Implemented read_header with concept based constraints. Currently only provided in the best case scenario (readable directly from the file into the struct).

Navmesher/esx_reader.cpp

@@ -1,4 +1,8 @@
 #include "esx_reader.hpp"
 
+#include <fstream>
+#include <bit>
+
+using namespace esxr;
 
 

Navmesher/esx_reader.hpp

@@ -8,6 +8,7 @@
 #include <compare>
 #include <vector>
 #include <type_traits>
+#include <fstream>
 
 #include "utility.hpp"
 
@@ -20,6 +21,14 @@ namespace esxr {
 class GroupNode;
 class RecordNode;
 
+//
+// Constants
+//
+
+static constexpr auto esx_endianness = std::endian::little;
+static constexpr std::streamsize header_size = 24;
+static constexpr bool same_endianness = std::endian::native == esx_endianness;
+
 //
 // Enumerations
 //
@@ -135,6 +144,23 @@ struct RecordHeader {
         uint16_t   unknown;
 };
 
+//
+// Concepts
+//
+
+template <typename T, size_t N>
+concept packed = sizeof(T) == N;
+
+template <typename T>
+concept is_header = std::is_same_v<T, GroupHeader> || std::is_same_v<T, RecordHeader>;
+
+template <typename T>
+concept packed_header = is_header<T> && packed<T, static_cast<std::size_t>(header_size)>;
+
+template <typename T>
+concept directly_readable_header = packed_header<T> && same_endianness;
+
+
 // 
 // Classes
 // 
@@ -162,6 +188,12 @@ private:
 [[nodiscard]] std::optional<std::string_view> flag_to_description(Flag flag) noexcept;
 [[nodiscard]] std::optional<std::string_view> refr_flag_to_description(RefrFlag refr_flag) noexcept;
 
+void read_header(std::ifstream &in, directly_readable_header auto &out)
+{
+        auto char_ptr = reinterpret_cast<char *>(&out);
+        in.read(char_ptr, header_size);
+}
+
 }
 
 #endif

Navmesher/main.cpp

@@ -24,10 +24,7 @@ static constexpr auto esm_name = "Skyrim.esm";
 int main()
 {
         auto esm_fs = open_esm();
-        std::array<char, 4> fourcc{};
-        esm_fs.read(fourcc.data(), static_cast<std::streamsize>(fourcc.size()));
-        for (auto c : fourcc)
-                std::cout << c;
-        std::cout << '\n';
-        return 0;
-}
+        esxr::RecordHeader header{};
+        esxr::read_header(esm_fs, header);
+        return static_cast<int>(header.type);
+}