![]() |
HDF5
1.15.0.9c85c6e
API Reference
|
Navigate back: Main / Getting Started with HDF5 / Learning the Basics
During a dataset I/O operation, the library transfers raw data between memory and the file. The data in memory can have a datatype different from that of the file and can also be of a different size (i.e., the data in memory is a subset of the dataset elements, or vice versa). Therefore, to perform read or write operations, the application program must specify:
The steps to read from or write to a dataset are as follows:
To read from or write to a dataset, the H5Dread and H5Dwrite routines are used.
C
Fortran
The High Level HDF5 Lite APIs (H5LT,H5LD) include functions that simplify and condense the steps for creating and reading datasets. Please be sure to review them, in addition to this tutorial.
See Examples from Learning the Basics for the examples used in the Learning the Basics tutorial.
The example shows how to read and write an existing dataset. It opens the file created in the previous example, obtains the dataset identifier for the dataset /dset
, writes the dataset to the file, then reads the dataset back. It then closes the dataset and file.
Note that H5S_ALL is passed in for both the memory and file dataspace parameters in the read and write calls. This indicates that the entire dataspace of the dataset will be read or written to. H5S_ALL by itself does not necessarily have this meaning. See the HDF5 Reference Manual entry for H5Dread or H5Dwrite for more information on using H5S_ALL.
For details on compiling an HDF5 application: [ Compiling HDF5 Applications ]
H5Fopen opens an existing file and returns a file identifier.
H5Dopen opens an existing dataset with the specified name and location.
H5Dwrite writes raw data from an application buffer to the specified dataset, converting from the datatype and dataspace of the dataset in memory to the datatype and dataspace of the dataset in the file. Specifying H5S_ALL for both the memory and file dataspaces indicates that the entire dataspace of the dataset is to be written to. H5S_ALL by itself does not necessarily have this meaning. See the HDF5 Reference Manual entry for H5Dwrite for more information on using H5S_ALL.
H5Dread reads raw data from the specified dataset to an application buffer, converting from the file datatype and dataspace to the memory datatype and dataspace. Specifying H5S_ALL for both the memory and file dataspaces indicates that the entire dataspace of the dataset is to be read. H5S_ALL by itself does not necessarily have this meaning. See the HDF5 Reference Manual entry for H5Dread for more information on using H5S_ALL.
Shown below is the contents of dset.h5 (created by the C program).
dset.h5 in DDL
Shown below is the contents of dsetf.h5 (created by the FORTRAN program).
dsetf.h5 in DDL
Navigate back: Main / Getting Started with HDF5 / Learning the Basics