Hi Daniel,
On May 4, 2011, at 3:13 AM, Sentenac Daniel wrote:
> Hello,
> I am currently doing a very small test to retreive the size of a just created
> HDF5 file using the function
> H5Fget_filesize and cannot understand why the size returned is actually
> different from the real one.
>
> Here is the simple example piece of code:
>
> hsize_t size;
> hid_t file_id = H5Fcreate("file.hdf5", H5F_ACC_TRUNC, H5P_DEFAULT,
> H5P_DEFAULT);
> H5Fget_filesize( file_id, &size );
>
> The real size of the file appears to be 800 bytes, while the size returned
> fromH5Fget_filesize is 2144 bytes.
The library allocates a 2KB buffer to sub-allocate metadata from (in
addition to the ~100 byte superblock for the file), but then truncates the
file's size down to the actual amount of data used in the file, when the file
is closed.
> I would like to use the function H5Fget_vfd_handle to get a (char*) buffer
> copy of the file. Can someone help me to do that correctly ?
I would recommend against this sort of mucking with the bytes - the
HDF5 library does a lot of work behind the scenes and you probably won't get a
coherent picture of the file by just looking at the bytes.
That said, why do you want to do this? Possibly the "core" VFD
(H5Pset_fapl_core) would meet your needs?
Quincey
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