on_set_file_size Event
Fires when the OS needs to change the size of an open file.
Syntax
class CBFSSetFileSizeEventParams(object): @property def file_name() -> str: ... @property def size() -> int: ... @property def handle_info() -> int: ... @property def file_context() -> int: ... @file_context.setter def file_context(value) -> None: ... @property def handle_context() -> int: ... @handle_context.setter def handle_context(value) -> None: ... @property def result_code() -> int: ... @result_code.setter def result_code(value) -> None: ... # In class CBFS: @property def on_set_file_size() -> Callable[[CBFSSetFileSizeEventParams], None]: ... @on_set_file_size.setter def on_set_file_size(event_hook: Callable[[CBFSSetFileSizeEventParams], None]) -> None: ...
Remarks
This event fires when the OS needs to change the size of the already-open file specified by FileName. All files have three sizes associated with them:
| Description | Associated Event | |
| File size | The length, in bytes, of the file's contents. | on_set_file_size |
| Allocation size | The number of bytes allocated locally for the file. | on_set_allocation_size |
| Valid data length | The number of bytes that have been written to the file. | on_set_valid_data_length |
To handle this event properly, applications must perform any actions needed to resize the specified file in their backend storage.
The Size parameter specifies the new size of the file, in bytes. Extending a file does not require actual space to be allocated; however, NTFS allocates and zeroes the newly-added space, and some third-party applications might expect such behavior if the virtual filesystem is identified (via file_system_name) as NTFS.
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: get_handle_creator_process_id, get_handle_creator_process_name, get_handle_creator_thread_id, or get_handle_creator_token.
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.