mirror of
https://github.com/blawar/GLideN64.git
synced 2024-07-07 03:13:49 +00:00
87 lines
1.5 KiB
C++
87 lines
1.5 KiB
C++
#include "Types.h"
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#define CRC32_POLYNOMIAL 0x04C11DB7
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unsigned int CRCTable[ 256 ];
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u32 Reflect( u32 ref, char ch )
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{
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u32 value = 0;
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// Swap bit 0 for bit 7
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// bit 1 for bit 6, etc.
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for (int i = 1; i < (ch + 1); ++i) {
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if(ref & 1)
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value |= 1 << (ch - i);
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ref >>= 1;
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}
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return value;
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}
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void CRC_BuildTable()
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{
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u32 crc;
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for (int i = 0; i < 256; ++i) {
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crc = Reflect( i, 8 ) << 24;
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for (int j = 0; j < 8; ++j)
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crc = (crc << 1) ^ (crc & (1 << 31) ? CRC32_POLYNOMIAL : 0);
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CRCTable[i] = Reflect( crc, 32 );
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}
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}
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u32 CRC_Calculate( u32 crc, const void * buffer, u32 count )
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{
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u8 *p;
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u32 orig = crc;
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p = (u8*) buffer;
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while (count--)
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crc = (crc >> 8) ^ CRCTable[(crc & 0xFF) ^ *p++];
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return crc ^ orig;
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}
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u32 CRC_CalculatePalette(u32 crc, const void * buffer, u32 count )
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{
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u8 *p;
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u32 orig = crc;
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p = (u8*) buffer;
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while (count--) {
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crc = (crc >> 8) ^ CRCTable[(crc & 0xFF) ^ *p++];
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crc = (crc >> 8) ^ CRCTable[(crc & 0xFF) ^ *p++];
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p += 6;
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}
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return crc ^ orig;
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}
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u32 Adler32(u32 crc, const void *buffer, u32 count)
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{
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register u32 s1 = crc & 0xFFFF;
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register u32 s2 = (crc >> 16) & 0xFFFF;
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int k;
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const u8 *Buffer = (const u8*)buffer;
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if (Buffer == NULL)
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return 0;
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while (count > 0) {
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/* 5552 is the largest n such that 255n(n+1)/2 + (n+1)(BASE-1) <= 2^32-1 */
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k = (count < 5552 ? count : 5552);
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count -= k;
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while (k--) {
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s1 += *Buffer++;
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s2 += s1;
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}
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/* 65521 is the largest prime smaller than 65536 */
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s1 %= 65521;
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s2 %= 65521;
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}
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return (s2 << 16) | s1;
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}
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