BeforeSetAllocationSize Event

Fires before a file's allocation size is changed.


virtual int FireBeforeSetAllocationSize(CBFilterBeforeSetAllocationSizeEventParams *e);
typedef struct {
const char *FileName;
int64 *pAllocationSize;
void *FileContext;
void *HandleContext;
int ProcessRequest;
int ResultCode; int reserved; } CBFilterBeforeSetAllocationSizeEventParams;
virtual INT FireBeforeSetAllocationSize(CBFilterBeforeSetAllocationSizeEventParams *e);
typedef struct {
LONG64 *pAllocationSize;
LPVOID FileContext;
LPVOID HandleContext;
BOOL ProcessRequest;
INT ResultCode; INT reserved; } CBFilterBeforeSetAllocationSizeEventParams;


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 NULL.)

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 C++ Edition - Version 20.0 [Build 7836]