implement ppu io registers

1 files changed, 72 insertions, 6 deletions

diff --git a/src/nes/mapper.cc b/src/nes/mapper.cc
index a451e3a..237ab47 100644
--- a/src/nes/mapper.cc
+++ b/src/nes/mapper.cc
@@ -4,10 +4,15 @@
 
 namespace nes
 {
-	mapper::mapper(cartridge& cartridge, read_func const read, write_func const write)
+	mapper::mapper(
+		cartridge& cartridge,
+		read_cpu_func const read_cpu, write_cpu_func const write_cpu,
+		read_ppu_func const read_ppu, write_ppu_func const write_ppu)
 		: cartridge_{ cartridge }
-		, read_{ read }
-		, write_{ write }
+		, read_cpu_{ read_cpu }
+		, write_cpu_{ write_cpu }
+		, read_ppu_{ read_ppu }
+		, write_ppu_{ write_ppu }
 	{
 	}
 
@@ -16,16 +21,21 @@ namespace nes
 		switch (cartridge.get_mapper_number())
 		{
 			case 0x00:
-				return mapper{ cartridge, &mapper::nrom_read, &mapper::nrom_write };
+				return mapper{
+					cartridge,
+					&mapper::nrom_read_cpu, &mapper::nrom_write_cpu,
+					&mapper::nrom_read_ppu, &mapper::nrom_write_ppu };
 			default:
 				std::cerr << "Mapper not implemented: " << std::hex << cartridge.get_mapper_number() << std::endl;
 				std::abort();
 		}
 	}
 
+	// -----------------------------------------------------------------------------------------------------------------
 	// NROM
+	// -----------------------------------------------------------------------------------------------------------------
 
-	auto mapper::nrom_read(address const addr) -> std::uint8_t
+	auto mapper::nrom_read_cpu(address const addr) -> std::uint8_t
 	{
 		if (addr <= address{ 0x5FFF })
 		{
@@ -54,7 +64,7 @@ namespace nes
 		return 0x0;
 	}
 
-	auto mapper::nrom_write(address const addr, std::uint8_t const value) -> void
+	auto mapper::nrom_write_cpu(address const addr, std::uint8_t const value) -> void
 	{
 		if (addr <= address{ 0x5FFF })
 		{
@@ -63,7 +73,63 @@ namespace nes
 		if (addr <= address{ 0x7FFF })
 		{
 			cartridge_.get_ram_mut()[addr.get_absolute() - 0x6000] = value;
+			return;
+		}
+	}
+
+	auto mapper::nrom_read_ppu(address const addr, std::uint8_t const* vram) -> std::uint8_t
+	{
+		if (addr <= address{ 0x1FFF })
+		{
+			auto const rel = addr.get_absolute();
+			if (rel >= cartridge_.get_chr_rom_length()) { return 0x0; }
+
+			return cartridge_.get_chr_rom()[rel];
+		}
+		if (addr <= address{ 0x3EFF })
+		{
+			return vram[nrom_mirrored_vram_address(addr)];
+		}
+
+		return 0x0;
+	}
+
+	auto mapper::nrom_write_ppu(address const addr, std::uint8_t* vram, std::uint8_t const value) -> void
+	{
+		if (addr <= address{ 0x1FFF })
+		{
+			return;
+		}
+		if (addr <= address{ 0x3EFF })
+		{
+			vram[nrom_mirrored_vram_address(addr)] = value;
+			return;
 		}
 	}
 
+	auto mapper::nrom_mirrored_vram_address(address const addr) const -> unsigned
+	{
+		auto rel = addr.get_absolute();
+		if (rel >= 0x3000) { rel -= 0x1000; }
+
+		switch (cartridge_.get_name_table_arrangement())
+		{
+			case name_table_arrangement::horizontal:
+				// $2000 = $2400, $2800 = $2c00
+				if (rel <= 0x23FF) { return 0x000 + (rel % 0x400); }
+				if (rel <= 0x27FF) { return 0x000 + (rel % 0x400); }
+				if (rel <= 0x2BFF) { return 0x400 + (rel % 0x400); }
+				if (rel <= 0x2FFF) { return 0x400 + (rel % 0x400); }
+				break;
+			case name_table_arrangement::vertical:
+				// $2000 = $2800, $2400 = $2c00
+				if (rel <= 0x23FF) { return 0x000 + (rel % 0x400); }
+				if (rel <= 0x27FF) { return 0x400 + (rel % 0x400); }
+				if (rel <= 0x2BFF) { return 0x000 + (rel % 0x400); }
+				if (rel <= 0x2FFF) { return 0x400 + (rel % 0x400); }
+				break;
+		}
+
+		return 0;
+	}
 } // namespace nes
\ No newline at end of file