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68 lines
1.4 KiB
C
68 lines
1.4 KiB
C
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#include <ultra64.h>
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#include <global.h>
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#include <ultra64/controller.h>
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// Valid addr up to 0x7FF
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// It's the address of a block of 0x20 bytes in the mempak
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// So that means the whole mempak has a 16-bit address space
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u8 osMempakAddrCRC(u16 addr) {
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u32 addr32 = addr;
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u32 ret = 0;
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u32 bit;
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s32 i;
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for (bit = 0x400; bit; bit /= 2) {
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ret *= 2;
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if (addr32 & bit) {
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if (ret & 0x20) {
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ret ^= 0x14;
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} else {
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++ret;
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}
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} else {
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if (ret & 0x20) {
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ret ^= 0x15;
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}
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}
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}
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for (i = 0; i < 5; ++i) {
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ret <<= 1;
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if (ret & 0x20) {
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ret ^= 0x15;
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}
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}
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return ret & 0x1f;
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}
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u8 osMempakDataCRC(u8* data) {
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s32 ret;
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u32 bit;
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u32 byte;
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ret = 0;
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for (byte = 0x20; byte; --byte, ++data) {
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for (bit = 0x80; bit; bit /= 2) {
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ret *= 2;
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if ((*data & bit) != 0) {
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if ((ret & 0x100) != 0) {
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ret ^= 0x84;
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} else {
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++ret;
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}
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} else {
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if (ret & 0x100) {
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ret ^= 0x85;
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}
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}
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}
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}
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do {
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ret *= 2;
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if (ret & 0x100) {
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ret ^= 0x85;
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}
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++byte;
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} while (byte < 8U);
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return ret;
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}
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