mirror of https://github.com/zeldaret/oot.git
86 lines
1.7 KiB
C
86 lines
1.7 KiB
C
#include <assert.h>
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#include <stdbool.h>
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#include <stdint.h>
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#include <stdlib.h>
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#include "n64chksum.h"
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#include "util.h"
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//Based on uCON64's N64 checksum algorithm by Andreas Sterbenz
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#define ROL(i, b) (((i) << (b)) | ((i) >> (32 - (b))))
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bool n64chksum_calculate(const uint8_t *romData, int cicType, uint32_t *chksum)
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{
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unsigned int seed;
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unsigned int t1, t2, t3, t4, t5, t6;
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size_t pos;
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const size_t START = 0x1000;
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const size_t END = START + 0x100000;
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// determine initial seed
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switch (cicType)
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{
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case 6101:
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case 6102:
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seed = 0xF8CA4DDC;
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break;
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case 6103:
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seed = 0xA3886759;
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break;
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case 6105:
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seed = 0xDF26F436;
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break;
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case 6106:
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seed = 0x1FEA617A;
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break;
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default:
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return false; // unknown CIC type
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}
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t1 = t2 = t3 = t4 = t5 = t6 = seed;
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for (pos = START; pos < END; pos += 4)
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{
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unsigned int d = util_read_uint32_be(romData + pos);
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unsigned int r = ROL(d, (d & 0x1F));
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// increment t4 if t6 overflows
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if ((t6 + d) < t6)
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t4++;
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t6 += d;
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t3 ^= d;
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t5 += r;
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if (t2 > d)
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t2 ^= r;
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else
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t2 ^= t6 ^ d;
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if (cicType == 6105)
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t1 += util_read_uint32_be(&romData[0x0750 + (pos & 0xFF)]) ^ d;
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else
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t1 += t5 ^ d;
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}
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if (cicType == 6103)
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{
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chksum[0] = (t6 ^ t4) + t3;
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chksum[1] = (t5 ^ t2) + t1;
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}
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else if (cicType == 6106)
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{
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chksum[0] = (t6 * t4) + t3;
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chksum[1] = (t5 * t2) + t1;
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}
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else
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{
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chksum[0] = t6 ^ t4 ^ t3;
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chksum[1] = t5 ^ t2 ^ t1;
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}
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return true;
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}
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