same issue,Reading fixed length string from attribute #322

[wadv1232]

version:2.4.1
code：

HighFive::FixedLenStringArray<8> v;
file.getGroup("/what").getAttribute("date").read(v);

error:

inline bool checkDimensions(const DataSpace& mem_space, size_t input_dims) {

for (auto i = dims.crbegin(); i != --dims.crend() && *i == 1; ++i)

same issue ：Reading fixed length string from attribute #322

[N-damo]

same issue

[N-damo]

dimension of the attribute is 0,so "Impossible to read DataSet of dimensions 0 into arrays of dimensions 1"?

[1uc]

It sounds like you want to read a single fixed length string, not an array of fixed length strings. The class HighFive::FixedLenStringArray<8> models an array of strings, each of which has length 8.

In order to read a fixed length string you do something along the lines of:

    using fixed_len_str_t = std::array<char, 6>;
    // Create a new file using the default property lists.
    {
        File file(FILE_NAME, File::ReadWrite | File::Create | File::Truncate);
        auto attr = fixed_len_str_t{"Hello"};
        file.createAttribute("str", attr);
    }
    // Re-read it
    {
        File file(FILE_NAME);

        // without pre-allocation
        {
            auto attr = file.getAttribute("str").read<fixed_len_str_t>();
            CHECK(attr.data() == std::string("Hello"));
        }

        // with pre-allocation
        {
            auto attr = fixed_len_str_t{};
            file.getAttribute("str").read(attr);
            CHECK(attr.data() == std::string("Hello"));
        }
    }

Probably a char [6] would work too. Naturally, you could also read the string as a std::string.

[N-damo]

not work.
error:
Can't output std::string as fixed-length. Use raw arrays or FixedLenStringArray

[kailvn]

same issue, but the test case "HighFiveFixedLenStringArrayAttribute" work.

[andrewliuhui]

@kailvn testcase has dimensions 1, so it can work.
If fixed-len-string attribute with dimension 0 , highfive cannot read that attribute.

[1uc]

Thank you for this subtle difference.

We've been working towards improving std::string support. In particular, making it possible to read/write std::strings and containers (std::vector, std::array, etc) of std::string to/from any HDF5 string datatype.

This would hopefully eliminate the need for FixedLenStringArray entirely. The PR is #744.

[1uc]

With #744 merged std::strings and containers thereof, e.g. std::vectorstd::string can be read and written to fixed or variable length HDF5 strings. There's an example here:
https://github.com/BlueBrain/HighFive/blob/master/src/examples/read_write_std_strings.cpp