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struct FamicomDisk : FloppyDisk {
auto name() -> string override { return "Famicom Disk"; }
auto extensions() -> vector<string> override { return {"fds"}; }
auto load(string location) -> bool override;
auto save(string location) -> bool override;
auto analyze() -> string;
auto transform(array_view<u8> input) -> vector<u8>;
};
auto FamicomDisk::load(string location) -> bool {
if(directory::exists(location)) {
this->location = location;
this->manifest = analyze();
pak = new vfs::directory;
pak->setAttribute("title", Medium::name(location));
pak->append("manifest.bml", manifest);
for(auto& filename : directory::files(location, "disk?*.side?*")) {
pak->append(filename, file::read({location, filename}));
}
}
if(file::exists(location)) {
this->location = location;
this->manifest = analyze();
pak = new vfs::directory;
pak->setAttribute("title", Medium::name(location));
pak->append("manifest.bml", manifest);
vector<u8> input = FloppyDisk::read(location);
array_view<u8> view{input};
if(view.size() % 65500 == 16) view += 16; //skip iNES / fwNES header
u32 index = 0;
while(auto output = transform(view)) {
string name;
name.append("disk", (char)('1' + index / 2), ".");
name.append("side", (char)('A' + index % 2));
pak->append(name, output);
view += 65500;
index++;
}
}
if(!pak) return false;
Pak::load("disk1.sideA", ".d1a");
Pak::load("disk1.sideB", ".d1b");
Pak::load("disk2.sideA", ".d2a");
Pak::load("disk2.sideB", ".d2b");
return true;
}
auto FamicomDisk::save(string location) -> bool {
auto document = BML::unserialize(manifest);
Pak::save("disk1.sideA", ".d1a");
Pak::save("disk1.sideB", ".d1b");
Pak::save("disk2.sideA", ".d2a");
Pak::save("disk2.sideB", ".d2b");
return true;
}
auto FamicomDisk::analyze() -> string {
string s;
s += "game\n";
s +={" name: ", Medium::name(location), "\n"};
s +={" title: ", Medium::name(location), "\n"};
return s;
}
auto FamicomDisk::transform(array_view<u8> input) -> vector<u8> {
if(input.size() < 65500) return {};
array_view<u8> data{input.data(), 65500};
if(data[0x00] != 0x01) return {};
if(data[0x38] != 0x02) return {};
if(data[0x3a] != 0x03) return {};
if(data[0x4a] != 0x04) return {};
vector<u8> output;
u16 crc16 = 0;
auto hash = [&](u8 byte) {
for(u32 bit : range(8)) {
bool carry = crc16 & 1;
crc16 = crc16 >> 1 | bool(byte & 1 << bit) << 15;
if(carry) crc16 ^= 0x8408;
}
};
auto write = [&](u8 byte) {
hash(byte);
output.append(byte);
};
auto flush = [&] {
hash(0x00);
hash(0x00);
output.append(crc16 >> 0);
output.append(crc16 >> 8);
crc16 = 0;
};
//block 1
for(u32 n : range(0xe00)) write(0x00); //pregap
write(0x80);
for(u32 n : range(0x38)) write(*data++);
flush();
//block 2
for(u32 n : range(0x80)) write(0x00); //gap
write(0x80);
for(u32 n : range(0x02)) write(*data++);
flush();
while(true) {
if(data[0x00] != 0x03 || data.size() < 0x11) break;
u16 size = data[0x0d] << 0 | data[0x0e] << 8;
if(data[0x10] != 0x04 || data.size() < 0x11 + size) break;
//block 3
for(u32 n : range(0x80)) write(0x00); //gap
write(0x80);
for(u32 n : range(0x10)) write(*data++);
flush();
//block 4
for(u32 n : range(0x80)) write(0x00); //gap
write(0x80);
for(u32 n : range(1 + size)) write(*data++);
flush();
}
//note: actual maximum capacity of a Famicom Disk is currently unknown
while(output.size() < 0x12000) output.append(0x00); //expand if too small
output.resize(0x12000); //shrink if too large
return output;
}
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