Read is used to read a part of the file starting from the current file position. The file position is advanced by the number of bytes read.

Signature

Read(

[in] UInt32 fileHandle

[in] Int32 length

[out] ByteString data

);

Argument

Description

fileHandle

A handle indicating the access request and thus indirectly the position inside the file.

Length

Defines the length in bytes that should be returned in data, starting from the current position of the file handle. If the end of file is reached all data until the end of the file is returned. The Serveris allowed to return less data than specified length.

Only positive values are allowed.

Data

Contains the returned data of the file. If the ByteString is empty it indicates that the end of the file is reached.

Method Result Codes (defined in Call Service)

Result Code

Description

Bad_InvalidArgument

See OPC 10000-4Invalid file handle in call or non-positive length.

Bad_UnexpectedError

See OPC 10000-4for a general description.

Bad_InvalidState

See OPC 10000-4for a general description. File was not opened for read access.

Table C.4 specifies the AddressSpacerepresentation for the Read Method.

Table C.4– Read Method AddressSpace Definition

Attribute

Value

BrowseName

Read

References

NodeClass

BrowseName

DataType

TypeDefinition

ModellingRule

HasProperty

Variable

InputArguments

Argument[]

PropertyType

Mandatory

HasProperty

Variable

OutputArguments

Argument[]

PropertyType

Mandatory