z64crc.c

#include <stdlib.h>
#include <stdint.h>
#include <string.h>
#include "bSwap.h"

/* Macros */
#define ROTL(i, n) ((i << n) | (i >> (32 - n)))
#define B2I(b) ((b[0] << 24) | (b[1] << 16) | (b[2] << 8) | b[3])

/* Header offsets */
#define N64_HEADER_SIZE 0x40
#define N64_BOOT_SIZE   0xFC0
#define N64_CRC1        0x10
#define N64_CRC2        0x14
#define CHECKSUM_START  0x1000
#define CHECKSUM_LEN    0x100000
#define CHECKSUM_END    0x101000

/* Possible bootcode CRC values */
#define CIC6101 0x6170A4A1
#define CIC6102 0x90BB6CB5
#define CIC6103 0x0B050EE0
#define CIC6105 0x98BC2C86
#define CIC6106 0xACC8580A

/* The seeds for CRC by CIC chip */
static const uint32_t cicSeeds[7] =
{
	0x00000000, 0xF8CA4DDC, 0xF8CA4DDC,
	0xA3886759, 0x00000000, 0xDF26F436,
	0x1FEA617A
};

/* Several things need this table, so just static const */
static const int32_t crcTable[256] =
{
	0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419, 0x706af48f,
	0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4, 0xe0d5e91e, 0x97d2d988,
	0x09b64c2b, 0x7eb17cbd, 0xe7b82d07, 0x90bf1d91, 0x1db71064, 0x6ab020f2,
	0xf3b97148, 0x84be41de, 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7,
	0x136c9856, 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
	0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4, 0xa2677172,
	0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b, 0x35b5a8fa, 0x42b2986c,
	0xdbbbc9d6, 0xacbcf940, 0x32d86ce3, 0x45df5c75, 0xdcd60dcf, 0xabd13d59,
	0x26d930ac, 0x51de003a, 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423,
	0xcfba9599, 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
	0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190, 0x01db7106,
	0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f, 0x9fbfe4a5, 0xe8b8d433,
	0x7807c9a2, 0x0f00f934, 0x9609a88e, 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d,
	0x91646c97, 0xe6635c01, 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e,
	0x6c0695ed, 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
	0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3, 0xfbd44c65,
	0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2, 0x4adfa541, 0x3dd895d7,
	0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a, 0x346ed9fc, 0xad678846, 0xda60b8d0,
	0x44042d73, 0x33031de5, 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa,
	0xbe0b1010, 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
	0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17, 0x2eb40d81,
	0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6, 0x03b6e20c, 0x74b1d29a,
	0xead54739, 0x9dd277af, 0x04db2615, 0x73dc1683, 0xe3630b12, 0x94643b84,
	0x0d6d6a3e, 0x7a6a5aa8, 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1,
	0xf00f9344, 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
	0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a, 0x67dd4acc,
	0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5, 0xd6d6a3e8, 0xa1d1937e,
	0x38d8c2c4, 0x4fdff252, 0xd1bb67f1, 0xa6bc5767, 0x3fb506dd, 0x48b2364b,
	0xd80d2bda, 0xaf0a1b4c, 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55,
	0x316e8eef, 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
	0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe, 0xb2bd0b28,
	0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31, 0x2cd99e8b, 0x5bdeae1d,
	0x9b64c2b0, 0xec63f226, 0x756aa39c, 0x026d930a, 0x9c0906a9, 0xeb0e363f,
	0x72076785, 0x05005713, 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38,
	0x92d28e9b, 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
	0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1, 0x18b74777,
	0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c, 0x8f659eff, 0xf862ae69,
	0x616bffd3, 0x166ccf45, 0xa00ae278, 0xd70dd2ee, 0x4e048354, 0x3903b3c2,
	0xa7672661, 0xd06016f7, 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc,
	0x40df0b66, 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
	0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605, 0xcdd70693,
	0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8, 0x5d681b02, 0x2a6f2b94,
	0xb40bbe37, 0xc30c8ea1, 0x5a05df1b, 0x2d02ef8d
};

static uint32_t crc32(uint8_t* buf, int32_t l)
{
	uint32_t i, c;

	for(c = ~0, i = 0; i < l; ++i)
		c = (c >> 8) ^ crcTable[(c ^ buf[i]) & 0xFF];
	return(~c);
}

static int32_t getCIC(uint8_t* buf)
{
	/* Figure out which CIC the cart uses */
	/* by getting the CRC32 of the boot code */
	switch(crc32(&(buf[N64_HEADER_SIZE]), N64_BOOT_SIZE))
	{
		case CIC6101:
			return(6101);
		case CIC6102:
			return(6102);
		case CIC6103:
			return(6103);
		case CIC6105:
			return(6105);
		case CIC6106:
			return(6106);
	}

	return(6100);
}

static int32_t calcCRC(uint32_t* crc, uint8_t* buf)
{
	uint32_t bcode, i, r, d;
	uint32_t t1, t2, t3, t4, t5, t6;

	/* Get the seed from the CIC */
	bcode = getCIC(buf);
	t1 = t2 = t3 = t4 = t5 = t6 = cicSeeds[bcode - 6100];

	/* I assume this was taken from an n64? */
	for(i = CHECKSUM_START; i < CHECKSUM_END; i += 4)
	{
		d = B2I((&buf[i]));

		if((t6 + d) < t6)
			++t4;
		t6 += d;
		t3 ^= d;

		r = ROTL(d, (d & 0X1F));
		t5 += r;

		if(t2 > d)
			t2 ^= r;
		else
		 	t2 ^= t6 ^ d;

		if(bcode == 6105)
			t1 += B2I((&buf[N64_HEADER_SIZE + 0X710 + (i & 0xFF)])) ^ d;
		else
		 	t1 += t5 ^ d;
	}

	if(bcode == 6103)
	{
		crc[0] = (t6 ^ t4) + t3;
		crc[1] = (t5 ^ t2) + t1;
	}
	else if(bcode == 6106)
	{
		crc[0] = (t6 * t4) + t3;
		crc[1] = (t5 * t2) + t1;
	}
	else
	{
		crc[0] = t6 ^ t4 ^ t3;
		crc[1] = t5 ^ t2 ^ t1;
	}

	return(1);
}

void fixCRC(uint8_t* buf)
{
	uint8_t CRC1[4];
	uint8_t CRC2[4];
	uint32_t crc[2];
	uint32_t i;

	/* If the CRC calc was successful, do stuff */
	if(calcCRC(crc, buf))
	{
		for(i = 0; i < 4; i++)
		{
			CRC1[i] = (crc[0] >> (24 - (8 * i))) & 0xFF;
			CRC2[i] = (crc[1] >> (24 - (8 * i))) & 0xFF;
		}

		/* If the CRC1 changed, update it */
		if(crc[0] != B2I((&buf[N64_CRC1])))
			memcpy(buf + N64_CRC1, CRC1, 4);
        
		/* If the CRC2 changed, update it */
		if (crc[1] != B2I((&buf[N64_CRC2])))
			memcpy(buf + N64_CRC2, CRC2, 4);
	}

	return;
}