Writing 2-D array int[n][m] to HDF5 file using Visual C++

I'm just getting started with HDF5 and would appreciate some advice on the following.

I have a 2-d array: data[][] passed into a method. The method looks like:

void WriteData( int data[48][100], int sizes[48])

The size of the data is not actually 48 x 100 but rather 48 x sizes[i]. I.e. each row could be a different length! In one simple case I'm dealing with, all rows are the same size (but not 100), so you can say that the array is 48 X sizes[0].

How best to write this to HDF5?

I have some working code where I loop through 0 to 48 and create a new dataset for each row.

Something like:

for (int i = 0; i < 48; i++) { hsize_t dsSize[2]; dsSize[0] = 48; dsSize[1] = sizes[0]; // use sizes[i] in most general case // Create the Data Space DataSpace dataSpace = DataSpace(2, dsSize); DataSet dataSet = group.createDataSet(dataSetName, intDataType, dataSpace); dataSet.write(data[i], intDataType); }

Is there a way to write the data all at once in one DataSet? Perhaps one solution for the simpler case of all rows the same length, and another for the ragged rows?

I've tried a few things to no avail. I called dataSet.write(data, intDataType), i.e. I threw the whole array at it. I seemed to get garbage in the file, I suspect because the array the data is stored in is actually 48x100 and I only need a small part of that.

It occurred to me that I could maybe use double ptrs int** or vector> but I'm stuck on that. As far as I can tell, "write" need a void* ptr. Also, I'd like the file to "look correct". I.e. one giant row with all rows of data is not desirable, if I must go that route, someone would need to communicate a slick way to store the info that would allow me to read the data back in from file (perhaps store row lengths as attributes?).

Perhaps my real problem is finding C++ examples of non-trivial use cases.

Any help is much appreciated.



Here is how you can do it using variable length arrays if your data is a vector of vectors (which seems to make sense for your use case):

void WriteData(const std::vector< std::vector<int> >& data) { hsize_t dim(data.size()); H5::DataSpace dspace(1, &dim); H5::VarLenType dtype(H5::PredType::NATIVE_INT); H5::DataSet dset(group.createDataSet(dataSetName, dtype, dspace)); hvl_t vl[dim]; for (hsize_t i = 0; i < dim; ++i) { vl[i].len = data[i].size(); vl[i].p = &data[i][0]; } dset.write(vl, dtype); }


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