public static void Update(N64Rom rom, int cic)
{
var sums = Compute(rom, cic);
rom.CRC1 = sums.Item1;
rom.CRC2 = sums.Item2;
}
public unsafe static Tuple <uint, uint> Compute(N64Rom rom, int cic)
{
if (rom.RawRom.Length < CHECKSUM_START)
throw new N64CheckSumException("Invalid File Lenght");
fixed(byte *data8 = rom.RawRom)
{
uint *data32 = (uint *)data8;
uint seed;
uint t1, t2, t3, t4, t5, t6;
uint pos;
// initial seed
switch (cic)
{
case 6101:
case 6102:
seed = 0xF8CA4DDC;
break;
case 6103:
seed = 0xA3886759;
break;
case 6105:
seed = 0xDF26F436;
break;
case 6106:
seed = 0x1FEA617A;
break;
default:
throw new N64CheckSumException("Invalid CIC");
}
t1 = t2 = t3 = t4 = t5 = t6 = seed;
for (pos = CHECKSUM_START; pos < CHECKSUM_END; pos += 4)
{
uint d = BomSwap(data32[pos / 4]);
uint r = ROL(d, (int)(d & 0x1F));
// increment t4 if t6 overflows
if ((t6 + d) < t6)
{
t4++;
}
t6 += d;
t3 ^= d;
t5 += r;
if (t2 > d)
{
t2 ^= r;
}
else
{
t2 ^= t6 ^ d;
}
if (cic == 6105)
{
t1 += BomSwap(*(uint *)&data8[0x0750 + (pos & 0xFF)]) ^ d;
}
else
{
t1 += t5 ^ d;
}
}
if (cic == 6103)
{
return(new Tuple <uint, uint>(
(t6 ^ t4) + t3,
(t5 ^ t2) + t1));
}
else if (cic == 6106)
{
return(new Tuple <uint, uint>(
(t6 * t4) + t3,
(t5 * t2) + t1));
}
else
{
return(new Tuple <uint, uint>(
t6 ^ t4 ^ t3,
t5 ^ t2 ^ t1));
}
}
}
public static bool Validate(N64Rom rom, int cic)
{
var sums = Compute(rom, cic);
return(sums.Item1 == rom.CRC1 && sums.Item2 == rom.CRC2);
}
