BeforeSetAllocationSize Event

Fires before a file's allocation size is changed.

Syntax

// CBFilterBeforeSetAllocationSizeEventArgs carries the CBFilter BeforeSetAllocationSize event's parameters.
type CBFilterBeforeSetAllocationSizeEventArgs struct {...}

func (args *CBFilterBeforeSetAllocationSizeEventArgs) FileName() string
func (args *CBFilterBeforeSetAllocationSizeEventArgs) AllocationSize() int64
func (args *CBFilterBeforeSetAllocationSizeEventArgs) SetAllocationSize(value int64)
func (args *CBFilterBeforeSetAllocationSizeEventArgs) FileContext() int64
func (args *CBFilterBeforeSetAllocationSizeEventArgs) SetFileContext(value int64)
func (args *CBFilterBeforeSetAllocationSizeEventArgs) HandleContext() int64
func (args *CBFilterBeforeSetAllocationSizeEventArgs) SetHandleContext(value int64)
func (args *CBFilterBeforeSetAllocationSizeEventArgs) ProcessRequest() bool
func (args *CBFilterBeforeSetAllocationSizeEventArgs) SetProcessRequest(value bool)
func (args *CBFilterBeforeSetAllocationSizeEventArgs) ResultCode() int32
func (args *CBFilterBeforeSetAllocationSizeEventArgs) SetResultCode(value int32)

// CBFilterBeforeSetAllocationSizeEvent defines the signature of the CBFilter BeforeSetAllocationSize event's handler function.
type CBFilterBeforeSetAllocationSizeEvent func(sender *CBFilter, args *CBFilterBeforeSetAllocationSizeEventArgs)

func (obj *CBFilter) GetOnBeforeSetAllocationSizeHandler() CBFilterBeforeSetAllocationSizeEvent
func (obj *CBFilter) SetOnBeforeSetAllocationSizeHandler(handlerFunc CBFilterBeforeSetAllocationSizeEvent)

Remarks

This event fires before the allocation size of the file specified by FileName is changed.

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_SET_SIZES flag.

The AllocationSize parameter specifies the new allocation size, in bytes. A file's allocation size is typically larger than its actual size since filesystem operations often reserve space on disk before writing additional data to a file. Applications may track such situations and avoid reallocating disk space where possible to improve performance.

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. (If the system's cache manager or memory manager initiated the operation, HandleContext may be absent, in which case it will be nil.)

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.