CBFS Filter 2020 Delphi Edition

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BeforeLock Event

Fires before a range of bytes in a file is locked.


type TBeforeLockEvent = procedure (
  Sender: TObject;
  const FileName: String;
  var Offset: Int64;
  var Length: Int64;
  Key: Int64;
  var FailImmediately: Boolean;
  var ExclusiveLock: Boolean;
  var FileContext: Pointer;
  var HandleContext: Pointer;
  var ProcessRequest: Boolean;
  var ResultCode: Integer
) of Object;

property OnBeforeLock: TBeforeLockEvent read FOnBeforeLock write FOnBeforeLock;


This event fires before a range of bytes in the file specified by FileName is locked; either by the OS, or on behalf of a user mode application that called the Windows API's LockFile or LockFileEx function.

Applications may use this event to modify the request's parameters.

Applications only need to handle this event if they've added a standard filter rule that includes the FS_CE_BEFORE_LOCK_CONTROL flag.

The Offset parameter specifies the byte offset where the byte range lock should start.

The Length parameter specifies the length of the byte range lock.

The Key parameter reflects the key that the byte range lock will be associated with. This key is used to identify the byte range lock in later unlock-by-key requests.

The FailImmediately parameter specifies whether the request should fail if the lock cannot be granted immediately.

The ExclusiveLock parameter specifies whether the byte range lock should be exclusive (True) or shared (False).

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 ProcessRequest parameter controls whether the request is sent onwards for further processing by subsequent filter drivers and the filesystem; it is True by default.

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.

This event is fired synchronously; please refer to the Event Types topic for more information.

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CBFS Filter 2020 Delphi Edition - Version 20.0 [Build 8124]