CRC8.cpp

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00032 */
00033 #include <stdint.h>
00034 
00035 /*
00036  * CRC-8:
00037  *
00038  * Width:   8
00039  * Poly:    0x07
00040  * Init:    0x00
00041  * RefIn:   False
00042  * RefOut:  False
00043  * XOROur:  0x00
00044  * Check:   0xF4
00045  */
00046 
00047 static const uint8_t CRC8_POLY = 0x07;
00048 static bool crc8_initialized = false;
00049 
00050 static uint8_t crc8_table[256];
00051 
00052 
00053 static void init_crc8()
00054 {
00055     uint8_t msb = 1 << 7;
00056     uint8_t bit;
00057     uint8_t rem;
00058     uint32_t byte = 0;
00059 
00060     if (crc8_initialized)
00061         return;
00062 
00063     while (byte < 256) {
00064         rem = byte;
00065         for (bit = 0; bit < 8; bit++) {
00066             if (rem & msb)
00067                 rem = (rem << 1) ^ CRC8_POLY;
00068             else
00069                 rem <<= 1;
00070         }
00071 
00072         crc8_table[byte++] = rem;
00073     }
00074 
00075     crc8_initialized = true;
00076 }
00077 
00078 uint8_t crc8(uint8_t *data, uint32_t length)
00079 {
00080     uint8_t crc = 0x00;
00081     uint32_t msg_idx = 0;
00082 
00083     if (length == 0xFFFFFFFF)
00084         return 0;
00085 
00086     init_crc8();
00087 
00088     while (msg_idx < length) {
00089         crc = crc8_table[crc ^ data[msg_idx++]];
00090     }
00091 
00092     return crc;
00093 }