CloseFile Event

Fires when the OS needs to close a file.


class CBFSCloseFileEventParams {
  const QString &FileName();
  bool DeleteFile();
  qint64 HandleInfo();
  void *FileContext();
  void *HandleContext();
  int ResultCode();
  void SetResultCode(int iResultCode);
  int EventRetVal();
  void SetEventRetVal(int iRetVal);
// To handle, connect one or more slots to this signal. void CloseFile(CBFSCloseFileEventParams *e);
// Or, subclass CBFS and override this emitter function. virtual int FireCloseFile(CBFSCloseFileEventParams *e) {...}


This event fires when the OS needs to close the file specified by FileName. If the FireAllOpenCloseEvents property is disabled, this event will only fire after the last handle to the specified file is closed.

To handle this event properly, applications can (if necessary/applicable) check to see if there are any other handles open for the file, and if not, close whatever backend resources are currently open for it.

The DeleteFile parameter indicates whether the file should be deleted; if it's true, the DeleteFile event will fire immediately after this event. The application may delete the file from either event handler.

If an application uses some object to store user context, uses FileContext to store the reference to this object, and deletes an object referenced in FileContext, the pointer stored in FileContext becomes invalid. In this scenario, if the DeleteFile parameter is true, the DeleteFile event will fire with the invalid value in its FileContext parameter. The solution to this issue is to inspect the value of the DeleteFile parameter and if it is true, postpone deletion of the object referenced in FileContext till the DeleteFile event.

The HandleInfo parameter carries a handle to an object with information about the file handle. While within the event handler, it can be used to call any of the following methods: GetHandleCreatorProcessId, GetHandleCreatorProcessName, GetHandleCreatorThreadId, or GetHandleCreatorToken.

The FileContext and HandleContext parameters are placeholders for application-defined data associated with the file and specific handle, respectively. Please refer to the Contexts topic for more information.

The ResultCode parameter will always be 0 when the event is fired. If the event cannot be handled in a "successful" manner for some reason (e.g., a resource isn't available, security checks failed, etc.), set it to a non-zero value to report an appropriate error. Please refer to the Error Reporting and Handling topic for more information.

Note: The OS sends a file close request asynchronously, later than a process closes its handle(s) to the opened file. Due to this, the result code returned by the event handler does not get back to the process that closed the file handle.

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CBFS Connect 2020 Qt Edition - Version 20.0 [Build 8348]