66 行
1.6 KiB
C++
66 行
1.6 KiB
C++
#pragma once
|
|
|
|
//error detection code
|
|
|
|
namespace nall::CD::EDC {
|
|
|
|
//polynomial(x) = (x^16 + x^15 + x^2 + 1) * (x^16 + x^2 + x + 1)
|
|
inline auto polynomial(u8 x) -> u32 {
|
|
static u32 lookup[256]{};
|
|
static bool once = false;
|
|
if(!once) { once = true;
|
|
for(u32 n : range(256)) {
|
|
u32 edc = n;
|
|
for(u32 b : range(8)) edc = edc >> 1 ^ (edc & 1 ? 0xd8018001 : 0);
|
|
lookup[n] = edc;
|
|
}
|
|
}
|
|
return lookup[x];
|
|
}
|
|
|
|
//
|
|
|
|
inline auto create(array_view<u8> input) -> u32 {
|
|
u32 sum = 0;
|
|
for(auto& byte : input) sum = sum >> 8 ^ polynomial(sum ^ byte);
|
|
return sum;
|
|
}
|
|
|
|
inline auto create(array_view<u8> input, array_span<u8> output) -> bool {
|
|
if(output.size() != 4) return false;
|
|
auto sum = create(input);
|
|
output[0] = sum >> 0;
|
|
output[1] = sum >> 8;
|
|
output[2] = sum >> 16;
|
|
output[3] = sum >> 24;
|
|
return true;
|
|
}
|
|
|
|
inline auto createMode1(array_span<u8> sector) -> bool {
|
|
if(sector.size() != 2352) return false;
|
|
return create({sector.data(), 2064}, {sector.data() + 2064, 4});
|
|
}
|
|
|
|
//
|
|
|
|
inline auto verify(array_view<u8> input, u32 edc) -> bool {
|
|
return edc == create(input);
|
|
}
|
|
|
|
inline auto verify(array_view<u8> input, array_view<u8> compare) -> bool {
|
|
if(compare.size() != 4) return false;
|
|
auto sum = create(input);
|
|
if(compare[0] != u8(sum >> 0)) return false;
|
|
if(compare[1] != u8(sum >> 8)) return false;
|
|
if(compare[2] != u8(sum >> 16)) return false;
|
|
if(compare[3] != u8(sum >> 24)) return false;
|
|
return true;
|
|
}
|
|
|
|
inline auto verifyMode1(array_view<u8> sector) -> bool {
|
|
if(sector.size() != 2352) return false;
|
|
return verify({sector.data(), 2064}, {sector.data() + 2064, 4});
|
|
}
|
|
|
|
}
|