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#include <avr/io.h>
#include <stdlib.h>
#include "fecmodem.h"
uint8_t FECModem::parity128(uint8_t byte)
{
return pgm_read_byte(&hammingParityLow[byte & 0x0f]) ^ pgm_read_byte(&hammingParityHigh[byte >> 4]);
}
uint8_t FECModem::parity2416(uint8_t byte1, uint8_t byte2)
{
return parity128(byte1) | (parity128(byte2) << 4);
}
uint8_t FECModem::correct128(uint8_t *byte, uint8_t err)
{
uint8_t result = pgm_read_byte(&hammingParityCheck[err & 0x0f]);
if (result != NO_ERROR) {
if (result == UNCORRECTABLE || byte == NULL) {
return 3;
} else {
if (result != ERROR_IN_PARITY) {
*byte ^= result;
}
return 1;
}
}
return 0;
}
uint8_t FECModem::hamming2416(uint8_t *byte1, uint8_t *byte2, uint8_t parity)
{
uint8_t err;
if (byte1 == NULL || byte2 == NULL) {
return 3;
}
err = parity2416(*byte1, *byte2) ^ parity;
if (err) {
return correct128(byte1, err) + correct128(byte2, err >> 4);
}
return 0;
}
FECModem modem;
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