Implement library magic checking & error handling

src/main.cpp

@@ -4,12 +4,12 @@
 #include <base/MmapFile.hpp>
 #include <filesystem>
 #include <format>
+#include <fstream>
 #include <iostream>
 #include <structs/BoltStructs.hpp>
+#include <type_traits>
 #include <vector>
 
-#include <fstream>
-
 namespace fs = std::filesystem;
 
 std::vector<u8> BoltDecompress(u8* input, usize decompressedSize) {
@@ -72,6 +72,41 @@ std::vector<u8> BoltDecompress(u8* input, usize decompressedSize) {
 	return res;
 }
 
+// error code boilerplate. This should be moved later
+enum class BoltErrc { InvalidMagic = 1 };
+
+struct BoltErrorCategory : std::error_category {
+	const char* name() const noexcept override { return "boltio"; }
+	std::string message(i32 ev) const override {
+		switch(static_cast<BoltErrc>(ev)) {
+			case BoltErrc::InvalidMagic: return "invalid bolt library file magic";
+			default: return "unknown error";
+		}
+	}
+};
+
+const BoltErrorCategory boltCategory {};
+
+std::error_code make_error_code(BoltErrc errc) {
+	return { static_cast<i32>(errc), boltCategory };
+}
+
+namespace std {
+	template <>
+	struct is_error_code_enum<BoltErrc> : true_type {};
+
+	/// Custom formatter for std::error_code. As far as I know, this is
+	/// Not going to be added in C++23, despite the fact fmt already has a specialization for it,
+	/// so I have to implement one myself. At least it's not that awful to.
+	template <>
+	struct formatter<error_code> : formatter<string_view> {
+		template <typename FormatContext>
+		inline auto format(const error_code& ec, FormatContext& ctx) const {
+			return std::format_to(ctx.out(), "{} [{}.{}]", ec.message(), ec.category().name(), ec.value());
+		}
+	};
+} // namespace std
+
 struct BoltReader {
 	struct ParsedTableEntry {
 		std::string_view filename;
@@ -98,6 +133,15 @@ struct BoltReader {
 	BoltReader() {}
 
 	ErrorOr<void> OpenBolt(const fs::path& path) {
+		// Load the BOLT file
+		if(auto error = boltFile.Open(path); error.HasError())
+			return error;
+
+		lib = std::bit_cast<lightningbolt::BoltLibraryHeader*>(boltFile.GetMapping());
+
+		if(!lib->Validate())
+			return make_error_code(BoltErrc::InvalidMagic);
+
 		auto p = path;
 		p.replace_filename("SLUS_201.14");
 
@@ -107,11 +151,6 @@ struct BoltReader {
 		// Load table entries.
 		GetTableEntries();
 
-		// Load the BOLT file
-		if(auto error = boltFile.Open(path); error.HasError())
-			return error;
-
-		lib = std::bit_cast<lightningbolt::BoltLibraryHeader*>(boltFile.GetMapping());
 		return {};
 	}
 
@@ -169,7 +208,7 @@ struct BoltReader {
 int main() {
 	BoltReader reader;
 	if(auto error = reader.OpenBolt(fs::current_path() / "ASSETS.BLT"); error.HasError()) {
-		std::cout << "Error opening Bolt file: " << error.Error();
+		std::cout << std::format("Error initalizing bolt reader: {}\n", error.Error());
 	}
 
 	reader.ForEachFile([](BoltReader::ParsedTableEntry& ent) {