor, fileHandle, length: 20);
                    Console.WriteLine($"Third section: {BitConverter.ToString(bytes3)}");

                    Console.WriteLine("Closing file...");
                    fileTransferClient.CloseFile(endpointDescriptor, fileNodeDescriptor, fileHandle);
                }
            }
            catch (UAException uaException)
            {
                Console.WriteLine("*** Failure: {0}", uaException.GetBaseException().Message);
                return;
            }

            Console.WriteLine("Finished...");
        }
    }
}

# Shows how to read different sections from an OPC UA file, using the file transfer client.
# Note: Consider using a higher-level abstraction, OPC UA file provider, instead.
#
# Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
# OPC client and subscriber examples in Python on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-Python .
# The QuickOPC package is needed. Install it using "pip install opclabs_quickopc".
import opclabs_quickopc

# Import .NET namespaces.
from System import *
from OpcLabs.EasyOpc.UA import *
from OpcLabs.EasyOpc.UA.FileTransfer import *
from OpcLabs.EasyOpc.UA.OperationModel import *


# Unified Automation .NET based demo server (UaNETServer/UaServerNET.exe).
endpointDescriptor = UAEndpointDescriptor('opc.tcp://localhost:48030')

# A node that represents an instance of OPC UA FileType object.
fileNodeDescriptor = UANodeDescriptor('nsu=http://www.unifiedautomation.com/DemoServer/ ;s=Demo.Files.TextFile')

# Instantiate the file transfer client object.
fileTransferClient = EasyUAFileTransferClient()

# Open the file, read two separate sections of it, and close it.
fileHandle = None
try:
    print('Opening file...')
    fileHandle = fileTransferClient.OpenFile(endpointDescriptor, fileNodeDescriptor, UAOpenFileModes.Read)

    print('Reading first file section...')
    bytes1 = fileTransferClient.ReadFile(endpointDescriptor, fileNodeDescriptor, fileHandle, 16)    # length
    print('First section: ', BitConverter.ToString(bytes1), sep='')

    print('Reading second file section...')
    bytes2 = fileTransferClient.ReadFile(endpointDescriptor, fileNodeDescriptor, fileHandle, 10)    # length
    print('Second section: ', BitConverter.ToString(bytes2), sep='')

    print('Setting file position...')
    fileTransferClient.SetFilePosition(endpointDescriptor, fileNodeDescriptor, fileHandle, 100) # position

    print('Reading third file section...')
    bytes3 = fileTransferClient.ReadFile(endpointDescriptor, fileNodeDescriptor, fileHandle, 20)    # length
    print('Third section: ', BitConverter.ToString(bytes3), sep='')

    print('Closing file...')
    fileTransferClient.CloseFile(endpointDescriptor, fileNodeDescriptor, fileHandle)

except UAException as uaException:
    print('*** Failure: ' + uaException.GetBaseException().Message)
    exit()

finally:
    fileHandle and fileHandle.Dispose()

print()
print('Finished.')

' Shows how to read different sections from an OPC UA file, using the file transfer client.
' Note: Consider using a higher-level abstraction, OPC UA file provider, instead.
'
' Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .

Imports OpcLabs.EasyOpc.UA
Imports OpcLabs.EasyOpc.UA.FileTransfer
Imports OpcLabs.EasyOpc.UA.OperationModel

Namespace FileTransfer._EasyUAFileTransferClient

    Friend Class ReadAndSetFilePosition

        Public Shared Sub Main1()

            ' Unified Automation .NET based demo server (UaNETServer/UaServerNET.exe)
            Dim endpointDescriptor As UAEndpointDescriptor = "opc.tcp://localhost:48030"

            ' A node that represents an instance of OPC UA FileType object.
            Dim fileNodeDescriptor As UANodeDescriptor = "nsu=http://www.unifiedautomation.com/DemoServer/ ;s=Demo.Files.TextFile"

            ' Instantiate the file transfer client object
            Dim fileTransferClient = New EasyUAFileTransferClient

            ' Open the file, read two separate sections of it, and close it.
            Try
                Console.WriteLine("Opening file...")
                Using fileHandle As UAFileHandle = fileTransferClient.OpenFile(endpointDescriptor, fileNodeDescriptor, UAOpenFileModes.Read)
                    Console.WriteLine("Reading first file section...")
                    Dim bytes1 As Byte() = fileTransferClient.ReadFile(endpointDescriptor, fileNodeDescriptor, fileHandle, 16)
                    Console.WriteLine($"First section: {BitConverter.ToString(bytes1)}")

                    Console.WriteLine("Reading second file section...")
                    Dim bytes2 As Byte() = fileTransferClient.ReadFile(endpointDescriptor, fileNodeDescriptor, fileHandle, 10)
                    Console.WriteLine($"Second section: {BitConverter.ToString(bytes2)}")

                    Console.WriteLine("Setting file position...")
                    fileTransferClient.SetFilePosition(endpointDescriptor, fileNodeDescriptor, fileHandle, 100)

                    Console.WriteLine("Reading third file section...")
                    Dim bytes3 As Byte() = fileTransferClient.ReadFile(endpointDescriptor, fileNodeDescriptor, fileHandle, 20)
                    Console.WriteLine($"Third section: {BitConverter.ToString(bytes3)}")

                    Console.WriteLine("Closing file...")
                    fileTransferClient.CloseFile(endpointDescriptor, fileNodeDescriptor, fileHandle)
                End Using
            Catch uaException As UAException
                Console.WriteLine("*** Failure: {0}", uaException.GetBaseException.Message)
                Exit Sub
            End Try

            Console.WriteLine("Finished...")
        End Sub
    End Class
End Namespace

Requirements

Target Platforms: .NET Framework: Windows 10 (selected versions), Windows 11 (selected versions), Windows Server 2016, Windows Server 2022; .NET: Linux, macOS, Microsoft Windows

Reference

EasyUAFileTransferClientCore Class
EasyUAFileTransferClientCore Members
CreateFile Method
GetFilePosition Method
OpenFile Method
System.IO.Stream.Seek(System.Int64,System.IO.SeekOrigin)
Size Property

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