I understand that while transitioning code to MATLAB, an error occurs when writing strings, indicating a datatype mismatch between the expected integer type and the provided character type. Despite converting strings to characters and ensuring uniform lengths, the issue persists. The problem is specific to strings, as removing them allows numeric data to be written successfully.
According to my understanding these are the required changes that might solve the above issue.
- Null-Termination for Strings: The string length, say “maxLength”, is set to include a space for the null terminator. This ensures that strings are correctly handled as fixed-length strings.
- Datatype Size: For each string, the datatype size is set to accommodate the full length including the null terminator.
Here is the modified code that takes care of the issues mentioned above:
params.floc = 'C:\Folder1';
params.fname = 'fname.txt';
params.value = 10;
outname = 'test09.h5';
plist = 'H5P_DEFAULT';
fNames = fieldnames(params);
Vsize = zeros(1, numel(fNames));
Vclass = cell(1, numel(fNames));
for ii = 1:numel(fNames)
temp = params.(fNames{ii});
if isnumeric(temp)
Vsize(ii) = 8; % Size for double
Vclass{ii} = 'H5T_NATIVE_DOUBLE';
elseif ischar(temp)
maxLength = length(temp) + 1; % Include null terminator
temp = char(pad(params.(fNames{ii}), maxLength - 1, 'right'));
params.(fNames{ii}) = temp;
Vsize(ii) = maxLength;
Vclass{ii} = 'H5T_NATIVE_CHAR';
end
end
H5F.create(outname, 'H5F_ACC_TRUNC', 'H5P_DEFAULT', 'H5P_DEFAULT');
fid = H5F.open(outname, 'H5F_ACC_RDWR', plist);
H5G.create(fid, '/SETTINGS', plist, plist, plist);
gid = H5G.open(fid, '/SETTINGS');
cid = H5T.create('H5T_COMPOUND', sum(Vsize));
offset = 0;
for ii = 1:numel(fNames)
if strcmp(Vclass{ii}, 'H5T_NATIVE_CHAR')
string_type = H5T.copy('H5T_C_S1');
H5T.set_size(string_type, Vsize(ii)); // Set size for null-terminated strings
H5T.insert(cid, fNames{ii}, offset, string_type);
else
H5T.insert(cid, fNames{ii}, offset, H5T.copy(Vclass{ii}));
end
offset = offset + Vsize(ii);
end
dsid = H5S.create_simple(1, 1, []);
dsetid = H5D.create(fid, '/SETTINGS/PASS', cid, dsid, 'H5P_DEFAULT');
H5D.write(dsetid, cid, 'H5S_ALL', 'H5S_ALL', 'H5P_DEFAULT', params);
H5D.close(dsetid);
H5S.close(dsid);
H5T.close(cid);
H5G.close(gid);
H5F.close(fid);
I have added comments wherever required. Since I don’t have the artifacts and the files which you are using, I was unable to verify the solution at my end, but this might work for you.
Additional Resource : Write Strings to Existing HDF5 file - Help Center Answers - MATLAB & Simulink
