moved reading of metadata into NumpyFile

file_io/src/NumpyFile.cpp

@@ -4,8 +4,13 @@
 namespace aare{
 
 NumpyFile::NumpyFile(const std::filesystem::path& fname) {
+    //TODO! add opts to constructor
     m_fname = fname;
     fp = fopen(m_fname.c_str(), "rb");
+    if (!fp) {
+        throw std::runtime_error(fmt::format("Could not open: {} for reading", m_fname.c_str()));
+    }
+    load_metadata();
 }
 NumpyFile::NumpyFile(FileConfig config, header_t header) {
     mode = "w";
@@ -102,4 +107,77 @@ NumpyFile::~NumpyFile() {
     }
 }
 
+void NumpyFile::load_metadata(){
+
+    // auto file = dynamic_cast<NumpyFile *>(_file);
+    // // open ifsteam to file
+    // f = std::ifstream(file->m_fname, std::ios::binary);
+    // // check if file exists
+    // if (!f.is_open()) {
+    //     throw std::runtime_error(fmt::format("Could not open: \"{}\" for reading", file->m_fname.c_str()));
+    // }
+    
+    // read magic number
+    std::array<char, 6> tmp{};
+    fread(tmp.data(), tmp.size(), 1, fp);
+    if (tmp != aare::NumpyHelpers::magic_str) {
+        for (auto item : tmp)
+            fmt::print("{}, ", int(item));
+        fmt::print("\n");
+        throw std::runtime_error("Not a numpy file");
+    }
+
+    // read version
+    fread(reinterpret_cast<char *>(&major_ver_),sizeof(major_ver_), 1,fp);
+    fread(reinterpret_cast<char *>(&minor_ver_), sizeof(minor_ver_),1,fp);
+
+    if (major_ver_ == 1) {
+        header_len_size = 2;
+    } else if (major_ver_ == 2) {
+        header_len_size = 4;
+    } else {
+        throw std::runtime_error("Unsupported numpy version");
+    }
+
+    // read header length
+    fread(reinterpret_cast<char *>(&header_len), header_len_size,1, fp);
+    header_size = aare::NumpyHelpers::magic_string_length + 2 + header_len_size + header_len;
+    if (header_size % 16 != 0) {
+        fmt::print("Warning: header length is not a multiple of 16\n");
+    }
+    // read header
+    auto buf_v = std::vector<char>(header_len);
+    fread(buf_v.data(), header_len,1,fp);
+    std::string header(buf_v.data(), header_len);
+
+    // parse header
+
+    std::vector<std::string> keys{"descr", "fortran_order", "shape"};
+    aare::logger::debug("original header: \"header\"");
+
+    auto dict_map = aare::NumpyHelpers::parse_dict(header, keys);
+    if (dict_map.size() == 0)
+        throw std::runtime_error("invalid dictionary in header");
+
+    std::string descr_s = dict_map["descr"];
+    std::string fortran_s = dict_map["fortran_order"];
+    std::string shape_s = dict_map["shape"];
+
+    std::string descr = aare::NumpyHelpers::parse_str(descr_s);
+    aare::DType dtype = aare::NumpyHelpers::parse_descr(descr);
+
+    // convert literal Python bool to C++ bool
+    bool fortran_order = aare::NumpyHelpers::parse_bool(fortran_s);
+
+    // parse the shape tuple
+    auto shape_v = aare::NumpyHelpers::parse_tuple(shape_s);
+    shape_t shape;
+    for (auto item : shape_v) {
+        auto dim = static_cast<unsigned long>(std::stoul(item));
+        shape.push_back(dim);
+    }
+    m_header = {dtype, fortran_order, shape};
+}
+
+
 } // namespace aare