May 30-31, 2012 HDF5 Workshop at PSIMay 30-31

Writing Your Own HDF5Virtual File Driver (VFD)

Dana RobinsonThe HDF Group

Efficient Use of HDF5 With High Data Rate X-Ray DetectorsPaul Scherrer Institut

May 30-31, 2012 HDF5 Workshop at PSI

Main Idea:

Users should be able to write their own VFD without having to rebuild the HDF5 library.

May 30-31, 2012 HDF5 Workshop at PSI

HDF5 API

Virtual File Layer

VFD VFD User-Supplied VFD

disk

HDF5 Library

May 30-31, 2012 HDF5 Workshop at PSI

What do I have to do?

1) Implement H5FDset_fapl_foo().

This will need to work with H5Pset_driver()

2) Implement appropriate VFD functions – read, write, etc.

3) Compile your code into a library or directly into your app.

May 30-31, 2012 HDF5 Workshop at PSI

"Demo" VFD

The STDIO VFD is a demo driver which uses no internal HDF5 calls.

Not intended for production use!

Unfortunately, this means that you do not get HDF5's platform-independent wrapper functions.

Can copy and paste as a basis for your own VFD.

May 30-31, 2012 HDF5 Workshop at PSI

static const H5FD_class_t H5FD_sec2_g = { "sec2", /*name */ MAXADDR, /*maxaddr */ H5F_CLOSE_WEAK, /*fc_degree */ H5FD_sec2_term, /*terminate */ NULL, /*sb_size */ NULL, /*sb_encode */ NULL, /*sb_decode */ 0, /*fapl_size */ NULL, /*fapl_get */ NULL, /*fapl_copy */ NULL, /*fapl_free */ 0, /*dxpl_size */ NULL, /*dxpl_copy */ NULL, /*dxpl_free */ H5FD_sec2_open, /*open */ H5FD_sec2_close, /*close */ H5FD_sec2_cmp, /*cmp */ H5FD_sec2_query, /*query */ NULL, /*get_type_map */ NULL, /*alloc */ NULL, /*free */ H5FD_sec2_get_eoa, /*get_eoa */ H5FD_sec2_set_eoa, /*set_eoa */ H5FD_sec2_get_eof, /*get_eof */ H5FD_sec2_get_handle, /*get_handle */ H5FD_sec2_read, /*read */ H5FD_sec2_write, /*write */ NULL, /*flush */ H5FD_sec2_truncate, /*truncate */ NULL, /*lock */ NULL, /*unlock */ H5FD_FLMAP_SINGLE /*fl_map */};

Each VFD contains a struct which maps our abstract VFL

calls to your VFDs functions

Use NULL when not implemented