1 files changed, 68 insertions, 0 deletions
diff --git a/lib/nes/sys/cartridge.cc b/lib/nes/sys/cartridge.cc
new file mode 100644
index 0000000..d60ea8b
--- /dev/null
+++ b/lib/nes/sys/cartridge.cc
@@ -0,0 +1,68 @@
+#include "nes/sys/cartridge.hh"
+#include "nes/sys/types/status.hh"
+#include <fstream>
+
+namespace nes
+{
+	cartridge::cartridge(status const status)
+		: status_{ status }
+	{
+	}
+
+	auto cartridge::from_data(void const* data, std::size_t const length) -> cartridge
+	{
+		// See: https://www.nesdev.org/wiki/INES
+
+		auto const bytes = static_cast<std::uint8_t const*>(data);
+		auto res = cartridge{ status::success };
+
+		// Parse header.
+		if (length < header_length) { return cartridge{ status::error_invalid_ines_data }; }
+		auto const h = header{ bytes };
+		if (h.get_magic_0() != 'N' || h.get_magic_1() != 'E' || h.get_magic_2() != 'S' || h.get_magic_3() != 0x1A)
+		{
+			return cartridge{ status::error_invalid_ines_data };
+		}
+		auto const mapper_number = static_cast<std::uint8_t>((h.get_mapper_high() << 4) | (h.get_mapper_low() << 0));
+
+		res.mapper_ = &mapper::get(mapper_number);
+		res.name_table_arrangement_ = h.get_name_table_arrangement();
+
+		// Load program data.
+		auto offset = std::size_t{ 16 };
+		if (h.get_has_trainer()) { offset += 512; }
+
+		auto const prg_rom_size = h.get_prg_rom_banks() * prg_rom_bank_size;
+		if (length < offset + prg_rom_size) { return cartridge{ status::error_invalid_ines_data }; }
+		res.prg_rom_ = std::vector(&bytes[offset], &bytes[offset + prg_rom_size]);
+
+		offset += prg_rom_size;
+
+		auto const chr_rom_size = h.get_chr_rom_banks() * chr_rom_bank_size;
+		if (length < offset + chr_rom_size) { return cartridge{ status::error_invalid_ines_data }; }
+		res.chr_rom_ = std::vector(&bytes[offset], &bytes[offset + chr_rom_size]);
+
+		res.ram_ = std::vector(std::max(h.get_ram_banks(), 1u) * ram_bank_size, std::uint8_t{ 0 });
+
+		if (auto const status = res.get_mapper().validate(res); status != status::success)
+		{
+			return cartridge{ status };
+		}
+
+		return res;
+	}
+
+	auto cartridge::from_file(std::string_view const path) -> cartridge
+	{
+		auto stream = std::ifstream{ path, std::ios::binary };
+		if (!stream.good()) { return cartridge{ status::error_system_error }; }
+
+		stream.seekg(0, std::ios::end);
+		auto const length = stream.tellg();
+		stream.seekg(0, std::ios::beg);
+		auto data = std::vector<std::uint8_t>(static_cast<std::size_t>(length));
+		stream.read(reinterpret_cast<char*>(data.data()), length);
+
+		return from_data(data.data(), data.size());
+	}
+} // namespace nes
+\ No newline at end of file