4.2 FileType

4.2.1 General

This ObjectType defines a type for files. It is formally defined in Table 1.

Size defines the size of the file in Bytes. When a file is opened for write, the size might not be accurate. If the Server can not accurately determine the size of the file, the Size Property shall be returned to a Client with a StatusCode of Bad_NotSupported.

Writable indicates whether the file is writable. It does not take any user access rights into account, i.e., although the file is writable this may be restricted to a certain user / user group. The Property does not consider whether the file is currently opened for writing by another client and thus currently locked and not writable by others.

UserWritable indicates whether the file is writable taking user access rights into account. The Property does not consider whether the file is currently opened for writing by another client and thus currently locked and not writable by others.

OpenCount indicates the number of currently valid file handles on the file.

The optional Property MimeType contains the media type of the file based on RFC 2046.

Note that all Methods on a file require a fileHandle, which is returned in the Open Method.

The optional MaxByteStringLength Property indicates the maximum number of bytes of the read and write buffers. If this Property is not present then the maximum size is defined by the MaxByteStringLength Property of the ServerCapabilitiesType defined in OPC 10000-5.

The optional LastModifiedTime Property indicates the time the file was last modified. The Property shall be updated whenever the Server detects that the file has changed.

4.2.2 Open

Open is used to open a file represented by an Object of FileType. When a client opens a file it gets a file handle that is valid while the session is open. Clients shall use the Close Method to release the handle when they do not need access to the file anymore. Clients can open the same file several times for read. A request to open for writing shall return Bad_NotWritable when the file is already opened. A request to open for reading shall return Bad_NotReadable when the file is already opened for writing.

Signature

	Open(
		 [in] Byte mode
		 [out] UInt32 fileHandle
		);

Method Result Codes (defined in Call Service)

Table 2 specifies the AddressSpace representation for the Open Method.

4.2.3 Close

Close is used to close a file represented by a FileType. When a client closes a file, the handle becomes invalid.

Signature

	Close(
		 [in] UInt32 fileHandle
		);

Method Result Codes (defined in Call Service)

Table 3 specifies the AddressSpace representation for the Close Method.

4.2.4 Read

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
		);

Method Result Codes (defined in Call Service)

Table 4 specifies the AddressSpace representation for the Read Method.

4.2.5 Write

Write is used to write a part of the file starting from the current file position. The file position is advanced by the number of bytes written.

Signature

	Write(
		 [in] UInt32 fileHandle
		 [in] ByteString data
		);

Method Result Codes (defined in Call Service)

Table 5 specifies the AddressSpace representation for the Write Method.

4.2.6 GetPosition

GetPosition is used to provide the current position of the file handle.

Signature

	GetPosition(
		 [in] UInt32 fileHandle
		 [out] UInt64 position
		);

Method Result Codes (defined in Call Service)

Table 6 specifies the AddressSpace representation for the GetPosition Method.

4.2.7 SetPosition

SetPosition is used to set the current position of the file handle.

Signature

	SetPosition(
		 [in] UInt32 fileHandle
		 [in] UInt64 position
		);

Method Result Codes (defined in Call Service)

Table 7 specifies the AddressSpace representation for the SetPosition Method.