|  | HDF5
    1.14.4.3
    API Reference | 
#include <src/H5FDonion.h>
Stores fapl information for creating onion VFD files.
| Data Fields | |
| uint8_t | version | 
| hid_t | backing_fapl_id | 
| uint32_t | page_size | 
| H5FD_onion_target_file_constant_t | store_target | 
| uint64_t | revision_num | 
| uint8_t | force_write_open | 
| uint8_t | creation_flags | 
| char | comment [255+1] | 
| hid_t backing_fapl_id | 
Backing or 'child' FAPL ID to handle I/O with the underlying backing store. It must use the same backing driver as the original file.
| char comment[255+ 1] | 
User-supplied NULL-terminated comment for a revision to be written. Cannot be longer than H5FD_ONION_FAPL_COMMENT_MAX_LEN. Ignored if part of a FAPL used to open in read mode.
| uint8_t creation_flags | 
Flag used only when instantiating an onion file. If the relevant bit is set to a nonzero value, its feature will be enabled.
| uint8_t force_write_open | 
Flag to ignore the write-lock flag in the onion data and attempt to open the file write-only anyway. This may be relevant if, for example, the library crashed while the file was open in write mode and the write-lock flag was not cleared. Must equal H5FD_ONION_FAPL_FLAG_FORCE_OPEN to enable.
| uint32_t page_size | 
page_size: Size of the amended data pages. If opening an existing file, must equal the existing page size or zero. If creating a new file or an initial revision of an existing file, must be a power of 2.
| uint64_t revision_num | 
Which revision to open. Valid values are 0 (the original file) or the revision number of an existing revision. H5FD_ONION_FAPL_INFO_REVISION_ID_LATEST refers to the most recently-created revision in the history.
| H5FD_onion_target_file_constant_t store_target | 
Identifies where the history data is stored.
| uint8_t version | 
Future-proofing identifier. Informs struct membership. Must equal H5FD_ONION_FAPL_VERSION_CURR to be considered valid.