46 lines
920 B
C++
46 lines
920 B
C++
/* CRC-32 calculator
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* Adapted from http://www.createwindow.org/programming/crc32/
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*/
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#include "crc32.h"
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CRC_Generator::CRC_Generator() {
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init();
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}
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void CRC_Generator::init(void) {
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Bit32u POLYNOMIAL = 0x04c11db7;
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int i;
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for(i = 0; i<0xFF; i++) {
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int j;
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crc32_table[i]=reflect(i,8) << 24;
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for(j=0; j<8; j++)
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crc32_table[i] = (crc32_table[i]<<1)^(crc32_table[i] & (1<<31) ? POLYNOMIAL : 0);
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crc32_table[i] = reflect(crc32_table[i], 32);
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}
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}
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Bit32u CRC_Generator::reflect(Bit32u ref, Bit8u ch) {
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Bit32u value(0);
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int i;
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for(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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Bit32u CRC_Generator::get_CRC(Bit8u * buf, Bit32u buflen) {
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Bit32u ulCRC(0xFFFFFFFF);
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Bit32u len(buflen);
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Bit8u * buffer=(Bit8u *) buf;
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while(len--)
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ulCRC=(ulCRC>>8)^crc32_table[(ulCRC & 0xFF)^*buffer++];
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return ulCRC ^ 0xFFFFFFFF;
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}
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