blob: 5970d2a849ed85acc8b5b09bcfda0bda210002dd (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
|
#include "nes/cartridge.hh"
#include <fstream>
namespace
{
constexpr auto prg_rom_bank_size = std::size_t{ 16 * 1024 };
constexpr auto chr_rom_bank_size = std::size_t{ 8 * 1024 };
constexpr auto ram_bank_size = std::size_t{ 8 * 1024 };
} // namespace
namespace nes
{
auto cartridge::from_data(void const* data, std::size_t const length) -> cartridge
{
auto const bytes = static_cast<std::uint8_t const*>(data);
auto res = cartridge{};
res.is_valid_ = true;
// Parse header.
if (length < 16) { return cartridge{}; }
if (bytes[0] != 'N' || bytes[1] != 'E' || bytes[2] != 'S' || bytes[3] != 0x1A) { return cartridge{}; }
auto const prg_rom_banks = bytes[4];
auto const chr_rom_banks = bytes[5];
auto const control_1 = bytes[6];
auto const control_2 = bytes[7];
auto const ram_banks = (bytes[8] != 0) ? bytes[8] : 1;
auto const has_trainer = (control_1 & 0b00000100) != 0;
res.mapper_number_ =
(control_1 & 0b11110000) >> 4 |
(control_2 & 0b11110000) >> 0;
// Load program data.
auto offset = 16;
if (has_trainer) { offset += 512; }
auto const prg_rom_size = prg_rom_banks * prg_rom_bank_size;
if (length < offset + prg_rom_size) { return cartridge{}; }
res.prg_rom_ = std::vector(&bytes[offset], &bytes[offset + prg_rom_size]);
offset += prg_rom_size;
auto const chr_rom_size = chr_rom_banks * chr_rom_bank_size;
if (length < offset + chr_rom_size) { return cartridge{}; }
res.chr_rom_ = std::vector(&bytes[offset], &bytes[offset + chr_rom_size]);
res.ram_ = std::vector(ram_banks * ram_bank_size, std::uint8_t{ 0 });
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{}; }
stream.seekg(0, std::ios::end);
auto const length = stream.tellg();
stream.seekg(0, std::ios::beg);
auto data = std::vector<std::uint8_t>(length);
stream.read(reinterpret_cast<char*>(data.data()), data.size());
return from_data(data.data(), data.size());
}
} // namespace nes
|
