Function read_idx

examples/common/idxio.h:42–78

template<class ty>
void read_idx(std::vector<dim_t> &dims, std::vector<ty> &data,
              const char *name) {
    std::ifstream f(name, std::ios::in | std::ios::binary);
    if (!f.is_open()) throw std::runtime_error("Unable to open file");

    Data d;
    f.read(d.bytes, sizeof(d.bytes));

    if (d.bytes[2] != 8) { throw std::runtime_error("Unsupported data type"); }

    unsigned numdims  = d.bytes[3];
    unsigned elemsize = 1;

    // Read the dimensions
    size_t elem = 1;
    dims        = std::vector<dim_t>(numdims);
    for (unsigned i = 0; i < numdims; i++) {
        f.read(d.bytes, sizeof(d.bytes));

        // Big endian to little endian
        for (int j = 0; j < 4; j++) d.bytes[j] = reverse_char(d.bytes[j]);
        unsigned dim = reverse(d.dim);

        elem *= dim;
        dims[i] = (dim_t)dim;
    }

    // Read the data
    std::vector<char> cdata(elem);
    f.read(&cdata[0], elem * elemsize);
    std::vector<unsigned char> ucdata(cdata.begin(), cdata.end());

    data = std::vector<ty>(ucdata.begin(), ucdata.end());

    f.close();
    return;
}