crc.cpp

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00032 
00033 #include "Utilities/crc.h"
00034 
00035 namespace OneWire
00036 {
00037     namespace crc
00038     {
00039         uint8_t calculateCrc8(uint8_t crc8, uint8_t data)
00040         {
00041             // See Application Note 27
00042             crc8 = crc8 ^ data;
00043             for (int i = 0; i < 8; i++)
00044             {
00045                 if (crc8 & 1)
00046                 {
00047                     crc8 = (crc8 >> 1) ^ 0x8c;
00048                 }
00049                 else
00050                 {
00051                     crc8 = (crc8 >> 1);
00052                 }
00053             }
00054          
00055             return crc8;
00056         }
00057          
00058         uint8_t calculateCrc8(const uint8_t * data, size_t dataLen, uint8_t crc)
00059         {
00060             for (size_t i = 0; i < dataLen; i++)
00061             {
00062                 crc = calculateCrc8(crc, data[i]);
00063             }
00064             return crc;
00065         }
00066          
00067         uint16_t calculateCrc16(uint16_t crc16, uint16_t data)
00068         {
00069             const uint16_t oddparity[] = { 0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0 };
00070 
00071             data = (data ^ (crc16 & 0xff)) & 0xff;
00072             crc16 >>= 8;
00073 
00074             if (oddparity[data & 0xf] ^ oddparity[data >> 4])
00075             {
00076                 crc16 ^= 0xc001;
00077             }
00078 
00079             data <<= 6;
00080             crc16 ^= data;
00081             data <<= 1;
00082             crc16 ^= data;
00083 
00084             return crc16;
00085         }
00086 
00087         uint16_t calculateCrc16(const uint8_t * data, size_t dataLen, uint16_t crc)
00088         {
00089             for (size_t i = 0; i < dataLen; i++)
00090             {
00091                 crc = calculateCrc16(crc, data[i]);
00092             }
00093             return crc;
00094         }
00095     }
00096 }