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fix and rewrite CRC routine

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This commit is contained in:
Connor Olding 2018-08-10 11:53:06 +02:00
parent b3f622cbee
commit 35132653f6
1 changed files with 26 additions and 32 deletions
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58
z64crc.c
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@ -22,7 +22,7 @@ CRC_SEEDS[] = {
0xF8CA4DDC // iQue 3
};
const static u32
static const u32
BOOTCODE_CRCS[] = {
0,
0x6170A4A1, // 6101
@ -87,51 +87,45 @@ calc_crc(u8 *data, int bootcode, u8 *lookup) {
calc_crc_ret ret = {};
u32 seed = CRC_SEEDS[bootcode];
u32 t1 = seed;
u32 t2 = seed;
u32 t3 = seed;
u32 t4 = seed;
u32 t5 = seed;
u32 t6 = seed;
// registers noted for one game's 6102 disassembly:
u32 r1 = seed; // T4, ???
u32 r2 = seed; // A2, ???
u32 r3 = seed; // T3, collective xor
u32 r4 = seed; // T2, r6 overflow counter
u32 r5 = seed; // S0, rotated summation
u32 r6 = seed; // A3, summation
for (size_t i = 0x1000; i < 0x101000; i += 4) {
u32 d = R4(data + i);
if (t6 + d < t6) {
t4++;
if (r6 + d < r6) {
r4++;
}
t6 += d;
t3 ^= d;
u32 r = ROL(d, d & 0x1F);
t5 += r;
if (t2 > d) {
t2 ^= r;
r6 += d;
r3 ^= d;
u32 rot = ROL(d, d & 0x1F); // A0
r5 += rot;
if (r2 < d) {
r2 ^= r6 ^ d;
} else {
t2 ^= t6 ^ d;
r2 ^= rot;
}
if (bootcode == 5) {
u32 o = i & 0xFF;
t1 += R4(lookup + o) ^ d;
r1 += d ^ R4(lookup + o);
} else {
t1 += t5;
r1 += d ^ r5;
}
}
if (bootcode == 3) {
ret.crc1 = (t6 ^ t4) + t3;
ret.crc2 = (t5 ^ t2) + t1;
ret.crc1 = (r6 ^ r4) + r3;
ret.crc2 = (r5 ^ r2) + r1;
} else if (bootcode == 6) {
ret.crc1 = t6 * t4 + t3;
ret.crc2 = t5 * t2 + t1;
ret.crc1 = r6 * r4 + r3;
ret.crc2 = r5 * r2 + r1;
} else {
ret.crc1 = t6 ^ t4 ^ t3;
ret.crc2 = t5 ^ t2 ^ t1;
ret.crc1 = r6 ^ r4 ^ r3;
ret.crc2 = r5 ^ r2 ^ r1;
}
return ret;
@ -147,7 +141,7 @@ crc_version(u8 *buf) {
return -1;
}
for (int i = 0; i < N_CRC; i++) {
for (int i = 0; i < (int)N_CRC; i++) {
if (bootsum == BOOTCODE_CRCS[i]) {
return i;
}